Fast-Response Oxygen Optical Fiber Sensor based on PEA2 SnI4 Perovskite with Extremely Low Limit of Detection

Microextraction-Driven Optical Fiber Sensor Coupled with Signal Enhancement by Gold Nanostars for Detection of Antibiotics in Food and Water

In this work, a portable optical fiber-based "microextraction sensing" platform coupled with gold nanostars (Au NSRs) was designed for the detection of kanamycin (Kana). Replaceable optical fibers were used as solid-phase microextraction (SPME) devices and sensing probes. Au NSRs and Kana aptamers were sequentially modified onto a fiber core as sensing elements. The evanescent wave generated from the fiber interacted with the surface of the Au NSR, and the localized surface plasmon resonance (LSPR) effect was triggered. In the presence of Kana, the refractive index of the Au NSR surface changed, causing the LSPR characteristic peak to shift, thereby enabling the quantitative detection of Kana. Benefiting from the strong "hot spot" effect produced by the sharp branches of the Au NSR, the intensity of the signals was greatly increased. Under optimal conditions, the sensing platform exhibited high selectivity toward Kana. The calibration linear range was 0.5-500 nM (r2 = 0.997), and a limit of detection of 0.138 nM was achieved. The optical fiber could be easily disassembled and reused. Signal stability remained intact even after a replaceable optical fiber probe was cleaned and used 10 times. The sensor was successfully applied to the analysis of Kana residues in genuine cow's milk samples. The procedure was also applied to river water samples. This assay has unique advantages of low cost, simplicity, and recyclability, making it a promising approach for food analysis and environmental monitoring.

CdSe/ZnS quantum dots-doped polymer optical fiber microprobe for pH sensing

pH is an important physiological parameter within organisms, playing a crucial role in functional activities in cells and tissues. Among various pH sensing methods, optical fiber pH sensors have gained a wide attention due to their unique advantages. However, current silica optical fiber-based pH sensors face some challenges such as weak biocompatibility, low biological safety, complex or unstable surface modification. Herein, we develop what we believe to be a novel pH sensor based on a CdSe/ZnS quantum dots-doped polymer optical fiber microprobe (POF MP) grown at the end of the silica optical fiber using the free radical photopolymerization process, which has the advantages of significant compactness, high flexibility, good biocompatibility, easy functionalization, high structural stability and safety. Moreover, the size of the POF MP are controllable, which is highly significant for applications requiring specific probe sizes or those used in special terrains. The proposed sensor is demonstrated to have a sensitivity of 0.18097/pH in a wide pH range from 4.5 to 9.0, while it exhibits a highly linear correlation between fluorescence intensity and pH value (R 2 = 0.99448) and good reversibility and reusability. This proposed pH sensor offers a promising solution for pH monitoring in biological environments, contributing to advancements in biosensing, microenvironment monitoring, and potential therapeutic applications.

Ammonia-sensitive halide CsCu2I3 film for gas sensor and stimuli-responsive anti-counterfeiting

Eco-friendly lead-free halide perovskites have emerged as promising materials for multiple applications due to their unique optoelectronic properties. In this work, we investigate the ammonia (NH3)-sensitive CsCu2I3 film for its potential in NH3 sensor and stimuli-responsive fluorescence anti-counterfeiting. CsCu2I3-based NH3 sensor demonstrates a high response to NH3 (△R/R0 = 1.07, at 100 ppm NH3) with rapid response/recovery time (21/19 s), as well as favorable gas selectivity. We proposed a potential NH3 sensing mechanism with the help of a series of semi-quantitative characterizations and excitation-dependent emission experiments. The electron-donating NH3 molecules can efficiently donate electrons to the p-type CsCu2I3 film, bringing about a decrease in film conductivity. Additionally, the adsorption of NH3 can also disorder the CsCu2I3 crystals with a high density of trap states, facilitating an energy transfer from self-trapped excitons (STEs) emission to defect-related emission, along with bright orange luminescence. Inspired by this phenomenon, we proposed a novel application of NH3-induced stimuli-responsive fluorescence for anti-counterfeiting. The results highlight the potential of CsCu2I3 for effective dual-function applications in gas sensors and gas-triggered anti-counterfeiting.

Controlled Sensor Derived from COF Materials for the Effective Detection of N-Methylpyrrolidone

N-methylpyrrolidone (NMP) is an excellent advanced solvent that can be easily absorbed by the human body and has the characteristics of flammability and explosion. To reduce the risk, the environmental concentrations of NMP need to be measured. A series of covalent organic frameworks (COF) connected by an imine bond have been successfully prepared at room temperature by changing the synthesis time catalyzed by scandium(III) trifluoromethanesulfonate (Sc(OTf)3). The effect of the synthesis time on the sample properties was compared by XRD, FT-IR, XPS, SEM, TEM, and BET. The results showed that synthesis time had almost no effect on the morphology, specific surface area, and functional groups of the COF samples but had a significant impact on the pore size distribution, residual bonds, and other defects, which in turn affected the gas sensing performance. The sensor results showed that all samples had good sensing performance for NMP, among which the sample synthesized for 48 h had the best sensing performance, with a limit of detection of 692 ppb and good stability and repeatability. The excellent performance of the COF samples benefits from the large specific surface area, hydrogen bonding interactions, electrostatic attraction, and high defects. This study provides an effective method for NMP detection and expands the application range of the COF materials.

Emerging Hybrid Metal Halide Glasses for Sensing and Displays

Glassy hybrid metal halides have emerged as promising materials in recent years due to their high structural adjustability and low melting points, offering unique merits that overcome the limitations of their crystalline and polycrystalline counterparts as well as other conventional amorphous semiconductors. This review article comprehensively explores the structural characteristics, electronic properties, and chemical coordination of hybrid metal halides, emphasizing their role in the glass transition from the crystalline phase to the amorphous phase. We examine the intrinsic disorder within the amorphous phase that facilitates light transmission and discuss recent advances in device architecture and interface engineering by optimizing the charge transport of glassy hybrid metal halides for high-quality applications. With full theoretical understanding and rational structural design, potential applications in displays, information storage, X-ray imaging, and sensing are highlighted, underscoring the transformative impact of glassy hybrid metal halides in the fields of materials science and information science.

2D Ruddlesden-Popper Sn-Based Perovskite Weak Light Detector for Image Transmission and Reflection Imaging

2D Ruddlesden-Popper Sn-based perovskite has excellent optoelectronic properties and weak halide ion migration characteristics, making it an ideal candidate for weak light detection, which has great potential in light communication, and medical applications. Although Sn-based perovskite photodetectors are developed, weak light detection is not demonstrated yet. Herein, a high-performance self-powered photodetector with the capability to detect ultra-weak light signals is designed based on vertical PEA2 SnI4 /Si nanowires heterojunction. Due to the low dark current and high light absorption efficiency, the devices present a remarkable responsivity of 42.4 mA W-1 , a high detectivity of 8 × 1011 Jones, and an ultralow noise current of 2.47 × 10-13 A Hz-1/2 . Especially, the device exhibits a high on-off current ratio of 18.6 at light signals as low as 4.60 nW cm-2 , revealing the capacity to detect ultra-weak light. The device is applied as a signal receiver and realized image transmission in light communication system. Moreover, high-resolution reflection imaging and multispectral imaging are obtained using the device as the sensor in the imaging system. These results reveal that 2D PEA2 SnI4 -based self-powered photodetectors with low-noise current possess enormous potential in future weak light detection.

A 0D hybrid lead-free halide with near-unity photoluminescence quantum yield toward multifunctional optoelectronic applications

Zero-dimensional (0D) hybrid metal halides have emerged as highly efficient luminescent materials, but integrated multifunction in a structural platform remains a significant challenge. Herein, a new hybrid 0D indium halide of (Im-BDMPA)InCl6·H2O was designed as a highly efficient luminescent emitter and X-ray scintillator toward multiple optoelectronic applications. Specifically, it displays strong broadband yellow light emission with near-unity photoluminescence quantum yield (PLQY) through Sb3+ doping, acting as a down-conversion phosphor to fabricate high-performance white light emitting diodes (WLEDs). Benefiting from the high PLQY and negligible self-absorption characteristics, this halide exhibits extraordinary X-ray scintillation performance with a high light yield of 55 320 photons per MeV, which represents a new scintillator in 0D hybrid indium halides. Further combined merits of a low detection limit (0.0853 μGyair s-1), ultra-high spatial resolution of 17.25 lp per mm and negligible afterglow time (0.48 ms) demonstrate its excellent application prospects in X-ray imaging. In addition, this 0D halide also exhibits reversible luminescence off-on switching toward tribromomethane (TBM) but fails in any other organic solvents with an ultra-low detection limit of 0.1 ppm, acting as a perfect real-time fluorescent probe to detect TBM with ultrahigh sensitivity, selectivity and repeatability. Therefore, this work highlights the multiple optoelectronic applications of 0D hybrid lead-free halides in white LEDs, X-ray scintillation, fluorescence sensors, etc.

Wafer-Level Manufacturing of MEMS H2 Sensing Chips Based on Pd Nanoparticles Modified SnO2 Film Patterns

In this manuscript, a simple method combining atomic layer deposition and magnetron sputtering is developed to fabricate high-performance Pd/SnO2 film patterns applied for micro-electro-mechanical systems (MEMS) H2 sensing chips. SnO2 film is first accurately deposited in the central areas of MEMS micro hotplate arrays by a mask-assistant method, leading the patterns with wafer-level high consistency in thickness. The grain size and density of Pd nanoparticles modified on the surface of the SnO2 film are further regulated to obtain an optimized sensing performance. The resulting MEMS H2 sensing chips show a wide detection range from 0.5 to 500 ppm, high resolution, and good repeatability. Based on the experiments and density functional theory calculations, a sensing enhancement mechanism is also proposed: a certain amount of Pd nanoparticles modified on the SnO2 surface could bring stronger H2 adsorption followed by dissociation, diffusion, and reaction with surface adsorbed oxygen species. Obviously, the method provided here is quite simple and effective for the manufacturing of MEMS H2 sensing chips with high consistency and optimized performance, which may also find broad applications in other MEMS chip technologies.

Ag/MoO3–Pd-mediated gasochromic reaction: An efficient dual-mode photoelectrochemical and photothermal immunoassay

Herein, we presented a dual-readout gasochromic immunosensing platform for accurate and sensitive detection of carcinoembryonic antigen (CEA) based on Ag-doped/Pd nanoparticles loaded MoO₃ nanorods (Ag/MoO₃-Pd). Initially, the presence of analyte CEA would prompt the formation of sandwich-type immunoreaction, accompanied by the introduction of Pt NPs labeled on detection antibody. Upon the addition of NH₃BH₃, the product hydrogen (H₂) will interact with Ag/MoO₃-Pd as a bridge between the sensing interface and the biological assembly platform. Both photocurrent and temperature signals can serve as readouts due to the significantly increased PEC performance and enhanced photothermal conversion capability of H-Ag/MoO₃-Pd (the product of Ag/MoO₃-Pd react with H₂) compared to Ag/MoO₃-Pd. In addition, the DFT results show that the band gap of Ag/MoO₃-Pd becomes narrower after the reaction with H₂, thus improving the utilization of light, which theoretically explains the internal mechanism of gas sensing reaction. Under optimal conditions, the designed immunosensing platform showed good sensitivity for CEA detection with the limit of detection (LOD) of 26 pg mL^-1 (photoelectrochemical mode) and 98 pg mL^-1 (photothermal mode). This work not only presents the possible reaction mechanism of Ag/MoO₃-Pd and H₂, but also creatively applicate it in photothermal biosensors that give a new path for devising dual-readout immunosensor.

Polyacrylic Acid/Polyaniline-Coated Multimode Interferometer for Ammonia Detection

A coaxial optical fiber interferometer (COFI) is proposed here for ammonia sensing, which comprises two light-carrying single-mode fibers (SMF) fused to a section of no-core fiber (NCF), thus forming an optical interferometer. The outer surface of the COFI is coated with a layer of polyacrylic acid (PAA)/polyaniline (PAni) film. The refractive index (RI) of the sensitive layer varies when PAA/PAni interacts with ammonia, which leads to the resonance wavelength shift. The surface morphology and structure of the PAA/PAni composites were characterized by using a scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) spectroscopy. When the sensor was exposed to an ammonia atmosphere of different concentrations at room temperature, the sensing performance of the PAA/PAni composite film was superior to that of a sensitive film formed by single-component PAA or PAni. According to the experimental results, the composite film formed by 5 wt% PAA mixed with 2 wt% PAni shows better performance when used for ammonia sensing. A maximum sensitivity of 9.8 pm/ppm was obtained under the ammonia concentration of 50 ppm. In addition, the sensor shows good performance in response time (100 s) and recovery time (180 s) and has good stability and selectivity. The proposed optical fiber ammonia sensor is adapted to monitor leakage in its production, storage, transportation, and application.