Highly Selective and Sensitive Detection of Hydrogen Sulfide by the Diffraction Peak of Periodic Au Nanoparticle Array with Silver Coating

Deep Learning-Assisted Colorimetric/Electrical Dual-Sensing System for Ultrafast Detection of Hydrogen Sulfide

This study presents a colorimetric/electrical dual-sensing system (CEDS) for low-power, high-precision, adaptable, and real-time detection of hydrogen sulfide (H2S) gas. The lead acetate/poly(vinyl alcohol) (Pb(Ac)2/PVA) nanofiber film was transferred onto a polyethylene terephthalate (PET) flexible substrate by electrospinning to obtain colorimetric/electrical sensors. The CEDS was constructed to simultaneously record both the visual and electrical response of the sensor, and the improved Manhattan segmentation algorithm and deep neural network (DNN) were used as its intelligent algorithmic aids to achieve quantitative exposure to H2S. By exploring the mechanism of color change and resistance response of the sensor, a dual-sensitivity mechanism explanation model was proposed to verify that the system, as a dual-mode parallel system, can adequately solve the sensor redundancy problem. The results show that the CEDS can achieve a wide detection range of H2S from 0.1-100 ppm and identify the H2S concentration in 4 s at the fastest. The sensor can be stabilized for 180 days with excellent selectivity and a low limit of detection (LOD) to 0.1 ppm of H2S. In addition, the feasibility of the CEDS for measuring H2S levels in underground waterways was validated. This work provides a new method for adaptable, wide range of applications and low-power, high-precision H2S gas detection.

Challenges and Opportunities of Chemiresistors Based on Microelectromechanical Systems for Chemical Olfaction

Microelectromechanical-system (MEMS)-based semiconductor gas sensors are considered one of the fastest-growing, interdisciplinary high technologies during the post-Moore era. Modern advancements within this arena include wearable electronics, Internet of Things, and artificial brain-inspired intelligence, among other modalities, thus bringing opportunities to drive MEMS-based gas sensors with higher performance, lower costs, and wider applicability. However, the high demand for miniature and micropower sensors with unified processes on a single chip imposes great challenges. This review focuses on recent developments and pitfalls in MEMS-based micro- and nanoscale gas sensors and details future trends. We also cover the background of the topic, seminal efforts, current applications and challenges, and opportunities for next-generation systems.

Deflection-based laser sensing platform for selective and sensitive detection of H2S using plasmonic nanostructures

Considering the severe hazards of abnormal concentration level of H₂S as an extremely toxic gas to the human body and due to the disability of olfactory system in sensing toxic level of H₂S concentration, a reliable, sensitive, selective and rapid method for the detection of H₂S is proposed and its efficacy is analyzed through simulation. The proposed system is based on the deflection of a laser beam in response to the temperature variations in its path. In order to provide selectivity and improve sensitivity, gold nanostructures were employed in the system. The selectivity was introduced based on the thiol-gold interactions and the sensitivity of the system was enhanced due to the modification of plasmon resonance behavior of gold nanostructures in response to gas adsorption. Results from our analysis demonstrate that compared with Au and SiO₂-Au, the Au nanomatryoshka structures (Au-SiO₂-Au) showed the highest sensitivity due to promoting higher deflections of the laser beam.

Plasmonic Nanomaterials for Colorimetric Biosensing: A Review

In the last few decades, plasmonic colorimetric biosensors raised increasing interest in bioanalytics thanks to their cost-effectiveness, responsiveness, and simplicity as compared to conventional laboratory techniques. Potential high-throughput screening and easy-to-use assay procedures make them also suitable for realizing point of care devices. Nevertheless, several challenges such as fabrication complexity, laborious biofunctionalization, and poor sensitivity compromise their technological transfer from research laboratories to industry and, hence, still hamper their adoption on large-scale. However, newly-developing plasmonic colorimetric biosensors boast impressive sensing performance in terms of sensitivity, dynamic range, limit of detection, reliability, and specificity thereby continuously encouraging further researches. In this review, recently reported plasmonic colorimetric biosensors are discussed with a focus on the following categories: (i) on-platform-based (localized surface plasmon resonance, coupled plasmon resonance and surface lattice resonance); (ii) colloid aggregation-based (label-based and label free); (iii) colloid non-aggregation-based (nanozyme, etching-based and growth-based).

Dual-channel Lanthanide-doped Nanoprobe for Reliable Multi-signal Ratiometric Detection of H2S in Whole Blood

The influence of wavelength-dependent absorbance of blood has been blocking the evolution of fluorescent biodetection in whole blood. Here, a multi-signal ratiometric biodetection method was proposed based on a dual-channel...

A petal-shaped MOF assembled with a gold nanocage and urate oxidase used as an artificial enzyme nanohybrid for tandem catalysis and dual-channel biosensing

A facile one-pot precipitation method was employed to prepare a petal-shaped hybrid under mild conditions. The hybrid is composed of urate oxidase (UOx) encapsulated into a zeolite-like metal-organic framework (MOF) with the doping of a hollow gold nanocage (AuNC). As one of the MOF-enzyme composites, a UOx@MOF(AuNC) hybrid with the features of artificial nanoenzymes was developed as a novel dual-channel biosensing platform for fluorescence (FL) and electrochemical detection of uric acid (UA). As for FL biosensing, enzymatic catalysis of the hybrid in the presence of UA triggered tandem catalysis and oxidation reactions to cause FL quenching. UA was linearly detected in the 0.1-10 μM and 10-300 μM ranges, with the limit of detection (LOD) of 20 nM. As for electrochemical biosensing, the hybrid was dropped on a glassy carbon electrode (GCE) surface to construct a hybrid/GCE platform. Based on the redox reaction of UA on the platform surface, UA was linearly detected in the 0.05-55 μM range, with a LOD of 15 nM. Experimental results confirmed that the hybrid-based dual-channel biosensing platform enabled selective and sensitive responses to UA over potential interferents. The platform has an excellent detection capability in physiological samples. The dual-channel biosensing platform facilitates the exploration of new bioanalysis techniques for early clinical diagnosis of diseases.

A Highly Sensitive and Flexible Metal-Organic Framework Polymer-Based H2S Gas Sensor

We report the fabrication of a novel metal-organic framework (MOF)-polymer mixed-matrix flexible membrane for the detection of hydrogen sulfide (H₂S) gas at room temperature. This high-performance gas sensor is based on MOF-5 microparticles embedded on a conductivity-controlled chitosan (CS) organic membrane. The conductivity of the organic membrane is controlled by blending it with a glycerol ionic liquid (IL) at different concentrations. The sensor showed a remarkable detection sensitivity for H₂S gas at a concentrations level as low as 1 ppm at room temperature. The MOF-5/CS/IL gas sensor demonstrates a highly desirable detection selectivity, fast response time (<8 s), recovery time of less than 30 s, and outstanding sensing stability averaging at 97% detection with 50 ppm of H₂S gas. This composite having high sensitivity, low-power consumption, and flexibility holds great promise for addressing current challenges pertinent to environmental sustainability.

Development of a piperazinyl-NBD-based fluorescent probe and its dual-channel detection for hydrogen sulfide

To selectively detect H₂S based on the thiolysis reaction of 7-nitro-1,2,3-benzoxadiazole (NBD), amines attracted increasing attention since NBD amine is regarded as a new H₂S reaction site. Herein, a novel fluorescent probe, triphenylamine piperazine NBD (TPA-Pz-NBD), was developed. The results showed that it exhibited high selectivity towards H₂S via fluorescence spectroscopy and solution color. Furthermore, TPA-Pz-NBD not only detected H₂S by a dual-channel, turn-on fluorescence signal at 500 nm and turn-off fluorescence signal at 545 nm, respectively, but also displayed a wide detection range of 0-125 μM. In addition, living cell imaging results indicated that TPA-Pz-NBD holds potential for the detection of intracellular H₂S.

Recent Advances in the Fabrication and Functionalization of Flexible Optical Biosensors: Toward Smart Life-Sciences Applications

Over the last 30 years, optical biosensors based on nanostructured materials have obtained increasing interest since they allow the screening of a wide variety of biomolecules with high specificity, low limits of detection, and great sensitivity. Among them, flexible optical platforms have the advantage of adapting to non-planar surfaces, suitable for in vivo and real-time monitoring of diseases and assessment of food safety. In this review, we summarize the newest and most advanced platforms coupling optically active materials (noble metal nanoparticles) and flexible substrates giving rise to hybrid nanomaterials and/or nanocomposites, whose performances are comparable to the ones obtained with hard substrates (e.g., glass and semiconductors). We focus on localized surface plasmon resonance (LSPR)-based and surface-enhanced Raman spectroscopy (SERS)-based biosensors. We show that large-scale, cost-effective plasmonic platforms can be realized with the currently available techniques and we emphasize the open issues associated with this topic.