Abstract The level of CO2 gas sensing is very crucial for applications such as medical and air quality monitoring. The conventional metal oxide-based CO2 sensors are sensitive but they need additional excitation like high temperature to be operated at room temperature. In this study, the effect of reduction time on the surface functional groups of the graphene-based sensing layer is investigated to achieve high performance of CO2 gas sensors to be operated at room temperature. Five reduction times (20, 30, 40, 50, 60 min) are examined to synthesize reduced graphene oxide (rGO) from GO precursor material using green reducing agent ascorbic acid. The structural and morphological properties of rGO-based ArGO samples are investigated using FTIR, Raman, and SEM characterization techniques exhibiting the layered, wrinkled structure with apparent folds on the ArGO thin film surface. The highest and the lowest number of oxygen functional groups are shown by the ArGO20 and ArGO60 thin films, respectively. The electrical characterization presents the highest sheet resistance of 786 KΩ/sq and the lowest sheet resistance of 103 KΩ/sq for ArGO20 and ArGO60 thin films, respectively. Five sensors are fabricated following the reduction time to detect the CO2 gas at room temperature. Among them, the ArGO40 sensor demonstrated optimum sensing response towards CO2 gas with high sensitivity, repeatability, selectivity, and long-term stability, revealing that the reduction time of 40 min is optimum to synthesize functionalized graphene sensing material for CO2 detection.

Abstract Hydrogel-based treatment strategies have proven their significance in the field of drug delivery, wound healing, and tissue scaffolds, offering significant advantages over conventional treatment methods. The present study attempts to assess the hydrogel formation capability of a biopolymer, bovine serum albumin(BSA), without the addition of any crosslinker agents. Next, the in-situ synthesis of silver (Ag) nanoparticles into the hydrogel was explored at two different concentrations of Ag as BSA + 5mM AgNPs(BSA5) and BSA + 10mM AgNPs(BSA10). The thermally aggregated BSA+Ag hydrogels exhibited excellent gel consistency with the successful formation of Ag nanoparticles. The incorporation of Ag nanoparticles(AgNPs) into the BSA hydrogel matrix was confirmed via the peaks obtained through Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. In FTIR, prominent redshifts (when compared with control BSA without Ag incorporation) suggested the interaction of peptide bonds of BSA with the surface of AgNPs, whereas the XRD analysis showed the presence of AgNPs in two distinct phases, i.e., Ag₂O and AgO. Field emission scanning electron microscopy(FESEM) revealed random distribution and irregular shapes of the synthesized AgNPs, with an average size of particles being 67 ± 20 nm and 62 ± 21 nm in BSA5 and BSA10, respectively. Moreover, the integration of AgNPs within the BSA hydrogel matrix tuned the hydrophobicity, swelling ratio, and rheological properties. The hydrogel became hydrophobic in the presence of nanoparticles, which, in turn, reduced the swelling ratio. The nanoparticles significantly enhanced the critical stress threshold for the hydrogel from 6.2 to 175 Pa. Antibacterial tests confirmed the broad-spectrum activity against pathogenic gram-positive and gram-negative bacteria in a dose-dependent manner. The cytotoxicity analysis of the synthesized BSA+Ag hydrogel exhibited over 90% cell viability, highlighting excellent biocompatibility. With effective antibacterial properties and low toxicity, the prepared BSA + Ag hydrogels highlighted their suitability for future biomedical applications.

Abstract The internalization of cerium oxide nanoparticles (CeOx NPs) in articular cartilage presents a novel approach to enhance imaging modalities for monitoring osteoarthritis (OA). This study introduces a bimodal cerium oxide-based nano-contrast agent synthesized via a one-step combustion method, aimed at addressing the limitations of earlier synthesis techniques that lacked dual functional properties for bioimaging. The combustion method produces high-yield nanoparticles that exhibit exceptional X-ray attenuation and redox properties, while also enhanced optical characteristics due to quench annealing processes. CeOx NPs quench annealed at 700 °C (C7 NPs) were identified as effective bimodal contrast agents for cartilage imaging. Characterization of C7 NPs revealed distinct fluorescence emissions: greenish-blue (λem = 381 nm) and yellowish-pink (λem = 406 and 454 nm) under UV-C and UV-A excitation, indicating efficient down-conversion due to their unique size and energy band structures. The X-ray attenuation properties were assessed using tissue-mimicking phantoms, demonstrating values between 502 and 783 HU·mL/mg at low X-ray tube voltages, utilizing a custom-built benchtop micro-CT system. Ex vivo optical imaging conducted on goat articular cartilage tissues confirmed the effective internalization of C7 NPs (~20 nm) within the transitional zone. This study is the first to report the internalization of combustion-synthesized CeOx NPs in goat articular cartilage explants, underscoring their potential as bimodal agents for X-ray and optical imaging in articular cartilage tracking.

Abstract This study presents the synthesis and characterization of MXene/Li4Mn5O12 nanocomposite electrocatalysts for enhanced oxygen evolution reaction (OER) performance. Through a systematic synthesis approach, we successfully integrated Ti3C2Tx MXene with Li4Mn5O12 in varying compositions. The optimized MLMO50 nanocomposite demonstrated exceptional electrocatalytic activity, requiring only 282 mV overpotential to achieve 10 mA cm−2 current density, significantly outperforming pristine MXene (415 mV) and Li4Mn5O12 (380 mV). The composite exhibited a favorable Tafel slope of 97 mV dec−1 and remarkably low charge transfer resistance of 116.4 Ω, indicating enhanced reaction kinetics. Comprehensive characterization using XRD, ATR-FTIR, FESEM, and XPS confirmed the successful synthesis and revealed the intimate interfacial interaction between MXene sheets and Li4Mn5O12. The MLMO50 catalyst showed excellent stability, maintaining performance over 3000 consecutive cycles with minimal overpotential shift (13.68 mV) and demonstrating robust durability during 15 h chronoamperometry testing. This work provides valuable insights into designing efficient composite electrocatalysts for clean energy applications.

Abstract Metal-assisted chemical etching of silicon, especially in the vapour phase, is a highly promising technique for fabricating nanostructures with high aspect ratios. Here, a nanoscale pattern of x-ray zone plates written by electron beam lithography works as a mould for Pt electroplating on a Au seed layer to realise a nanostructured AuPt bilayer pattern on a silicon substrate. Our approach shows that the silicon etching induced by the electroplated catalyst occurs in a vapour of HF and oxygen, producing nanostructures with feature sizes as small as 10 nm, demonstrating that this catalyst synthesis method is suitable for vapour-based metal assisted chemical etching.

Abstract Reducing the high recombination rate and the band gap of titania is vital and valuable for improving its photocatalytic activity. Herein, anatase (A) nanoslice and amido-grafted graphene oxide (AGO) nanocomposite with an armor structure were designed and prepared by a solvothermal method, in which the formation of the armor structure and nitrogen (N) doping into A nanoslice were carried out in one-pot successfully. The characterization results of the nanocomposites show that N doped A nanoslices with an average size of 7.8 nm and dominant {001} facets are distributed uniformly on the surface of AGO. The photocatalytic activity of the AGO-A nanocomposite is significantly enhanced by the combination of A nanoslice with AGO. Typically, the reaction rate constant of the nanocomposite is 3.34 times higher than that of A nanoslice. These can be ascribed to the synergistic effects among the armor structure, A nanoslice with dominant {001} facets, enhanced adsorption ability by AGO, N doped A nanoslice and excited electron transfer from A nanoslice to AGO. Furthermore, a mechanism on the enhancement of the photocatalytic activity of the nanocomposite is proposed. These provide new insights for designing and preparing the nanocomposite photocatalysts with novel structure and enhanced activity.

Abstract The temperature-dependent electrical behavior of an environmentally friendly, symmetric carbon-based supercapacitor with a gelatin-based hydrogel electrolyte containing acetate salt has been investigated. In addition to the electrolyte, the electrodes have been fabricated using sustainable components, including chitosan as a binder and activated carbon derived from coconut shells. To assess the impact of temperature on the electrochemical properties of the fabricated devices and overall performance, experimental measurements have been conducted over a temperature range of 277 K (4 °C) to 313 K (40 °C). These included cyclic voltammetry, galvanostatic charge/discharge, and impedance spectroscopy. The findings indicate that higher temperatures markedly augment the charge storage capacity and diminish the series resistance of the device. Within the tested temperature range, the supercapacitor exhibits a positive temperature coefficient of capacitance, ranging from 0.6% K−1 at 10 mV s−1 to 1.3% K−1 at 500 mV s−1. The charge storage mechanism of the supercapacitor involves both faradaic and double-layer contributions, with pseudocapacitance becoming more dominant at higher temperatures. At 305 K, near the gelation point of the hydrogel, ionic conductivity increases, leading to enhanced overall performance. Specifically, the specific energy density increases by approximately 50%, while the specific power density rises by about 7%. Furthermore, the series resistance decreases from 2.8 Ω to 0.3 Ω, representing a 90% reduction compared to its initial value.