Next Article in Journal
Transparent and Ultra-Thin Flexible Checkerboard Metasurface for Radar–Infrared Bi-Stealth
Next Article in Special Issue
Practical NIR Assay Derived from Cyanine to Evaluate Intracellular H2S in Living Cell Imaging
Previous Article in Journal
On-Chip Photonic Detection Techniques for Non-Invasive In Situ Characterizations at the Microfluidic Scale
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Sensors
Volume 24
Issue 5
10.3390/s24051530
sensors-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Recent Developments of Fluorescence Sensors Constructed from Pillar[n]arene-Based Supramolecular Architectures Containing Metal Coordination Sites

by
Xu Li
,
Yan Jin
,
Nansong Zhu
*,
Jinghua Yin
* and
Long Yi Jin
Department of Chemistry, National Demonstration Centre for Experimental Chemistry Education, Yanbian University, Yanji 133002, China
*
Authors to whom correspondence should be addressed.
Sensors 2024, 24(5), 1530; https://doi.org/10.3390/s24051530
Submission received: 9 February 2024 / Revised: 23 February 2024 / Accepted: 26 February 2024 / Published: 27 February 2024
(This article belongs to the Special Issue Applications of Fluorescent Chemical Sensors and Photocatalytic Materials in Environmental Monitoring and Remediation)
Browse Figures
Versions Notes

Abstract

:
The field of fluorescence sensing, leveraging various supramolecular self-assembled architectures constructed from macrocyclic pillar[n]arenes, has seen significant advancement in recent decades. This review comprehensively discusses, for the first time, the recent innovations in the synthesis and self-assembly of pillar[n]arene-based supramolecular architectures (PSAs) containing metal coordination sites, along with their practical applications and prospects in fluorescence sensing. Integrating hydrophobic and electron-rich cavities of pillar[n]arenes into these supramolecular structures endows the entire system with self-assembly behavior and stimulus responsiveness. Employing the host–guest interaction strategy and complementary coordination forces, PSAs exhibiting both intelligent and controllable properties are successfully constructed. This provides a broad horizon for advancing fluorescence sensors capable of detecting environmental pollutants. This review aims to establish a solid foundation for the future development of fluorescence sensing applications utilizing PSAs. Additionally, current challenges and future perspectives in this field are discussed.

Graphical Abstract

1. Introduction

Through noncovalent interactions, supramolecular chemistry unites components with different structures and functionalities [1,2,3,4,5,6,7,8], enabling the construction of dynamically reversible smart composites [9,10,11,12]. Increasing attention has been given to intelligent supramolecular structures formed by host–guest interactions, particularly for their stimuli-responsive properties and expansive application potential. As a vital segment of supramolecular chemistry, macrocyclic hosts have found extensive use across various domains. Presently, there are five prominent macrocyclic hosts, including cyclodextrins, calix[n]arenes, crown ethers, cucurbit[n]urils, and pillar[n]arenes. Each host can specifically accommodate different guest molecules by offering suitable cavities. Pillar[n]arenes, in particular, stand out due to their electron-rich and rigid cavities, symmetrical frame structure, and exceptional host–guest properties [13,14,15,16,17,18,19,20,21]. The positional modification of pillar[n]arenes endows them with distinct characteristics [22,23,24,25,26,27,28]. This review focuses on PSAs that are functionalized with chelating metal ions [29,30].
The coordination metal ions discussed in this review include Ag+, Hg2+, Cu2+, Zn2+, Pt2+, Fe3+, Al3+, Eu3+, and Tb3+. Host–guest complexes with metal coordination sites offer considerable scientific value, characterized by a structure resembling a pillar with many self-assembly driving forces, including cation–π, hydrophobic/hydrophilic, C–H–π, and π–π interactions, among others. We categorize two types of supramolecular architectures with metal ion coordination sites: (i) functional pillar[n]arenes with metal coordination sites are initially designed and synthesized. The existing studies on pillar[n]arenes derive from the successful synthesis of pillar[5]arenes [31], followed by pillar[6]arenes [32]. Additionally, pillar[n]arenes with larger cavities (n = 6–15) can be synthesized from pillar[5]arenes by ring expansion, a process driven by kinetic control [33]. Due to the unique advantages of pillar[n]arenes, many novel functional pillar[n]arenes have emerged one after another [34,35]. The key factors for the design and synthesis of functional pillar[n]arene molecules mainly lie in the following two aspects: Firstly, the reaction time, concentration, temperature, feeding order, and other external conditions should be strictly controlled to minimize the production of various polymer byproducts when synthesizing pillar[n]arenes. Secondly, considering that the kind, position, and quantity of substituents on both sides of pillar[n]arenes have significant effects on their solubility, conformation, and host–guest properties, which directly influences the practical application of pillar[n]arenes, it is also challenging to design functional pillar[n]arenes. Pillar[n]arene derivatives reviewed in this paper mostly concentrate on the single- or dual-functional modifications of the macrocyclic host, including mono, double, and total substitution of the benzene rings. Pillar[n]arenes before functionalization often contain halogen atoms, azide groups, hydroxyl groups, or amino groups as the modification sites. Different reaction sites can adopt specific synthesis strategies to achieve high yield, easy separation, green synthesis, and other goals. The pillar[n]arenes can be also substituted by molecules (e.g., adenin, quinoline, acylhydrazone, thymine, pyridine, triazole, 1,3,4-oxadiazole, bis-2,2′:6′,2″-terpyridin, carboxyl, naphthalimide, thioacetylhydrazine, et al.) to possess the metal coordination ability. These functional pillar[n]arenes can further coordinate with metal ions in the presence or absence of guest molecules, generating supramolecular architectures with specific sensing capacities through multiple noncovalent interaction forces. (ii) Guest molecules with both host–guest recognition abilities and metal coordination sites are firstly designed and synthesized. The host–guest recognition groups are generally composed of quaternary ammonium groups, cyanogen groups, halogen atoms, or nitrogen heterocycles. Additionally, the involved coordination sites mainly consist of phenazine imidazole, thienyl functionalized diketopyrrolopyrrole, or multiple amide groups. After combining these functional groups into a small molecule, these guests can form complexes through host–guest interactions with pillar[n]arenes, which further coordinate with metal ions to generate supramolecular architectures with specific sensing capacities.
Environmental pollutants, such as hydrazine hydrate, nitrobenzene, nitroaromatics, cyanide perchlorate, halides, and various metal ions, have been recognized as a critical global issue, posing significant threats to public health and natural ecosystems. Consequently, there is an urgent demand for the development of analytical methods to detect these toxic substances. However, challenges persist across multiple fronts. Analytical methods that offer high sensitivity, exceptional selectivity, adequate removal effectiveness, and a low limit of detection (LOD) are essential, requiring appropriate strategies. Among the methods reported, fluorescence sensing based on supramolecular systems stands out for its accuracy, convenience, and stability, offering superior temporal and spatial resolution, and enabling real-time analysis [36,37,38,39,40]. Aggregation-induced emission (AIE) has emerged as a promising sensing mechanism in recent years. This approach involves materials that exhibit negligible emission in dilute solutions and significantly increased fluorescence in aggregated states [41,42]. The unique host–guest interactions of pillar[n]arenes can be harnessed to manipulate AIEgens (aggregation-induced emission generators, indicating smart molecules with AIE properties), leading to supramolecular assembly-induced enhanced emission (SAIEE). This offers the potential to develop new materials with photoluminescent properties. Furthermore, materials based on PSAs containing metal coordination sites have shown promising results in detecting and absorbing heavy metal ion contamination and other pollutants.
Above all, to our knowledge, the recent advancements in fluorescence sensing using PSAs containing metal coordination sites have not been systematically reviewed. This review discusses recent research results, from molecular structure design and luminescence studies to practical application demonstrations in fluorescence sensing. This discussion should inspire further research into self-assembly systems based on PSAs in fluorescence sensing.

2. Fluorescence Sensors

Stimulation-responsive fluorescence materials represent a significant category of smart materials. In recent years, these materials have garnered attention due to their tunable luminescence, which can be affected by environmental factors including temperature, light, pressure, guest compounds, etc. In this section, PSAs are systematically categorized and described based on the range of external stimulus conditions they can respond to.

2.1. Single-Stimulus Responsive Sensors

Typically, most materials respond to a single stimulus with high sensitivity (Table 1). Scheme 1 lists the molecular structures of the guest molecules and pillar[n]arenes that are discussed in this section.
A prime example is the widespread concern over environmental pollution caused by heavy metal ions. Silver(I) (Ag+) ions are known for their excellent electrical and thermal conductivity, ductility, and stability. However, excessive silver can disrupt active enzymes by binding to sulfhydryl groups in proteins, leading to their accumulation in the food chain. Therefore, developing economical, simple, environmentally friendly, and efficient materials for detecting and removing Ag+ ions is crucial.
In 2022, Wang W.M. and Yang Y.W. designed a stable supramolecular system utilizing host–guest interactions and coordination effects [43]. They employed two adenine binding sites in pillar[5]arene (P1) and tetraphenylvinyl (TPE, G1) functionalized with cyano groups, which possess AIE properties (Figure 1). Spherical supramolecular aggregates formed via 1:1 coordination between P1’s adenines and Ag+ ions. The synergistic effect of coordination between P1 and Ag+, coupled with the host–guest interaction between P1 and G1, resulted in a crosslinked P1⊂G1@Ag+ assembly. This assembly triggered the restriction of intramolecular rotation (RIR) and SAIEE mechanisms. The fluorescence lifetime and fluorescence quantum yield of P1⊂G1@Ag+ were 4.60 ns and 58.38%, respectively, with the rate constant of nonradiative decay being half that of P1⊂G1. Under 365 nm UV lamp irradiation, the assembly displayed bright blue-green fluorescence upon Ag+ ion addition, permitting effective Ag+ ion adsorption and sensitive detection. Moreover, the supramolecular assembly could be easily processed without a decline in activity, offering a useful tool for practical applications.
The need for effective devices for sensitive toxic gas detection is also paramount. For instance, hydrazine hydrate (DH) is extensively used in synthesizing pesticides and medicines, fuels for satellites and rockets, and as a preservation agent in nuclear and power facilities. However, DH is very harmful, causing severe damage to the skin and central organs upon human absorption. Consequently, developing flexible, fast, and sensitive materials and methods for DH detection is critically important.
A year later, Lin Q.’s group developed a metallic gel by coordinating the nitrogen atom of 5-hydroxyquinoline functionalized pillar[5]arene (P2) with Ag+ ions [44]. P2 formed a one-dimensional coordination polymer through interaction with Ag+ ions via the N atoms on the quinoline groups (Figure 2). Adjacent coordination polymers were interconnected through π–π interactions between the P2 groups, facilitating the metallogel’s formation. The mean squared displacement of the gel P2 was lower than that of the P2-Ag gel, indicating that the inclusion of Ag+ improved the flexibility of the P2-Ag gel. The supramolecular assembly was further analyzed from a microscopic morphology perspective. P2 alone exhibited a lamellar structure. After adding Ag+ ions, the resultant metallogel P2-Ag transformed into a folded membrane structure, which is attributable to the coordination bond between Ag+ ions and P2. When exposed to DH vapor, the folded membrane structure of P2-Ag altered into a microspherical structure, suggesting the disruption of Ag+ ion coordination and the formation of a microspherical structure by P2 based on the hydrophobic effect. This gel enabled multichannel sensitive detection of DH through visual, fluorescence, and electrochemical means. DH disrupted the coordination by reducing Ag+ ions under DMSO/H2O conditions (fw = 20%), leading to the collapse and fluorescence quenching of the metallogel. The lowest critical gelation concentration (CGC) was 8% (w/v, 10 mg/mL = 1%). The gel–sol transition temperature was 62–63 °C. Multichannel detection of DH could be conveniently and efficiently realized in both water and air through sound and light alarms. The LOD reached 0.10 mg/m3 in air and 2.68 × 10−8 mol/L in water, below the US Environmental Protection Agency’s standard for drinking water.
Mercury (Hg2+), among the most hazardous heavy metals, poses significant health and environmental risks. Exposure to Hg2+ ions, even in minute concentrations, presents a potential hazard to humans. For instance, in 2018, the group led by Lin Q. designed and synthesized another sensor based on pillararene AIEgens, which utilized bi-pillar[5]arene-based assemblies incorporating advanced AIEgens (P3) [45]. The assembly was driven by intermolecular hydrogen bonding (such as –N–H⋯C=O– and –C–H⋯N=C–), π–π stacking interactions, and hydrophobic effects. The Tyndall effect was observed in a 30% aqueous solution, with the critical aggregation fraction of water being 24% for P3, which exhibited a fluorescence quantum yield of 21%. P3 formed a sharp rod-shaped structure in DMSO/H2O (fw = 50%). The aggregated P3 was disassembled at low concentrations or high temperatures. A 1:2 complex was formed by binding P3 with Hg2+ ions (binding constant: 2.50 × 103 L2/mol2). The coordination between the Hg2+ ions and the P3 acylhydrazone group served as the basis for the sensing mechanism. To explore practical applications, a glass sheet was submerged in a high concentration of P3 to generate a film. This film enabled the convenient detection of Hg2+ ions in water, effectively separating and sensitively detecting them with an LOD of 4.30 × 10−8 mol/L. This innovative bi-pillar[5]arene AIEgen could pave the way for new designs and developments in pillar[n]arene AIEgens.
The pillar[n]arenes discussed in this paper include two types: pillar[5]arene and pillar[6]arene [46]. The latter was developed by Yang Y.W.’s group. They utilized the strong interactions between thymine (T) and Hg2+ ions. Building on this, Dai D.H. and Yang Y.W. constructed a crosslinked supramolecular polymer through host–guest interactions, utilizing a TPE-bridged bis(quaternary ammonium) guest (G2) with AIE characteristics and a newly constructed [2]biphenyl-extended pillar[6]arene with two thymine sites as arms (P4) (Figure 3). The thymine groups’ close T-Hg2+-T coupling with the Hg2+ ions led to the formation of spherical assemblies with an average diameter of 164 nm. Fluorescent emission occurred immediately upon the addition of Hg2+ ions. The introduction of Hg2+ ions into the supramolecular system initiated supramolecular SAIEE. With its integrated mode of operation, great selectivity, and a quick adsorption rate (removal efficiency: 90%), this supramolecular polymer effectively accomplished the real-time detection and removal of Hg2+ ions from water. The assembly of P4 and G2 demonstrated excellent recyclability, maintaining effectiveness over more than five cycles of the removal process.
Beyond the contributions of the previously mentioned research groups, a self-assembly consisting of carboxylatepillar[5]arene sodium salts (P5) and a diketopyrrole-bridged bis-quaternary ammonium guest (G3) was reported by Jiang X.M. and Cao D.R. [47]. Adding P5 to a G3 aqueous solution resulted in the morphological transformation of multilayer nanostructures (Figure 4). This host–guest complex exhibited multiple forces, including electrostatic, hydrophobic interactions, and π–π stacking interactions in aqueous solutions. The developed supramolecular system effectively detected and removed Hg2+ in real environmental water samples. The Hg2+ ions demonstrated synergistic interactions, including coordination with G3 and P5 and the Hg2+-cavity, forming a crosslinked network of P5⊂G3@Hg2+. The method exhibited good selectivity with a low LOD of 7.17 × 10−7 mol/L. Furthermore, the quenched fluorescence could be recovered post-treatment with Na2S, exhibiting a reversible process.
Copper ions (Cu2+) are also critical in various industries, and can result in soil contamination, bioaccumulation, and decreased agricultural production. Therefore, developing a selective and sensitive Cu2+ ion fluorescent chemical sensor, preferably a proportional chemical sensor, remains crucial in ion sensing research.
Pillar[5]arene was modified by Chang R. and Chang K.C. with five neighboring naphthalimide groups to form a new ligand, P6, for metal ion coordination, effectively serving as a ratiometric fluorescence sensor for Cu2+ ions in a CH2Cl2/CH3CN = 1/1 system [48]. This sensitivity was also observed in 10% aqueous methanol solutions. The introduction of naphthalimide groups enhanced intramolecular π–π stacking. P6 exhibited dual emission, comprising both the monomer and excimer emissions of the naphthalimide moieties. A synergistic interaction occurred between Cu2+ ions and the triazole groups on P6. P6 rapidly bound with Cu2+, maintaining stable fluorescence intensity. Upon complexing with Cu2+ ions, the excimer emission of ligand P6 was weakened, while the monomer emission intensified. The binding complexation ratio of P6 with Cu2+ ions was 1:1, with a binding constant of (3.39 ± 0.40) × 105 L2/mol2 and an LOD of 1.85 × 10−6 mol/L. Particles varying in diameters from (192 ± 65) to (206 ± 67) nm were produced. The relative fluorescence quantum yields of P1 and P1-Cu2+ were 0.13 and 0.11, respectively. The pillar[5]arene framework may be further functionalized in future studies to improve its selectivity for particular metal ions, or to modify it for use with different sensing platforms.
Liu S.Y. and Han J. developed another sensor for Cu2+ ions [49]. They designed a pillar[5]arene framework by functionalizing it with a cyanobutoxy moiety (P7) and a 1,3,4-oxadiazole subunit. This structure facilitated host–guest interactions between the electron-rich pillar[5]arene cavities and appropriately-sized neutral cyanobutoxy moieties, resulting in brush supramolecular polymers. Notably, the larger electron-deficient 1,3,4-oxadiazole groups remained outside the pillar[n]arene (P7) cavity after the creation of the host–guest inclusions, acting as a “brush” and enhancing the ability of the self-assembled supramolecular materials to interact with metal ions, such as Cu2+ ions. The critical aggregation concentration of P7 was 6.00 × 10−2 mol/L. These supramolecular brush-polymer architectures displayed distinct structural changes in response to fluorescence quenching after adding Cu2+ ions, suggesting a potential transformation into a crosslinked supramolecular network. The Irving–Williams order of stability might provide an explanation for the particular recognition of Cu2+. Therefore, this supramolecular brush polymer holds potential for application in metal cationic fluorescent chemical sensors.
In 2021, Chong H. et al. prepared a “three-component” supramolecular assembly by combining terpyridine attached pillar[5]arene (P8), cyano- and triazole-bearing alkyl chain (G4), and Zn2+ ions in a CHCl3 and CH3CN solvent system [50]. Terpyridine’s strong affinity for a variety of transition metal ions makes it an adaptable building block. The resulting composition exhibited a closely crosslinked porous morphology with nanoscale pore size. The P8 segment was incorporated into the cyano and triazole segment upon encapsulation. An organogel formed at a concentration of 1.00 mol/L. The polymerization was driven by host–guest interaction and metal-chelate cooperative forces. The P8 and Zn2+ assembly had a flake-like morphology. Nitrobenzene (picric acid, o-nitrobenzene, and phenol) was used as a sample. Of the three analytes, the assembly exhibited the highest sensitivity to picric acid, with an LOD of 1.66 × 10−4 mol/L. The quenching mechanism was believed to involve mixed processes of photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET). This study represents a practical illustration of creating functional “multi-component” supramolecular systems with capabilities for explosive detection.
The role of Fe3+ ions as an essential metal element in human physiology is well-recognized. However, both deficiency and excess of Fe3+ ions beyond permissible limits can lead to severe health issues, such as anemia, tumorigenesis, organ dysfunction, and neurodegenerative diseases such as Alzheimer’s and Parkinson’s. Consequently, sensitive detection of Fe3+ ions is a critical concern in environmental and health monitoring. In 2018, Zhang Y.M. and Qi L. discovered that the pillar[5]arene structure (P9) could self-assemble into high-molecular-weight supramolecular π-gels with AIE properties [51]. Notably, the simplicity of the supramolecular system components enhanced its practical application value. Through π–π stacking interactions, P9 self-assembled into one-dimensional linear supramolecular π–gel chains. These π–gel chains interacted with the pillar[5]arene and naphthalimide to produce a two-dimensional supramolecular network. Subsequently, hydrophobic interactions compressed the two-dimensional network into microspheres. The CGC was 5% (w/v, 10 mg/mL = 1%). The gel–sol transition temperature was 43–45 °C. The LOD was 6.06 × 10−8 mol/L for Fe3+ ions. The gel demonstrated excellent recyclability and a 99.80% removal rate for Fe3+ ions in aqueous solutions. Additionally, the Fe3+ ion-coordinated supramolecular gel selectively sensed L-Cys with an LOD of 1.00 × 10−8 mol/L. This gel could be utilized in logic gates, offering significant advantages over previous logic devices in terms of reversibility, sensitivity, and prospective uses for ongoing transition metal and amino acid detection.
Because of their vital functions in chemical, biological, and environmental applications, the development of ultrasensitive materials and reactions has received a lot of attention recently. In light of this, the above-mentioned group continued to enhance the sensitivity and stability of sensor materials based on their prior findings. They achieved an LOD for Fe3+ ions detection reduced from 10−8 to 10−9 magnitude [52]. They specifically created a new supramolecular organic framework (SOF) that is based on two pillar[5]arene molecules: P9, which is functionalized with bis-naphthalimide, and P10, which is functionalized with bis-ammonium. Through the competition of cation–π and π–π interactions, this SOF developed a persistent supramolecular gel in cyclohexanol, enabling an ultrasensitive response to Fe3+ ions. Upon adding 0.50 equivalent of Fe3+ ions, the yellow fluorescence of the gel was quenched with an LOD of 7.54 × 10−9 mol/L. The Fe3+ ion-coordinated gel could sense H2PO4− ions with a fluorescence “turn-on” response and an LOD of 4.21 × 10−9 mol/L. Response films were prepared using these soft gels, which could also function as sensitive logic gates, fluorescent display materials, and ultra-sensitive ion sensors.

2.2. Dual-Stimuli Responsive Sensors

The development of dual-response materials (Table 2) for complex systems is of great significance and challenge. The molecular structures of pillar[n]arenes and guest molecules associated with these smart materials are listed in Scheme 2.
In 2018, the group of Zhang Y.M. and Wei T.B. constructed an advanced bifunctional supramolecular pseudorotaxane chemosensor using host pillar[5]arene P11 and guest G5 [53]. Adding Ag+ and Hg2+ ions to this system resulted in fluorescence quenching and significant changes in fluorescence color, respectively. This method demonstrated high sensitivity and selectivity, with LODs of 1.20 × 10−8 and 5.00 × 10−7 mol/L for Ag+ and Hg2+ ions, respectively.
The group led by Wei T.B. [54] developed a novel metallosupramolecular polypseudorotaxane by integrating thioacetylhydrazine functionalized pillar[5]arene (P12) and bis-butyltrimethyl ammonium functionalized pillar[5]arene (P13) with Zn2+ ions (Figure 5). The hydrazyl groups served as coordination and hydrogen bond sites for self-assembly with Zn2+ ions. This gel acted as an ultrasensitive fluorescence sensor for detecting Fe3+ and Cu2+ ions, with LODs of 8.93 × 10−10 and 4.57 × 10−8 mol/L, respectively. Thin films based on this gel could be used as convenient test kits. Furthermore, this study presented a simple and effective strategy for achieving multiple stimulus responses by introducing multiple noncovalent interactions in metal supramolecular gels.
In the context of escalating environmental pollution and its threats to human health and safety, nitroaromatic compounds (NACs) have been identified as major pollutants. NACs are widely utilized in the chemical, dye, explosive, pesticide, and medicinal sectors. P-nitrophenol, for example, can result in major health problems such as methemoglobinemia, fever, liver, and kidney damage. In 2023, Yu D.Y., Deng W.T., and Wei X.Q. synthesized a blue-green fluorescent supramolecular aggregate capable of self-assembling from pillar[5]arene-based Cu2+ ions coordination complexes [55]. Two carboxyl O atoms from one P14 molecule and four O atoms from four water molecules made up the octahedral coordination of the Cu2+ ions (Figure 6). These coordination complexes were self-assembled into spherical aggregates through multiple noncovalent forces, including hydrophobic effects, van der Waals forces, and CH–π interactions. The aggregate exhibited high sensitivity and selectivity to nitroaromatic compounds and metal ions. The fluorescence emission of the aggregate was specifically and significantly quenched by p-nitrophenol and Fe3+ ions, with low LOD values of 3.90 × 10−7 and 4.90 × 10−6 mol/L, respectively. Additionally, due to their exceptional performances, these coordinated supramolecular aggregates based on pillar[n]arenes hold promise for various applications in adsorption, sensing, cargo transport, and catalysis.
Sulfur substituent-decorated pillar[5]arene (P15) showed control over binding affinities toward encapsulations of organic guests inside its cavity [56]. The exterior cavity of P15 tended to form metal-ion coordination bonds (Figure 7). Adding a dinitrile guest (G6) containing a bis-triazole benzene spacer led to the creation of pseudorotaxane host–guest complexes. The fluorescence emission signals were significantly reduced in the presence of Hg2+ and Cu2+ ions. These macrocycles facilitated the transfer of Cu2+ ions from the aqueous to the organic phase, enhancing efficiency compared to extraction processes without pillar[5]arene.
Zhang Y.M. and Lin Q. created a unique SOF gel using pillar[5]arene host (P2) and a bilateral bromohexyl functionalized pillar[5]arene guest (P16) [57]. The SOF gel was constructed through CH–π, CH–O, and “exo–wall π–π” interactions between P2 and P16. The introduction of Fe3+ ions into the gel resulted in quenched fluorescence. The gel exhibited an LOD of 1.02 × 10−10 mol/L for Fe3+ ions. The coordinated metallogel of Fe3+ ions exhibited a fluorescent “turn-on” response due to the competitive coordination of F− anions, having an LOD of 9.79 × 10−9 mol/L. The xerogel of this SOF gel demonstrated an adsorption rate of 99.90% for removing Fe3+ ions. This SOF gel and the Fe3+ coordinated metallogel served as an ultrasensitive and reversible fluorescence sensor and test kit for Fe3+ ions and F− anions.
Toxic contaminant ion detection is always a significant problem. Many anions are harmful to human health. Perchlorates (ClO4− anions) disrupt the production and secretion of thyroxine and, therefore, affect the normal metabolism and metabolism of the human body. Cyanide (CN− anion) is a highly toxic compound, and is common in industry and found in nature. Therefore, it is crucial to monitor and eliminate these harmful anions. Zhang Q. and Lin Q. have been actively working to address these challenges [58]. The powder of P17 displayed a rod-like structure, while G7 formed a blocky structure. P17 and G7 assembled via π–π interactions to create a xerogel structure with a crosslinked network. This xerogel exhibited strong yellow AIE properties. It demonstrated the ability to coordinate the rare earth metal ions Eu3+ and Tb3+, enabling it to detect ClO4− and CN− anions through a fluorescence “turn-on” mode. Additionally, the xerogel demonstrated efficient removal capabilities for these two anions.

2.3. Multi-Stimuli Responsive Sensors

To accomplish multi-stimuli-responsive detection in complex environments, it is crucial to continuously explore various units to construct novel multi-stimuli-responsive fluorescence materials. The sensing capacities of these materials are presented in Table 3, and the molecular structures of pillar[n]arenes and guest molecules newly mentioned in this section are listed in Scheme 3.
Yang H.B.’s group synthesized a dipyridyl donor (P18) containing a TPE scaffold and two pillar[5]arene units [59]. P18 exhibited broad absorption bands at a wavelength of 336 nm with molar absorption coefficients of 2.10 × 104 L·mol−1·cm−1. Utilizing P18, they constructed a rhomboidal metallacycle with four pillar[5]arene units and a hexagonal metallacycle with six pillar[5]arene units (Figure 8). These structures led to a new family of crosslinked AIE supramolecular polymer gels, driven by hierarchical self-assembly involving coordination between the nitrogen and platinum atoms and host–guest interactions. These supramolecular polymer gels demonstrated gel–sol transitions responsive to various stimuli, including temperature, competing guest molecules, halides, and reversible “on-off” fluorescence. With their multifaceted response characteristics, it is anticipated that these crosslinked AIE supramolecular polymer gels will have a major impact on a number of sectors, including drug delivery, biological imaging, and molecular sensors.
The pillar[5]arene (P2) was able to coordinate with Al3+ ions, forming a supramolecular polymer metallogel that exhibited light blue AIE in the DMSO/H2O binary solution [60]. This gel showed responsiveness to multiple external stimuli, including temperature, guest compounds, ions (Fe3+ ions, F− anions), acids (trifluoroacetic acid, TFA), and bases (triethylamine, TEA). The LODs ranged from 4.39 × 10−9 to 1.82 × 10−7 mol/L for Fe3+ ions, F− anions, TFA, and TEA. The gel could detect Fe3+ ions, and Fe3+ ions coordinated metallogel could detect F− anions through cation–π interactions and competitive coordination. The value of LOD for Fe3+ ions in the gel was 4.39 × 10−9 mol/L, while the LOD for F− anions in the Fe3+ ion-coordinated metallogel was approximately 2.75 × 10−8 mol/L. Furthermore, the gel could detect TFA and TEA sequentially through protonation and deprotonation processes. Protonation enhanced the π–π stacking interaction between P2 molecules. This material could be employed for multiple “write–erase–write” cycles, showcasing its versatility in detecting various stimuli.
Functional supramolecular polymer networks (SPNs) exhibit tunable luminescence properties [61]. These features set macrocyclic arene-based supramolecular gels apart from conventional pillar[n]arenes by expanding their range of functional building pieces. Developing soft materials based on pillar[n]arenes has captured the interest of many researchers. In 2019, Liu Z.J. and Yang Y.W. synthesized a monofunctionalized pillar[6]arene (P19) bearing a single terpyridine arm. They constructed a fluorescent SPN from P19, a TPE aggregation-induced emission generator G8, and Zn2+ ions as a coordinating linkage. The disruption of metal coordination and/or host–guest interactions by competitive binders such as TFA or pillar[5]arene, as well as heating, could weaken noncovalent interactions in the supramolecular polymer gels, inducing a gel–to–sol transition. These new architectural designs present encouraging paths for the creation of fluorescent SPN materials.
Zn2+ ions, a ditopic guest (G9), and a double-armed pillar[5]arene host (P20) assembled hierarchically to form another SPN [62]. Figure 9 shows that this assembly demonstrated sol–gel transition behaviors in response to a range of external stimuli, including as temperature, redox, pH variations, and competing guests. This assembly also functioned as a practical and easy-to-use test kit for the detection of OH− anions. Given the advantageous properties of host–guest molecular recognition and the induction of metal–ligand coordination interactions, this work laid the groundwork for creating multi-stimuli-responsive metal supramolecular gels based on pillar[n]arene. The advancement of intelligent supramolecular materials with unique architectures and a variety of functions is greatly aided by these discoveries.

3. Conclusions and Outlooks

This review outlines the most recent studies in PSAs for developing fluorescence sensors capable of detecting environmental pollutants. In the last five years, notable advancements have been achieved in delineating the molecular structures, self-assembly mechanisms, photophysical properties, and sensing applications of these compounds. Recent PSAs-based sensors demonstrate enhanced capabilities in detecting various pollutants, offering superior solvent compatibility, porosity, versatility, and diverse detection capacities compared to traditional fluorescence sensors.
As highlighted above, fluorescence sensors have achieved notable success in designing and synthesizing innovative molecular structures and applying stimulus-responsive smart materials. However, the field faces new challenges and opportunities for future exploration and innovation. Firstly, the low concentration of analytes in real samples necessitates improvements in sensitivity and selectivity. Secondly, the fluorescence modulation mechanism under supramolecular regulation remains unclear, warranting further investigation into the luminescence mechanism, particularly concerning charge distribution and molecular architecture accumulation. Thirdly, the complexity of the constructed supramolecular systems often results in poor stability, posing challenges in practical applications. Simplifying these assemblies while maintaining or enhancing detection performance is critical for future research. Fourthly, developing supramolecular architectures that combine detection and adsorption functions requires further study, particularly in creating stable, reusable materials. Fifthly, there is a need for more research into PSAs capable of detecting multiple analytes simultaneously. Finally, while significant research has been conducted in developing supramolecular fluorescence sensors, their reliance on organic solvents hinders their applicability in biological and environmental systems.
In summary, fluorescence sensors based on PSAs containing metal coordination sites have been rapidly and continuously developed. We hope this review can help to promote design strategies for these sensors to better detect and adsorb environmental pollutants.

Author Contributions

Conceptualization, L.Y.J., N.Z. and Y.J.; writing—original draft, X.L.; writing—review and editing, N.Z., J.Y., X.L. and Y.J.; supervision, N.Z., J.Y. and L.Y.J.; project administration, N.Z., J.Y. and L.Y.J.; funding acquisition, N.Z. and L.Y.J. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Education Department of Jilin Province (grant number JJKH20230612KJ), the National Natural Science Foundation of China (grant number 21961041), the PhD Research Startup Foundation of Yanbian University (grant number ydbq202304), and the Higher Education Discipline Innovation Project (grant number D18012).

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

AIEAggregation-induced emission
CGCCritical gelation concentration
FRETFluorescence resonance energy transfer
DHHydrazine hydrate
RIRRestriction of intramolecular rotation
LODLimit of detection
NACNitro aromatic compound
PETPhoto-induced electron transfer
PNPP-nitrophenol
SAIEESupramolecular assembly induced emission enhancement
SOFSupramolecular organic framework
SPNSupramolecules polymer network
TPETetraphenylvinyl
TFATrifluoroacetic acid
TEATriethylamine

References

  1. Belmont-Sánchez, J.C.; Choquesillo-Lazarte, D.; García-Rubiño, M.E.; Matilla-Hernández, A.; Niclós-Gutiérrez, J.; Castiñeiras, A.; Frontera, A. Supramolecular nature of multicomponent crystals formed from 2,2′-thiodiacetic acid with 2,6-diaminopurine or N9-(2-Hydroxyethyl)adenine. Int. J. Mol. Sci. 2023, 24, 17381. [Google Scholar] [CrossRef]
  2. Groschel, A.H.; Mueller, A.H.E. Self-assembly concepts for multicompartment nanostructures. Nanoscale 2015, 7, 11841–11876. [Google Scholar] [CrossRef]
  3. Mujahid, A.; Afzal, A.; Dickert, F.L. Transitioning from Supramolecular Chemistry to Molecularly Imprinted Polymers in Chemical Sensing. Sensors 2023, 23, 7457. [Google Scholar] [CrossRef]
  4. Liu, Q.; Sun, Z.; Dou, Y.; Kim, J.; Dou, X. Two-step self-assembly of hierarchically-ordered nanostructures. J. Mater. Chem. A 2015, 3, 11688–11699. [Google Scholar] [CrossRef]
  5. Xu, L.; Wang, Z.; Wang, R.; Wang, L.; He, X.; Jiang, H.; Tang, H.; Cao, D.; Tang, B. A conjugated polymeric supramolecular network with aggregation-induced emission enhancement: An efficient light-harvesting system with an ultrahigh antenna effect. Angew. Chem. Int. Ed. 2020, 59, 9908–9913. [Google Scholar] [CrossRef]
  6. An, D.; Shi, L.; Li, T.; Zhang, H.Y.; Chen, Y.; Hao, X.Q.; Song, M.P. Tailored supramolecular cage for efficient bio-labeling. Int. J. Mol. Sci. 2023, 24, 2147. [Google Scholar] [CrossRef] [PubMed]
  7. Zhang, W.; Gao, C. Morphology transformation of self-assembled organic nanomaterials in aqueous solution induced by stimuli-triggered chemical structure changes. J. Mater. Chem. A 2017, 5, 16059–16104. [Google Scholar] [CrossRef]
  8. Li, Z.; Hu, Y.; Wang, L.; Liu, H.F.; Ren, T.L.; Wang, C.; Li, D.L. Selective and accurate detection of nitrate in aquaculture water with surface-enhanced raman scattering (SERS) using gold nanoparticles decorated with β-cyclodextrins. Sensors 2024, 24, 1093. [Google Scholar] [CrossRef] [PubMed]
  9. Jin, L.Y.; Bae, J.; Ryu, J.H.; Lee, M. Ordered nanostructures from the self-assembly of reactive coil-rod-coil molecules. Angew. Chem. Int. Ed. 2006, 45, 650–653. [Google Scholar] [CrossRef] [PubMed]
  10. Pugliese, R. Structural and biomechanical properties of supramolecular nanofiber-based hydrogels in biomedicine. Biomedicines 2024, 12, 205. [Google Scholar] [CrossRef] [PubMed]
  11. Roche, T.P.; Nedumpurath, P.J.; Karunakaran, S.C.; Schuster, G.B.; Hud, N.V. One-pot formation of pairing proto-RNA nucleotides and their supramolecular assemblies. Life 2023, 13, 2200. [Google Scholar] [CrossRef]
  12. Croitoriu, A.; Chiriac, A.P.; Rusu, A.G.; Ghilan, A.; Ciolacu, D.E.; Stoica, I.; Nita, L.E. Morphological evaluation of supramolecular soft materials obtained through co-assembly processes. Gels 2023, 9, 886. [Google Scholar] [CrossRef]
  13. Li, X.; Jin, Y.; Zhu, N.S.; Jin, L.Y. Applications of supramolecular polymers generated from pillar[n]arene-based molecules. Polymers 2023, 15, 4543. [Google Scholar] [CrossRef] [PubMed]
  14. Lu, J.; Liu, P.; Deng, Y.; Zhu, N.; Jin, L.Y. Supramolecular nanoassemblies of rim-differentiated pillar[5]arene-rod-coil macromolecules via host-guest interactions for the sensing of cis-trans isomers of 1,4-diol-2-butene. J. Mol. Struct. 2023, 1291, 136054. [Google Scholar] [CrossRef]
  15. Lu, P.; Cheng, J.; Li, Y.; Li, L.; Wang, Q.; He, C. Novel porous beta-cyclodextrin/pillar[5]arene copolymer for rapid removal of organic pollutants from water. Carbohyd. Polym. 2019, 216, 149–156. [Google Scholar] [CrossRef] [PubMed]
  16. Li, Z.Y.; Zhang, Y.; Zhang, C.W.; Chen, L.J.; Wang, C.; Tan, H.W.; Yu, Y.H.; Li, X.P.; Yang, H.B. Cross-linked supramolecular polymer gels constructed from discrete multi-pillar[5]arene metallacycles and their multiple stimuli-responsive behavior. J. Am. Chem. Soc. 2014, 136, 8577–8589. [Google Scholar] [CrossRef] [PubMed]
  17. Lou, X.Y.; Yang, Y.W. Pyridine-conjugated pillar[5]arene: From molecular crystals of blue luminescence to red-emissive coordination nanocrystals. J. Am. Chem. Soc. 2021, 143, 11976–11981. [Google Scholar] [CrossRef] [PubMed]
  18. Zhu, H.; Li, Q.; Shi, B.; Xing, H.; Sun, Y.; Lu, S.; Shangguan, L.; Li, X.; Huang, F.; Stang, P.J. Formation of planar chiral platinum triangles via pillar[5]arene for circularly polarized luminescence. J. Am. Chem. Soc. 2020, 142, 17340–17345. [Google Scholar] [CrossRef] [PubMed]
  19. Yan, H.; Yin, X.; Wang, D.; Han, T.; Tang, B.Z. Synergistically boosting the circularly polarized luminescence of functionalized pillar[5]arenes by polymerization and aggregation. Adv. Sci. 2023, 10, 2305149. [Google Scholar] [CrossRef]
  20. Mei, Y.; Zhang, Q.W.; Gu, Q.; Liu, Z.; He, X.; Tian, Y. Pillar[5]arene-based fluorescent sensor array for biosensing of intracellular multi-neurotransmitters through host–guest recognitions. J. Am. Chem. Soc. 2022, 144, 2351–2359. [Google Scholar] [CrossRef]
  21. Tuo, W.; Sun, Y.; Lu, S.; Li, X.; Sun, Y.; Stang, P.J. Pillar[5]arene-containing metallacycles and host-guest interaction caused aggregation-induced emission enhancement platforms. J. Am. Chem. Soc. 2020, 142, 16930–16934. [Google Scholar] [CrossRef] [PubMed]
  22. Ogoshi, T.; Yamagishi, T.; Nakamoto, Y. Pillar-shaped macrocyclic hosts pillar[n]arenes: New key players for supramolecular chemistry. Chem. Rev. 2016, 116, 7937–8002. [Google Scholar] [CrossRef] [PubMed]
  23. Lescop, C. Coordination-driven syntheses of compact supramolecular metallacycles toward extended metallo-organic stacked supramolecular assemblies. Acc. Chem. Res. 2017, 50, 885–894. [Google Scholar] [CrossRef] [PubMed]
  24. St Onge, P.B.J.; Chen, T.C.; Langlois, A. Iron-coordinating π-conjugated semiconducting polymer: Morphology and charge transport in organic field-effect transistors. J. Mater. Chem. C 2020, 8, 8213–8223. [Google Scholar] [CrossRef]
  25. Ni, X.L.; Xiao, X.; Cong, H. Cucurbit[n]uril-based coordination chemistry: From simple coordination complexes to novel poly-dimensional coordination polymers. Chem. Soc. Rev. 2013, 42, 9480–9508. [Google Scholar] [CrossRef] [PubMed]
  26. Datta, S.; Saha, M.L.; Stang, P.J. Hierarchical assemblies of supramolecular coordination complexes. Acc. Chem. Res. 2018, 51, 2047–2063. [Google Scholar] [CrossRef] [PubMed]
  27. Xia, D.; Wang, L.; Lv, X.; Chao, J.; Wei, X.; Wang, P. Dual-responsive [2]Pseudorotaxane on the basis of a pH-Sensitive pillar[5]arene and its application in the fabrication of metallosupramolecular polypseudorotaxane. Macromolecules 2018, 51, 2716–2722. [Google Scholar] [CrossRef]
  28. Liu, Y.; Shangguan, L.; Shi, B. A multi-responsive cross-linked supramolecular polymer network constructed by mussel yield coordination interaction and pillar[5]arene-based host–guest complexation. Chem. Commun. 2018, 54, 12230–12233. [Google Scholar] [CrossRef]
  29. Wu, Y.; Zhong, W.; Wang, X.; Wu, W.; Muddassir, M.; Daniel, O.; Raj Jayswal, M.; Prakash, O.; Dai, Z.; Ma, A. New transition metal coordination polymers derived from 2-(3,5-Dicarboxyphenyl)-6-carboxybenzimidazole as photocatalysts for dye and antibiotic decomposition. Molecules 2023, 28, 7318. [Google Scholar] [CrossRef]
  30. Castriciano, M.A.; Zagami, R.; Mazzaglia, A.; Romeo, A.; Monsù Scolaro, L. A kinetic investigation of the supramolecular chiral self-assembling process of cationic organometallic (2,2′:6′,2″-terpyridine)methylplatinum(II) complexes with poly(L-glutamic acid). Int. J. Mol. Sci. 2024, 25, 1176. [Google Scholar] [CrossRef]
  31. Ogoshi, T.; Kanai, S.; Fujinami, S.; Yamagishi, T.; Nakamoto, Y. Para-bridged symmetrical pillar[5]arenes: Their lewis acid catalyzed synthesis and host–guest property. J. Am. Chem. Soc. 2008, 130, 5022–5023. [Google Scholar] [CrossRef]
  32. Cao, D.R.; Kou, Y.H.; Liang, J.Q.; Chen, J.J.; Wang, L.Y.; Meier, H. A facile and efficient preparation of pillararenes and a pillarquinone. Angew. Chem. Int. Ed. 2009, 48, 9721–9723. [Google Scholar] [CrossRef]
  33. Ogoshi, T.; Ueshima, N.; Sakakibara, F.; Yamagishi, T.; Haino, T. Conversion from pillar[5]arene to pillar[6–15]arenes by ring expansion and encapsulation of C60 by pillar[n]arenes with nanosize. Org. Lett. 2014, 16, 2896–2899. [Google Scholar] [CrossRef]
  34. Xiao, T.X.; Zhou, L.; Xu, L.X.; Zhong, W.W.; Zhao, W.; Sun, X.Q.; Elmes, R.B.P. Dynamic materials fabricated from water soluble pillar[n]arenes bearing triethylene oxide groups. Chin. Chem. Lett. 2019, 30, 271–276. [Google Scholar] [CrossRef]
  35. Wu, J.R.; Wu, G.X.; Yang, Y.W. Pillararene-inspired macrocycles: From extended pillar[n]arenes to geminiarenes. Acc. Chem. Res. 2022, 55, 3191–3204. [Google Scholar] [CrossRef] [PubMed]
  36. Zhu, N.; Guo, X.; Chang, Y.; Shi, Z.; Jin, L.Y.; Feng, S. A mitochondria-tracing fluorescent probe for real-time detection of mitochondrial dynamics and hypochlorous acid in live cells. Dyes Pigment. 2022, 201, 110227. [Google Scholar] [CrossRef]
  37. Guo, C.; Sedgwick, A.C.; Hirao, T.; Sessler, J.L. Supramolecular fluorescent sensors: An historical overview and update. Coordin. Chem. Rev. 2021, 427, 213560. [Google Scholar] [CrossRef] [PubMed]
  38. Song, N.; Chen, D.X.; Qiu, Y.C.; Yang, X.Y.; Xu, B.; Tian, W.J.; Yang, Y.X. Stimuli-responsive blue fluorescent supramolecular polymers based on a pillar[5]arene tetramer. Chem Commun. 2014, 50, 8231–8234. [Google Scholar] [CrossRef] [PubMed]
  39. Zhao, L.; Chen, Y.; Yuan, J.; Chen, M.H.; Zhang, H.; Li, X.H. Electrospun fibrous mats with conjugated tetraphenylethylene and mannose for sensitive turn–on fluorescent sensing of Escherichia coli. ACS Appl. Mater. Interfaces 2015, 7, 5177–5186. [Google Scholar] [CrossRef] [PubMed]
  40. Sun, S.; Hu, X.Y.; Chen, D.; Shi, J.B.; Dong, Y.P.; Lin, C.; Pan, Y.; Wang, L.Y. Pillar[5]arene-based side-chain polypseudorotaxanes as an anion-responsive fluorescent sensor. Polym. Chem. 2013, 4, 2224–2229. [Google Scholar] [CrossRef]
  41. Gao, M.; Tang, B.Z. Fluorescent sensors based on aggregation-induced emission: Recent advances and perspectives. ACS Sens. 2017, 2, 1382–1399. [Google Scholar] [CrossRef]
  42. Shi, H.P.; Wang, S.J.; Qin, L.Y.; Gui, C.; Zhang, X.L.; Fang, L.; Chen, S.M.; Tang, B.Z. Construction of two AIE luminogens comprised of a tetra-/tri-phenylethene core and carbazole units for non-doped organic light-emitting diodes. Dyes Pigment. 2018, 149, 323–330. [Google Scholar] [CrossRef]
  43. Wang, W.M.; Dai, D.; Wu, J.R.; Wang, C.; Wang, Y.; Yang, Y.W. Renewable supramolecular assembly-induced emission enhancement system for efficient detection and removal of silver(I). Dyes Pigment. 2022, 207, 110712. [Google Scholar] [CrossRef]
  44. Jia, Y.; Guan, W.L.; Liu, J.; Hu, J.P.; Shi, B.; Yao, H.; Zhang, Y.M.; Wei, T.B.; Lin, Q. Novel conductive metallo-supramolecular polymer AIE gel for multi-channel highly sensitive detection of hydrazine hydrate. Chin. Chem. Lett. 2023, 34, 108082. [Google Scholar] [CrossRef]
  45. Lin, Q.; Jiang, X.M.; Ma, X.Q.; Liu, J.; Yao, H.; Zhang, Y.M.; Wei, T.B. Novel bispillar[5]arene-based AIEgen and its’ application in mercury(II) detection. Sens. Actuat. B Chem. 2018, 272, 139–145. [Google Scholar] [CrossRef]
  46. Dai, D.H.; Li, Z.; Yang, J.; Wang, C.Y.; Wu, J.R.; Wang, Y.; Zhang, D.M.; Yang, Y.W. Supramolecular assembly-induced emission enhancement for efficient mercury(II) detection and removal. J. Am. Chem. Soc. 2019, 141, 4756–4763. [Google Scholar] [CrossRef]
  47. Jiang, X.; Wang, L.; Ran, X.; Tang, H.; Cao, D. Green, efficient detection and removal of Hg2+ by water-soluble fluorescent pillar[5]arene supramolecular self-assembly. Biosensors 2022, 12, 571. [Google Scholar] [CrossRef]
  48. Chang, R.; Chen, C.Y.; Gao, L.; Li, Y.; Lee, Z.H.; Zhao, H.; Sue, A.C.; Chang, K.C. Highly selective Cu2+ detection with a naphthalimide-functionalised pillar[5]arene fluorescent chemosensor. Org. Biomol. Chem. 2024, 22, 745–752. [Google Scholar] [CrossRef] [PubMed]
  49. Liu, S.; Wu, Q.; Zhang, T.; Zhang, H.; Han, J. Supramolecular brush polymers prepared from 1,3,4-oxadiazole and cyanobutoxy functionalised pillar[5]arene for detecting Cu2+. Org. Biomol. Chem. 2021, 19, 1287–1291. [Google Scholar] [CrossRef]
  50. Chong, H.; Xu, Y.H.; Han, Y.; Yan, C.G.; Su, D.W.; Wang, C.Y. Pillar[5]arene-based “three-components” supramolecular assembly and the performance of nitrobenzene-based explosive fluorescence sensing. ChemistrySelect 2021, 6, 9363–9367. [Google Scholar] [CrossRef]
  51. Zhang, Y.M.; Li, Y.F.; Zhong, K.P.; Qu, W.J.; Yao, H.; Wei, T.B.; Lin, Q. A bis-naphthalimide functionalized pillar[5]arene-based supramolecular π-gel acts as a multi-stimuli-responsive material. New J. Chem. 2018, 42, 16167–16173. [Google Scholar] [CrossRef]
  52. Zhang, Y.M.; Li, Y.F.; Zhong, K.P.; Qu, W.J.; Chen, X.P.; Yao, H.; Wei, T.B.; Lin, Q. A novel pillar[5]arene-based supramolecular organic framework gel to achieve an ultrasensitive response by introducing the competition of cation⋯π and π⋯π interactions. Soft Matter. 2018, 14, 3624–3631. [Google Scholar] [CrossRef]
  53. Zhang, Y.M.; Chen, X.P.; Liang, G.Y.; Zhong, K.P.; Lin, Q.; Yao, H.; Wei, T.B. A novel water soluble pillar[5]arene and phenazine derivative self-assembled pseudorotaxane sensor for the selective detection of Hg2+ and Ag+ with high selectivity and sensitivity. New J. Chem. 2018, 42, 10148–10152. [Google Scholar] [CrossRef]
  54. Ding, J.D.; Chen, J.F.; Lin, Q.; Yao, H.; Zhang, Y.M.; Wei, T.B. A multi-stimuli responsive metallosupramolecular polypseudorotaxane gel constructed by self-assembly of a pillar[5]arene-based pseudo[3]rotaxane via zinc ion coordination and its application for highly sensitive fluorescence recognition of metal ions. Polym. Chem. 2018, 9, 5370–5376. [Google Scholar] [CrossRef]
  55. Yu, D.; Deng, W.; Wei, X. Supramolecular aggregate of pillar[5]arene-based Cu(II) coordination complexes as a highly selective fluorescence sensor for nitroaromatics and metal ions. Dyes Pigment. 2023, 210, 110968. [Google Scholar] [CrossRef]
  56. Todee, B.; Sanae, P.; Ruengsuk, A.; Janthakit, P.; Promarak, V.; Tantirungrotechai, J.; Sukwattanasinitt, M.; Limpanuparb, T.; Harding, D.J.; Bunchuay, T. Switchable metal-ion selectivity in sulfur-functionalised pillar[5]arenes and their host-guest complexes. Chem. Asian J. 2024, 19, e202300913. [Google Scholar] [CrossRef]
  57. Zhang, Y.M.; He, J.X.; Zhu, W.; Li, Y.F.; Fang, H.; Yao, H.; Wei, T.B.; Lin, Q. Novel pillar[5]arene-based supramolecular organic framework gel for ultrasensitive response Fe3+ and F− in water. Mat. Sci. Eng. C 2019, 100, 62–69. [Google Scholar] [CrossRef] [PubMed]
  58. Zhang, Q.; Zhang, Y.M.; Yao, H.; Wei, T.B.; Shi, B.; Lin, Q. Supramolecular AIE polymer-based rare earth metallogels for the selective detection and high efficiency removal of cyanide and perchlorate. Polym. Chem. 2021, 12, 2001–2008. [Google Scholar] [CrossRef]
  59. Zhang, C.W.; Ou, B.; Jiang, S.T.; Yin, G.Q.; Chen, L.J.; Xu, L.; Li, X.; Yang, H.B. Cross-linked AIE supramolecular polymer gels with multiple stimuli-responsive behaviours constructed by hierarchical self-assembly. Polym. Chem. 2018, 9, 2021–2030. [Google Scholar] [CrossRef]
  60. He, J.X.; Zhang, Y.M.; Hu, J.P.; Li, Y.J.; Zhang, Q.; Qu, W.J.; Yao, H.; Wei, T.B.; Lin, Q. Novel fluorescent supramolecular polymer metallogel based on Al3+ coordinated cross-linking of quinoline functionalized-pillar[5]arene act as multi-stimuli-responsive materials. Appl. Organomet. Chem. 2020, 34, e5519. [Google Scholar] [CrossRef]
  61. Liu, Z.; Wu, J.; Wang, C.; Yang, J.; Wang, Y.; Yang, Y.W. Stimuli-responsive fluorescent supramolecular polymer network based on a monofunctionalized leaning tower[6]arene. Chin. Chem. Lett. 2019, 30, 2299–2303. [Google Scholar] [CrossRef]
  62. Li, Y.F.; Guan, W.L.; Wang, C.Y.; Wang, Y.; Lin, Q.; Yang, Y.W. A multi-stimuli-responsive metallosupramolecular gel based on pillararene hierarchical assembly. Polym. Chem. 2023, 14, 633–643. [Google Scholar] [CrossRef]
Sensors 24 01530 sch001
Scheme 1. Molecular structures of pillar[n]arenes and guests in the section of single-stimulus responsive fluorescence sensors.
Scheme 1. Molecular structures of pillar[n]arenes and guests in the section of single-stimulus responsive fluorescence sensors.
Sensors 24 01530 sch001
Sensors 24 01530 g001
Figure 1. Schematic diagram showing how to detect and remove Ag+ ions from water using the supramolecular assembly and the assembly regeneration process [43]. Copyright 2022, Elsevier.
Figure 1. Schematic diagram showing how to detect and remove Ag+ ions from water using the supramolecular assembly and the assembly regeneration process [43]. Copyright 2022, Elsevier.
Sensors 24 01530 g001
Sensors 24 01530 g002
Figure 2. (a) A cartoon depicting the metallo-supramolecular polymer gel’s assembly method, (b) the PQ-Ag’s multichannel DH detection, and (c) the DH alarm circuit schematic diagram (1: electric source; 2: switch; 3: resistance; 4: electric capacity; 5: NPN triode; 6: resistance; 7: bulb; 8: PNP triode; 9: buzzer; 10: gel probe) [44]. Copyright 2023, Elsevier.
Figure 2. (a) A cartoon depicting the metallo-supramolecular polymer gel’s assembly method, (b) the PQ-Ag’s multichannel DH detection, and (c) the DH alarm circuit schematic diagram (1: electric source; 2: switch; 3: resistance; 4: electric capacity; 5: NPN triode; 6: resistance; 7: bulb; 8: PNP triode; 9: buzzer; 10: gel probe) [44]. Copyright 2023, Elsevier.
Sensors 24 01530 g002
Sensors 24 01530 g003
Figure 3. Schematic illustration showing how to detect and remove Hg2+ ions from water using the regeneration–recycling process and the “switch-on” fluorescence of supramolecular polymers [46]. Copyright 2019, American Chemical Society.
Figure 3. Schematic illustration showing how to detect and remove Hg2+ ions from water using the regeneration–recycling process and the “switch-on” fluorescence of supramolecular polymers [46]. Copyright 2019, American Chemical Society.
Sensors 24 01530 g003
Sensors 24 01530 g004
Figure 4. Schematic representations of the self-assembly of carboxylatopillar[5]arene sodium salts in the presence and absence of Hg2+ ions in water, as well as chemical structures and cartoon representations of the diketopyrrolopyrrole-bridged bis(quaternary ammonium) guest [47].
Figure 4. Schematic representations of the self-assembly of carboxylatopillar[5]arene sodium salts in the presence and absence of Hg2+ ions in water, as well as chemical structures and cartoon representations of the diketopyrrolopyrrole-bridged bis(quaternary ammonium) guest [47].
Sensors 24 01530 g004
Sensors 24 01530 sch002
Scheme 2. Molecular structures of pillar[n]arenes and guests in the section of dual-stimuli responsive fluorescence sensors.
Scheme 2. Molecular structures of pillar[n]arenes and guests in the section of dual-stimuli responsive fluorescence sensors.
Sensors 24 01530 sch002
Sensors 24 01530 g005
Figure 5. HP5 and G’s chemical structures, proton designations, and a cartoon depicting the creation of the linear metallo-supramolecular polypseudorotaxane framework [54]. Copyright 2018, The Royal Society of Chemistry.
Figure 5. HP5 and G’s chemical structures, proton designations, and a cartoon depicting the creation of the linear metallo-supramolecular polypseudorotaxane framework [54]. Copyright 2018, The Royal Society of Chemistry.
Sensors 24 01530 g005
Sensors 24 01530 g006
Figure 6. Diagrammatic representation of the pillar[5]arene-based Cu(II) coordination supramolecular aggregate’s structure, as well as p-nitrophenol (PNP) and Fe3+ ion detection capabilities [55]. Copyright 2022, Elsevier.
Figure 6. Diagrammatic representation of the pillar[5]arene-based Cu(II) coordination supramolecular aggregate’s structure, as well as p-nitrophenol (PNP) and Fe3+ ion detection capabilities [55]. Copyright 2022, Elsevier.
Sensors 24 01530 g006
Sensors 24 01530 g007
Figure 7. Cartoon illustrating functionalized pillar[5]arenes with sulfur substituents and associated pseudorotaxane complexes [56].
Figure 7. Cartoon illustrating functionalized pillar[5]arenes with sulfur substituents and associated pseudorotaxane complexes [56].
Sensors 24 01530 g007
Sensors 24 01530 sch003
Scheme 3. Molecular structures of pillar[n]arenes and guests in the section of multi-stimuli-responsive fluorescence sensors.
Scheme 3. Molecular structures of pillar[n]arenes and guests in the section of multi-stimuli-responsive fluorescence sensors.
Sensors 24 01530 sch003
Sensors 24 01530 g008
Figure 8. Diagrammatic depiction of the disassembly of supramolecular polymer gels caused by the bromide anion and competitive guest stimuli [59]. (A) The gel assembled by the hexagonal metallacycle with six pillar[5]arene units. (B) The gel assembled by the rhomboidal metallacycle with four pillar[5]arene units. Copyright 2018, The Royal Society of Chemistry.
Figure 8. Diagrammatic depiction of the disassembly of supramolecular polymer gels caused by the bromide anion and competitive guest stimuli [59]. (A) The gel assembled by the hexagonal metallacycle with six pillar[5]arene units. (B) The gel assembled by the rhomboidal metallacycle with four pillar[5]arene units. Copyright 2018, The Royal Society of Chemistry.
Sensors 24 01530 g008
Sensors 24 01530 g009
Figure 9. The development of the metallosupra-molecular gel DSPy⊂SHP5@Zn-G is schematically shown by the chemical structures of the host SHP5 and the guest DSPy, as well as by hierarchical host–guest recognition and metal ion coordination [62]. Copyright 2023, The Royal Society of Chemistry.
Figure 9. The development of the metallosupra-molecular gel DSPy⊂SHP5@Zn-G is schematically shown by the chemical structures of the host SHP5 and the guest DSPy, as well as by hierarchical host–guest recognition and metal ion coordination [62]. Copyright 2023, The Royal Society of Chemistry.
Sensors 24 01530 g009
Table 1. Summary of fluorescence sensors described in the section of single-stimulus responsiveness.
Table 1. Summary of fluorescence sensors described in the section of single-stimulus responsiveness.
Pillar[n]arenesGuestsCoordinated
Metal Ions		Sensing PropertiesRef.
P1G1Ag+Analyte: Ag+.
Detection type: turn-on.
λex/λem: 310/470 nm.
LOD: 1.50 × 10−7 mol/L.
Liner range: 0–8.00 × 10−6 mol/L.
Solvent: DMSO/H2O = 1/99.		[43]
P2−Ag+Analyte: hydrazine hydrate.
Detection type: turn-off.
λex/λem: 310/450 nm.
LOD: 2.68 × 10−8 mol/L.
Solvent: DMSO/H2O = 4/1.		[44]
P3−Hg2+Analyte: Hg2+.
Detection type: turn-off.
λex/λem: 332/486 nm.
LOD: 4.30 × 10−8 mol/L.
Solvent: DMSO/H2O = 1/1.		[45]
P4G2Hg2+Analyte: Hg2+.
Detection type: turn-on.
λex/λem: 312/388 nm.
LOD: 3.00 × 10−7 mol/L.
Liner range: 0–1.50 × 10−5 mol/L.
Solvent:
CHCl3/acetone/H2O = 1/4/495.		[46]
P5G3Hg2+Analyte: Hg2+.
Detection type: turn-off.
λex/λem: 510/565 nm.
LOD: 7.17 × 10−7 mol/L.
Solvent: H2O.		[47]
P6−Cu2+Analyte: Cu2+.
Detection type: ratiometric.
λex/λem: 333/384 nm.
LOD: 1.85 × 10−7 mol/L.
Solvent: CH2Cl2/CH3CN = 1/1.		[48]
P7−Cu2+Analyte: Cu2+.
Detection type: turn-off.
λex/λem = 310/411 nm.
Solvent: chloroform.		[49]
P8G4Zn2+Analyte: nitrobenzene.
Detection type: turn-off.
λex/λem: 295/460 nm.
LOD: 1.66 × 10−4 mol/L.
Liner range: 1.00–5.00 × 10−5 mol/L.
Solvent: CH3CN/CHCl3 = 1/1.		[50]
P9−Fe3+Analyte: Fe3+, L-Cys.
Detection type: turn-off/on.
λex/λem: 375/535 nm.
LOD: 6.06 × 10−8 mol/L (Fe3+);
1.00 × 10−8 mol/L (L-Cys).
Solvent: cyclohexanol.		[51]
P9, P10P10Fe3+Analyte: Fe3+, H2PO4−.
Detection type: turn-off/on.
λex/λem: 375/530 nm.
LOD: 7.54 × 10−9 mol/L.
Solvent:
cyclohexanol/H2O = 1/20.		[52]
Table 2. Summary of fluorescence sensors described in the section of dual-stimuli responsiveness.
Table 2. Summary of fluorescence sensors described in the section of dual-stimuli responsiveness.
Pillar[n]arenesGuestsCoordinated Metal IonsSensing PropertiesRef.
P11G5Ag+, Hg2+Analyte: Ag+, Hg2+.
Detection type: ratiometric/turn-on.
λex/λem: 385/545 nm.
LOD: 1.20 × 10−8 mol/L (Ag+);
5.00 × 10−7 mol/L (Hg+).
Solvent: DMSO/H2O = 1/1.		[53]
P12, P13P13Fe3+, Cu2+Analyte: Fe3+, Cu2+.
Detection type: turn-off.
λex/λem: 330/460–560 nm.
LOD: 8.53 × 10−10 mol/L (Fe3+);
4.57 × 10−8 mol/L (Cu2+).		[54]
P14−Cu2+Analyte: nitroaromatics, Fe3+.
Detection type: turn-off.
λex/λem: 380/487 nm.
LOD: 3.90 × 10−7 mol/L (Fe3+);
4.90 × 10−6 mol/L (nitroaromatics).
Liner range: 0–1.20 × 10−3 mol/L (Fe3+);
0–1.80 × 10−4 mol/L (nitroaromatics).
Solvent: DMF/H2O = 1/4.		[55]
P15G6Cu2+, Hg2+Analyte: Cu2+, Hg2+.
Detection type: turn-off.
λex/λem: 293/324 nm.
Solvent: CH3CN/water = 1/1.		[56]
P2, P16P16Fe3+Analyte: Fe3+, F−.
λex/λem: 290/470 nm.
LOD: 1.02 × 10−10 mol/L (Fe3+);
9.79 × 10−9 mol/L (F−).
Liner range: 0–1.18 eq. (Fe3+);
0–0.86 eq. (F−).
Solvent: cyclohexanol/H2O = 3/17.		[57]
P17G7Eu3+, Tb3+Analyte: cyanide, perchlorate.
Detection type: turn-on.
λex/λem: 290/470 nm.
LOD: 5.96 × 10−8 mol/L (cyanide);
3.36 × 10−6 mol/L (perchlorate).
Solvent: DMSO/H2O = 2/1.		[58]
Table 3. Summary of fluorescence sensors described in the section of multi-stimuli-responsiveness.
Table 3. Summary of fluorescence sensors described in the section of multi-stimuli-responsiveness.
Pillar[n]arenesGuestsCoordinated
Metal Ions		Sensing PropertiesRef.
P18−Pt2+Analyte: temperature, competitive guest molecules, halides.
λex/λem: 336/500 nm.
Solvent: acetone/water = 1/19.		[59]
P2−Al3+Analyte: Fe3+, F−, trifluoroacetic acid, triethylamine.
Detection type: turn-off/on.
λex/λem: 380/470 nm.
LOD:
4.39 × 10−9 mol/L (Fe3+);
2.75 × 10−8 mol/L (F−);
1.80 × 10−5 mol/L (trifluoroacetic acid);
1.80 × 10−5 mol/L (triethylamine).
Solvent: DMSO/H2O = 4/1.		[60]
P19G8Zn2+Analyte: competitive binding agents, trifluoroacetic acid, pillar[5]arene.
λex/λem: 349/385 nm.
Solvent: CHCl3/CH3CN = 4:1.		[61]
P20G9Zn2+Analyte: thermal, redox, pH, competitive guests.
λex/λem: 375/385 nm.
Solvent: DMSO:H2O = 7/3.		[62]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Li, X.; Jin, Y.; Zhu, N.; Yin, J.; Jin, L.Y. Recent Developments of Fluorescence Sensors Constructed from Pillar[n]arene-Based Supramolecular Architectures Containing Metal Coordination Sites. Sensors 2024, 24, 1530. https://doi.org/10.3390/s24051530

AMA Style

Li X, Jin Y, Zhu N, Yin J, Jin LY. Recent Developments of Fluorescence Sensors Constructed from Pillar[n]arene-Based Supramolecular Architectures Containing Metal Coordination Sites. Sensors. 2024; 24(5):1530. https://doi.org/10.3390/s24051530

Chicago/Turabian Style

Li, Xu, Yan Jin, Nansong Zhu, Jinghua Yin, and Long Yi Jin. 2024. "Recent Developments of Fluorescence Sensors Constructed from Pillar[n]arene-Based Supramolecular Architectures Containing Metal Coordination Sites" Sensors 24, no. 5: 1530. https://doi.org/10.3390/s24051530

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop