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ZnO nanomaterials have been extensively used as photocatalysts for the removal of pollutants in aqueous environments. This study explores the enhanced photocatalytic performance of porous ZnO coral-like nanoplates synthesized via a one-pot wet-chemical method and subsequent annealing treatment. Characterization through scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, photoluminescence (PL) spectroscopy, and Brunauer-Emmett-Teller (BET) measurements confirmed the nanoplates' porous structure, single-crystal structure, 100 nm thickness, and 80 nm pore size. These unique structural characteristics of the ZnO coral-like nanoplates enabled effective photodegradation of the organic dye rhodamine B (RhB) under visible light irradiation. Under simulated sunlight, the ZnO photocatalyst exhibited exceptional performance, achieving a 97.3% removal rate of RhB after 210 minutes of irradiation. The prepared ZnO photocatalyst also showed remarkable photostability and regeneration capability for RhB photodegradation with a decreased efficiency of less than 15% after eight testing cycles. The potential mechanism of the ZnO photocatalyst toward RhB degradation was also studied and is discussed in detail., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)

Acetone is a well-known volatile organic compound that is widely used in different industrial and domestic areas, but it can cause dangerous effects on human health. Thus, the fabrication of highly sensitive and selective sensors for recognition of acetone is incredibly important. Here, we prepared the SnO 2 /Pd-NiO (SPN) nanowires-based gas sensor for the detection of acetone, in which, the amount of Pd nanoparticles were varied to enhance the performance of the devices. We demonstrated that the acetone gas sensing performance of the SPN device was significantly enhanced, showing increases of 3.72 and 6.53 folds compared to pristine SnO 2 and NiO sensors, respectively. The Pd-NiO 0.01% wt Pd SPN sensor (SPN-1) exhibited an excellent response ( R a / R g = 14.88) toward 500 ppm acetone gas. The SPN-1 sensor also showed a fast gas response time of 11/150 seconds with 500 ppm Acetone at 450 °C, while the recovery time was 468/526 seconds. Additionally, the sensor showed good selectivity toward acetone over other reducing gases, such as NH 3 , CH 4 , and VOCs. With those results, the SPN-1 sensor shows superiority compared to sensors based on pure materials., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The real-time monitoring of food freshness in refrigerators is of significant importance in detecting potential food spoiling and preventing serious health issues. One method that is commonly reported and has received substantial attention is the discrimination of food freshness via the tracking of volatile molecules. Nevertheless, the ambient environment of low temperature (normally below 4 °C) and high humidity (90% R.H.), as well as poor selectivity in sensing gas species remain the challenge. In this research, an integrated smart gas-tracking device is designed and fabricated. By applying pump voltage on the yttria-stabilized zirconia (YSZ) membrane, the oxygen concentration in the testing chamber can be manually tailored. Due to the working principle of the sensor following the mixed potential behavior, distinct differences in sensitivity and selectivity are observed for the sensor that operated at different oxygen concentrations. Typically, the sensor gives satisfactory selectivity to H 2 S, NH 3 , and C 2 H 5 OH at the oxygen concentrations of 10%, 30%, and 40%, respectively. In addition, an acceptable response/recovery rate (within 24 s) is also confirmed. Finally, a refrigerator prototype that includes the smart gas sensor is built, and satisfactory performance in discriminating food freshness status of fresh or semi-fresh is verified for the proposed refrigerator prototype. In conclusion, these aforementioned promising results suggest that the proposed integrated smart gas sensor could be a potential candidate for alarming food spoilage.

Thiol functionalization of two-dimensional (2D) metal sulfides has been demonstrated as an effective approach to enhance the sensing performances. However, most thiol functionalization is realized by multiple-step approaches in liquid medium and depends on the dispersity of 2D materials. Here, we utilize a three-dimensional (3D) In 2 S 3 nano-porous structure that self-assembled from 2D components as the nanoreactor, in which the surface-absorbed thiol molecules from the chemical residues of the nanoreactor are used for the in-situ covalent functionalization. Such functionalization is realized by facile heat the nanoreactor at 100 °C, leading to the recombing sulfur vacancies with thiol-terminated groups. The NO 2 sensing performances of such functionalized nanoreactor are investigated at room temperature, in which In 2 S 3 -100 exhibits a response magnitude of 21.5 towards 10 ppm NO 2 with full reversibility, high selectivity, and excellent repeatability. Such high-performance gas sensors can be attributed to the additional electrons that transferring from the functional group into the host, thus significantly modifying the electronic band structure. This work provides a guideline for the facile in-situ functionalization of metal sulfides and an efficient strategy for the high performances gas sensors without external stimulus., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

The adverse effects of NO 2 on the environment and human health promote the development of high-performance gas sensors to address the need for monitoring. Two-dimensional (2D) metal chalcogenides have been considered an emerging group of NO 2 -sensitive materials, while incomplete recovery and low long-term stability are the two major hurdles for their practical implementation. The transformation into oxychalcogenides is an effective strategy to alleviate these drawbacks, but usually requires multiple-step synthesis and lacks controllability. Here, we prepare tailorable 2D p-type gallium oxyselenide with the thicknesses of 3-4 nm, through a single-step mechanochemical synthesis that combines the in-situ exfoliation and oxidation of bulk crystals. The optoelectronic NO 2 sensing performances of such 2D gallium oxyselenide with different oxygen contents are investigated at room temperature, in which 2D GaSe 0.58 O 0.42 exhibits the largest response magnitude of 82.2% towards 10 ppm NO 2 at the irradiation of UV, with full reversibility, excellent selectivity, and long term stability for at least one month. Such overall performances are significantly improved over those of reported oxygen-incorporated metal chalcogenide-based NO 2 sensors. This work provides a feasible approach to prepare 2D metal oxychalcogenides in a single-step manner and demonstrates their great potential for room-temperature fully reversible gas sensing., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

As a source of clean energy, hydrogen (H 2 ) is a promising alternative to fossil fuels in reducing the carbon footprint. However, due to the highly explosive nature of H 2 , developing a high-performance sensor for real-time detection of H 2 gas at low concentration is essential. Here, we demonstrated the H 2 gas sensing performance of Ag/Pd nanoparticle-functionalized ZnO nanoplates. Bimetallic Ag/Pd nanoparticles with an average size of 8 nm were prepared and decorated on the surface of ZnO nanoplates to enhance the H 2 gas sensing performance. Compared with pristine ZnO, the sensor based on ZnO nanoplate doped with Ag/Pd (0.025 wt%) exhibited an outstanding response upon exposure to H 2 gas ( R a / R g = 78 for 500 ppm) with fast response time and speedy recovery. The sensor also showed excellent selectivity for the detection of H 2 over the interfering gases ( i.e. , CO, NH 3 , H 2 S, and VOCs). The superior gas sensing of the sensor was dominated by the morphological structure of ZnO, and the synergistic effect of strong adsorption and the optimum catalytic characteristics of the bimetallic Ag/Pd enhances the hydrogen response of the sensors. Thus, bimetallic Ag/Pd-doped ZnO is a promising sensing material for the quantitative determination of H 2 concentration towards industrial applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Gas sensors play an important role in many areas of human life, including the monitoring of production processes, occupational safety, food quality assessment, and air pollution monitoring. Therefore, the need for gas sensors to monitor hazardous gases, such as ammonia, at low operating temperatures has become increasingly important in many fields. Sensitivity, selectivity, low cost, and ease of production are crucial characteristics for creating a capillary network of sensors for the protection of the environment and human health. However, developing gas sensors that are not only efficient but also small and inexpensive and therefore integrable into everyday life is a difficult challenge. In this paper, we report on a resistive sensor for ammonia detection based on thin V 2 O 5 nanosheets operating at room temperature. The small thickness and porosity of the V 2 O 5 nanosheets give the sensors good performance for sensing ammonia at room temperature (RT), with a relative change of resistance of 9.4% to 5 ppm ammonia (NH 3 ) and an estimated detection limit of 0.4 ppm. The sensor is selective with respect to the seven interferents tested; it is repeatable and stable over the long term (four months). Although V 2 O 5 is generally an n-type semiconductor, in this case the nanosheets show a p-type semiconductor behavior, and thus a possible sensing mechanism is proposed. The device's performance, along with its size, low cost, and low power consumption, makes it a good candidate for monitoring freshness and spoilage along the food supply chain.

Gas sensor-embedded smartphones would offer the opportunity of on-site tracking of gas molecules for various applications, for example, harmful air pollutant alarms or noninvasive assessment of health status. Nevertheless, high power consumption and difficulty in replacing malfunctioned sensors as well as limited space in the smartphone to host the sensor restrain the relevant advancements. In this article, we create a smartphone case-based sensing platform by integrating the functional units into a smartphone case, which performs a low detection limit of 117 ppb to acetone and high specificity. Particularly, dimming glass-regulated light fidelity (Li-Fi) communication is successfully developed, allowing the sensing platform to operate with relatively low power consumption (around 217 mW). Experimental proof on harmful gas sensing and potential clinic application is implemented with the sensing platform, demonstrating satisfactory sensing performance and acceptable health risk pre-warning accuracy (87%). Thus, the developed smartphone case-based sensing platform would be a good candidate for realizing harmful gas alarms and noninvasive assessment of health status.

Chemoresistive gas sensors play an important role in detecting toxic gases for air pollution monitoring. However, the demand for suitable nanostructures that could process high sensing performance remains high. In this study, hollow ZnO nanorices were synthesized by a simple hydrothermal method to detect NO 2 and SO 2 toxic gases efficiently. Material characterization by some advanced techniques, such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy, demonstrated that the hollow ZnO nanorices had a length and diameter size of less than 500 and 160 nm, respectively. In addition, they had a thin shell thickness of less than 30 nm, formed by an assembly of tiny nanoparticles. The sensor based on the hollow ZnO nanorices could detect low concentration of NO 2 and SO 2 gasses at sub-ppm level. At an optimum operating temperature of 200 °C, the sensor had response values of approximately 15.3 and 4.8 for 1 ppm NO 2 and 1 ppm SO 2 , respectively. The sensor also exhibited good stability and selectivity, suggesting that the sensor can be applied to NO 2 and SO 2 toxic gas detection in ambient air., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The effect of MoS 2 nanosheet (NS) decoration on the gas-sensing properties of SnO 2 nanofibers (NFs) was investigated. The decorated sensors were fabricated by facile on-chip electrospinning technique and subsequently dropping MoS 2 NSs-dispersed solution. The MoS 2 NS decoration resulted in enhanced the response and reduced the operating temperature of SnO 2 NFs towards SO 2 gas. The SnO 2 NF sensor decorated with the optimum density of MoS 2 NSs exhibited about 10-fold enhancement in gas response to 10 ppm SO 2 at 150 °C as compared with the bare SnO 2 NF sensor. Furthermore, the decorated sensors exhibited an extremely low detection limit and good selectivity for SO 2 gas against other interfering gases, such as CO, NH 3 , and H 2 . The enhanced SO 2 gas-sensing performance of MoS 2 NSs-decorated SnO 2 NFs was attributed to the chemical sensitization of MoS 2 NSs and charge transfer through heterojunctions between the NSs and SnO 2 nanograins. The classification of toxic gases such as CO, H 2, and NH 3 by the MoS 2 NSs-decorated SnO 2 NF sensors can achieve high accuracy with linear discriminant analysis (LDA). Our results suggest that the one-dimensional nanostructures of semiconductor metal oxides decorated with two-dimensional transition metal dichalcogenides are attractive candidates for the detection of hazardous gases., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The selective detection and classification of NH 3 and H 2 S gases with H 2 S gas interference based on conventional SnO 2 thin film sensors is still the main problem. In this work, three layers of SnO 2 /Pt/WO 3 nanofilms with different WO 3 thicknesses (50, 80, 140, and 260 nm) were fabricated using the sputtering technique. The WO 3 top layer were used as a gas filter to further improve the selectivity of sensors. The effect of WO 3 thickness on the (NH 3 , H 2 , and H 2 S) gas-sensing properties of the sensors was investigated. At the optimal WO 3 thickness of 140 nm, the gas responses of SnO 2 /Pt/WO 3 sensors toward NH 3 and H 2 gases were slightly lower than those of Pt/SnO 2 sensor film, and the gas response of SnO 2 /Pt/WO 3 sensor films to H 2 S gas was almost negligible. The calcification of NH 3 and H 2 gases was effectively conducted by machine learning algorithms. These evidences manifested that SnO 2 /Pt/WO 3 sensor films are suitable for the actual NH 3 detection of NH 3 and H 2 S gases., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Gas sensor technology is widely utilized in various areas ranging from home security, environment and air pollution, to industrial production. It also hold great promise in non-invasive exhaled breath detection and an essential device in future internet of things. The past decade has witnessed giant advance in both fundamental research and industrial development of gas sensors, yet current efforts are being explored to achieve better selectivity, higher sensitivity and lower power consumption. The sensing layer in gas sensors have attracted dominant attention in the past research. In addition to the conventional metal oxide semiconductors, emerging nanocomposites and graphene-like two-dimensional materials also have drawn considerable research interest. This inspires us to organize this comprehensive 2020 gas sensing materials roadmap to discuss the current status, state-of-the-art progress, and present and future challenges in various materials that is potentially useful for gas sensors., (© 2021 IOP Publishing Ltd.)

In the current work, we report the on-chip fabrication of a low-temperature H₂S sensor based on p -type Co₃O₄ nanofibers (NFs) using the electrospinning method. The FESEM images show the typical spider-net like morphologies of synthesized Co₃O₄ NFs with an average diameter of 90 nm formed on the comb-like electrodes. The EDX data indicate the presence of Co and O elements in the NFs. The XRD analysis results confirm the formation of single-phase cubic spinel nanocrystalline structures ( Fd3 m ) for the synthesized Co₃O₄ NFs. The Raman results are in agreement with the XRD data through the presence of five typical vibration modes of the nanocrystalline Co₃O₄. The gas sensing properties of the fabricated Co₃O₄ NF sensors are tested to 1 ppm H₂S within a temperature range of 150 °C to 450 °C. The results indicate a highest sensor response to 1 ppm H₂S with the gas response of aproximately 2.1 times and the gas response/recovery times of 75 s/258 s at a low temperature of 250 °C. The fabricated sensor also demonstrates good selectivity and a low detection limit of 18 ppb. The overall results suggest a simple and effective fabrication process for the p -type Co₃O₄ NF sensor for practical applications in detecting H₂S gas at low temperature.

In this work, four identical micro sensors on the same chip with noble metal decorated tin oxide nanowires as gas sensing material were located at different distances from an integrated heater to work at different temperatures. Their responses are combined in highly informative 4D points that can qualitatively (gas recognition) and quantitatively (concentration estimate) discriminate all the tested gases. Two identical chips were fabricated with tin oxide (SnO 2 ) nanowires decorated with different metal nanoparticles: one decorated with Ag nanoparticles and one with Pt nanoparticles. Support Vector Machine was used as the "brain" of the sensing system. The results show that the systems using these multisensor chips were capable of achieving perfect classification (100%) and good estimation of the concentration of tested gases (errors in the range 8-28%). The Ag decorated sensors did not have a preferential gas, while Pt decorated sensors showed a lower error towards acetone, hydrogen and ammonia. Combination of the two sensor chips improved the overall estimation of gas concentrations, but the individual sensor chips were better for some specific target gases., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

SnO 2 nanowires (NWs) are used in gas sensors, but their response to highly toxic gas H 2 S is low. Thus, their performance toward the effective detection of low-level H 2 S in air should be improved for environmental-pollution control and monitoring. Herein, Ag 2 O nanoparticle decorated SnO 2 NWs were prepared by a simple on-chip growth and subsequent dip-coating method. The amount of decorated Ag 2 O nanoparticles on the surface of SnO 2 NWs was modified by changing the concentration of AgNO 3 solution and/or dipping times. Gas-sensing measurements were conducted at various working temperatures (200-400 °C) toward different H 2 S concentrations ranging within 0.1-1 ppm. The selectivity of Ag 2 O-decorated SnO 2 NW sensors for ammonia and hydrogen gases was tested. Results confirmed that the Ag 2 O-decorated SnO 2 NW sensors had excellent response, selectivity, and reproducibility. The gas-sensing mechanism was interpreted under the light of energy-band bending by sulfurization, which converted the p-n junction into n-n, thereby significantly enhancing the sensing performance., Competing Interests: The authors hereby declare that they have no conflict of interests regarding the publication of this paper., (This journal is © The Royal Society of Chemistry.)

Fabrication of a high-performance room-temperature (RT) gas sensor is important for the future integration of sensors into smart, portable and Internet-of-Things (IoT)-based devices. Herein, we developed a NO 2 gas sensor based on ultrathin MoS 2 nanoflowers with high sensitivity at RT. The MoS 2 flower-like nanostructures were synthesised via a simple hydrothermal method with different growth times of 24, 36, 48, and 60 h. The synthesised MoS 2 nanoflowers were subsequently characterised by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy. The petal-like nanosheets in pure MoS 2 agglomerated to form a flower-like structure with Raman vibrational modes at 378 and 403 cm -1 and crystallisation in the hexagonal phase. The specific surface areas of the MoS 2 grown at different times were measured by using the Brunauer-Emmett-Teller method. The largest specific surface area of 56.57 m 2 g -1 was obtained for the MoS 2 nanoflowers grown for 48 h. This sample also possessed the smallest activation energy of 0.08 eV. The gas-sensing characteristics of sensors based on the synthesised MoS 2 nanostructures were investigated using oxidising and reducing gases, such as NO 2 , SO 2 , H 2 , CH 4 , CO and NH 3 , at different concentrations and at working temperatures ranging from RT to 150 °C. The sensor based on the MoS 2 nanoflowers grown for 48 h showed a high gas response of 67.4% and high selectivity to 10 ppm NO 2 at RT. This finding can be ascribed to the synergistic effects of largest specific surface area, smallest crystallite size and lowest activation energy of the MoS 2 -48 h sample among the samples. The sensors also exhibited a relative humidity-independent sensing characteristic at RT and a low detection limit of 84 ppb, thereby allowing their practical application to portable IoT-based devices., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Objective: We aimed to evaluate the efficacy of the treatment of knee osteoarthritis (OA) patients by using microfracture technique in combination with autologous bone marrow stem cell transplantation., Methods: A clinical study was conducted between November 2011 and January 2015 and involved 46 patients (aged from 46 to 69) with primary knee OA grade II and III (according to Kellgren-Lawrence classification) at the Orthopedic Trauma Department, Vietnam-Germany Friendship Hospital. Patients were randomly assigned to receive knee arthroscopy and then bone-marrow stem cells from their pelvic bones via injection., Results: The mean Visual Analogue Scale (VAS) score of present pain decreased from 5.68 before surgery to 1.7 24 months after surgery. The mean preoperative Knee Injury and Osteoarthritis Outcome Score (KOOS) was 36.34 (± 3.13), which increased to 74.62 (± 2.86) 24 months after surgery. On the MRI scans, the average Noyes score decreased from 12 (± 1.46) to 7 (± 1.50). Cartilage volume increased on average from 0.4512 (± 0.26) cm3 to 0.5463 (± 0.29) cm3 12-24 months after surgery., Conclusion: Treatment of osteoarthritis by a combination of arthroscopic microfracture and transplantation of autologous bone-marrow stem cells was an invasive, safe and effective method which showed an improvement in the clinical symptoms (VAS score) and knee functions (KOOS points).

Backgroud: Spinal cord injury (SCI) is damage that can cause a temporary or permanent change in spinal cord functions., Aim: This work evaluates clinical signs, mental signs, and quality of life (QoL) after autologous adipose-derived stem cells (ADSCs) transplantation to treat acute spinal cord injury (SCI)., Methods: In this study, 47 SCI patients were recruited and divided into two groups: intervention and control. ADSCs were isolated and cultured under the cell culture quality control procedure. All patients in both groups underwent neurosurgery with or without ADSC transplantation. The recovery regarding neurological muscle, QoL, neurogenic bladder, and mental improvement was assessed after transplantation., Results: All patients had improved in terms of motor function, bladder function, and daily living. No patients reported any side effect. MRI imaging showed significant changes in the lesion length of the spinal canal and the thickening of the spinal cord. Mental improvement was highest at six months after transplantation and lowest at one month after transplantation. The proportion of patients whose quality of life improved after treatment was 100%, while 80% of patients were satisfied with treatment outcomes., Conclusions: Thus, our data suggested that ADSCs transplantation was safe and effective for the treatment of SCI patients. Neurological muscle and neurogenic bladder were improved significantly after transplantation., (Copyright: © 2019 Nguyen Le Bao Tien, Nguyen Dinh Hoa, Vo Van Thanh, Nguyen Van Thach, Vo Truong Nhu Ngoc, Thien Chu Dinh, Thuy Nguyen Thi Phuong, Phung Lam Toi, Dinh Toi Chu.)

Multisensor systems with low-power consumption are emerging for the Internet of Things. In this work, we demonstrate the use of self-heated networked Ag-decorated SnO 2 NW sensors integrated into a portable module for selective detection of H 2 S gas at low power consumption, and the integrated system is simulated as a virtual multisensor under varying heating powers for identifying and quantifying different reducing gases. The H 2 S gas-sensing characterisations at the different self-heating powers of 2-10 mW showed that the gas response significantly increased with the increase in Ag density decoration and the heated power strongly affected the gas-sensing performance and sensor stability. Excellent response of 21.2 to 0.5 ppm H 2 S gas was obtained at a low heating power of 2 mW with an acceptable response/recovery time of 18/980 s. The increase of the heating power over 20 mW can destroy the devices. The integrated system could selectively detect H 2 S at the heating power below 4 mW and H 2 , C 2 H 5 OH and NH 3 gases at the heating power upon 4 mW. The virtual multisensor could discriminate qualitatively (with an accuracy of 100%) and quantitatively H 2 S, H 2 , NH 3 , C 2 H 5 OH (Ethanol) and CH 3 COCH 3 (Aceton) gases with average errors of 13.5%, 14.7%, 16.8%, 16.9%, and 14.8%, respectively. The proposed sensing platform is a promising candidate for selective detection of H 2 S gas and virtual multisensor with low power consumption for mobile or wireless network devices., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The highly toxic hydrogen sulphide (H 2 S) present in air can cause negative effects on human health. Thus, monitoring of this gas is vital in gas leak alarms and security. Efforts have been devoted to the fabrication and enhancement of the H 2 S-sensing performance of gas sensors. Herein, we used electron beam evaporation to decorate nickel oxide (NiO) nanoparticles on the surface of tin oxide (SnO 2 ) nanowires to enhance their H 2 S gas-sensing performance. The synthesised NiO-SnO 2 materials were characterised by field-emission scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy analysis. H 2 S gas-sensing characteristics were measured at various concentrations (1-10 ppm) at 200-350 °C. The results show that with effective decoration of NiO nanoparticles, the H 2 S gas-sensing characteristics of SnO 2 nanowires are significantly enhanced by one or two orders compared with those of the bare material. The sensors showed an effective response to low-level concentrations of H 2 S in the range of 1-10 ppm, suitable for application in monitoring of H 2 S in biogas and in industrial controls. We also clarified the sensing mechanism of the sensor based on band structure and sulphurisation process., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The long duration of a working device with a limited battery capacity requires gas sensors with low power consumption. A self-heated gas sensor is a highly promising candidate to satisfy this requirement. In this study, two gas sensors with sparse and dense SnO 2 nanowire (NW) networks were investigated under the Joule heating effect at the nanojunction. Results showed that the local heating nanojunction was effective for NO 2 sensing but generally not for reduction gases. At 1 μW, the sparse NW sensor showed a good sensing performance to the NO 2 gas. The dense SnO 2 NW network required a high-power supply for gas-sensitive activation, but was suitable for reduction gases. A power of approximately 500 μW was also needed for a fast recovery time. Notably, the dense NW sensor can response to ethanol and H 2 S gases. Results also showed that the self-heated sensors were simple in design and reproducible in terms of the fabrication process., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

ZnFe 2 O 4 nanofiber gas sensors are cost-effectively fabricated by direct electrospinning on microelectrode chip with Pt interdigitated electrodes and subsequent calcination under different conditions to maximize their response to H 2 S gas. The synthesized nanofibers of approximately 30-100 nm in diameter show typical spider-net-like morphology of the electrospun nanofibers. The ZnFe 2 O 4 nanofibers comprise many 10-25 nm nanograins, which results in multi-porous structures. Moreover, the nanofibers exhibit the single phase of cubic-spinel-structure ZnFe 2 O 4 . The density, crystallinity and grain size of ZnFe 2 O 4 nanofiber that strongly affect gas-sensing properties can be optimized by controlling electrospun time, annealing temperature, annealing time and heating rate. Under optimal conditions, the ZnFe 2 O 4 nanofiber sensors exhibit high sensitivity and selectivity to H 2 S at sub-ppm levels. Excellent gas-sensing performances are attributed to effects of multi-porous structure, nanograin size and crystallinity, which is explained by the sensing mechanisms of ZnFe 2 O 4 nanofiber sensors to H 2 S gas., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Metal oxide nanostructures have been extensively used in electrochemical devices due to their advantages, including high active surface area and chemical stability. However, the electrochemical properties of metal oxides are strongly dependent on their structural characteristics. We performed a comparative study on the electrochemical performance of nanoporous nickel oxide (NiO) nanosheets and nanowires. The advanced nanoporous NiO nanomaterials were synthesized by a facile hydrothermal method followed by thermal calcination. The synthesized nanomaterials, as characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, and nitrogen adsorption/desorption isotherms, demonstrated the nanoporosity and high crystallinity of the NiO nanosheets and nanowires. Cyclic voltammetry measurement was performed using a three-electrode system to evaluate the electrochemical properties of the synthesized materials. Results showed that the nanoporous NiO nanosheets possessed a higher current density than that of the nanowires by approximately ten times. Moreover, the nanoporous NiO nanosheets showed exceptionally high stability of almost 100%, after three cycles in strong alkaline environments, thereby suggesting possible application in electrochemical devices., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In our search for novel small molecules targeting histone deacetylases, we have designed and synthesized several series of novel N-hydroxybenzamides/N-hydroxypropenamides incorporating quinazolin-4(3H)-ones (4a-h, 8a-d, 10a-d). Biological evaluation showed that these hydroxamic acids were generally cytotoxic against three human cancer cell lines (SW620, colon; PC-3, prostate; NCI-H23, lung cancer). It was found that the N-hydroxypropenamides (10a-d) were the most potent, both in term of HDAC inhibition and cytotoxicity. Several compounds, e.g. 4e, 8b-c, and 10a-c, displayed up to 4-fold more potent than SAHA (suberoylanilide hydroxamic acid, vorinostat) in term of cytotoxicity. These compounds also comparably inhibited HDACs with IC 50 values in sub-micromolar range. Docking experiments on HDAC2 isozyme revealed some important features contributing to the inhibitory activity of synthesized compounds, especially for propenamide analogues. Importantly, the free binding energy computed was found to have high quantitative correlation (R 2  ∼ 95%) with experimental results., (Copyright © 2017 Elsevier Inc. All rights reserved.)

ZnO nanostructures can be synthesized using different techniques for gas sensor applications, but different synthesis methods produce different morphologies, specific surface areas, crystal sizes, and physical properties, which consequently influence the gas-sensing properties of materials. Many parameters such as morphology, specific surface areas, crystal sizes, and defect level can influence the gas-sensing properties of ZnO nanostructures. However, it is not clear which parameter dominates the gas-sensing performance. This study clarified the correlation between crystal size, defect level, and gas-sensing properties of ZnO nanostructures prepared from hydrozincite counterparts by means of field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and photoluminescence spectra. Results showed that the average crystal size of the ZnO nanoparticles increased with thermal decomposition temperatures from 500 °C to 700 °C. However, the sample treated at 600 °C, which has the lowest visible-to-ultraviolet band intensity ratio showed the highest response to ethanol and NO 2 . These results suggested that defect level but not size is the main parameter dominating the sensor performance. The gas sensing mechanism was also elucidated on the basis of the correlation among decomposition temperatures, crystal size, defect level, and gas sensitivity., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The on-chip growth and surface-functionalization have been recently regarded as promising techniques for large-scale fabrication of high performance nanowires gas sensors. Here we demonstrate a good NO2 gas-sensing performance of the tungsten oxide nanowires (TONWs) sensors realized by scalable on-chip fabrication and RuO2-functionalization. The gas response (Rg/Ra) of the RuO2-functionalized TONWs to 5 ppm of NO2 was 186.1 at 250 °C, which increased up to ∼18.6-fold compared with that of the bare TONWs. On the contrary, the responses of the bare and functionalized sensors to 10 ppm of NH3, 10 ppm of H2S and 10 ppm of CO gases were very low of about 1.5, indicating the good selectivity. In addition, the TONW sensors fabricated by the on-chip growth technique exhibited a good reversibility up to 7 cycles switching from air-to-gas with a response of 19.8 ± 0.033 (to 1 ppm of NO2), and this value was almost the same (about 19.5 ± 0.027) for 11 cycles after three months storage in laboratory condition. The response and selectivity enhancement of RuO2-functionalzied TONWs sensors was attributed to the variation of electron depletion layer due to the formation of RuO2/TONWs Schottky junctions and/or the promotion of more adsorption sites for NO2 gas molecule on the surface of TONWs, whereas the good reversibility was attributed to the formation of the stable monoclinic WO3 from the single crystal of monoclinic W18O49 after annealing at 600 °C.

Decoration of noble metal nanoparticles (NPs) on the surface of semiconducting metal oxide nanowires (NWs) to enhance material characteristics, functionalization, and sensing abilities has attracted increasing interests from researchers worldwide. In this study, we introduce an effective method for the decoration of Pd NPs on the surface of SnO2 NWs to enhance CO gas-sensing performance. Single-crystal SnO2 NWs were fabricated by chemical vapor deposition, whereas Pd NPs were decorated on the surface of SnO2 NWs by in situ reduction of the Pd complex at room temperature without using any linker or reduction agent excepting the copolymer P123. The materials were characterized by advanced techniques, such as high-resolution transmission electron microscopy, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The Pd NPs were effectively decorated on the surface of SnO2 NWs. As an example, the CO sensing characteristics of SnO2 NWs decorated with Pd NPs were investigated at different temperatures. Results revealed that the gas sensor exhibited excellent sensing performance to CO at low concentration (1-25ppm) with ultrafast response-recovery time (in seconds), high responsivity, good stability, and reproducibility., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Carbon dioxide (CO(2)) and carbon monoxide (CO) emissions from industries and combustion fuels such as coal, oil, hydrocarbon, and natural gases are increasing, thus causing environmental pollution and climate change. The selective detection of CO(2) and CO gases is important for environmental monitoring and industrial safety applications. In this work, LaOCl-coated ZnO nanowires (NWs) sensors are fabricated and characterized for the detection of CO(2) (250-4000 ppm) and CO (10-200 ppm) gases at different operating temperatures. The effects of the LaCl(3) coating concentration and calcination temperature of the sensors are studied. They are found to have a strong influence on the sensing performance to CO(2) gas, but a relatively slight influence on that to CO. The LaOCl coating enhances the response and shortens the response and recovery times to CO(2) compared with those to CO. The enhanced response of the LaOCl-coated ZnO NW sensors is attributed to the extension of the electron depletion layer due to the formation of p-LaOCl/n-ZnO junctions on the surfaces of the ZnO NWs., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Tin oxide-single wall carbon nanotube (SWCNT) nano composites are synthesized for gas sensor application. The fabrication includes deposition of porous SWCNTs on thermally oxidized SiO2 substrates followed by rheotaxial growth of Sn and thermal oxidation at 300, 400, 500, and 600 degrees C in air. The effects of oxidation temperature on morphology, microstructure, and gas sensing properties are investigated for process optimization. The tin monoxide oxidized at 400 degrees C showed the highest response at the operating temperature of 200 degrees C. Under the optimized test condition, the composite structure showed better response than both structures of SWCNTs and thin film SnO.

Achieving proper designs of nanosensors for highly sensitive and selective detection of toxic environmental gases is one of the crucial issues in the field of gas sensor technology, because such designs can lead to the enhancement of gas sensor performance and expansion of their applications. Different geometrical designs of porous tungsten oxide nanostructures, including the mesocages, hollow spheres and nanowires, are synthesized for toxic gas sensor applications. Nanosensor designs with small crystalline size, large specific surface area, and superior physical characteristics enable the highly sensitive and selective detection of low concentration (ppm levels), highly toxic NO(2) among CO, as well as volatile organic compound gases, such as acetone, benzene, and ethanol. The experimental results showed that the sensor response was not only dependent on the specific surface area, but also on the geometries and crystal size of materials. Among the designed nanosensors, the nanowires showed the highest sensitivity, followed by the mesocages and hollow spheres-despite the fact that mesocages had the largest specific surface area of 80.9 m(2) g( - 1), followed by nanowires (69.4 m(2) g( - 1)), and hollow spheres (6.5 m(2) g( - 1)). The nanowire sensors had a moderate specific surface area (69.4 m(2) g( - 1)) but they exhibited the highest sensitivity because of their small diameter (∼5 nm), which approximates the Debye length of WO(3). This led to the depletion of the entire volume of the nanowires upon exposure to NO(2), resulting in an enormous increase in sensor resistance.

The electrical and gas sensing properties of mat-type thin films fabricated by the packing of single-walled carbon nanotubes are investigated. The responses of the sensors with various thicknesses or resistances are measured, and the behavior is explained by a diffusion model. The successful explanation of the sensor response using the diffusion model suggests that the mat-type structure of compacted carbon nanotubes can be treated as a porous medium for gas sensor applications.

We develop a simple method to synthesize nano tube or wire structure of tin-oxide for gas sensor application. It is realized by the rheotaxial growth and thermal oxidation (RGTO) of tin on porous single-wall carbon nanotubes (SWNTs) as a template. The morphology and chemical property of thus formed nanostructures are examined. The electrical and NO(x) gas sensing properties are also investigated. The sensor exhibits a fast response time of less than 100 seconds and a good recovery. A sensing response of 23,400% to 10 ppm concentration at 200 degrees C is observed.