Colorimetric and Fluorescent Sensors: Current Status and Future Development

Dear Colleagues,

The detection of important and harmful metal ions and anions has become essential to maintaining clean and safe ecosystems. Numerous analytical techniques, including surface plasmon resonance (SPR) investigations, organic-probe-based fluorescent/colorimetric sensors, nanomaterial-based colorimetric/fluorometric/immunoassays , metal–organic framework (MOFs)-facilitated quantification, dye-molecule-driven colorimetric recognition studies, and composite-structure-mediated ion detection, have been proposed and demonstrated with real-time applications. Comparing these analytical methods, the colorimetric and fluorometric approaches are exceptional due to their unique applications, such as paper strips, in vitro/in vivo bioimaging, and real-time  water analysis. Moreover, advanced and easily synthesizable organic colorimetric probes and fluorophores with specific ion binding sites have been demonstrated by researchers. More recently, reports on easily operable nanomaterial-based colorimetric and fluorometric sensors under sustainable environments have also attracted much attention. For example, silver and gold nanoparticle (Ag NP and Au NP)-driven colorimetric sensors and carbon dots (CDs), graphene quantum dots (GQDs), MOFs, metal halide perovskites (HPs), and composite-based fluorescent sensors are becoming the focus of environmental research with real-time applications. The aim of this Special Issue is to collect and publish these innovative colorimetric and fluorometric sensors, analytical techniques, and studies that could drive future developments in related research fields.

Dr. Kien Wen Sun
Dr. Shellaiah Muthaiah
Guest Editors

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• colorimetric sensors
• fluorescent detection
• metal ion detection
• anion recognition
• metal–organic frameworks (MOFs)

Title: Pyrene Derivatives for Hg2+ and Explosives Detection
Authors: Muthaiah Shellaiah1; Kien Wen Sun2*
Affiliation: 1 Department of Research and Analytics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences (SIMATS), Saveetha University, Chennai 600077, India 2 Department of Applied Chemistry, National Yang-Ming Chiao Tung University, Hsinchu 300, Taiwan;
Abstract: Mercury and explosives are well-known hazards that affect our environment and threatening to living society. Mercury mostly exists as inorganic mercuric (Hg2+) salts which can be accurately detected via highly sensitive fluorometric responses. Likewise, detecting and quantifying majority of explosives containing nitrogen dioxide (-NO2) functional units has been demonstrated in numerous reports. Among the available literatures, pyrene derivatives based fluorometric detection of Hg2+ and explosives has attracted much concern for their environmental and biological applicability. In the presence of Hg2+, pyrene derivatives tend to form excimers, which are able to exhibit “turn-on” or “turn-off’ fluorescence responses via the chelation-enhanced fluorescence (CHEF), photo-induced electron transfer (PET), or Fluorescence resonance energy transfer (FRET), etc. On the other hand, π-π stacking of emissive pyrene-derivatives leading to J- or H-type aggregation via self-excimers (Py-Py*) can be quenched/enhanced by explosive hazards. In fact, -NO2-containing explosives interacting with pyrene derivatives can lead to considerable quenching or enhancement in fluorescence intensity. This review provides in depth discussions on the pyrene derivatives towards the sensing of Hg2+ and explosives with demonstrated applications. Moreover, the synthesis, sensory mechanism, advantages, limitations, and future scope of reported pyrene derivatives in Hg2+ and explosives sensors are presented to the readers. KEYWORDS: Hg2+ detection, Aggregation-induced emission (AIE), Turn-on, Fluorescence quenching, Nitro-explosives sensors, Real-time applications, Bioimaging, H-bonding, Excimers, Hazard quantification.

Title: Recent development of nanostructured fiber for colorimetric detection of metal ions: A review
Authors: Sungbo Cho; Mohanraj Jagannathan
Affiliation: Department of Electronic Engineering, Gachon University, Seongnam-si, Gyeonggi-do 13210, Republic of korea
Abstract: Recently, there have been rapid advances in the colorimetric detection of metal ions using nanostructured fiber, which is becoming a powerful platform for environmental remediation and detection applications. Due to its porous structure, higher sensitivity, selectivity, non-intrusiveness, rapid response, robustness, and easy handling, it can be an effective tool for naked-eye detection in harsh and remote places. In this review, we concisely discuss the recent development of nanostructured fiber and its cutting-edge preparation method for colorimetric detection of various heavy metal ions in real samples. Based on the advent of nanostructured fiber, it can be a well-known and efficient platform for determining a heavy metal ion through colorimetric detection in an economically feasible way in the future.