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Flower-like In(OH) 3 was synthesized by a facile homogeneous precipitation method and subsequently calcined at 300 °C to prepare nanosheets assembled 3D flower-like mesoporous In 2 O 3 , which was then modified with Au nanoparticles via sol-immobilization method to produce 3D hierarchical mesoporous Au/In 2 O 3 for ethanol detection. The as-prepared Au/In 2 O 3 were carefully characterized by XRD, SEM, HRTEM and XPS techniques. The flower-like structure was assembled by many ultrathin coarse mesoporous In 2 O 3 nanosheets, and Au nanoparticles with an average size of 3.3 nm were evenly dispersed on In 2 O 3 nanosheets. The 3D flower-like mesoporous 1%Au/In 2 O 3 has a high specific surface area of about 130 m2 g−1 and shows the best sensitivity to ethanol among the flower-like mesoporous Au/In 2 O 3 materials. It can sensitively detect ethanol gas at a relatively low temperature of 160 °C with a response of 115–50 ppm ethanol, increased by nearly 11 times compared to In 2 O 3 at 210 °C. The 3D flower-like mesoporous 1%Au/In 2 O 3 also has good selectivity to ethanol with response about 9.4, 26.1, 20.9 and 29.5 times higher than that to acetone, methanol, toluene and xylene, and it displays excellent linear relationship between the response and the ethanol concentration. The markedly improved sensitivity and selectivity of the 3D flower-like mesoporous 1%Au/In 2 O 3 results from both the electronic sensitization and chemical sensitization effects of Au nanoparticles. In short, the 3D flower-like mesoporous 1%Au/In 2 O 3 possesses excellent sensitivity, selectivity, repeatability, linear relationship and long-term stability at 160 °C. Therefore, the obtained 3D flower-like mesoporous 1%Au/In 2 O 3 has great potential for ethanol gas detection. [Display omitted] • 3D flower-like mesoporous In 2 O 3 was synthesized via facile precipitation and calcination process. • 3D flower-like mesoporous Au/In 2 O 3 was prepared by sol-immobilization method. • 3D flower-like mesoporous Au/In 2 O 3 showed excellent ethanol sensing performance. [ABSTRACT FROM AUTHOR]

Non-metallic surface-enhanced Raman scattering (SERS) demonstrates an attractive potential in clinical immunoassay thanks to the brilliant biocompatibility and chemical enhancement of semiconductor substrates. Herein, SERS-based quantitative assay of SARS-CoV-2 in saliva was carried out by constructing SiC@RP nanotowers (NTs) and Si nanoparticles. Ascribed to the efficient light absorption and molecular enrichment capacity of the hierarchical tower morphology as well as the synergistic chemical enhancement in the semiconductor heterojunction, the SiC@RP NTs achieved a minimum limit of detection as 7.6 × 10-11 g/mL for SARS-CoV-2. Concurrently, the correction of the detection signal by the intrinsic Raman signal of Si nanoparticles drastically improved the stability and reliability of the detection, facilitating a relative standard deviation (RSD) data within ± 9.53%. Ultimately, the real-time SERS monitoring of saliva samples displayed an ultra-high response rate of no less than 83.2%. Such a non-metallic SERS immunoassay with high sensitivity and attractive reliability is expected to play a key role in future clinical monitoring application. • Sensitivity was enhanced by utilizing the synergistic chemical enhancement of SiC@RP compound semiconductor. • Light-limiting effect and molecular enrichment was improved by the unique morphology of SiC nanotowers. • The intrinsic Raman signal of silicon probes was used as an internal standard signal. • High throughput detection of SARS-CoV-2 in saliva with a LOD of 7.6 × 10-11 g/mL was realized. [ABSTRACT FROM AUTHOR]

The formulation of substrates with reliable quantitative detection and robust molecular anchoring is crucial for surface-enhanced Raman scattering (SERS) technique. In this context, an appealing hydrophilic-hydrophobic polymer strip with Raman internal standard (IS) was generated by in-situ growing hydrophilic non-metallic black phosphorus/metal-organic frameworks (BP/ZIF-67) onto special regions of hydrophobic polydimethylsiloxane (PDMS) matrix, which dramatically promoted the concentration of target molecules. Furthermore, a specific detection of coronavirus disease 2019 (SARS-CoV-2) N-protein with a limit of 6.4 × 10−6 mg/mL was facilitated, benefiting from the selective capture rendered by the mesoporous surface of ZIF-67 and the ultra-high enhancement effect arose from BP/ZIF-67 hybrid structure-triggered charge transfer resonance process. Moreover, the extent of quantification in the SERS assay was significantly remedied due to the IS strategy. Especially, the slight local surface plasmon resonance (LSPR) capability of BP could readily provoke additional electromagnetic field to complement its powerful chemical enhancement, which was significantly superior to other non-metallic substrates. Such an upgraded platform may deliver another prospering technology for dependable virus monitoring. [Display omitted] • SERS-active polymer strip with BP/ZIF-67 for straightforward virus detection. • Comprehensive explanation of chemical-electromagnetic synergistic enrichment mechanism. • Quantitative detection of SARS-CoV-2 with LOD of 6.4 × 10−6 mg/mL was achieved. [ABSTRACT FROM AUTHOR]

Chemiresistive gas sensors have emerged as a promising generation of detection systems for identifying trace biomarker molecules in exhaled breath, potentially replacing conventional devices for early-stage disease diagnosis. However, their potential is currently limited by the absence of sensing materials that exhibit both humidity resistance and ultrasensitivity. In this study, we investigate the potential of WO 3 nanoparticles (NPs) supported by Nb 2 CTx MXene (WO 3 /Nb 2 CTx) as a highly efficient material for acetone sensing. Our results demonstrate that the synergistic interplay between WO 3 NPs and Nb 2 CTx MXene support generates an intriguing interface with chemical/electronic coupling, thereby further enhancing the gas sensing performance. The WO 3 /Nb 2 CTx sensor exhibits exceptional sensing performance for acetone, with ultrasensitivity (Ra/Rg = 2.4 at 50 ppb) and an ultrafast response time (8 s), surpassing that of WO 3 alone, while maintaining excellent stability. Moreover, the sensor exhibits outstanding response intensity, rapid response time (9 s), superior selectivity, and remarkable reversibility at a relative humidity of approximately 90 %. Additionally, we evaluate the gas-sensing properties of the sensor towards simulated exhaled breath of diabetic patients. In conclusion, our study presents a novel approach that integrates NPs and MXenes, which holds promise for the development of gas sensors with resistance to humidity interference. • WO 3 /Nb 2 CTx heterojunction is designed for acetone detection. • WO 3 /Nb 2 CTx sensor demonstrates ultrasensitive acetone detection at ∼90 % RH. • The Nb 2 CTx facilitates the generation of oxygen vacancies and enhances charge transfer. [ABSTRACT FROM AUTHOR]

Colloidal quantum dots (CQDs) are promising materials candidates for next-generation semiconductor gas sensors, due to their high surface activity and solution-processability. Despite the improved sensitivity demonstrated by PbS CQDs, their long-term stability remains a challenge for practical applications. In this paper, we propose a stabilization strategy for PbS CQD gas sensors by using atomic-ligand engineering. The oleic acid ligands surrounding PbS CQDs are replaced by halide ligands (Cl–, Br– and I–, respectively) via a phase-transfer ligand exchange method. The sensitivity and long-term stability of the PbS CQD gas sensor towards nitrogen dioxide (NO 2) at room temperature are impressively improved. The excellent humidity stability of the iodine ligand exchanged PbS CQD gas sensor is also demonstrated. The mechanism is investigated by real-time electrical measurement, combined with operando diffuse reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis. The results indicate that the large atomic radius and high binding energy of iodide ligands enhance surface passivation and provide favorable conditions for NO 2 adsorption and charge transfer. This study highlights the importance of surface ligand engineering in the development of practical CQD gas sensors. • Atomic-ligand engineering is proposed to stabilize PbS CQD for NO 2 detection. • Iodine ligands improve detection limit to 0.78 ppb with stability in 0–90% RH range. • Iodide ligands enhance passivation and facilitate NO 2 adsorption & charge transfer. [ABSTRACT FROM AUTHOR]

Human health and environmental safety are imperceptibly disturbed by illegally used plasticizers. A fluorescence sensor array based on B-doped graphene quantum dots was designed to detect six plasticizers. Specifically, the dexterous design is the first to disperse B-doped graphene quantum dots in two solvents of different polarities (N,N-Dimethylformamide and Cyclohexane), select three characteristic fluorescence peaks of B-doped graphene quantum dots in the above two solvents, and construct a 3 × 2 array, with a total of 6 array points. The basis of the detection is that the plasticizers affect the dispersion of B-doped graphene quantum dots in different solutions, which are accompanied by the change of its fluorescence signals. Or the plasticizers affect the electron transfer process of B-doped graphene quantum dots in different solvents, resulting in fluorescence quenching. Fluorescence information output by the sensor array showed a good linear relationship with the concentrations of the six plasticizers. The quantitative detection capability can be specified as: the detection range is 100 ng/mL-195 mg/mL, and the detection limit is 1.05–11.58 ng/mL. The fluorescence sensor array also showed good analytical performance in real samples, with recoveries ranging from 95% to 106%. This method has satisfactory specificity, reproducibility, stability and practicality, making it potential for application. • B-GQDs fluorescence sensor array for detecting plasticizers. • B-GQDs have diverse fluorescence properties in different polar solvents. • The plasticizer affects the polarity of the solvent as the detection principle. • The highly sensitive and ultra-rapid detection of six plasticizers was completed. [ABSTRACT FROM AUTHOR]

Human health and environmental safety are imperceptibly disturbed by illegally used plasticizers. A fluorescence sensor array based on B-doped graphene quantum dots was designed to detect six plasticizers. Specifically, the dexterous design is the first to disperse B-doped graphene quantum dots in two solvents of different polarities (N,N-Dimethylformamide and Cyclohexane), select three characteristic fluorescence peaks of B-doped graphene quantum dots in the above two solvents, and construct a 3 × 2 array, with a total of 6 array points. The basis of the detection is that the plasticizers affect the dispersion of B-doped graphene quantum dots in different solutions, which are accompanied by the change of its fluorescence signals. Or the plasticizers affect the electron transfer process of B-doped graphene quantum dots in different solvents, resulting in fluorescence quenching. Fluorescence information output by the sensor array showed a good linear relationship with the concentrations of the six plasticizers. The quantitative detection capability can be specified as: the detection range is 100 ng/mL-195 mg/mL, and the detection limit is 1.05–11.58 ng/mL. The fluorescence sensor array also showed good analytical performance in real samples, with recoveries ranging from 95% to 106%. This method has satisfactory specificity, reproducibility, stability and practicality, making it potential for application. • B-GQDs fluorescence sensor array for detecting plasticizers. • B-GQDs have diverse fluorescence properties in different polar solvents. • The plasticizer affects the polarity of the solvent as the detection principle. • The highly sensitive and ultra-rapid detection of six plasticizers was completed. [ABSTRACT FROM AUTHOR]

This study proposed a high sensitivity optical fiber relative humidity sensor (OFHS). Besides, a fullerene derivative, C 60 -THAM, was synthesized and firstly reported as a molecule receptor in the OFHS. Compared with the widely researched carbon-based materials in OFHS, the C 60 -THAM film has abundant amino dangling bonds, hence emerges naturally as excellent receptors for water molecules. Besides, a cascaded Fabry-Perot interferometer (FPI) was fabricated in the core of single-mode fiber (SMF) without surface damage by femtosecond laser. In the OFHS, the relative humidity (RH) was measured by the Vernier effect. The working principle of the OFHS was analyzed through calculation and simulation. In the experiment, C 60 -THAM was coated on the plant fiber end. The sensitivity of the sensor is about 0.42 nm/RH as the relative humidity change from 30 % to 65 % while the optical-matter reaction length is only about 150 nm. Moreover, the sensor exhibited a stable performance as the RH was decreasing from 65 % to 30 %. The OFHS in this work is fast response and the response time for the rising and decay process was about 2.2 s and 3.2 s respectively. • A fullerene derivative, C 60 -THAM, was synthesized and its application in the fiber humidity sensor was researched. • The humidity sensor is fast response and the rising and decay time is about 2.2 s and 3.2 s respectively. • The sensitivity is 0.42 nm/RH while the optical-matter reaction length is 150 nm. [ABSTRACT FROM AUTHOR]

The discovery of odorant receptors inspiring researchers to refine the artificial olfactory system with the better design of receptor function and transducer function. Colloidal quantum dots (CQDs) offer an abundance of available surface area for chemical and electronic interactions, making them ideal receptors for gas molecules. In this paper, we propose optical fiber antenna (OFA) that mimic the structure and function of biological antenna by using CQDs as the artificial receptors for gas molecules. The charge transfer between the gas molecules and quantum dots is designed to modulate the interaction between the quantum dot solids and light through the variation of refractive index (RI) of quantum receptors. Specifically, lead sulfide (PbS) CQDs serving as NO 2 receptors were deposited on the optical structure for comparison. The solution-processability of CQDs enable their uniform and conformal coating on the fiber. The OFA exhibited a sensitivity of 35 pm ppm−1 for NO 2 sensing at room temperature with the detection limit estimated to be 1 ppb. The proof of OFA concept may pave the way to artificial olfactory networking and will benefit for the development of high precise, large scale, real time distributed gas monitoring application beyond human olfaction. • Optical fiber antenna that mimics the structure and function of biological antenna for gas molecules detection was proposed. • The charge transfer will modulate the interaction between the QD solids and light through the variation of RI of receptors. • OFA exhibited a sensitivity of 35 pm ppm-1 for NO 2 sensing with the detection limit estimated to be 1 ppb. [ABSTRACT FROM AUTHOR]

Surface acoustic wave (SAW) sensors have great advantages in real-time and in-situ gas detection due to the inherent advantages of passive and wireless operation. This inevitably requires the sensor to improve gas sensing performances at room temperature. The facet engineering of metal oxide (MOS) provided an effective way to obtain MOS gas-sensitive materials with superior performance by the facet-dependent properties. Here, we developed a novel strategy to prepare SnO 2 quantum wires with different (110) facets ratio by adjusting the synthesis time. The as-prepared SnO 2 quantum wires were integrated into SAW devices to optimize the performance of the gas sensor. When the synthesis time was 8 h, the response of the SAW gas sensor was enhanced with the frequency change of 17 kHz, the response and recovery times of 45 s and 96 s, respectively. Our experimental results revealed that the effect of mass loading was the responsible underlying mechanism for the superior NO 2 gas sensing performances. In addition, the adsorption and charge transfer properties between the SnO 2 surface and NO 2 molecules were further discussed by QCM and resistance measurement, respectively. The calculation of density functional theory (DFT) also proves the adsorption energy of NO 2 on the SnO 2 (110) facet is larger than the (101) facet and (211) facet, indicating that the (110) facet is more beneficial to the adsorption of NO 2 molecules. This indicated that the facet engineering of MOS by facet-dependent properties to enhance gas sensitivity may open new opportunities for the design of SAW sensor. [Display omitted] • The SnO 2 with different (110) facets ratio were prepared by adjusting the synthesis time. • The SnO 2 with more exposed (110) facets exhibited high sensor response and low detection limit. • Chemiresistor sensor and QCM sensor were used to understand the SAW sensing mechanism for the NO 2. [ABSTRACT FROM AUTHOR]

Aqueous organic amines are threatening to organisms and ecosystem balance. Although many techniques have been used for detection, the simultaneous identification of both its type and concentration is still challenging due to its structural similarity and low environmental concentration. Sensor array is a powerful sensing technology to identify analytes via unique fingerprint patterns. However, the information from general sensor array based on the weak interaction limited its discernibility ability to similar substances. Here, we propose to design molecules with various sensing units based on strong interactions and hence rich spectral change, then construct a tri-probe sensor array for efficient fluorescent differentiation of aqueous organic amine. Different fluorescence responses to different concentrations and types of organic amines were produced by this array. Varied interaction between the probes and the amines was proved by NMR spectra analysis. The combination of probes can produce rich and complementary fluorescence changes. These unique fluorescence response patterns can be well identified and processed using hierarchical analysis (HCA) and linear discriminant analysis (LDA), enabling the 99.35% accurate differentiation of 5 concentration orders (1 μM ~ 10 mM) of 6 kinds of amines. Blind detections for samples of diethylamine, diisopropylamine in tap water and propylamine, hexylamine, trimethylamine, triethylamine in other five domestic wastewater all can be classified and distinguished successfully. The influence of temperature, pH and mental ions are also considered. This sensing method, with the feature of facile preparation, fast response, and excellent discrimination accuracy, can provide a potential option for fast quality test of water. The colorimetric sensor array based on molecular design and algorithm (HCA and LDA) can detect amine components in water environments with the accuracy of 99.35%, whose concentration covers the concentration of 1 μM to 10 mM. The detection and differentiation of amines helps pinpoint types of pollutant, which is of great significance to the rap-id primary screening of the concentration of organic amines in environmental water and the preliminary location of the source of drug production. [Display omitted] • A fluorescent sensor array based on RGB changes which can classify types and concentration of amines is provided. • By molecular design, a maximum output with minimum probes to detect multiple amines are realized. • Through HCA and LDA, this fluorescent sensor array can identify amines (1 μM to 10 mM) in water with the accuracy of 99.35%. [ABSTRACT FROM AUTHOR]

[Display omitted] • SnO2 colloidal nanowires was synthesized by solvothermal without high-temperature sintering. • Pd-SnO2 colloidal nanowires exhibited high response, fast response/recovery H2 sensing at 150 ℃. • Sensing mechanism was investigated by theoretical calculation and adsorption kinetics study. Sensitive H 2 gas sensors are highly desirable for the prediction and early-warning of H 2 leakage. Low-dimensional nanostructures of metal oxide semiconductor emerge as promising materials candidates, but it remains a challenge to preserve the nanostructures in the real sensors. In this work, we demonstrated highly sensitive H 2 gas sensors based on porous network of SnO 2 nanowires that exhibited ultrasmall diameter ∼ 2 nm. Colloidal SnO 2 nanowires synthesized via a solvothermal process were drop-coated onto the commercial alumina substrates, followed by in-situ annealing treatment at 350 °C to remove the surface ligands. The sensors exhibited sensitive response with linear dependence on the H 2 gas concentration ranging from 2 ppm to 100 ppm when operated at 250 °C. Typically, the sensor had a response of 13 toward 40 ppm of H 2 , with the response and recovery time being 15 s and 31 s, respectively. To further improve the sensor performance, Palladium doped SnO 2 nanowires were thoroughly investigated. It's shown that, the operating temperature of the sensor decreased from 250 °C to 150 °C after Pd doping, and the response and recovery time decreased to 6 s/3 s. The superb sensitivity was attributed to the enhanced gas reception, electron transport as well as utility factor owing to the network nanostructure of ultrathin SnO 2 nanowires and catalytic activity of Pd, according to theoretical calculation and adsorption kinetics studies. Combined with the excellent solution processability, the colloidal SnO 2 nanowires are potentially attractive for next-generation gas sensors with lower power consumption and integration with silicon-based substrates. [ABSTRACT FROM AUTHOR]