Search Results (10,443)

The buckling-like mechanical behavior of functionally graded graphene platelet-reinforced composite (FG-GPLRC) structures is increasingly attracting research attention. However, buckling behavior has previously been studied separately as thermal buckling and mechanical buckling. In this context, this study investigates the buckling behavior of FG-GPLRC plates under combined thermal and mechanical loads. The coupled buckling problem is formulated according to the minimum potential energy theorem using first-order shear deformation theory (FSDT). In addition, the problem is approximated by the 2-D natural element method (NEM), and the resulting coupled eigen matrix equations are derived to compute the critical buckling temperature rise (CBTR) and the mechanical buckling load. The developed numerical method can solve thermal, mechanical, and coupled thermo-mechanical buckling problems, and its reliability is examined through convergence and benchmark tests. Using the developed numerical method, the buckling behavior of FG-GPLRC plates under thermal and mechanical buckling loads is examined in depth with respect to the key parameters. In addition, a comparison with functionally graded CNT-reinforced composite (FG-CNTRC) plates is also presented. Full article

Mesoscopic billiard systems for electrons and light, realized as quantum dots or optical microcavities, have enriched the fields of quantum chaos and nonlinear dynamics not only by enlarging the class of model systems, but also by providing access to their experimental realization. Here, we add yet another system class, two-dimensional billiards with anisotropies. One example is the anisotropic dispersion relation relevant in bilayer graphene known as trigonal warping, and another is the birefringent closed optical disk cavity. We demonstrate that the established concept of ray–wave correspondence also provides useful insight for anisotropic billiard systems. First, we approach the dynamics of the anisotropic disk from the ray-tracing side that takes the anisotropy in momentum space into account, based on the non-spherical index ellipsoid. Second, we use transformation optics to solve the wave problem and find the resonances to be those of the isotropic elliptical cavity. We illustrate ray–wave correspondence and mark differences in the description of optical and electronic anisotropic systems. Full article

A novel bacterial cellulose (BC)-based composite hydrogel with graphene quantum dots (BC-GQDs) was developed for photodynamic therapy using blue and green light (BC-GQD_blue and BC-GQD_green) to target pathogenic bacterial biofilms. This approach aims to address complications in treating nosocomial infections and combating multi-drug-resistant organisms. Short-term illumination (30 min) of both BC-GQD samples led to singlet oxygen production and a reduction in pathogenic biofilms. Significant antibiofilm activity (>50% reduction) was achieved against Staphylococcus aureus and Escherichia coli with BC-GQD_green, and against Pseudomonas aeruginosa with BC-GQD_blue. Atomic force microscopy images revealed a substantial decrease in biofilm mass, accompanied by changes in surface roughness and area, further confirming the antibiofilm efficacy of BC-GQDs under blue and green light, without any observed chemical alterations. Additionally, the biocompatibility of BC-GQDs was demonstrated with human gingival fibroblasts (HGFs). For the first time, in vitro studies explored the visible light-induced potential of BC-GQD composites to promote wound healing processes, showing increased migratory potential and the upregulation of eNOS and MMP9 gene expressions in HGFs. Chemical characterization revealed a 70 nm upshift in the photoluminescence emission spectra compared to the excitation wavelength. These novel photoactive BC-GQD hydrogel composites show great promise as effective agents for wound healing regeneration and infection management. Full article

Green energy harvesting is one of the most important and evolving research areas. Solar energy is an inexhaustible and environmentally friendly energy source, and phase change materials (PCMs) are capable of improving photovoltaic devices by heat storage and could have a positive impact on sustainable energy utilization. This review presents the current state of the art on PCMs and their modifications for electrothermal energy conversion applications. The paper focuses on PCMs characteristics and their properties required for electrothermal energy conversion systems, and it presents various methods of PCMs modification intended to obtain multifunctional systems based on these materials as well as electrothermal conversion and energy storage mechanisms and selected applications. The goal of this review is to present different types of PCM modifications to obtain multifunctional PCM-based systems for electrothermal energy conversion. Full article

Maintenance and service are important tasks for any industrial enterprise. This article presents a methodology for technical maintenance that employs a smart glove equipped with tactile sensors, an electronic unit responsible for processing and transmitting information, and a unit designed to interpret the results. Tactile sensors are graphene-based. The main idea of the method is to use sensors to record the strength of contact between the operator’s fingertips and the equipment. Afterwards, these values are recorded, transferred to processing, and the output signal from the sensors is compared with the steps of various repair works. The work contains methods for creating each component of the glove, their effectiveness is evaluated, and experiments are described to assess the feasibility of using the developed device for the maintenance and repair of equipment. The device discussed in this work is a wearable device. The obtained results demonstrate the applicability of the smart glove for equipment maintenance and repair. Full article

In this work, an amino-functionalized graphene oxide/polypyrrole (AMGO/PPy) composite-based novel sensing platform was established to monitor lead ions (Pb²⁺) at high sensitivity. AMGO was synthesized through a hydrothermal process and later formed a composite with PPy at varying concentrations. A physicochemical investigation of the synthesized materials was carried out using various characterization tools, while the electrochemical properties were examined by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) methods. The AMGO/PPy composite was deposited on a glassy carbon electrode (GCE), which was used for the real-time electrochemical detection of Pb²⁺. The AMGO/PPy sensor exhibited lower limits of detection (LOD) of 0.91 nM. In addition, the developed Pb²⁺ sensor exhibited excellent reproducibility, repeatability, selectivity, sensitivity, and long-term stability for 25 days. The AMGO/PPy composite emerges as a ground-breaking material for the electrochemical detection of Pb²⁺, holding significant potential for environmental monitoring and the protection of human health. Full article

The objective of this study was to investigate the distribution of pyrolysis products and the chemical reaction kinetics of a novel composite, GO@CL-20. The GO@CL-20 composite powder was synthesized using a solvent–non-solvent method. The thermal decomposition process of GO@CL-20 was analyzed through thermogravimetric differential scanning calorimetry (TG-DSC). The results indicate that the incorporation of graphene oxide (GO) reduces the activation energy of the sample, thereby catalyzing the thermal decomposition process of the complex. Subsequently, single pulse shock tube experiments were conducted to assess ignition delay time distribution, from which corresponding data on pyrolysis product distribution for GO@CL-20 were obtained. The findings regarding ignition delay times demonstrate that adding GO decreases the energy within the complex system and mitigates its reactivity, consequently prolonging ignition delay times. An important carbon and nitrogen molecule, C₂N₂, was identified in the pyrolysis product distribution; notably, its yield increased progressively with higher concentrations of GO. Finally, mass transfer characteristics and sensitivity analyses for GO@CL-20 samples were performed using CHEMKIN software to preliminarily determine pyrolysis reaction pathways. The results reveal that incorporating GO can significantly alter the thermal decomposition behavior of the entire system; moreover, C₂N₂ exhibits a high cleavage rate along this reaction pathway—findings that align well with experimental observations. This study aims to enhance understanding of CL-20 and GO reaction kinetics—materials with extensive applications in military operations as well as aviation and aerospace—and provides valuable insights for propellant development. Full article

Graphene oxide (GO) and reduced graphene oxides (RGOs) show intrinsic electrocatalytic activity towards the electrocatalytic reduction of H₂O₂. Combining these materials with gold nanoparticles results in highly sensitive electrodes, with sensitivity in the nanomolar range because the electrocatalytic properties of GO and nanoparticles are synergistically enhanced. Understanding the factors influencing such synergy is crucial to designing novel catalytically active materials. In this contribution, we study gold nanostructures having shapes of nanospheres (AuNSs), nanourchins (AuNUs), and nanobowls (AuNBs) combined with GO or electrochemically reduced graphene oxide (ERGO). We investigate the amperometric responses of the hybrid layers to H₂O₂. The AuNUs show the highest sensitivity compared to AuNBs and AuNSs. All materials are characterized by electron microscopy and Raman spectroscopy. Raman spectra are deconvoluted by fitting them with five components in th e1000–1800 cm⁻¹ range (D*, D, D”, G, and D′). The interaction between nanoparticles and GO is visualized by the relative intensities of Raman bands (ID/IG) and other parameters in the Raman spectra, like various D”, D* band positions and intensities. The ID/IG parameter is linearly correlated with the sensitivity (R² = 0.97), suggesting that defects in the graphene structure are significant factors influencing the electrocatalytic H₂O₂ reduction. Full article

A cutting-edge biosensor has been developed to monitor blood glucose levels, which is particularly vital for people with diabetes. This advanced technology uses a miniaturized and membraneless enzymatic fuel cell (EFC) as a compact electrical reader for rapid on-site diabetes diagnosis. Using disposable screen-printed gold electrodes (Au-SPE) modified with the enzyme glucose oxidase (GOx), the biosensor enables the oxidation of glucose at both the anode (counter electrode) and cathode (working electrode) of the EFC. The cathode contains graphene oxide/Prussian blue nanocubes (GO/PBNCs), while the anode uses a biographene layer. Both electrodes were modified with GOx by electrostatic/hydrogen bonding the enzyme to the modified electrodes surface. Individual evaluations of each electrode system emphasized their effectiveness. The integration of both electrodes resulted in an EFC that can generate an output power of approximately 1.8 μW/cm² at a glucose concentration of 5 mmol/L, which is very close to physiological conditions (3.8 to 6.9 mmol/L). This technology represents a significant advance and promises fully autonomous diagnostic devices suitable for a wide range of analytes. It paves the way for diagnostics everywhere and marks a fundamental shift in point-of-care (PoC) diagnostics. Full article

Achieving high energy density while maintaining high power density and long cycle life in supercapacitors, particularly in supercapatteries (SCs), through a thermally stable, greener ionic liquid approach remains a significant challenge for an advanced energy storage application. In this work, we prepared high conductive and high charge storage capability bimetallic transition metal molybdate [Ag₂Mo₂O₇ (AgM)], synergistic with reduced graphene oxide (rGO) coated on nickel foam (AgM/rGO/NF). The physio-chemical characterization revealed a ball-like cluster morphology wrapped in rGO nanosheets and a spinel-type cubic structure using scanning electron microscopy (FE-SEM) displays and X-ray diffraction (XRD) analyses. Further, the electrochemical performance of AgM/rGO/NF electrode achieved a remarkable specific C_sp value of 573.63 F/g at a current density of 1.0 A/g in 3 M KOH electrolyte. An asymmetric SCs (ASCs) device was fabricated using AgM/rGO/NF as the positive and rGO as the negative electrodes, achieving a wide potential window of 1.3 V. The ASC demonstrated an energy density of 16.71 Wh/kg at a power density of 642.98 W/kg, highlighting AgM/rGO/NF’s potential as an advanced electrode material for energy storage applications. Full article

Based on the angular spectrum expansion, the spatial Goos–Hänchen (GH) shift of an Airy vortex beam reflected from the graphene/hexagonal boron nitride (hBN) heterostructure is investigated analytically. The influences of graphene/hBN heterostructure parameters and incident Airy vortex beam parameters on the spatial GH shifts are analyzed in detail. It is found that the position of the Brewster angle mainly depends on the relaxation time and hBN thickness of the heterostructure, and the magnitude and sign of GH shifts at a certain Brewster angle can be controlled effectively by tuning the Fermi energy and layer numbers of graphene. Moreover, the variation in the GH shifts with the Fermi energy and hBN thickness exhibits hyperbolicity at the Brewster angle, similar to the variation in the permittivity of hBN. For the incident beam, the vortex position and the decay factor in the x direction have a great effect on the GH shifts. The influence of the vortex position on the GH shift is related to the distance of the vortex position from the origin point. The magnitude of the GH shift decreases as the decay factor in the x direction increases, and a large GH shift can be obtained by adjusting the decay factor in the x direction. Finally, the application of spatial GH shift in sensing is discussed. The results presented here may provide some supports to the design of optical switch and optical sensor. Full article

This study investigates the humidity-sensing properties of two semiconductor metal oxide (SMO)-reduced graphene oxide (RGO) nanocomposites: TiO₂/RGO and α-Fe₂O₃/RGO, at room temperature. Both nanocomposites are synthesized via hydrothermal methods and coated onto printed circuit board (PCB) interdigital electrodes to construct humidity sensors. The surface morphology and crystallographic structure of the materials are characterized using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The sensors are tested across a humidity range of 11%RH to 97%RH, and the impedance is measured over a frequency range of 1 Hz to 1 MHz. The results show that both TiO₂/RGO and α-Fe₂O₃/RGO exhibit favorable humidity-sensing performance at room temperature. The sensitivity and humidity hysteresis of TiO₂/RGO are 12.2 MΩ/%RH and 3.811%RH, respectively, while those of α-Fe₂O₃/RGO are 0.826 MΩ/%RH and 8.229%RH. The response and recovery times of TiO₂/RGO are 72 s and 99 s, respectively, while those of α-Fe₂O₃/RGO are 48 s and 54 s. Both sensors demonstrate good repeatability and stability. These findings suggest that SMO/RGO nanocomposites are promising materials for the development of low-cost, high-sensitivity, and stable humidity sensors. Full article

Mycotoxins are highly toxic secondary metabolites that can pose a serious threat to food safety, human health, and the environment. As a promising detoxification method, photocatalysis has shown great potential for mycotoxin degradation due to its high efficiency, low cost, and green advantages. Heterogeneous photocatalysis using a semiconductor as a mediator is now regarded as an effective approach for mycotoxin degradation. The aim of this study was to review the recent developments, mainly in the photocatalytic degradation of mycotoxin (e.g., AFB1, FB1, DON, and ZEN). The principle, feasibility, and main semiconducting catalysts of mycotoxin photodegradation are introduced and discussed, including metal oxides (transition, noble, and rare earth metals), carbons (graphene, carbon nitride, and biochar) and other composites (MOFs and LDHs). This review will contribute to the development of semiconductor photocatalysts and photocatalytic degradation for mycotoxins decontamination. Full article

Azulene-based polycyclic hydrocarbons have garnered much attention as potential materials for organic optoelectronic devices and as molecular models for graphene nanosheets with structural defects. Although various methods for ring fusions to an azulene core have been established for ring fusions to an azulene core, efficient synthetic methodologies for ortho- and peri-fusion to an azulene core are still lacking, which hinders the investigation of the effect of the ortho- and peri-fusion on the electronic properties of the embedded azulene core. Herein, we describe the synthesis and characterization of quinoxaline-fused cyclopenta[cd]azulene 4 as a new ortho- and peri-fused azulene derivative. The target molecule 4 was successfully synthesized in four steps from 4-methylazulene. The ring annulation decreased the lowest excitation energy compared with that of azulene and its structural isomer 5 and led to multiple reversible reduction processes. Characterization of the molecular geometry and optoelectronic properties of 4 revealed that the embedded azulene core preserves its original aromaticity, while the fused quinoxaline acts as a nucleophilic and basic site. These features suggest that 4 could serve as a metal ligand, a near-infrared absorber, and a component in organic functional devices. Full article

Infrared (IR) sensors are widely used in various applications due to their ability to detect infrared radiation. Currently, infrared detector technology is in its third generation and faces enormous challenges. IR radiation propagation is categorized into distinct transmission windows with the most intriguing aspects of thermal imaging being mid-wave infrared (MWIR) and long-wave infrared (LWIR). Infrared detectors for thermal imaging have many uses in industrial applications, security, search and rescue, surveillance, medical, research, meteorology, climatology, and astronomy. Presently, high-performance infrared imaging technology mostly relies on epitaxially grown structures of the small-bandgap bulk alloy mercury–cadmium–telluride (MCT), indium antimonide (InSb), and GaAs-based quantum well infrared photodetectors (QWIPs), contingent upon the application and wavelength range. Nanostructures and nanomaterials exhibiting appropriate electrical and mechanical properties including two-dimensional materials, graphene, quantum dots (QDs), quantum dot in well (DWELL), and colloidal quantum dot (CQD) will significantly enhance the electronic characteristics of infrared photodetectors, transition metal dichalcogenides, and metal oxides, which are garnering heightened interest. The present manuscript gives an overview of IR sensors, their types, materials commonly used in them, and examples of related applications. Finally, a summary of the manuscript and an outlook on prospects are given. Full article