The CdS nanowires–reduced graphene oxide nanocomposites (CdS NWs–RGO NCs) combining one-dimensional (1-D) with two-dimensional (2-D) structures are successfully synthesized by a simple and efficient electrostatic self-assembly method, followed by a hydrothermal reduction process. The probe reactions for photocatalytic selective reduction of aromatic nitro organics in water under visible light irradiation are utilized to evaluate the photoactivity of the as-prepared CdS NWs–RGO NCs. The CdS NWs–RGO NCs exhibit significantly enhanced photoactivity as compared with the CdS nanowires (CdS NWs). The addition of RGO into the matrix of CdS NWs in a controlled manner is able to efficiently enhance the lifetime and transfer of photogenerated charge carriers from CdS NWs under visible light irradiation. Furthermore, the presence of RGO also improves the adsorption capacity of CdS NWs–RGO NCs toward aromatic nitro organics. These two primary factors result in the drastic photoactivity improvement of CdS NWs–RGO NCs toward selective reduction of nitro organics to the corresponding amino organics in water under visible light irradiation. In addition, the possible photocatalytic reaction mechanism is proposed. It is hoped that our work could not only offer useful information on the fabrication of various specific 1-D semiconductor–2-D RGO nanocomposites but also open a new window of such 1-D semiconductor–2-D RGO nanocomposites as visible light photocatalyst in the promising field of selective organic transformations.
A series of cadmium sulfide–graphene (CdS–GR) nanocomposites with different weight addition ratios of graphene (GR) have been synthesized via a facile one-step hydrothermal approach, during which the formation of CdS nanoparticles and the reduction of graphene oxide (GO) occur simultaneously. X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), field-emission scanning electron microscopy (FE-SEM), transmission scanning electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), nitrogen adsorption–desorption, photoluminescence spectra (PL), and electron spin resonance spectra (ESR) are employed to determine the properties of the samples. It is found that the CdS nanoparticles evenly overspread on the graphene scaffold, and the properties of the samples, including morphology, pore structure, optical, and electronic nature, are able to be tuned by the addition of GR as compared with blank-CdS prepared in the absence of GR. The photocatalytic activities of the as-prepared CdS–GR nanocomposites are evaluated by selective oxidation of a range of alcohols under mild conditions. To our best knowledge, it is the first time to use CdS–GR nanocomposites as visible light photocatalyst for selective organic transformation. Our results demonstrate that the as-prepared CdS–GR nanocomposites can serve as a promising visible-light-driven photocatalyst for selective oxidation of alcohols to corresponding aldehydes. The high photoactivity of CdS–GR can be ascribed to the integrative effect of enhanced light absorption intensity, high electron conductivity of GR, and its significant influence on the morphology and structure of the samples. It is hoped that our current work could widen the application of CdS–GR nanocomposites and open promising prospects for the utilization of GR-based semiconductor nanocomposites as visible light photocatalyst for selective organic transformations.
Here, we put forward an effective strategy to regulate the interface structure of carbon nanotubes/polyaniline (CNTs/PANI) composite films and improve their thermoelectric (TE) properties by sequential dedoping-redoping treatment. Dedoping induces conductive resistance-undoped PANI to enhance the energy barrier between CNTs and PANI, leading to a greatly increased Seebeck coefficient and deteriorated conductivity. Subsequently, upon the redoping process, the electrical conductivity is dramatically improved owing to the generated conductive PANI chains, while Seebeck coefficient is maintained at 90% of the dedoped composites. This yields a significantly improved power factor of 407 μW m–1 K–2 from the as-prepared composites (234 μW m–1 K–2), which is the highest value among those of all the reported CNTs/PANI composites. The outstanding TE performanceis probably ascribed to the multiple interface structure of the PANI composite generated from incomplete dedoping and redoping processes, contributing to the enhanced carrier-filtering effect to retain a relatively high Seebeck coefficient and efficient charge transport to improve conductivity. Furthermore, the flexible TE device generates a high power of 1.5 μW at ΔT = 50 K, demonstrating the applicability of this composite for energy-harvesting electronic devices.
The impact of PM2.5 on the environment and human health has garnered significant attention. While research on PM2.5 composition is increasing, fewer studies have focused on how dusty conditions in a special region affect the PM2.5 composition. This region’s unique environmental conditions, characterized by frequent dust events, complicate air quality management. The study investigates the seasonal distribution of inorganic elements in the PM2.5 under both dusty and non-dusty conditions through systematic sampling. Selective screening methods identified key pollutant elements, and a respiratory system model was developed to examine their diffusion and deposition patterns in the upper respiratory tract. Key findings reveal that inorganic element concentrations in the PM2.5 follow consistent seasonal trends, with significantly higher levels during dust events compared to non-dusty periods. Crustal elements are dominated in the PM2.5, but non-metallic elements (Cl, S) and metallic/quasi-metallic elements (Mn, Cd, Cr, As, Hg) are also prevalent, likely influenced by anthropogenic activities and industrial emissions. By PCA with human health assessments, six characteristic pollutants were identified: As, Co, Cd, Cr, V, and Mn. Simulations using COMSOL Multiphysics 6.2 software demonstrated distinct behaviors: As tends to concentrate in the posterior regions of the respiratory tract, while Co and Cd exhibit relatively uniform distributions, primarily affecting areas where airflow slows upstream. Cr, V, and Mn show dispersed and uniform patterns. Notably, even during dusty conditions, the concentration of the six pollutants remains relatively low in the different parts of the upper respiratory tract, suggesting minimal immediate health impacts. Our study provides valuable insights into the behavior of inorganic elements in the PM2.5 and their potential health implications, highlighting the need for further research on the effects of dusty conditions on air quality and public health.
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