Self-powered triboelectric nanogenerator sensor for detecting humidity level and monitoring ethanol variation in a simulated exhalation environment

Respiration stands as a vital process reflecting physiological and pathological human health status. Exhaled breath analysis offers a facile, non-invasive, swift, and cost-effective approach for diagnosing and monitoring diseases by detecting concentration changes of specific biomarkers. In this study, we employed Polyethylene oxide/copper (I) oxide composite nanofibers (PCNFs), synthesized via the electrospinning method as the sensing material to measure ethanol levels (1-200 ppm) in an exhaled breath simulator environment. The integrated contact-separation triboelectric nanogenerator was utilized to power the self-powered PCNFs exhaled breath sensor. The PCNFs-based gas sensor demonstrates promising results with values of 0.9 and 3.2 for detecting 5 ppm and 200 ppm ethanol, respectively, in the presence of interfering gas at 90% relative humidity (RH). Notably, the sensor displayed remarkable ethanol selectivity, with ratios of 10:1 to methanol and 25:1 to acetone. Response and recovery times for 200 ppm ethanol at 90 RH% were rapid, at 2.7 s and 5.8 s, respectively. The PCNFs-based exhaled breath sensor demonstrated consistent and stable performance in practical conditions, showcasing its potential for integration into wearable devices. This self-powered breath sensor enabling continuous monitoring of lung cancer symptoms and facilitating compliance checks with legal alcohol consumption limits.

Green synthesize of copper nanoparticles on the cotton fabric as a self-regenerating and high-efficient plasmonic solar evaporator

Harvesting solar energy, as a clean and abundant resource, in the photothermal process, is the winning point of solar steam generation (SSG) systems. Herein, copper plasmonic nanoparticles were synthesized through a green method via red sanders extraction on the cotton fabric as the reducing matrix. The prepared fabrics were analyzed using FESEM, EDS, XRD, PL, Raman, and contact angle. The treated fabric on the stitched PU foam with cotton yarns with bio-inspired jellyfish structure was used for heat localization and water transmission, simultaneously. The evaporation rate, enhancement, and conversion efficiency of the plasmonic SSG were 1.73 kg m-2 h-1, 179%, and ~ 98%, under one sun irradiation, respectively. The quality of the collected water was investigated via induced coupled plasma which presents the proper solar desalination (> 99.83% for filtration of Na+ ion). Regenerating features of the treated fabric along with the simple and cost-effective preparation method promises viable aspects of our system for large-scale applications.

Room temperature and high response ethanol sensor based on two dimensional hybrid nanostructures of WS2/GONRs

Here in this research, room temperature ethanol and humidity sensors were prepared based on two dimensional (2D) hybrid nanostructures of tungsten di-sulfide (WS2) nanosheets and graphene oxide nanoribbons (GONRs) as GOWS. The characterization results based on scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (ESD), Raman spectroscopy and X-ray diffraction (XRD) analysis confirmed the hybrid formations. Ethanol sensing of drop-casted GOWS films on SiO2 substrate indicated increasing in gas response up to 5 and 55 times higher compared to pristine GONRs and WS2 films respectively. The sensing performance of GOWS hybrid nanostructures was investigated in different concentrations of WS2, and the highest response was about 126.5 at 1 ppm of ethanol in 40% relative humidity (R.H.) for WS2/GONRs molar ratio of 10. Flexibility of GOWS was studied on Kapton substrate with bending radius of 1 cm, and the gas response decreased less than 10% after 30th bending cycles. The high response and flexibility of the sensors inspired that GOWS are promising materials for fabrication of wearable gas sensing devices.

A graphene/TiS3 heterojunction for resistive sensing of polar vapors at room temperature

The room temperature polar vapor sensing behavior of a graphene-TiS₃ heterojunction material and TiS₃ nanoribbons is described. The nanoribbons were synthesized via chemical vapor transport (CVT) and their structure was investigated by scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman and Fourier transform infrared spectroscopies. The gas sensing performance was assessed by following the changes in their resistivities. Sensing devices were fabricated with gold contacts and with lithographically patterned graphene (Gr) electrodes in a heterojunction Gr-TiS₃-Gr. The gold contacted TiS₃ device has a rather linear I-V behavior while the Gr-TiS₃-Gr heterojunction forms a contact with a higher Schottky barrier (250 meV). The I-V responses of the sensors were recorded at room temperature at a relative humidity of 55% and for different ethanol vapor concentrations (varying from 2 to 20 ppm). The plots indicate an increase in the resistance of Gr-TiS₃-Gr due to adsorption of water and ethanol with a relatively high sensing response (~495% at 2 ppm). The results reveal that stable responses to 2 ppm concentrations of ethanol are achieved at room temperature. The response and recovery times are around 8 s and 72 s, respectively. Weaker responses are obtained for methanol and acetone. Graphical abstract Schematic representation of resistance sensor for detection of low concentration of ethanol vapor. The graphene and TiS₃ nanoribbons were synthesized using chemical vapor deposition and chemical vapor transport technique respectively. The 2D graphene/TiS₃ heterojunction device was fabricated to make a high response sensor due to their synergy effect.

Optimization of CuIn1-XGaXS2 Nanoparticles and Their Application in the Hole-Transporting Layer of Highly Efficient and Stable Mixed-Halide Perovskite Solar Cells

Inorganic hole-transport materials (HTMs) have been frequently applied in perovskite solar cells (PSCs) and are a promising solution to improve the poor stability of PSCs. In this study, we investigate solution-processed copper indium gallium disulfide (CIGS) nanocrystals (NCs) as a dopant-free inorganic HTM in n-i-p type PSCs. Moreover, Cs_0.05(MA_0.17-FA_0.83)_0.95Pb(I_0.83Br_0.17)₃ mixed-halide perovskite with proper crystalline quality and long-time stability was utilized as the light-absorbing layer under ambient conditions. To optimize the cell performance and better charge extraction from the perovskite layer, the Ga concentration in the Cu(In_1-XGa_X)S₂ composition was changed, and the X value was altered between 0.0 and 0.75. It was shown that the CIGS band gap enhances with increasing Ga content; thus, with tunable band gaps and engineering of the energy level alignment, a better collection of photogenerated holes and a reduced electron-hole recombination rate could be achieved. The maximum power conversion efficiency of 15.6% was obtained for the PSC with Cu(In_0.5Ga_0.5)S₂ hole-transport layer composition, which is the highest efficiency reported so far for CIGS-based dopant-free PSCs. This value is very close to the efficiency of devices fabricated with doped spiro-OMeTAD as an organic HTM. Additionally, the stability of nonencapsulated PSCs was studied, and CIGS-based devices demonstrated 70% retention after 90 days of aging in the dark and in 50% relative humidity conditions. This result is quite better than the similar measurements for the doped spiro-OMeTAD-based devices.

Computational investigation of gas detection and selectivity on TiS3 nanoflakes supported by experimental evidence

Titanium trisulfide (TiS3), a transition metal chalcogenide, bears the potential to replace silicon, when taking the form of nanoflakes, due to its favorable band gap and optical response. In this paper, we investigate the response of TiS3 nanoflakes to gas detection through a careful quantum computational approach and a few succinct measurements. The computations are benchmarked and compared with a relevant experiment at each step, where their results/conclusions are discussed. The most stable surface of TiS3 particles is determined as (001), in agreement with the literature. The adsorption of 5 gas molecules is characterized through formulating and estimating their adsorption intensity values, rather than using singled-out values of binding energies. This formulation, which is rooted in a statistical view of the gas adsorption process, distinguishes H2 and CH4 molecules from H2O and O2 explicitly and unambiguously through comparing their adsorption profiles. The difference in the adsorption intensities thus predicts and elucidates the difference in the sensing behaviour of TiS3 particles. This work suggests that the computationally obtained profile for the adsorption spectrum of gas molecules serves as a tool/criterion to predict the selectivity of their detection by TiS3.

Hydrogen sensing properties of nanocomposite graphene oxide/Co-based metal organic frameworks (Co-MOFs@GO)

This paper reports on hydrogen sensing based graphene oxide hybrid with Co-based metal organic frameworks (Co-MOFs@GO) prepared by the hydrothermal process. The texture and morphology of the hybrid were characterized by powder x-ray diffraction, scanning electron microscopy and Brunauer-Emmett-Teller analysis. Porous flower like structures assembled from Co-MOFs and GO flakes with sufficient specific surface area are obtained, which are ideal for gas molecules diffusion and interactions. Sensing performance of Co-MOFs@GO were tested and also improved by sputtering platinum (Pt) as a catalyst. The Pt-sputtered Co-MOFs@GO show outstanding hydrogen resistive-sensing with response and recovery times below 12 s at 15 °C. Also, they show stable, repeatable and selective responses to the target gas which make it suitable for the development of a high performance hydrogen sensor.

Hierarchical core–shell structure of ZnO nanotube/MnO2 nanosheet arrays on a 3D graphene network as a high performance biosensing platform

A hierarchical core–shell structure composed of ZnO nanotubes/MnO₂ nanosheets was fabricated via a two-step electrochemical deposition procedure on the surface of a 3D graphene network (3DGN) as a free-standing monolithic electrode.

Voltammetric studies of Azathioprine on the surface of graphite electrode modified with graphene nanosheets decorated with Ag nanoparticles

By using graphene nanosheets decorated with Ag nanoparticles (AgNPs-G) as an effective approach for the surface modification of pyrolytic graphite electrode (PGE), a sensing platform was fabricated for the sensitive voltammetric determination of Azathioprine (Aza). The prepared AgNPs-G nanosheets were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis and Raman spectroscopy techniques. The electrochemical behavior of Aza was investigated by means of cyclic voltammetry. Comparing to the bare PGE, a remarkable enhancement was observed in the response characteristics of Aza on the surface of the modified electrode (AgNPs-G/PGE) as well as a noticeable decrease in its reduction overpotential. These results can be attributed to the incredible enlargement in the microscopic surface area of the electrode due to the presence of graphene nanosheets together with strong adsorption of Aza on its surface. The effect of experimental parameters such as accumulation time, the amount of modifier suspension and pH of the supporting electrolyte were also optimized toward obtaining the maximum sensitivity. Under the optimum conditions, the calibration curve studies demonstrated that the peak current increased linearly with Aza concentrations in the range of 7 × 10(-7) to 1 × 10(-4)mol L(-1) with the detection limit of 68 nM. Further experiments revealed that the modified electrode can be successfully applied for the accurate determination of Aza in pharmaceutical preparations.

Comparison of trap-state distribution and carrier transport in nanotubular and nanoparticulate TiO(2) electrodes for dye-sensitized solar cells

Dye-sensitized solar cells (DSCs) with nanotubular TiO(2) electrodes of varying thicknesses are compared to DSCs based on conventional nanoparticulate electrodes. Despite the higher degree of order in one-dimensional nanotubular electrodes, electron transport times and diffusion coefficients, determined under short-circuit conditions, are comparable to those of nanoparticulate electrodes. The quasi-Fermi level, however, is much lower in the nanotubes, suggesting a lower concentration of conduction band electrons. This provides evidence for a much higher diffusion coefficient for conduction band electrons in nanotubes than in nanoparticulate films. The electron lifetime and the diffusion length are significantly longer in nanotubular TiO(2) electrodes than in nanoparticulate films. Nanotubular electrodes have a trap distribution that differs significantly from nanoparticulate electrodes; they possess relatively deeper traps and have a characteristic energy of the exponential distribution that is more than two times that of nanoparticulate electrodes.