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One of the effective approaches to safeguard human health is the rapid and sensitive identification of food additives, environmental pollutants, and disease markers. This study developed a portable intelligent paper-based sensor for point-of-care detection of hydrogen peroxide (H 2 O 2) and sarcosine (SA) using smartphone colorimetric analysis, supplemented by UV-Vis verification. The paper-based sensor utilizes a chemical modification of conventional filter paper by immobilizing horseradish peroxidase (HRP) from the horseradish plant, achieved through boronate affinity and metal chelation techniques. For H 2 O 2 detection, the sensor exhibited a linear range of 2–100 µmol L−1 and a limit of detection (LOD) of 1.0 µmol L−1. Similarly, a range of 2–400 μmol L−1 for SA detection and an LOD of 1.0 μmol L−1. The sensors were successfully employed for determining the H 2 O 2 concentration in liquor samples, environmental water, and the amount of SA in urine. Significantly, the detection ranges of these sensors surpassed those of commercially available test strips. In summary, we first proposed enzyme-immobilized paper-based sensors for immobilizing HRP from plants to detect H 2 O 2 and SA, which are intelligent, portable, fast, green, low-cost, highly sensitive, and selective, with broad application prospects in food analysis, environmental monitoring, and medical diagnostics. [Display omitted] • An intelligent paper-based sensor for instant colorimetric analysis of H 2 O 2 and sarcosine was successfully prepared. • This sensor is chemically modified on the basis of filter paper and immobilizes HRP from plant horseradish. • This intelligent sensor has the advantages of high sensitivity, strong selectivity, and visualization. • The H 2 O 2 -test paper is suitable for food quality testing, environmental monitoring and early screening of prostate cancer. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We developed a deep-red fluorogenic probe (BT-NH), with high sensitivity and good selectivity to detect NO. • The probe was successfully used to visualize exogenous/endogenous NO level in living cells. • The probe was further applied to detect NO in PD models. Abstract Nitric oxide (NO), as one of important gaseous signaling molecule in human body, has been associated with a variety of physiologic processes. However, excessive production of NO has been profoundly implicated in the pathogenesis of neurodegenerative disorders in particular, Parkinson's disease (PD). Therefore, accurate and facile detection of NO is of great significance for investigating its functions in PD, and the subsequent diagnosis and/or treatment. Herein, we developed a deep-red fluorogenic probe (BT-NH), with high sensitivity and good selectivity to detect NO, which was successfully used to visualize exogenous/endogenous NO level in living cells, and further applied to in vitro and in vivo PD models. Therefore, BT-NH could be a potential biological fluorogenic tool to explore the roles of NO in PD. [ABSTRACT FROM AUTHOR]

In this article, CeO 2 -based mixed potential type gas sensor attached with sensing electrodes (SEs) consisting of perovskite-type La 1-x Sr x CoO 3 (x = 0.1, 0.2, 0.3 and 0.5) composite oxides has been developed for acetone detection. The effect of different Sr 2+ doping content in La 1-x Sr x CoO 3 oxide material and calcination temperature on acetone sensing characteristics was investigated. It was seen that the sensor using La 0.8 Sr 0.2 CoO 3 calcined at 1000 °C as SE gave the largest sensing signal to acetone in the concentration range of 1–50 ppm at 600 °C among these sensors. The response value (ΔV) of the sensor was sectionally linearly changed with the logarithm of acetone concentration within the ranges of 1–5 ppm and 5–50 ppm, and the sensitivities were −26 and −49 mV/decade, respectively. In addition, it is noteworthy that the response of the sensor to 1 ppm acetone was approximately −8.7 mV. The sensor also exhibited consistent response and recovery characteristics in five cycles, indicating the sensing device had good reproducibility. Besides, the sensor exhibited the highest response to 10 and 50 ppm acetone and less effective response to other tested gases, it indicates that the sensor has good selectivity. Furthermore, the long-term stability for the sensor to 20 ppm acetone was good because that only a slight attenuation in the sensing response was observed during 30 days. The sensing characteristics of the sensor attached with La 0.8 Sr 0.2 CoO 3 -SE sintered at 1000 °C to acetone were explained in terms of electrocatalytic activity changes induced by effects of doped Sr divalent cation. [ABSTRACT FROM AUTHOR]

Standoff detection of flammable and toxic gases simultaneously is important for leakage warning and safe production in oil and gas industries. A portable and robust single-ended laser sensor is developed to retrieve path-averaged gas concentrations of methane (CH 4) and hydrogen sulfide (H 2 S) by collecting the backscattered light from a distant non-cooperative target. Time-division multiplexing of two semiconductor lasers with pigtails are employed to cover the absorption lines of CH 4 and H 2 S at 1653.73 nm and 1578.13 nm, respectively. Wavelength modulation spectroscopy with 1 f normalized 2 f detection (WMS-2 f /1 f) method is used for gas measurement to eliminate the change of return light intensity caused by different distances and different non cooperative targets. Kalman filter is developed as a post-processing method to reduce the output fluctuations during standoff gas measurement. The performance of the sensor is assessed, including signal noise ratio under different standoff distances and hard targets, measurement precision, time-response and the detection limit. The reported sensor allows for real-time non-contact standoff detection of CH 4 and H 2 S, with great potential for its application in oil and gas industries. [Display omitted] • Simultaneous standoff gas detection for CH 4 and H 2 S using WMS-2f/1f method. • Adaptive Kalman filter reduces the standard deviation to 30–75% with a response time of 3 s. • SNRs are evaluated under different standoff distances and common topographic hard targets. • It has great potential for multi-species remote sensing applications in the oil and gas industries. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is a signal molecule that is significantly involved in cell protection, vascular regulation, and neuro-transmission. Nevertheless, abnormal levels of H 2 S are intimately relevant to Alzheimer's disease, liver cirrhosis, diabetes mellitus, and Down syndrome. To improve the H 2 S detection in vitro and in vivo , we developed RDM-H 2 S , a novel red-emission fluorescent probe. RDM-H 2 S has a rapid response (120 s), high sensitivity (LOD = 310 nM), obvious response degree (234 folds), relatively long excitation/emission wavelength (565 nm/620 nm), and steady emission in pH 6–9. In addition, RDM-H 2 S showed high specificity to H 2 S in various species. Due to the low cytotoxicity of RDM-H 2 S , it was beneficial to the application of biological depth imaging. In addition, RDM-H 2 S could measure exogenous and endogenous H 2 S in distinct biological models, such as HeLa cells and zebrafish. Besides, RDM-H 2 S had excellent mitochondrial targeting ability and could be used to monitor H 2 S in living mice. RDM-H 2 S could visualize endogenous H 2 S in different tissues and 4T1-xenograft tumor mice. Additionally, RDM-H 2 S also exhibited immense application potential for the visualization of H 2 S in the process of inflammation. RDM-H 2 S was applied for measuring the level of H 2 S in human plasma samples. Consequently, RDM-H 2 S was determined to be a valuable tool for monitoring H 2 S in pre-clinical diagnosis. [Display omitted] • A rapid response mitochondria-targeting fluorescent probe for detection of H 2 S. • The probe could determine the exogenous and endogenous level of H 2 S in living cells and zebrafish. • The probe could visualize endogenous H 2 S in different tissues and 4T1-xenograft tumor mice. • The probe could image the dynamic processes of H 2 S in inflammation mice. • The probe could measure the level of H 2 S in human plasma samples. [ABSTRACT FROM AUTHOR]

A high performance mixed potential type gas sensor based on stabilized zirconia (YSZ) and NiNb 2 O 6 as sensing electrode was fabricated and used for detection of acetone at 650 °C. NiNb 2 O 6 prepared via a facile sol–gel method and sintered at different temperatures was characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The present study mainly focused on the effect of sintering temperature (800 °C, 1000 °C, 1200 °C) of NiNb 2 O 6 -SE materials on acetone sensing characteristics at 650 °C. Results indicated that the sensor using NiNb 2 O 6 -SE sintered at 1000 °C exhibited the largest sensitivity to acetone in the concentration range of 5–500 ppm at 650 °C, which the slope was −79 mV/decade. The response for the sensor attached with a NiNb 2 O 6 -SE sintered at 1000 °C to 100 ppm of acetone was approximately −113 mV. Moreover, the present sensor could detect even 500 ppb acetone with an acceptable response. The present device also displayed fast response and recovery times, good repeatability, slight sensitive effect to humidity, small drifts in 40 days measured periods, and acceptable selectivity at 650 °C. Additionally, the mixed potential mechanism was further demonstrated by polarization curve. [ABSTRACT FROM AUTHOR]

Highlights • Mixed potential type acetone sensors based on MFeO 3 (M: Bi, La and Sm)-SE and CeO 2 have been first developed. • The response of the sensor utilizing BiFeO 3 (sintered at 800 °C)-SE to 100 ppm acetone was −99 mV. • The sensitivity of the sensor to 5–200 ppm acetone were −75 mV/decade. • The sensor also displayed excellent long-term stability after 40 days continuous measurement at 600 °C. Abstract In order to obtain high-performance CeO 2 -based mixed potential type acetone sensors, MFeO 3 (M: Bi, La and Sm) sensing electrode materials were prepared by sol-gel method. The present study mainly focused on the effect of sensing electrode material and sintering temperature on sensing performance of sensors. The results showed that the sensor used BiFeO 3 -SE sintered at 800 °C presented the best sensing characteristic to acetone at 600 °C, which can detect even 1 ppm acetone with an acceptable response value. The response value (ΔV) of the sensor changed proportionally with the logarithm of acetone concentration at the ranges of 1–5 ppm and 5–200 ppm, and the slopes of which were −7 and −75 mV/decade, respectively. The sensor also showed excellent repeatability, relatively good selectivity, resistance to humidity and good long-term stability. The high-sensing characteristics of the sensor attached with BiFeO 3 -SE sintered at 800 °C to acetone were explained in terms of morphology and electrocatalytic activity of sensing electrode, which are validated by SEM, BET, XPS, polarization curves and complex impedance. [ABSTRACT FROM AUTHOR]

A NASICON-based mixed-potential gas sensor utilizing the perovskite-type orthoferrite La x Sm 1-x FeO 3 (x = 0.2, 0.4, 0.5, 0.6, 0.8) sensing electrode (SE) was designed for SO 2 detection. The research mainly put emphasis on the effect of different La 3+ doping ratios in La x Sm 1-x FeO 3 on the sensing characteristics, and the highest response value (-86.5 mV) to 1 ppm SO 2 was observed for the sensor using La 0.5 Sm 0.5 FeO 3 -SE. The response value of the fabricated sensor displayed segmentally linear relationship with the logarithm of SO 2 concentration in the ranges of 0.005-0.2 ppm and 0.2–5 ppm, and the slopes were −8 and −86 mV/decade, respectively. Otherwise, the low detection limit of the present sensor even could reach to 5 ppb with an accurate response value (-8.4 mV). Meanwhile, the sensor also showed good repeatability, long-term stability and selectivity toward other interfering gases. Furthermore, the electrochemical impendence curves indicated the reason that the sensor attached with La 0.5 Sm 0.5 FeO 3 -SE displayed the higher response values than the other sensors. The result indicated that differences of electrocatalytic activity was caused by diverse La 3+ doping content in sensing electrode. The sensing mechanism related to the mixed potential was demonstrated by the polarization curve. [ABSTRACT FROM AUTHOR]

In this paper, mixed potential electrochemical sensors based on YSZ and La 2 NiO 4 sensing electrode were fabricated for the sub-ppm H 2 S detection. The sensing materials La 2 NiO 4 was prepared by a sol-gel method. The different moles citric acid (CA) were used as complex agent to change the micro-structure of the La 2 NiO 4 . In comparison with other mole proportions, the sensor based on La 2 NiO 4 -SE with n(CA):n(La 3+ + Ni 2+ ) = 1:1 performed the highest response of −55 mV to 500 ppb H 2 S at 500 °C. Moreover, a short temperature pulse of 700 °C was used to decrease the recovery time and the result shows a significance decrease for the sensor to 500 ppb H 2 S, which is changed from 20 min to about 150s. In addition, the sensor displayed good stability for H 2 S during the testing period and excellent selectivity toward H 2 S in comparison to the other interference gases, such as SO 2 , NO 2 , NO, CO, CH 4 and NH 3 . The sensing mechanism related to the mixed potential ws proposed for the sensor based on YSZ and oxide electrodes. [ABSTRACT FROM AUTHOR]

A mixed-potential type NO 2 sensor based on stabilized-zirconia (YSZ) solid electrolyte and novel trirutile CoTa 2 O 6 sensing electrode (SE) prepared through the sol-gel method was developed at high temperature. The effect of CoTa 2 O 6 sensing electrode material calcinated at different temperatures on NO 2 sensing property was mainly investigated and the device attached with CoTa 2 O 6 -SE sintered at 1000 °C gave the highest response of 93 mV to 100 ppm NO 2 and fast response and recovery times at 650 °C. The response of the sensor utilizing CoTa 2 O 6 -SE annealed at 1000 °C displayed segmentally linear relationship to the logarithm of NO 2 concentration in the ranges of 0.5–5 ppm and 5–500 ppm, which the sensitivities were 12 and 80 mV/decade, respectively. Meanwhile, the present fabricated device also showed good reproducibility, selectivity, long-term stability and slight effect of oxygen and moisture at 650 °C. Furthermore, the mixed potential sensing mechanism proposed was discussed quantitatively and further verified by polarization curve measurement. [ABSTRACT FROM AUTHOR]

Mixed potential type solid-state electrochemical gas sensors using yttria- stabilized zirconia (YSZ) and columbite composite oxide sensing electrodes (SEs) prepared via a facile sol-gel method were developed for detection of sub-ppm acetone at 600 °C. In the comparison of different devices, the sensor attached with CdNb 2 O 6 -SE displayed the highest response of −25 mV to 5 ppm acetone and even could achieve low detection limit of 200 ppb at 600 °C. The fabricated sensor using CdNb 2 O 6 -SE exhibited rapid response and recovery times to 2 ppm acetone at 600 °C, which are 9 and 21 s, respectively. Additionally, the present device also showed good repeatability, selectivity, wet-resistance and stability in 30 day measured periods at 600 °C. Moreover, the sensing mechanism related to mixed potential was proposed and analyzed quantitatively and further demonstrated by polarization curve. [ABSTRACT FROM AUTHOR]

Mixed-potential type sensors utilizing stabilized-zirconia (YSZ) and MNb 2 O 6 (M: Co, Zn and Ni) sensing electrodes (SEs) were fabricated and examined for NO 2 detection at high temperature. For mixed potential type NO 2 sensor present fabricated, the device attached with CoNb 2 O 6 -SE has been found to give the highest response at 750 °C compared with the other two devices and could detect even 0.1 ppm NO 2 with an acceptable response value (5 mV). The present sensor showed fast response and recovery times to 100 ppm NO 2 at 750 °C, which are 3 s and 15 s, respectively. ΔV of the sensor attached with CoNb 2 O 6 –SE exhibited segmentally linear relationship to the logarithm of NO 2 concentration in the ranges of 0.1–2 ppm and 2–300 ppm, which the sensitivities were 10 and 52 mV/decade, respectively. Moreover, the present device also displayed good repeatability, good wet resistance, slight drifts in 30 days high- temperature measured period, and excellent selectivity in the presence of various interfering gases at 750 °C. Additionally, the mixed potential sensing mechanism was explained quantitatively and further demonstrated from the measurement of polarization curve. [ABSTRACT FROM AUTHOR]

In this work, a novel fluorescent probe, YT , was developed for monitoring the fluctuation of sulfite in biological applications. The quinoxaline moiety was chosen as the fluorophore to obtain the naked-eye signals in the green channel. The levulinate was selected to achieve the specific and relatively steady recognition reaction. Compared with the reported fluorescent probes for sulfite, YT indicated above moderate performances including remarkable and rapid response (120 folds, within 10 min), high sensitivity (limit of detection = 0.15 μM), and high selectivity. The detecting system showed a green emission and the fluorescence was stable within the pH range of 6–10. In addition, YT could be further applied into living cells and mouse models. Focusing on the serviceability in the breadth of application scope, we imaged the fluctuation of sulfite in both mouse tumor and inflammation models. In the xenograft model, YT could indicate the fluctuation of sulfite which was caused by both addition of exogenous sulfite and induction of different agents including sulfite donor, Na 2 S 2 O 3 , phorbol-12-myristate-13-acetate, and GSH. In the LPS-induced inflammation model, YT could visualize the dose-dependent increase of sulfite level (0–2 mg/mL). More than providing a practical fluorescent implement for monitoring sulfite, this work also raised informatic parameters for developing fluorescent tools into broadened animal models. In this work, a novel fluorescent probe, YT , was developed for monitoring the fluctuation of sulfite in biological applications. The quinoxaline moiety was chosen as the fluorophore to obtain the naked-eye signals in the green channel. The levulinate was selected to achieve the specific and relatively steady recognition reaction. Compared with the reported fluorescent probes for sulfite, YT indicated above moderate performances including remarkable and rapid response, high sensitivity, and high selectivity. The detecting system showed a green emission and the fluorescence was stable within the pH range of 6–10. In addition, YT could be further applied into living cells and mouse models. Focusing on the serviceability in the breadth of application scope, we imaged the fluctuation of sulfite in both mouse tumor and inflammation models. In the xenograft model, YT could indicate the fluctuation of sulfite which was caused by both addition of exogenous sulfite and induction of different agents. In the LPS-induced inflammation model, YT could visualize the dose-dependent increase of sulfite level (0–2 mg/mL). More than providing a practical fluorescent implement for monitoring sulfite, this work also raised informatic parameters for developing fluorescent tools into broadened animal models. [Display omitted] • A novel fluorescent probe, YT , developed for monitoring the fluctuation of sulfite. • Selecting the quinoxaline moiety as the fluorophore to obtain the naked-eye signals. • Remarkable and rapid response, high sensitivity, and high selectivity. • Serviceability in the breadth of application scope including both mouse tumor and inflammation models. • Xenograft model with both addition of exogenous sulfite and induction of different agents. [ABSTRACT FROM AUTHOR]

• Fe-Co-Co PBAs as a novel co-reaction accelerator of the C-g-C 3 N 4 /S 2 O 8 2− ECL system to amplify the ECL signal. • The proposed method holds a new perspective of PBAs nanomaterials in biosensing. • The synthesis method of core-shell Fe-Co-Co PBAs@C-g-C 3 N 4 is facile and green. • The ECL biosensor achieved a sensitive and selective detection of MTX. An ultrasensitive electrochemiluminescence (ECL) biosensor was constructed by using Fe y Co 3-y [Co(CN) 6 ] 2 prussian blue analogues (Fe-Co-Co PBAs) as a novel electrochemically regenerable co-reaction accelerator for methotrexate (MTX) detection. In this work, we synthesized the core-shell Fe-Co-Co PBAs@C-g-C 3 N 4 tags with luminophores and co-reaction accelerators via a facile and green method. To the best of our knowledge, it is the first time that Fe-Co-Co PBAs was used as an efficient co-reaction accelerator of the carboxylated graphene-like carbon nitride /peroxydisulfate (C-g-C 3 N 4 /S 2 O 8 2−) ECL system for signal amplification. In view of the prominent quenching effect of MTX on the ECL response of the C-g-C 3 N 4 , the proposed ECL biosensor exhibited high sensitivity to quantify the concentration of MTX from 5 pM to 10 μM with a detection limit of 1.1 pM. Simultaneously, the biosensor has also been successfully applied to MTX detection in human serum and urine samples with reasonable recoveries. Hence, the proposed method holds a new perspective of PBAs nanomaterials in biosensing and provides a potential analysis method for the rapid detection of MTX in biological systems. [ABSTRACT FROM AUTHOR]

The potential sensor materials of scroll-like dodecylamine-templated vanadium oxide VO x nanotubes doped with Co 2+ or Fe 3+ have been prepared using a sol-gel technique followed by the hydrothermal treatment. The resultant samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning and transmission electron microscopies, thermal and elemental analysis. The gas sensing properties of the metal cations doped VO x nanotubes have been tested in the wide range of working temperatures and targets’ concentrations towards ammonia, ethanol, methanol, toluene and acetone. The highest sensor activity was revealed for ethanol. Stability and electronic properties of pristine and metal doped VO x layers as well as their ad-complexes with O 2 as intermediates during the working process of a sensor were studied by DFT calculations. The study suggests two different mechanisms of cations' action on sensing properties of a VO x compound. In absence of steric obstacles, Co 2+ doing is predicted to be the most efficient dopants for beneficial activation of VO x sensing properties. [ABSTRACT FROM AUTHOR]

A series of spinel oxides Co 1-x Zn x Fe 2 O 4 (x = 0, 0.3, 0.5, 0.7 and 1) prepared by a facile sol-gel method were used as sensing electrodes of mixed potential type yttria stabilized-zirconia (YSZ)-based gas sensor for detection of acetone. The present study mainly focused on the influence of different proportions of cobalt and zinc in Co 1-x Zn x Fe 2 O 4 −sensing electrode (SE) on the acetone sensing properties for the sensor, and the results showed that when x = 0.5, the fabricated sensor exhibited a largest sensitivity of −63 mV/decade to 5–100 ppm acetone at 650 °C. The response signal of the present sensor to 50 ppm acetone was as large as −112 mV, and even could achieve low detection limit of 300 ppb at 650 °C, which had a faithful response at this concentration. In addition, the present device also displayed good reliability, good cross sensitivities in the presence of various interfering gases, slight sensitive effect to humidity and good stability over 40 days at 650 °C. Moreover, the polarization curve was measured to further demonstrate the mixed potential mechanism. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor based on 3D reduced graphene oxide supported high-index Au NCs@CuO (RGO-Au NCs@CuO) for detection of glucose was reported in this work. A facile one-pot hydrothermal synthetic method was employed at room temperature with electrostatic self-assembly technology for the synthesis of reduced graphene oxide supported high-index Au nanocrystals. Morphology, structure and composition of RGO-Au NCs@CuO were characterized by various technologies including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Significantly, with the combination of large active surface area and high conductivity, electrocatalytic activity toward the oxidation of glucose was markedly enhanced. Under the best experimental conditions, the steady-state current response was linearly proportional to glucose concentration in the range from 0.1 μM to 3 mM with a low detection limit (30 nM). Meanwhile, the sensor was of excellent selectivity and stability and successfully applied to the detection of glucose in human serum. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent nanosensor was reported for the first time for the sensitive and selective analysis of Ag + ions by employing graphene quantum dots (GQDs) as the reference fluorophore and o -phenylenediamine (OPD) as the specific recognition probe. Upon the addition of Ag + ions, OPD could be oxidized to produce 2,3-diaminophenazine (DAP) with a strong fluorescence emission at 557 nm, whereas the fluorescence of GQDs at 445 nm would be simultaneously quenched by the so generated DAP through fluorescence resonance energy transfer (FRET). A ratiometric fluorescent Ag + nanosensor was thus developed. The fluorescence intensity ratios of DAP to GQDs linearly increased with the increasing of Ag + concentrations in the range of 0–115.2 μM, with a detection limit down to 250 nM. Furthermore, the feasibility of practical applications of the developed detection strategy for probing Ag + ions in real water samples was demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, a novel type of icosahedron AuPd – copper oxide (CuO) core shell nanoparticles (AuPd@CuO NPs) – modified multi-walled carbon nanotubes (MWCNT) electrode for sensitive nonenzymatic glucose detection has been fabricated. AuPd@CuO core shell NPs were synthesized with icosahedron bimetallic AuPd nanocrystals as core and CuO nanoparticles (CuO NPs) as shell in a mild condition and a short time. MWCNT and AuPd@CuO NPs were characterized by field emission electron microscopy (FESEM), transmission electron microscope (TEM), energy dispersive X-ray detector (EDS) and Fourier transform infrared spectra (FT-IR). In this sensor, icosahedron AuPd@CuO NPs showed much higher electrocatalytic activity towards glucose oxidation. At an applied potential of +0.34 V, this sensor showed a good sensitivity of 744.98 μA mM −1 cm −2 to glucose. In addition, a linear range of 3.00 × 10 −5 to 9.31 × 10 −3 M ( R 2 = 0.997) was obtained with a detection limit of 0.10 μM ( S / N = 3). More importantly, the AuPd@CuO NPs/MWCNT modified electrode is highly resistant against poisoning by chloride ion and inference and was used to analyze glucose concentration in human serum samples. The modified electrode exhibits an enhanced electrocatalytic property, low working potential, good sensitivity, low detection limit, excellent selectivity, and good stability towards glucose oxidation, thus the AuPd@CuO NPs/MWCNT modified electrode is promising for the future development of nonenzymatic glucose sensors. [ABSTRACT FROM AUTHOR]

In this paper, a novel amperometric CO sensor using Nafion and Pt/C composite electrodes was fabricated. Three kinds of carbon materials (carbon fibers, multiwall carbon nanotubes and carbon blacks) were utilized as the supports of the sensing and reference electrodes for the CO sensors. The results revealed that the effective Pt loadings on the electrodes increased in the following order: carbon fibers (CFs) > multiwall carbon nanotubes (MWCNTs) > carbon blacks (CBs), leading to the increasing of the sensitivities toward CO in same order. In other words, the sensor using Pt/CFs as the sensing electrode (SE) showed the highest sensitivity with the value of 0.077 μA/ppm and shortest response time in the range of CO concentration from 1 to 200 ppm at room temperature. Further, a reproducible and stable response against 50 ppm CO was obtained for the sensor with Pt/CFs SE materials. Moreover, a low detection limit of 0.1 ppm for CO was also examined, suggesting that the sensor can be convenient for detecting very low traces of CO. [ABSTRACT FROM AUTHOR]

A compact stabilized zirconia-based planar-type solid state electrochemical gas sensor using columbite type MnNb 2 O 6 sensing electrode (SE) was designed and developed, aiming at monitoring low concentration of SO 2 at high temperature. Among the different sensing electrode materials calcinated at 800, 1000 and 1200 °C, the device utilizing MnNb 2 O 6 -SE sintered at 1000 °C displayed the highest response of −27 mV to 5 ppm SO 2 and the low detection limit of 50 ppb at 700 °C. A linear dependence of ΔV for the sensor attached with MnNb 2 O 6 -SE sintered at 1000 °C on the logarithm of SO 2 concentration in the range of 0.05–5 ppm at an operating temperature of 700 °C was achieved, which the sensitivity was −13 mV/decade. The present sensor showed fast response time of 37 s to 1 ppm SO 2 at 700 °C. Furthermore, the present device also displayed good continuous response and recovery, high temperature stability and selectivity toward various interfering gases at 700 °C. Additionally, the sensing mechanism related to mixed potential was proposed and further demonstrated based on the measurement of polarization curve. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is an extremely flammable and toxic gas. In this work, we have synthesized WO 3 and CuO/WO 3 composites for H 2 S detection using a simple hydrothermal method. The morphology, structure, chemical composition, and gas-sensitive properties of the samples are comprehensively characterized. The results show that the WO 3 structure comprises of hierarchical hollow microspheres self-assembled by nanoparticles, and the CuO/WO 3 composite retains the hollow microspherical structure of the pure WO 3. Furthermore, the gas sensing performance of the CuO/WO 3 sensor is significantly improved compared with that of WO 3 , with a response value of 1297 for 10 ppm H 2 S at an optimum operating temperature of 70 ℃, which is nearly 103 times that of WO 3 (12.5). It also exhibits a rapid response capability (13 s), lower detection limit (100 ppb), and excellent selectivity. In addition, the sensing mechanism of CuO/WO 3 composites for H 2 S gas detection is analyzed in detail. The improved performance may be related to the morphological structure of the CuO/WO 3 material and the formation of p-n heterojunction and CuS intermediates. [Display omitted] • Preparation of the hierarchical hollow microsphere CuO/WO 3 sensors by a simple two-step hydrothermal route without any surfactant or template. • The response of CuO/WO 3 composite to 10 ppm H 2 S was 1297, which was about 103 times higher than that of WO 3 and 56.3 % higher than the response value (830 10 ppm) reported in the literature for this material so far. • High H 2 S signal at low temperature (70 ℃) due to sulfurization of CuO and the presence of p-n heterojunction. • The CuO/WO 3 sensor provides continuous cycle gas detection of H 2 S from 0.1 to 50 ppm with good repeatability and a lower detection limit as low as 100 ppb. [ABSTRACT FROM AUTHOR]

In situ visual detection of microRNAs (miRNAs) is of great significance for early diagnosis of miRNA-related diseases. In this study, we designed a rolling circle replication-driven self-assembled nucleic acid nanosphere (NS) for imaging miRNAs in living cells, which was loaded with four functional oligonucleotides (THp, H1, H2, H3) through hybridization. The DNA/RNA NS showed excellent biocompatibility, stability and RNase H-responsiveness, enabling on-demand delivery of sensing components and live-cell applications. In the presence of the target miRNA, the cascade amplification of catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) would be triggered to generate a strong fluorescence signal. Taking miRNA 155 as a model, the developed DNA/RNA NS achieved sensitive detection of the target in vitro and in tumor cells, demonstrating the potential of miRNA-based tumor screening. • A DNA/RNA nanosphere-based cascade signal amplifier was developed. • The DNA/RNA nanosphere was formed by RCR-driven self-assembly. • The RNase H-responsive nanoplatform performed on-demand delivery of multiple sensing elements. • The conducted sensing platform exhibited inherent biocompatible, high sensitivity and excellent specificity. • Both in vitro and in situ imaging of the target microRNA was successfully achieved. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenide are attracting increasing attention in electrochemical sensing due to unique nanoconstruction and electronic properties. The present work reports the preparation of flower-like vanadium disulfide (VS2) by a simple one-step hydrothermal process and its properties are characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Data from XRD, SEM and TEM demonstrate that the as-prepared VS2 product has ordered nanosheets stacking flower-structure which is constructed with many irregular nanosheets as a petal-like structure with thickness of several nanometers. A novel electrochemical biosensor was constructed for the determination of 17β-estradiol by immobilizing aptamer on the surface of VS2 nanoflowers and gold nanoparticles modified glassy carbon electrode. Differential pulse voltammetry is applied for the determination of 17β-estradiol and a good linear relationship between the peak current and the logarithm of 17β-estradiol concentration from 1.0×10−11 to 1.0×10−8 M with a detection limit of 1.0×10−12 M (3σ/S). The aptamer sensor exhibits a high sensitivity and remarkable reproducible analytical performance, and was successfully applied for the determination of 17β-estradiol in urine samples with recoveries of 92.0–105.2%. Our attempt will extend the application of VS2 nanoflowers to electrochemical biosensing and catalytic areas. [ABSTRACT FROM AUTHOR]