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Indirectly monitoring halitosis via the detection of hydrogen sulfide (H2S) biomarkers using gas sensors is a newly emerging technique. However, such H2S sensors are required with critically high selectivity and sensitivity, as well as a ppb-level detection limit, which remains technologically challenging. To address such issues, here, we have developed highly sensitive and selective H2S sensors with NiO/WO3 nanoparticles (NPs), which have been synthesized by firstly hydrolyzing WO3 NPs and subsequently decorating with NiO NPs in a hydrothermal process. Theoretically, the NiO/WO3 NPs assist in forming a thicker electron depletion layer, adsorbing more oxygen species O2- to oxidize H2S and finally release more electrons. Beneficially, 2.1 wt % NiO/WO3 NPs show high sensitivity to H2S (Ra/Rg = 15031 ± 1370 @ 10 ppm, 100 °C), which is 42.6-fold higher than that of the pristine WO3 NPs (Ra/Rg = 353 ± 5.6 @ 10 ppm, 100 °C). Further, the H2S sensor shows ppb-level detection limit (Ra/Rg = 4.95 ± 2.9 @ 0.05 ppm, 100 °C) and high selectivity. Practically, NiO/WO3 NP sensor prototype has been employed to detect the simulated exhaled halitosis compared with that of gas chromatography, revealing a close concentration of H2S. Our investigation offers an experimental base in future intelligent medical applications.

Gas sensors built with metal oxide semiconductors have attracted tremendous attention due to the growing demand for the detection of inflammable, explosive and toxic gases. Herein, to improve the sensing response, WO3 nanoparticles decorated with Ag and Pt bimetals (Ag and Pt/WO3 NPs) have been developed via combined hydrolysis and hydrothermal strategies. Such sensors prototypes show high response to acetone (Ra/Rg = 250 @ 100 × 10–6, 140 °C), which is 6.1 fold as high as that of the pristine WO3 NPs (Ra/Rg = 41 @ 100 × 10–6, 140 °C). Moreover, the recovery time of Ag and Pt/WO3 NPs was reduced from 138 to 13 s compared with that of the pristine WO3 NPs. The improved acetone sensing performance may be attributed to that the chemical and electronic sensitization of Ag and Pt to WO3 NPs increases adsorbed oxygen species, speeds up the reaction and thus boosts the sensing response. Our strategy that decoration of dual precious metals onto WO3 NPs improves the acetone sensing performance may be applied to the gas sensors of other sensing materials.

Hydrogen sensing simultaneously endowed with fast response, high sensitivity and selectivity is highly desired in detecting hydrogen leakages such as in hydrogen-driven vehicles and space rockets. Here, hydrogen sensing reined via a hydrogen spillover effect has been developed using palladium nanoparticles photochemically decorated on WO3 nanoparticles (Pd-NPs@WO3-NPs). Theoretically, the Pd-NP catalysts and WO3-NP support are used to construct the hydrogen spillover system, in which Pd NPs possess high catalytic activity, promoting the electron transfer and therefore the reaction kinetics. Beneficially, the Pd-NPs@WO3-NP sensor prototypes toward 500 ppm hydrogen simultaneously exhibit fast response time (∼1.2 s), high response (Ra/Rg = 22 867) and selectivity at a working temperature of 50 °C. Such advanced hydrogen sensing provides an experimental basis for the smart detection of hydrogen leakage in the future hydrogen economy.

Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fiber has been developed as a more promising candidate compared with bulk and film to achieve wearable thermoelectric energy harvesting. Single-walled carbon nanotubes (SWCNTs) with nanostructures are considered as an effective conductive filter for the further improvement in the thermoelectric (TE) performance of PEDOT:PSS fibers. However, the previous research primarily focused on PEDOT:PSS/SWCNT films instead of fibers. In this study, PEDOT:PSS/SWCNT hybrid fibers were synthesized via gelation process, which presents a 30% enhancement of the electrical conductivity with negligible changes in Seebeck coefficient. Moreover, there was a significant increase in the Young’s modulus in accordance with the addition of an appropriate amount of SWCNTs. Thereafter, the as-prepared hybrid fibers were treated using ethylene glycol (EG) to further optimize the TE performance. Moreover, the influence of the treatment time and temperature was systematically investigated. The EG treatment resulted in a significant improvement in the electrical conductivity without a significant decrease in the Seebeck coefficient. Furthermore, the hybrid fibers were subject to EG treatment at elevated temperature, whose optimal power factor was approximately 30% higher than that of the EG-treated PEDOT:PSS/SWCNT fibers at 25 °C. This indicates that the solvent treatment at higher temperature improves the TE performance of hybrid fibers. The findings of this study can serve as a guide for the preparation of flexible and metal-free hybrid fiber with enhanced TE performance and Young’s modulus.

Ceramic TiB2, a layered metal diboride with remarkable conductivity and chemical stability, are potential electrocatalyst towards hydrogen evolution reaction (HER). However, high overpotential (>1 V) is required for pristine TiB2 to drive water splitting, which is less than satisfactory in future hydrogen economy. Herein, conductive polypyrrole (PPy) encapsulating TiB2 (TiB2@PPy) has been developed via vapor phase polymerization, as the electrocatalyst for HER. Theoretically, the PPy shell serves both as electron-transfer channels to accelerate electron migration, and as Mott-Schottky centre to modify the electronic structure of TiB2. Beneficially, more improved HER performance has been achieved with the overpotential of 432 mV at 10 mA cm−2, superior to that of pristine TiB2 (848 mV at 10 mA cm−2). Moreover, excellent stability is presented during 1000 CV cycles and 10 h constant evaluation. Our study provides a new avenue to create efficient HER electrocatalyst via conductive PPy engineering.

Hydrogen sensing simultaneously endowed with fast response, high sensitivity and selectivity is highly desired in detecting hydrogen leakages such as in hydrogen-driven vehicles and space rockets. Here, hydrogen sensing reined via a hydrogen spillover effect has been developed using palladium nanoparticles photochemically decorated on WO

Novel hollow structure based on CuO modified V2O5 nano-string of pearls (V2O5/CuO NSPs) were synthesized via electrospinning technique. The achieved V2O5/CuO NSPs exhibit interesting shapes of string of pearls, endowed with transparent and hollow structure under TEM observation. The V2O5/CuO NSPs sensors demonstrated that the sensitivity (Ra/Rg = 8.8 at 500 ppm) towards acetone was 3.2 times as high as that of pristine V2O5 nanofibers (NFs) (Ra/Rg = 2.5 at 500 ppm) at 440 °C. The improved sensitivity may be ascribed to the formation of V2O5/CuO p-n heterojunctions at the interfaces, which elevates the barrier height and enlarges depleted electron region.

In this study, hematite (α-Fe2O3) micro-spheres coated with ultrafine particles (MSUPs) have been obtained for sensitive acetone sensors via first hydrothermal process with NH4F as the morphological regulator and then annealing of akaganeite. The role of fluoride ion concentration in precursor solution on the morphology has been demonstrated, and the corresponding reaction mechanism was discussed as well. The α-Fe2O3 MSUPs with 0.45 M NH4F (F0.5) in the precursor solution showed the highest response towards acetone compared to other α-Fe2O3 samples. Our α-Fe2O3 MSUPs sensors have potential in sensitive acetone detection.

Smart and reliable palladium (Pd)-based sensors that are able to operate in a large temperature range especially at low temperatures are highly desired but remain challenging because of the “revers...

Pseudocapacitive Bi2O3 is considered as a promising negative material on account of the advantage of high theoretical specific capacitance, but its capacitance is still limited by poor intrinsic electrical conductivity and poor ionic diffusion. Therefore, rationally engineering the surface and the structure are essential to decorate Bi2O3 with high capacitance. Here, we reported conductive PEDOT-engineered Bi2O3 nanosheet arrays (CC/Bi2O3@PEDOT NAs) constructed via a combined solvothermal and electrodeposition approach as high-performance negative electrodes. As-achieved CC/Bi2O3@PEDOT NAs present vertical and interconnected network architecture, which provid a huge surface to connect with the electrolyte and shorten the penetration pathways. Benefiting from the PEDOT-engineered surface, superior electrical conductivity and accelerated charge transport are obtained and thus, the electrode exhibits optimal areal capacitance of 1.7 F cm−2 at 10 mV s−1. Remarkably, maximum energy density of 1.2 mW h cm−3 (123 W h kg−1) is delivered at power density of 9.4 mW cm−3 for the constructed ASC device. This study provides a novel strategy to engineer Bi2O3 towards high capacitance; also, it may be applied to design other high-performance electrodes in the future.

Listeria monocytogenes (LMs) that release 3-hydroxy-2-butanone (3H-2B) biomarker, can cause serious human illness and even death; in this regard, conventional techniques for the smart detection of LMs are of vital importance; however, they still suffer from the requirement of either sophisticated techniques or complicated instrumentation. Herein, we report a metal-oxide semiconductor (MOS) sensor, built with 3D mesoporous nickel oxide nanocuboids (M-NiO NCs), for the detection of LMs. The M-NiO NCs were obtained by directly sacrificing nickel foam in oxalic acid, followed by subsequent annealing. The M-NiO NCs have a rough surface and many multichannel pathways. Impressively, gas sensors built with M-NiO NCs display excellent sensing performance towards the 3H-2B biomarker, exhibiting an ultrahigh sensitivity (Rg/Ra = 302 at 50 ppm) and excellent selectivity. Moreover, the 3H-2B sensor presents excellent long-term stability and, particularly, a low limit of detection (LOD = 0.5 ppm) at 120 °C. The multichannel pathways of the M-NiO NCs contribute to gas adsorption and diffusion, thus enhancing the sensing behavior. Our study provides an ingenious and low-cost strategy to produce mesoporous NiO nanostructures as well as new insights for the detection of pathogenic microbes in food.

Development of semiconductor sensing materials with fast response requires low reaction barrier between gas species and materials surface, hence contributing to real-time gas monitoring. Herein, mullite SmMn2O5 nanofibers (SNFs), nanotube-in-tubes (NT@NTs), and porous nanotubes (PNTs) have been achieved, via optimized electrospinning technique and annealing procedure. The formation mechanism for present shapes of SmMn2O5 nanostructures was discussed. With respect to the sensing properties to acetone, three sensors prototypes employed with SmMn2O5 NT@NTs, SNFs and PNTs were built and in detail studied by taking SmMn2O5 SNFs sensor as an example. Delightfully, the sensor exhibited the response and recovery time as short as 3 s and 8 s at 300 °C, respectively. The intrinsic high catalytic activity of SmMn2O5 lowers the sensing reaction barrier, which might contribute to the reaction kinetics thereby the fast sensing behavior. This work provides synthetic strategies towards one-dimensional (1D) mullite families and the novel material for acetone gas detection would facilitate further development of gas sensing.

An ideal way to boost the selectivity of sensing materials is that improving the sensitivity of the target gas while suppressing that of other interfering ones. Here, the "screening behavior" of the Li doped WO

Indirectly monitoring halitosis via the detection of hydrogen sulfide (H

Rational design of fiber-shaped gas sensors with both excellent mechanical properties and sensing performance is of great significance for boosting future portable and wearable sensing electronics, however, it is still a challenge. Herein, we develop a novel fiber-shaped hydrogen (H2) sensor by directly electrochemically growing palladium (Pd) sensing layer on conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) fiber electrode. This approach produces free-standing functional fiber (PEDOT:PSS@Pd) with promising mechanical features of flexibility, light weight, knittability and high mechanical strength, and good H2 sensing performance at room temperature. The PEDOT:PSS@Pd fiber sensor exhibits short response time of 34 (± 6) s@1% and 19 (± 4) s@4% H2 and excellent cycling stability. In addition, the fiber sensor remains good sensing behavior under different mechanical bending states, showing potential for constructing wearable sensor devices for timely H2 leak detection. Therefore, this work has provided a smart design strategy of fiber-based gas sensor, offering an effective sensing platform and is believed to stimulate the development of wearable electronics.

Rational and smart design of hydrogen (H

MoS2 has attracted attention as a promising hydrogen evolution reaction (HER) catalyst and a supercapacitor electrode material. However, its catalytic activity and capacitive performance are still hindered by its aggregation and poor intrinsic conductivity. Here, hollow rGO sphere-supported ultrathin MoS2 nanosheet arrays (h-rGO@MoS2) are constructed via a dual-template approach and employed as bifunctional HER catalyst and supercapacitor electrode material. Because of the expanded interlayer spacing in MoS2 nanosheets and more exposed electroactive S–Mo–S edges, the constructed h-rGO@MoS2 architectures exhibit enhanced HER performance. Furthermore, benefiting from the synergistic effect of the improved conductivity and boosted specific surface areas (144.9 m2 g−1, ca. 4.6-times that of pristine MoS2), the h-rGO@MoS2 architecture shows a high specific capacitance (238 F g−1 at a current density of 0.5 A g−1), excellent rate capacitance, and remarkable cycle stability. Our synthesis method may be extended to construct other vertically aligned hollow architectures, which may serve both as efficient HER catalysts and supercapacitor electrodes. Electronic supplementary material The online version of this article (10.1007/s40820-018-0215-3) contains supplementary material, which is available to authorized users.

Hybrid organic thermoelectric (HOTE) materials have been considered as a promising alternative for future energy harvesting. Herein, a HOTE thin film was proposed and fabricated by a simple method. Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) developed by vacuum filtration has significantly contributed to the optimization of single-walled carbon nanotubes (SWNTs)/PEDOT:PSS (SN–PP) thermoelectric composite films. PEDOT:PSS was coated on the surface of SWNTs, effectively creating electrical connecting junctions between SWNTs. The SN–PP composite films achieved high electrical conductivity and Seebeck coefficient as well as a relatively low thermal conductivity simultaneously. A notable ZT value of 0.12 was obtained at 60 wt% SWNTs, which is generally higher than those reported in previous studies. Our approach may provide quite a useful strategy to prepare HOTE materials with high performance.

Listeria monocytogenes, a virulent food pathogenic microbe exhaling the biomarker 3-hydroxy-2-butanone (3H-2B), can cause human illnesses and even deaths. Conventional techniques for the detection of Listeria monocytogenes suffer from requiring either sophisticated techniques or complicated facilities. Herein, we report an advanced gas sensor to sensitively and selectively detect the 3H-2B biomarker for the real-time monitoring of Listeria monocytogenes. The sensors are built with surface-oxygen-vacancy enriched chromium (Cr) doped WO3 nanofibers (NFs), obtained via an optimized electrospinning process. The 3H-2B biomarker sensors have an optimum working temperature of 140 °C. Remarkably, the WO3 NFs with 2% Cr dopant exhibit excellent sensitivity (Ra/Rg = 71.8; 5 ppm 3H-2B; 140 °C), showing five-fold improvement compared with pristine WO3 NFs (Ra/Rg = 14.1). Moreover, the sensors are able to detect concentrations as low as 0.05 ppm 3H-2B (Ra/Rg = 2.1), and show miraculous selectivity and long-term stability. We mainly attribute the excellent sensing performance towards 3H-2B to Cr dopants modulating the electron depletion layer (EDL) via enriching surface oxygen vacancies. The unique structure of the Cr doped WO3 NFs also benefits the sensing performance. Our synthetic strategy and building of sensors for the detection of the 3H-2B biomarker provide new insight into the future development of portable and inexpensive devices for food pathogenic microbes.

We report zinc oxide (core) coated with alumina (shell) single-shelled nanocables (ZnO@Al2O3 NCBs) for detection of 3-hydroxy-2-butanone (3H-2B) biomarker, which was prepared via aluminum-anodic-oxide (AAO) template confined electrodeposition, chemical etching and leaving thin AAO-channel wall with broken surface. In the core/shell nanostructure, the outer Al2O3 layer protects ZnO from interference gases, while the pores allow the target gas to react with the oxygen specie on the surface of ZnO. For as-built ZnO@Al2O3 NCBs sensors, the detection limit is as low as 1 ppm, and the response value to 50 ppm 3H-2B is 37.2 at 300 °C. Moreover, the ZnO@Al2O3 NCBs show excellent selectivity and cyclic stability. Our ZnO@Al2O3 NCBs sensors in future monitoring Listeria monocytogenes.

An ideal way to boost the selectivity of sensing materials is that improving the sensitivity of the target gas while suppressing that of other interfering ones. Here, the “screening behavior” of the Li doped WO3 nanofibers (Li/WO3 NFs) have been discovered in suppressing the response from interfering gases, while elevating the H2S sensing response. Beneficially, the H2S response of Li/WO3 NFs sensor prototype is three times (Ra / Rg = 64@10 ppm) as high as that of the pristine WO3 ones (Ra / Rg = 21@10 ppm) at ~75% relative humidity and 260 °C. Moreover, Li/WO3 NFs sensor prototype presents the detection limit as low as 100 ppb. Particularly, the Li/WO3 NFs sensors detect simulated halitosis breath, of which the accuracy is comparable with gas chromatography. Theoretically, the decrease of the responses of Li/WO3 NFs to interfering gases is ascribed to the enhancement of the adsorption of water molecules by Li dopant. While the improved response to H2S is attributed to stronger adsorption of H2S and WO3 and to the increased defect oxygen. The “screening behavior” of Li doped into WO3 NFs provides a new strategy that might improve the selectivity of other gas sensing.

Herein, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/silicon dioxide nanoparticles (SiO2-NPs) composite films were prepared via a simple method by direct vacuum filtration technique. The effect of SiO2-NPs contents on the thermoelectric performance of PEDOT:PSS was investigated systematically. PEDOT:PSS nanofilm without SiO2-NPs exhibited a maximum electrical conductivity of 1487 S cm−1 and a Seebeck coefficient of 17.4 µV/K. When the SiO2-NPs were introduced, the Seebeck coefficient of PEDOT:PSS/SiO2-NPs nanocomposite films increased to a peak value of 24.2 µV/K at 20 wt% SiO2-NPs, and the corresponding electrical conductivity was 1132 S/cm. Although a compromise in electrical conductivity, a large optimized power factor up to be 66.29 µW/m K2 was achieved due to the contribution of improved Seebeck coefficient. The presence of SiO2-NPs in the composite films with small-size structure and abundant grain boundaries may cause the carrier scattering and filtering effect, which accounts for the enhanced Seebeck coefficient.

To date, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) is considered to be one of the most successful organic thermoelectric (TE) material with a figure-of-merit ( ZT ) breakthrough of 0.42 in its field. It is highly expected to achieve higher performance for real application in the near future due to its great TE potential. Numerous effective treatment methods such as pre-treatments and post-treatments on PEDOT:PSS dispersions or films by polar organic solvents, non-ionic surfactant polymers, acids or alkalis and reducing reagents have been developed to enhance its TE performance, which are randomly distributed in different literatures from 14 research groups. To facilitate further research, in this mini-review, we summarize these methods and expound the origin of TE enhancement as well as that the future efforts and strategies are suggested. We are truly expecting this mini-review can be greatly helpful for further research and pave the way for developing more efficient organic TE materials.

Efficient, stable electrode catalysts and advanced hydrogen sensing materials are the core of the hydrogen production and hydrogen detection for guaranteeing the safe issues. Although a universal material to achieve the above missions is highly desirable, it remains challenging. Here, we report palladium/bismuth/copper hierarchical nanoarchitectures (Pd/Bi/Cu HNAs) for advanced dual-applications toward hydrogen evolution reaction (HER) and hydrogen detection, via first electrodeposition of cylindrical nanowires and subsequent wet-chemical etching art. For HER, the Pd/Bi/Cu HNAs present the overpotential (79 mV at 10 mA

There has recently been increased interest in tellurium nanomaterials (Te NMs)-based thermoelectric (TE) materials owing to their large Seebeck coefficient. Meanwhile, techniques such as doping, alloying, and composite have been intensively investigated to further enhance the TE performance of Te NMs-based energy conversion devices. However, the effects of certain inorganic salts on the TE performance of Te NMs have not been studied thus far. Herein, an inorganic salt NaNbO3 was employed to prepared the Te nanorods (Te-NRs) composite as TE material via a hydrothermal method. Furthermore, the chemical composition, microstructure, thermal stability, and TE performance were systematically investigated for NaNbO3/Te-NRs composites at room temperature. By optimization, the NaNbO3/Te-NRs composite with the mass ratio of 1:1 achieved a simultaneous improvement in Seebeck coefficient and electrical conductivity resulting a large TE power factor (PF) of 43.5 μW m−1 K−2 and a high figure of merit (ZT) of 0.081 which are 8 times higher than the pure Te-NRs. In addition, the introduction of NaNbO3 effectively improves the environmental stability of Te-NRs due to the formation of interfaces between NaNbO3 and Te-NRs. This composite strategy proposed a novel approach to develop a promising TE material.

Rational and smart design of hydrogen (H2) sensors especially those featured with flexibility and light weight is highly desirable, to meet the requirements for future development of portable H2 sensors. In this work, we demonstrate a novel paper film H2 sensor employing Ti3C2Tx MXene nanosheets with Pd colloidal nanoclusters (Pd CNC) as the activator. The MXene@ Pd CNC paper film was facilely prepared via an all-colloidal solution-based vacuum-filtration process, which is flexible, light-weight and endowed with a compact, glossy surface. The as-obtained MXene@ Pd CNC film sensor displayed moderate H2 response at room temperature at either flat or bent states. Specially, the MXene@Pd CNC film sensor delivered a response time of (32 ± 7) s and a sensitivity of S = (23.0 ± 4.0)%@4% H2. In addition, the MXene@Pd CNC sensor enabled "in-situ-mode" H2 detection directly along a piece of paper film with desired size. The strong H2 adsorption into lattice of ultrafine Pd CNC altered the work function thus induced the electron doping of MXene, which explained the gas sensing mechanism. Therefore, the facilely designed MXene@Pd CNC sensor is believed to contribute to development of future portable and wearable sensing electronics.

In this work, the electrical conductivity of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) films was effectively enhanced by binary secondary doping. Initially, doping with 5 vol.% dimethyl sulfoxide (DMSO) improved the electrical conductivity from 0.3 S cm−1 to 437 S cm−1 and a further increase to 950 S cm−1 was achieved by adding LiClO4. The conductivity value we report here is one of the highest reported for pretreated PEDOT:PSS films. The obtained maximum electrical conductivity is almost 3000 times higher than that shown by pristine PEDOT:PSS films. The increase in the electrical conductivity is ascribed to the synergistic effect of the two dopants. Fourier transform infrared spectra indicated the absence of any changes to the chemical structure of PEDOT:PSS. Atomic force microscopy images demonstrate an increased surface roughness and suggest the occurrence of conformational changes of PEDOT chains from the coiled to coil-extended one, which is the key reason for the electrical conductivity enhancement. The pretreatments we propose here are rapid, simple and effective for the large-scale preparation of high-conductivity PEDOT:PSS films.

Conjugated polymers containing selenophene have received attention due to their unique properties and promising application in organic electronics. Herein, to further improve the optoelectronic properties, two typical selenophenes containing [1,2,5]thiadiazolo[3,4-c]pyridine (PT)/[1,2,5]selenadiazolo[3,4-c]pyridine (PS) were synthesized by a donor–acceptor strategy and electropolymerized to form the donor–acceptor–donor polymers. The two precursors exhibited yellow and red emission characteristics with high quantum yields (∼0.48); the value was far greater than those for previously reported selenophenes. Furthermore, electrochromic studies demonstrated that the obtained polymers have superior coloration efficiencies (168 cm−2 C−1) than thiophene based analogues and fast response times (1.6 s).

Green DES (ChCl/urea fluid) as a novel surface treatment reagent has been proposed for improving the thermoelectric (TE) performance of PEDOT:PSS films and demonstrated satisfying effects as expected. Simultaneous increases were found in the electrical conductivity and Seebeck coefficient, which achieved further improvement by raising the treating temperature. This additional enhancement was probably attributed to that higher temperature led to decreased viscosity thus a better interaction between the DES mixture and the film surface. The maximum electrical conductivity and Seebeck coefficient were found at 120 °C, reaching 85.6 S cm−1 and 30.1 μV K−1. Further TE improvement was obtained when DMSO was introduced to make a mixture with DES at different ratios to act as the treatment reagent, giving rise to an optimized power factor of 25.26 μW m−1 K−2 with the corresponding electrical conductivity and Seebeck coefficient being 424.2 S cm−1 and 24.4 μV K−1, respectively.

The newly emerged gas sensing detection of 3-hydroxy-2-butanone (3H-2B) biomarker is deemed as an effective avenue to indirectly monitor Listeria monocytogenes (LM). However, 3H-2B sensing materials requiring critically high sensitivity and selectivity, and ppb-level detection limit, remain challenging. Here, we report the advanced gas sensors built with bismuth vanadate microdecahedron (BiVO4 MDCD) {010} facets selectively decorated with Pd nanoparticles (Pd NPs, Pd-{010}BiVO4 MDCDs) for boosted detection of the 3H-2B biomarker. Meanwhile, BiVO4 MDCDs with overall facets are randomly deposited with Pd NPs (Pd-BiVO4 MDCDs). Comparatively, Pd-{010}BiVO4 MDCD sensors show 1 order of magnitude higher response toward the 3H-2B biomarker at 200 °C. Further, Pd-{010}BiVO4 MDCD sensors enable to detect as low as 0.2 ppm 3H-2B and show best selectivity and stability, and fastest response and recovery. Density functional theory calculations reveal a lower adsorption energy of 3H-2B onto Pd-{010}BiVO4 MDCDs than those of pristine and Pd-BiVO4 MDCDs. The extraordinary Pd-{010}BiVO4 sensing performance is ascribed to the Pd NP-assisted synergetic effect of the preferential adsorption of 3H-2B target molecules, accumulated sensing agent of ionic oxygen species, and concentrated catalysts on the {010} facets. This strategy offers rapid and noninvasive detection of LMs and is thus of great potential in the upcoming Internet of Things.

Two-dimensional transition metal carbides and nitrides (MXenes) demonstrate excellent performances in various field as a result of their unique surface group structures and high electrical conductivity. In this work, we employ a simple strategy of surface group modification to optimize the semiconductor performance of a high-conductivity Ti3C2Tx film for thermoelectric energy conversion. In the process, the hydrothermal treatment with different concentrations, temperatures, and types of alkali solutions has significant effects on the thermoelectric properties of Ti3C2Tx. As a result, the modified free-standing Ti3C2Tx film maintained its originally high conductivity (1652 S cm−1) and the Seebeck coefficient is improved threefold, leading to an optimized power factor of 44.98 μW m−1K−2 at room temperature. This study provides a new method for the development of the thermoelectric performance of highly-conductive MXene films.

Detection of 3-hydroxy-2-butanone (3H-2B) biomarker is a newly emerging and feasible way to monitor Listeria monocytogenes (LMs). Although progress has been made in gas-sensing methodology, the long-term adsorption of the reactive products onto the sensing materials leads to a decrease in stability and selectivity. Herein, we report highly selective and stable 3H-2B sensors, which are developed from a core / shell structure of tin oxide nanowire coated with alumina (SnO2@Al2O3 NCBs), via combining AAO template-confined electrodeposition and wet-chemical etching. As-built sensors exhibit high sensitivity of Ra/Rg = 43.3 to 5 ppm 3H-2B at 120 °C, which is around 6–40 times against other interfering gases. Also, our sensors exhibit excellent stability after 42 days′ evaluation. Furthermore, the sensors can detect as low as 0.1 ppm 3H-2B (Ra/Rg = 2.4; 120 °C), and the sensitivity reach Ra/Rg = 27.2 at 50 °C. Our SnO2@Al2O3 NCBs sensors are endowed with ppb-level detection limit, excellent selectivity and stability at low temperature, which is of great potential in future detection of LMs.

A simple optimizing approach that effectively improves the thermoelectric performance of poly(3,4-ethylenedioxylthiophene):poly(styrenesulfonate) (PEDOT:PSS) films is presented in this paper. The optimizing process is performed by over-dropping a mixture of DMSO/NaOH ethanol solution onto the PEDOT:PSS films, achieving the facile combination of co-solvents effect and dedoping effect. Largely varied electrical conductivity from 837.2 to 0.04 S cm−1 and the Seebeck coefficient from 12.6 to 54.8 μV K−1 are observed by changing the ratios between DMSO and NaOH ethanol solution. Due to the precise control of the dedoping level of PEDOT chains, an optimized power factor of 33.04 μW m−1 K−2 is obtained at the ratio of 10:12 in volume, which is four orders of magnitude higher than that of the pristine film and more than twice the value of DMSO-treated one, simultaneously with the corresponding electrical conductivity and Seebeck coefficient being 598.2 S cm−1 and 23.5 μV K−1, respectively. Based on the measured thermal conductivity of 0.173 W m−1 K−1, the maximum ZT value is calculated to be 0.057 at room temperature.

In the present study, flexible organic poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films were employed as working electrodes for the facile electrodeposition of tellurium (Te). Dendritic Te nanostructures were successfully deposited at a current of 8 mA/cm2 for 700 s at 25 °C, using Na2TeO3 as the Te source and HNO3 as the electrolyte. The phase and morphology of the resulting dendritic nanostructures were characterized by X-ray diffraction, energy-dispersive spectrometry, and scanning electron microscopy. It was found that the deposition temperature had a remarkable influence on the morphologies of the samples. A certain concentration of HNO3 was indispensable in the formation of dendritic Te nanostructures. High deposition current density promoted the formation of dendritic Te nanostructures and the morphologies could be affected by the Na2TeO3 concentration. It is expected that flexible organic PEDOT:PSS film working electrodes may provide a facile and general method for synthesizing materials with a wide array of applications.

As conventional organic solvents present inherent toxicity, deep eutectic solvents (DES) have been considered as excellent candidates due to their green characteristics. In this work, thermoelectric properties enhancement of PEDOT:PSS films is achieved by introducing DES as an additive and post-treatment reagent. Direct addition and post-treatment approaches lead to a maximum Seebeck coefficient of 29.1 μV K−1 and electrical conductivity of 620.6 S cm−1, respectively. In addition, an optimal power factor is obtained by DES post-treatment, reaching up to 24.08 μW m−1 K−2, which is approximately four orders of magnitude higher than the pure PEDOT:PSS. Assuming a thermal conductivity of 0.17 W m−1 K−1, the maximum ZT value is estimated to be 0.042 at 300 K. Further, atomic force microscopy and X-ray photoelectron spectroscopy are performed and suggest that the remarkably enhanced electrical conductivity originates from the removal of the excess insulating PSS and the phase separation between the PEDOT and PSS chains. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 885–892