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Developing flexible gas sensors based on reduced graphene oxide (rGO) are highly promising for practical application, however, it is still challenging due to the sacrificed solution-processibility and mechanical properties after reduction. To address this issue, we here introduce solution-processed rGO and designed a flexible hydrogen (H 2) film sensor by coupling with Pd nanoclusters as the activators via direct colloids mixing and subsequent vacuum filtration. The rGO/Pd nanocluster film features with structural compactness, surface homogeneity, excellent mechanical flexibility, high-efficiency output, and simplification of compositing method. In addition, the film sensor exhibited high response value, fast behavior and stable sensing behavior towards high-concentration H 2 compared with bare rGO film owing to the significant activation role of Pd nanoclusters with ultrasmall sizes (average size: 3.3 nm). Conclusively, this work provides an ingenious and effective way for the design of rGO-based flexible sensor, and shows promise for efficient portable and cost-effective monitoring of environmentally H 2 gases leaks. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Substitution effects significantly impact the electropolymerization, morphology, properties and electrochemical performance of conducting polymers. In this work, the substitution effects of the electron-withdrawing cyano group on indole polymers are studied in detail. Polyindole (PIn) and its three cyano group substituted derivatives, i.e. , poly(5-cyanoindole) (P5CIn), poly(6-cyanoindole) (P6CIn), and poly(7-cyanoindole) (P7CIn), are successfully electrosynthesized in 0.1 M LiClO 4 /acetonitrile, while it is difficult to electrodeposit 4-cyanoindole into polymer due to the steric effects. Scanning electron microscopic images reveal that P5CIn, P6CIn, and P7CIn have nanofiber structures, while PIn has a dense and cracked structure. Furthermore, P5CIn displays the best capacitance performance with a specific capacitance of 493 F g-1 at 2.5 A g-1, and 87.1% capacitance retention after 5000 cycles charge/discharge. A detailed study of cyano-substituted PIn is provided by this work and it also presents a kind of high-performance supercapacitor material. • The substitution effects of cyano group on indole polymers are studied in detail. • Three kinds of polyindoles are successfully electrosynthesized. • The new polymers show excellent supercapacitor performance. [ABSTRACT FROM AUTHOR]

• The morphology of α-Fe 2 O 3 micro-spheres coated with ultrafine particles (MSUPs) is tuned by fluoride ion. • The mechanism of α-Fe 2 O 3 tuned by fluoride ion is discussed. • The α-Fe 2 O 3 MSUPs shows excellent acetone response. In this study, hematite (α -Fe 2 O 3) micro-spheres coated with ultrafine particles (MSUPs) have been obtained for sensitive acetone sensors via first hydrothermal process with NH 4 F as the morphological regulator and then annealing of akaganéite. 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 -Fe 2 O 3 MSUPs with 0.45 M NH 4 F (F0.5) in the precursor solution showed the highest response towards acetone compared to other α -Fe 2 O 3 samples. Our α -Fe 2 O 3 MSUPs sensors have potential in sensitive acetone detection. [ABSTRACT FROM AUTHOR]

Abstract 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 SmMn 2 O 5 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 SmMn 2 O 5 nanostructures was discussed. With respect to the sensing properties to acetone, three sensors prototypes employed with SmMn 2 O 5 NT@NTs, SNFs and PNTs were built and in detail studied by taking SmMn 2 O 5 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 SmMn 2 O 5 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. Graphical abstract fx1 Highlights • Mullite SmMn 2 O 5 solid nanofibers (SNFs), nanotube@tubes and porous nanotubes are firstly synthesized via electrospinning. • The unique shapes of 1D mullite SmMn 2 O 5 are tuned by optimized annealing. • The mullite sensors exhibit fast response and recovery to acetone (3 s and 8 s), for the real-time monitoring. [ABSTRACT FROM AUTHOR]

ZnO@Al 2 O 3 NCBs sensors show excellent response to 3-hydroxy-2-butanone biomarkers for indirectly monitoring Listeria monocytogenes. • ZnO@Al 2 O 3 nanocables are synthesized combined electrodeposition and etching. • The pores are made by optimized etching inside the cable-shell of Al 2 O 3. • ZnO@Al 2 O 3 nanocables are able to detect 3-hydroxy-2-butanone biomarkers. We report zinc oxide (core) coated with alumina (shell) single-shelled nanocables (ZnO@Al 2 O 3 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 Al 2 O 3 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@Al 2 O 3 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@Al 2 O 3 NCBs show excellent selectivity and cyclic stability. Our ZnO@Al 2 O 3 NCBs sensors in future monitoring Listeria monocytogenes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACT 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 [ABSTRACT FROM AUTHOR]

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 3 nanofibers (Li/WO 3 NFs) have been discovered in suppressing the response from interfering gases, while elevating the H 2 S sensing response. Beneficially, the H 2 S response of Li/WO 3 NFs sensor prototype is three times (R a / R g = 64@10 ppm) as high as that of the pristine WO 3 ones (R a / R g = 21@10 ppm) at ~75% relative humidity and 260 °C. Moreover, Li/WO 3 NFs sensor prototype presents the detection limit as low as 100 ppb. Particularly, the Li/WO 3 NFs sensors detect simulated halitosis breath, of which the accuracy is comparable with gas chromatography. Theoretically, the decrease of the responses of Li/WO 3 NFs to interfering gases is ascribed to the enhancement of the adsorption of water molecules by Li dopant. While the improved response to H 2 S is attributed to stronger adsorption of H 2 S and WO 3 and to the increased defect oxygen. The "screening behavior" of Li doped into WO 3 NFs provides a new strategy that might improve the selectivity of other gas sensing. [Display omitted] • The "screening behavior" of lithium are initially discovered. • The "screening blehavior" of lithium in boosting H 2 S selectivity of WO 3 nanofibers. • The gas chromatography testify the sensor's accuracy in detecting simulated H 2 S. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a dynamical problem is considered for an incompressible hyperelastic solid sphere composed of the classical isotropic neo-Hookean material, where the sphere is subjected to a class of periodic step radial tensile loads on its surface. A second-order non-linear ordinary differential equation that describes cavity formation and motion is proposed. The qualitative properties of the solutions of the equation are examined. Correspondingly, under a prescribed constant dead-load, it is proved that a cavity forms in the sphere as the dead-load exceeds a certain critical value and the motion of the formed cavity presents a class of singular periodic oscillations. Under periodic step loads, the existence conditions for periodic oscillation of the formed cavity are determined by using the phase diagrams of the motion equation of cavity. In each section, numerical examples are also carried out. [Copyright &y& Elsevier]

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 (H 2) 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 H 2 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% H 2 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 H 2 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. [Display omitted] • A novel flexible fiber-shaped H 2 sensor (PEDOT:PSS@Pd) was designed. • The fiber sensor possesses excellent mechanical properties and substrate-free. • The sensor displays short response time (19 ± 4 s@4% H 2) at room temperature. • The fiber sensor exhibits steady H 2 sensing behavior at different bending states. [ABSTRACT FROM AUTHOR]

• A novel MXene@Pd CNC film H2 sensor was facilely designed via an all-colloidal solution-based vacuum-filtration process. • The sensor featured with flexibility, lightweight and a compact, glossy surface and it can be tailored in desired size when necessary. • The film sensor displayed fast H2 response at room temperature at either flat or bent states. Rational and smart design of hydrogen (H 2) sensors especially those featured with flexibility and light weight is highly desirable, to meet the requirements for future development of portable H 2 sensors. In this work, we demonstrate a novel paper film H 2 sensor employing Ti 3 C 2 T x 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 H 2 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% H 2. In addition, the MXene@Pd CNC sensor enabled "in-situ-mode" H 2 detection directly along a piece of paper film with desired size. The strong H 2 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. [ABSTRACT FROM AUTHOR]

• SnO 2 @Al 2 O 3 nanocables (NCBs) are developed with burrs shell. • SnO 2 @Al 2 O 3 NCBs detect 3-hydroxy-2-butanone biomarker of Listeria monocytogene. • The SnO 2 @Al 2 O 3 NCBs present highly selective and stable sensing performance. 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 (SnO 2 @Al 2 O 3 NCBs), via combining AAO template-confined electrodeposition and wet-chemical etching. As-built sensors exhibit high sensitivity of R a /R g = 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 (R a /R g = 2.4; 120 °C), and the sensitivity reach R a /R g = 27.2 at 50 °C. Our SnO 2 @Al 2 O 3 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. [ABSTRACT FROM AUTHOR]

• V 2 O 5 /CuO nanostructures are tuned by combined electrospinning and annealing. • The V 2 O 5 /CuO nano-string of pearls (NSPs) are unique in morphology. • The V 2 O 5 /CuO NSPs show improved sensing performance to acetone. Novel hollow structure based on CuO modified V 2 O 5 nano-string of pearls (V 2 O 5 /CuO NSPs) were synthesized via electrospinning technique. The achieved V 2 O 5 /CuO NSPs exhibit interesting shapes of string of pearls, endowed with transparent and hollow structure under TEM observation. The V 2 O 5 /CuO NSPs sensors demonstrated that the sensitivity (R a /R g = 8.8 at 500 ppm) towards acetone was 3.2 times as high as that of pristine V 2 O 5 nanofibers (NFs) (R a /R g = 2.5 at 500 ppm) at 440 °C. The improved sensitivity may be ascribed to the formation of V 2 O 5 /CuO p-n heterojunctions at the interfaces, which elevates the barrier height and enlarges depleted electron region. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ceramic TiB 2 , 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 TiB 2 to drive water splitting, which is less than satisfactory in future hydrogen economy. Herein, conductive polypyrrole (PPy) encapsulating TiB 2 (TiB 2 @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 TiB 2. Beneficially, more improved HER performance has been achieved with the overpotential of 432 mV at 10 mA cm−2, superior to that of pristine TiB 2 (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. [ABSTRACT FROM AUTHOR]

Acetoin (also known as 3-hydroxy-2-butanone) is a metabolic biomarker gas of Listeria monocytogenes (food pathogenic bacteria). Sensitive and selective detection of acetoin biomarker can lead to indirect online monitoring of Listeria monocytogenes, which has attracted much attention in gas sensing field recent years. At present, different from the mature researches towards other VOCs biomarkers, the researches on acetoin gas sensors are newly emerged and still in the infancy. The structure of sensing materials needs to be optimized and the intrinsic sensing mechanism still needs to be further clarified. In order to promote the development of acetoin gas sensors, in this mini-review we present recent advances of acetoin gas sensors based on semiconductor metal oxides (SMOs) for the first time, expound the sensing mechanism, and put forward the research shortcomings and future prospects. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

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/cm for 700 s at 25 °C, using NaTeO as the Te source and HNO 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 HNO 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 NaTeO 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. [ABSTRACT FROM AUTHOR]

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 NaNbO 3 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 NaNbO 3 /Te-NRs composites at room temperature. By optimization, the NaNbO 3 /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 NaNbO 3 effectively improves the environmental stability of Te-NRs due to the formation of interfaces between NaNbO 3 and Te-NRs. This composite strategy proposed a novel approach to develop a promising TE material. This work realized the dramatically enhanced TE performance by compositing NaNbO 3 with Te-NRs. Image 1 • Inorganic salt NaNbO 3 composited Te nanorods were prepared via hydrothermal method. • NaNbO 3 shows great effect on the enhancement of Seebeck coefficient for the composites. • A large power factor was obtained for the as-fabricated NaNbO 3 /Te-NRs composites. • The as-fabricated composites thin slices are air-stable in TE performance. [ABSTRACT FROM AUTHOR]

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 Ti 3 C 2 T x 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 Ti 3 C 2 T x. As a result, the modified free-standing Ti 3 C 2 T x 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. Image 1 • The thermoelectric properties of the terminal groups modified Ti 3 C 2 T x film are systematically studied experimentally. • The Seebeck coefficient of the modified Ti 3 C 2 T x film increases by 3 times due to wider band gap. • The modified Ti 3 C 2 T x film still maintains the hig electrical conductivity (1652 S cm-1). [ABSTRACT FROM AUTHOR]