Crystals

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14 pages, 4345 KiB

Open AccessArticle

Analysis and Modification of a Colorimetric Nanosensor for Rapid Detection of Escherichia coli in Water

by Sarah Stabler, Ruby Anne Lang, Amro El Badawy, Marie Yeung and Jean Lee

Crystals 2024, 14(4), 386; https://doi.org/10.3390/cryst14040386 - 21 Apr 2024

Viewed by 1169

This research analyzed the mechanisms of work and modified a colorimetric nanosensor to make it more cost-effective for the detection of Escherichia coli (E. coli) in water. The base nanosensors modified herein rely on a competitive binding detection mechanism, where positively charged gold [...] Read more.

This research analyzed the mechanisms of work and modified a colorimetric nanosensor to make it more cost-effective for the detection of Escherichia coli (E. coli) in water. The base nanosensors modified herein rely on a competitive binding detection mechanism, where positively charged gold nanoparticles coated with polyethyleneimine (PEI-AuNPs) preferably bind to negatively charged E. coli in the presence of β-galactosidase (

β

-Gal) enzymes and chlorophenol red β-d-galactopyranosides (CPRG). The positive surface charge of the nanoparticle, rather than nanoparticle composition or type of chemical coating on its surface, was hypothesized herein as the governing factor for the nanosensor functionality. Thus, positively charged nanoparticles and polymers were tested as potential alternatives for gold nanoparticles for detecting E. coli. Positively charged silver and iron oxide nanoparticles coated with branched PEI detected E. coli as low as 10⁵ and 10⁷ colony-forming units per milliliter (CFU/mL), respectively. Furthermore, the branched PEI polymer itself (without nanomaterial) detected E. coli at 10⁷ CFU/mL. These findings suggest that the positive charge, rather than the nanoparticle type was likely responsible for the detection of E. coli using the competitive binding approach. Therefore, other types of recyclable and cost-effective nanomaterials and polymers can be developed for E. coli detection using this rapid colorimetric sensing technique. Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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10 pages, 3125 KiB

Open AccessArticle

Simultaneous Detection of Relative Humidity and Temperature Based on Silicon On-Chip Cascaded Photonic Crystal Nanobeam Cavities

by Lun Ye, Xiao Liu, Danyang Pei, Jing Peng, Shuchang Liu, Kai Guo, Xiaogang Li, Xuanyu Chen, Xuan Zhang and Daquan Yang

Crystals 2021, 11(12), 1559; https://doi.org/10.3390/cryst11121559 - 14 Dec 2021

Cited by 6 | Viewed by 2373

Abstract

In this paper, we propose and numerically demonstrate a novel cascaded silicon-on-insulator (SOI) photonic crystal nanobeam cavity (PCNC) dual-parameter sensor for the simultaneous detection of relative humidity (RH) and temperature. The structure consists of two independent PCNCs supporting two different resonant modes: a [...] Read more.

In this paper, we propose and numerically demonstrate a novel cascaded silicon-on-insulator (SOI) photonic crystal nanobeam cavity (PCNC) dual-parameter sensor for the simultaneous detection of relative humidity (RH) and temperature. The structure consists of two independent PCNCs supporting two different resonant modes: a dielectric-mode and an air-mode, respectively. The dielectric-mode nanobeam cavities (cav₁) are covered with SU-8 cladding to increase the sensitivity ratio contrast between RH sensing and temperature sensing. The air-mode nanobeam cavities (cav₂) are coated with a water-absorbing polyvinyl-alcohol (PVA) layer that converts the change in RH into a change in refractive index (RI) under different ambient RH levels, thereby inducing a wavelength shift. Due to the positive thermo-optic (TO) coefficient of silicon and the negative TO coefficient of SU-8 cladding, the wavelength responses take the form of a red shift for cav₂ and a blue shift for cav₁ as the ambient temperature increases. By using 3D finite-difference time-domain (3D-FDTD) simulations, we prove the feasibility of simultaneous sensing by monitoring a single output transmission spectrum and applying the sensor matrix. For cav₁, the RH and temperature sensitivities are 0 pm/%RH and −37.9 pm/K, while those of cav₂ are −389.2 pm/%RH and 58.6 pm/K. The sensitivity ratios of temperature and RH are −1.5 and 0, respectively, which is the reason for designing two different resonant modes and also implies great potential for realizing dual-parameter sensing detection. In particular, it is also noteworthy that we demonstrate the ability of the dual-parameter sensor to resist external interference by using the dual wavelength matrix method. The maximum RH and temperature detection errors caused by the deviation of resonance wavelength 1 pm are only 0.006% RH and 0.026 K, which indicates that it achieves an excellent anti-interference ability. Furthermore, the structure is very compact, occupying only 32 μm × 4 μm (length × width). Hence, the proposed sensor shows promising prospects for compact lab-on-chip integrated sensor arrays and sensing with multiple parameters. Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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12 pages, 3652 KiB

Open AccessArticle

Simulation Study of In-Phase and Out-Phase Enhanced Absorption of Graphene Based on Parity–Time Symmetry One-Dimensional Photonic Crystal Structure

by Lingjun Yi and Changhong Li

Crystals 2021, 11(12), 1513; https://doi.org/10.3390/cryst11121513 - 4 Dec 2021

Cited by 5 | Viewed by 2285

Abstract

In the field of modern optical communication systems and photoelectric detection, new components with complex functions and excellent performance are urgently needed. In this paper, a graphene-based parity–time (PT) symmetry structure is proposed, which is achieved by preparing the graphene layer on the [...] Read more.

In the field of modern optical communication systems and photoelectric detection, new components with complex functions and excellent performance are urgently needed. In this paper, a graphene-based parity–time (PT) symmetry structure is proposed, which is achieved by preparing the graphene layer on the top of a PT-symmetry photonic crystal. The transfer matrix method was used to calculate the absorptance of graphene, and a unique amplified absorption effect was found. Meanwhile, the peak value and wavelength position of the absorption can be modulated via the applied electric field. The results show that by adjusting the negative square-wave electric field from −3.5 × 10⁻⁵ to −13.5 × 10⁻⁵ V/nm (or the positive square-wave electric field from 2 × 10⁻⁵ to 11 × 10⁻⁵ V/nm), the proposed structure can achieve in-phase (or out-phase) enhanced absorption for the communication wavelength 1550 nm, with the absorption of graphene from 17 to 28 dB (or 30 to 15 dB) corresponding to the square-wave modulation electric field change. The modulable absorption properties of graphene in the structure have potential in optoelectronic devices and optical communication systems. Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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12 pages, 2209 KiB

Open AccessArticle

Plasmon-Based Label-Free Biosensor Using Gold Nanosphere for Dengue Detection

by Hafiz Zeeshan Mahmood, Asim Jilani, Sajid Farooq, Yasir Javed, Yasir Jamil, Javed Iqbal, Sami Ullah and Swelm Wageh

Crystals 2021, 11(11), 1340; https://doi.org/10.3390/cryst11111340 - 2 Nov 2021

Cited by 9 | Viewed by 2294

Abstract

In this study, a novel label-free immunosensor platform is developed to exploit the localized surface plasmon resonance (LSPR) phenomenon. The LSPR solution-based platform is designed by a gold nanospheres probe, functionalized with monoclonal anti-dengue antibody (IgG). Numerical calculations are performed to assess the [...] Read more.

In this study, a novel label-free immunosensor platform is developed to exploit the localized surface plasmon resonance (LSPR) phenomenon. The LSPR solution-based platform is designed by a gold nanospheres probe, functionalized with monoclonal anti-dengue antibody (IgG). Numerical calculations are performed to assess the LSPR extinction spectrum and spatial near electric field distribution around the nanoparticle surface. Important parameters that govern sensor performance, molecular and refractive index sensitivity are evaluated. On the evaluation of the platform as a molecular sensor, the detection of dengue NS1 antigens is presented. The results are consistent with the numerical simulations, which depicts the system’s ability to identify dengue NS1 antigen concentrations as low as 0.07 ± 0.01 µg/mL, along with fosters its potential application in plasmonic sensing. Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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9 pages, 2478 KiB

Open AccessArticle

Tunable Narrow-Linewidth Ring Laser Based on the Polarization Conversion in a Tapered Fiber-Coupled Whispering Gallery Mode Resonator

by Pengfa Chang, Chen Wang, Hong Han, Feng Gao, Ligang Huang and Anbang Wang

Crystals 2021, 11(11), 1285; https://doi.org/10.3390/cryst11111285 - 23 Oct 2021

Cited by 1 | Viewed by 2008

Abstract

Based on the polarization conversion in a tapered fiber-coupled whispering gallery mode (WGM) system, a simple-structured narrow linewidth band-pass filter was fabricated and a narrow linewidth ring laser was demonstrated. With a fiber Bragg grating (FBG) to further select the resonant mode, the [...] Read more.

Based on the polarization conversion in a tapered fiber-coupled whispering gallery mode (WGM) system, a simple-structured narrow linewidth band-pass filter was fabricated and a narrow linewidth ring laser was demonstrated. With a fiber Bragg grating (FBG) to further select the resonant mode, the ring laser could be in the single-longitudinal-mode with the linewidth about 6 kHz and its wavelength could be tuned from 1540.10 nm to 1570.01 nm. Benefit from the dense modes in the WGM resonator, high conversion efficiency, and better stability of the structure, a tunable dual-wavelength laser could be achieved based on two FBGs with different resonant wavelengths. The configuration of the proposed laser is simple and stable, which will benefit its applications in the future. Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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15 pages, 3423 KiB

Open AccessArticle

Simulation Research on Blood Detection Sensing with Parity-Time Symmetry Structure

by Lingjun Yi and Changhong Li

Crystals 2021, 11(9), 1030; https://doi.org/10.3390/cryst11091030 - 27 Aug 2021

Cited by 16 | Viewed by 2102

Abstract

To realize the design of a medical sensor with excellent comprehensive performance indexes, herein, a plasma concentration sensing model satisfying the Parity-Time (PT) symmetric condition is proposed. In this paper, the transfer matrix method was used to simulate the transmittance spectrum of the [...] Read more.

To realize the design of a medical sensor with excellent comprehensive performance indexes, herein, a plasma concentration sensing model satisfying the Parity-Time (PT) symmetric condition is proposed. In this paper, the transfer matrix method was used to simulate the transmittance spectrum of the structure, according to the amplification effect on defect mode transmission and various detection performance indexes of the structure. We numerically optimized the parameters of the structure, such as the number of PT-symmetry unit cell N, the sample layer thickness d_D as well as the macroscopic Lorentz oscillation intensity α in the PT-symmetry unit cell. The calculation results demonstrate that when the sample concentration changes from 0 g/L to 50 g/L, the wavelength of defect peak shifts from 1538 nm to 1561 nm, and the average quality factor, sensitivity, average figure of merit, average detection limit and average resolution of the structure can reach 78,564, 0.4409 nm/(g/L) (or 227.05 nm/RIU), 11,515 RIU⁻¹, 5.1 × 10⁻⁶ RIU and 0.038 g/L, respectively. Not only the sensitivity and resolution of the PT-symmetry structure are better than that of the similar sensors, but it also has excellent comprehensive detection performance, which indicates that the developed sensor can be used in high-precision biomedical detection devices. Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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10 pages, 4097 KiB

Open AccessArticle

Tin Disulfide-Coated Microfiber for Humidity Sensing with Fast Response and High Sensitivity

by Aijie Liang, Jingyuan Ming, Wenguo Zhu, Heyuan Guan, Xinyang Han, Shuo Zhang, Yuxin Lin, Jiangli Dong, Yaoming Huang, Wentao Qiu, Huihui Lu, Huadan Zheng, Yi Zhang, Jianhui Yu, Zhe Chen and Ganding Peng

Crystals 2021, 11(6), 648; https://doi.org/10.3390/cryst11060648 - 8 Jun 2021

Cited by 2 | Viewed by 2510

Abstract

Breath monitoring is significant in assessing human body conditions, such as cardiac and pulmonary symptoms. Optical fiber-based sensors have attracted much attention since they are immune to electromagnetic radiation, thus are safe for patients. Here, a microfiber (MF) humidity sensor is fabricated by [...] Read more.

Breath monitoring is significant in assessing human body conditions, such as cardiac and pulmonary symptoms. Optical fiber-based sensors have attracted much attention since they are immune to electromagnetic radiation, thus are safe for patients. Here, a microfiber (MF) humidity sensor is fabricated by coating tin disulfide (SnS₂) nanosheets onto the surface of MF. The small diameter (~8 μm) and the long length (~5 mm) of the MF promise strong interaction between guiding light and SnS₂. Thus, a small variation in the relative humidity (RH) will lead to a large change in optical transmitted power. A high RH sensitivity of 0.57 dB/%RH is therefore achieved. The response and recovery times are estimated to be 0.08 and 0.28 s, respectively. The high sensitivity and fast response speed enable our SnS₂-MF sensor to monitor human breath in real time. Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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11 pages, 4060 KiB

Open AccessArticle

Optical Parametric Oscillation with Ultra-Low Power Threshold in a Dimer of Active-Passive Cavities

by Bo Lu, Chen-Rui Fan, Jun-Yang Song and Chuan Wang

Crystals 2021, 11(5), 566; https://doi.org/10.3390/cryst11050566 - 19 May 2021

Cited by 5 | Viewed by 2479

Abstract

Optical parametric oscillation can convert the input laser into a couple of coherent optical output with signal and idler frequencies. It is an important method for the realization of the broadband middle infrared tunable lasers. The optical parametric oscillation process depends on the [...] Read more.

Optical parametric oscillation can convert the input laser into a couple of coherent optical output with signal and idler frequencies. It is an important method for the realization of the broadband middle infrared tunable lasers. The optical parametric oscillation process depends on the ultra-fast non-linear response of matter to light with a certain pump power. Therefore, reducing the pump threshold of the optical parametric oscillation process and improving the energy conversion efficiency are of great significance to the study of non-linear optics. In this paper, we construct a dimer system that couples a passive non-linear resonator to an active resonator. Based on the dimer system, an ultra-low threshold optical parametric oscillation generation method is proposed. By coupling the gain pump mode, the non-linear effect is effectively enhanced, the pump power threshold is reduced to half of when there is no gain, and the energy conversion efficiency is increased. We believe this research provides a feasible method for a low-threshold tunable and easy-to-integrate optical parametric oscillation laser source. Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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8 pages, 2216 KiB

Open AccessArticle

All-Fiber Frequency Shifter Based on an Acousto-Optic Tunable Filter Cascaded with a Tapered Fiber-Coupled Microcavity

by Xiaofang Han, Yue Hu, Jiwei Li, Pengfa Chang, Feng Gao, Xiao Dong, Fang Bo, Wending Zhang, Guoquan Zhang and Jingjun Xu

Crystals 2021, 11(5), 497; https://doi.org/10.3390/cryst11050497 - 1 May 2021

Cited by 3 | Viewed by 2371

Abstract

An all-fiber acousto-optic frequency shifter (AOFS) based on an acousto-optic tunable filter (AOTF) cascaded with a packaged tapered fiber (TF)-coupled microsphere was proposed and demonstrated in both theory and experiment. The configuration has the advantages of easy alignment, robustness, compact size, and low [...] Read more.

An all-fiber acousto-optic frequency shifter (AOFS) based on an acousto-optic tunable filter (AOTF) cascaded with a packaged tapered fiber (TF)-coupled microsphere was proposed and demonstrated in both theory and experiment. The configuration has the advantages of easy alignment, robustness, compact size, and low cost, which will improve its further application, such as in the optical heterodyne detection technique (OHDT). Full article

(This article belongs to the Special Issue Micro and Nano Optics for Advanced Sensing Technology)

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