Search Results (7)

Gel-type electrofluorochromic (EFC) devices, which reversibly modulate photoluminescence under electrical stimuli, have emerged as versatile platforms for advanced optoelectronic applications. By integrating redox-active luminophores with soft, ion-conductive gel matrices, these systems combine the structural robustness of solids with the ionic mobility of liquids, enabling a high-contrast, flexible, and multifunctional operation. This review provides a comprehensive overview of gel-based EFC technologies, outlining fundamental working principles, device architectures, and key performance metrics such as contrast ratio, switching time, and cycling stability. Gel matrices are categorized into ionogels, organogels, and hydrogels, and their physicochemical properties are discussed in relation to EFC device performance. Recent advances are highlighted across applications ranging from flexible displays and rewritable electronic paper to strain and biosensors, data encryption, smart windows, and hybrid energy-interactive systems. Finally, current challenges and emerging strategies are analyzed to guide the design of next-generation adaptive, intelligent, and energy-efficient optoelectronic platforms. Full article

Titanium dioxide (TiO₂) is a wide-bandgap semiconductor material with broad application potential, known for its excellent photocatalytic performance, high chemical stability, low cost, and non-toxicity. These properties make it highly attractive for applications in photovoltaic energy, environmental remediation, and optoelectronic devices. For instance, TiO₂ is widely used as a photocatalyst for hydrogen production via water splitting and for degrading organic pollutants, thanks to its efficient photo-generated electron–hole separation. Additionally, TiO₂ exhibits remarkable performance in dye-sensitized solar cells and photodetectors, providing critical support for advancements in green energy and photoelectric conversion technologies. Boron-doped diamond (BDD) is renowned for its exceptional electrical conductivity, high hardness, wide electrochemical window, and outstanding chemical inertness. These unique characteristics enable its extensive use in fields such as electrochemical analysis, electrocatalysis, sensors, and biomedicine. For example, BDD electrodes exhibit high sensitivity and stability in detecting trace chemicals and pollutants, while also demonstrating excellent performance in electrocatalytic water splitting and industrial wastewater treatment. Its chemical stability and biocompatibility make it an ideal material for biosensors and implantable devices. Research indicates that the combination of TiO₂ nanostructures and BDD into heterostructures can exhibit unexpected optical and electrical performance and transport behavior, opening up new possibilities for photoluminescence and rectifier diode devices. However, applications based on this heterostructure still face challenges, particularly in terms of photodetector, photoelectric emitter, optical modulator, and optical fiber devices under high-temperature conditions. This article explores the potential and prospects of their combined heterostructures in the field of optoelectronic devices such as photodetector, light emitting diode (LED), memory, field effect transistor (FET) and sensing. TiO₂/BDD heterojunction can enhance photoresponsivity and extend the spectral detection range which enables stability in high-temperature and harsh environments due to BDD’s thermal conductivity. This article proposes future research directions and prospects to facilitate the development of TiO₂ nanostructured materials and BDD-based heterostructures, providing a foundation for enhancing photoresponsivity and extending the spectral detection range enables stability in high-temperature and high-frequency optoelectronic devices field. Further research and exploration of optoelectronic devices based on TiO₂-BDD heterostructures hold significant importance, offering new breakthroughs and innovations for the future development of optoelectronic technology. Full article

Novel wide-bandgap ZnO, BeO, and ZnBeO materials have recently gained considerable interest due to their stellar optoelectronic properties. These semiconductors are being used in developing high-resolution, flexible, transparent nanoelectronics/photonics and achieving high-power radio frequency modules for sensors/biosensors, photodetectors/solar cells, and resistive random-access memory applications. Despite earlier evidence of attaining p-type wz ZnO with N doping, the problem persists in achieving reproducible p-type conductivity. This issue is linked to charging compensation by intrinsic donors and/or background impurities. In ZnO: Al (Li), the vibrational features by infrared and Raman spectroscopy have been ascribed to the presence of isolated ${\mathrm{A}\mathrm{l}}_{\mathrm{Z}\mathrm{n}}{(\mathrm{L}\mathrm{i}}_{\mathrm{Z}\mathrm{n}})$ defects, nearest-neighbor (NN) ${[\mathrm{A}\mathrm{l}}_{\mathrm{Z}\mathrm{n}}{-\mathrm{N}}_{\mathrm{O}}$] pairs, and second NN ${[\mathrm{A}\mathrm{l}}_{\mathrm{Z}\mathrm{n}}{-\mathrm{O}-\mathrm{L}\mathrm{i}}_{\mathrm{Z}\mathrm{n}};{\mathrm{V}}_{\mathrm{Z}\mathrm{n}}-\mathrm{O}{-\mathrm{L}\mathrm{i}}_{\mathrm{Z}\mathrm{n}}]$ complexes. However, no firm identification has been established. By integrating accurate perturbation models in a realistic Green’s function method, we have meticulously simulated the impurity vibrational modes of ${\mathrm{A}\mathrm{l}}_{\mathrm{Z}\mathrm{n}}$${(\mathrm{L}\mathrm{i}}_{\mathrm{Z}\mathrm{n}})$ and their bonding to form complexes with dopants as well as intrinsic defects. We strongly feel that these phonon features in doped ZnO will encourage spectroscopists to perform similar measurements to check our theoretical conjectures. Full article

Colloidal quantum dots (QDs) and graphene hybrids have emerged as promising platforms for optoelectronic and biosensing applications due to their unique photophysical and electronic properties. This study investigates the fundamental mechanism underlying the photoluminescence (PL) quenching and recovery in graphene–QD hybrid systems using single-layer graphene field-effect transistors (SLG-FETs) and time-resolved photoluminescence (TRPL) spectroscopy. We demonstrate that PL quenching and its recovery are primarily driven by charge transfer, as evidenced by an unchanged fluorescence lifetime upon quenching. Density functional theory calculations reveal a significant charge redistribution at the graphene–QD interface, corroborating experimental observations. We also provide a simple analytical quantum mechanical model to differentiate charge transfer-induced PL quenching from resonance energy transfer. Furthermore, we leverage the charge transfer mechanism for ultrasensitive biosensing to detect biomarkers such as immunoglobulin G (IgG) at femtomolar concentrations. The sensor’s electrical response, characterized by systematic shifts in the Dirac point of SLG-FETs, confirms the role of analyte-induced charge modulation in PL recovery. Our findings provide a fundamental framework for designing next-generation graphene-based biosensors with exceptional sensitivity and specificity. Full article

We present a generic quantitative chemical sensing methodology for assessing the concentration of a target material (TM) in an aqueous solution by using bioluminescent microbial bioreporters as the core sensing elements. Such bioreporters, genetically engineered to respond to the presence of a TM in their microenvironment by emitting bioluminescence, have previously been mostly designed to report the presence or absence of the TM in the sample. We extend this methodology to also assess the TM concentration, by exploiting the dose-dependency of the TM-induced luminescence. To overcome luminescence intensity variations due to bacterial batch differences and the ambient temperature, simultaneous measurements were carried out on sample solutions containing known concentrations of the TM. A “standard ratio” parameter, defined as the ratio between the two measurements, is shown to be independent of the bacterial batch and the temperature, and hence provides the conceptual basis for a generic quantitative chemical sensing methodology. Assessment of 2,4-dinitrotoluene (DNT) concentration in solutions is demonstrated with an accuracy of 2.5% over a wide dynamic range. Full article

In many electro-optical devices, the conductive layer is an important key functional element. Among others, unique indium tin oxide (ITO) contacts take priority. ITO structure is widely used as the optical transparent and electrically conductive material in general optoelectronics, biosensors and electrochemistry. ITO is one of the key elements in the liquid crystal (LC) displays, spatial light modulators (SLMs) and LC convertors. It should be mentioned that not only the morphology of this layer structure but also the surface features play an important role in the study of the physical parameters of the ITO. In order to switch the surface properties (roughness, average tilt angle and surface free energy) of the ITO via the laser-oriented deposition (LOD) method, carbon nanotubes (CNTs) were implanted. In the LOD technique, the CO₂ laser (λ = 10.6 μm, P = 30 W) with the control electric grid was used. The switching of the deposition conditions was provided via the varying electrical strength of the control grid in the range of 100–600 V/cm. The diagnostics of the surfaces were performed using AFM analysis and wetting angle measurements. The components of the surface free energy (SFE) were calculated using the OWRK method. The main experimental results are as follows: the roughness increases with a rise in the electric field strength during the deposition of the CNTs; the carbon nanotubes provide a higher level of the dispersive component of SFE (25.0–31.4 mJ/m² against 22.2 mJ/m² in the case of pure ITO); the CNTs allow an increase in the wetting angle of the 5CB liquid crystal drops from 38.35° to 58.95°. Due to the possibility of the switching properties of the ITO/CNT surfaces, these modifications have potential interest in microfluidics applications and are useful for the liquid crystal’s electro-optics. Full article

Due to their peculiar qualities, metal-based nanostructures have been extensively used in applications such as catalysis, electronics, photography, and information storage, among others. New applications for metals in areas such as photonics, sensing, imaging, and medicine are also being developed. Significantly, most of these applications require the use of metals in the form of nanostructures with specific controlled properties. The properties of nanoscale metals are determined by a set of physical parameters that include size, shape, composition, and structure. In recent years, many research fields have focused on the synthesis of nanoscale-sized metallic materials with complex shape and composition in order to optimize the optical and electrical response of devices containing metallic nanostructures. The present paper aims to overview the most recent results—in terms of fabrication methodologies, characterization of the physico-chemical properties and applications—of complex-morphology metal-based nanostructures. The paper strongly focuses on the correlation between the complex morphology and the structures’ properties, showing how the morphological complexity (and its nanoscale control) can often give access to a wide range of innovative properties exploitable for innovative functional device production. We begin with an overview of the basic concepts on the correlation between structural and optical parameters of nanoscale metallic materials with complex shape and composition, and the possible solutions offered by nanotechnology in a large range of applications (catalysis, electronics, photonics, sensing). The aim is to assess the state of the art, and then show the innovative contributions that can be proposed in this research field. We subsequently report on innovative, versatile and low-cost synthesis techniques, suitable for providing a good control on the size, surface density, composition and geometry of the metallic nanostructures. The main purpose of this study is the fabrication of functional nanoscale-sized materials, whose properties can be tailored (in a wide range) simply by controlling the structural characteristics. The modulation of the structural parameters is required to tune the plasmonic properties of the nanostructures for applications such as biosensors, opto-electronic or photovoltaic devices and surface-enhanced Raman scattering (SERS) substrates. The structural characterization of the obtained nanoscale materials is employed in order to define how the synthesis parameters affect the structural characteristics of the resulting metallic nanostructures. Then, macroscopic measurements are used to probe their electrical and optical properties. Phenomenological growth models are drafted to explain the processes involved in the growth and evolution of such composite systems. After the synthesis and characterization of the metallic nanostructures, we study the effects of the incorporation of the complex morphologies on the optical and electrical responses of each specific device. Full article