Novel microwave synthesis of near-metallic copper sulfide nanodiscs with size control: experimental and DFT studies of charge carrier density.
Ontology highlight
ABSTRACT:
SUBMITTER: Sheardy AT
PROVIDER: S-EPMC9419483 | biostudies-literature | 2020 Mar
REPOSITORIES: biostudies-literature
Publications
Novel microwave synthesis of near-metallic copper sulfide nanodiscs with size control: experimental and DFT studies of charge carrier density.
Sheardy Alex T AT Arvapalli Durga M DM Wei Jianjun J
Nanoscale advances 20200212 3
A simple unprecedented microwave synthesis of size controllable copper sufide (CuS) nanodiscs is reported. The experimental results and density functional theory (DFT)-calculated results show charge carrier densities on the order of 10<sup>21</sup> cm<sup>-3</sup> with an effective mass of 0.3<i>m</i> <sub>e</sub>, resulting in near-metallic properties. ...[more]
Similar Datasets
Project description:Excited carrier dynamics in plasmonic nanostructures determines many important optical properties such as nonlinear optical response and photocatalytic activity. Here it is shown that mesoscopic plasmonic covellite nanocrystals with low free-carrier concentration exhibit a much faster carrier relaxation than in traditional plasmonic materials. A nonequilibrium hot-carrier population thermalizes within first 20 fs after photoexcitation. A decreased thermalization time in nanocrystals compared to a bulk covellite is consistent with the reduced Coulomb screening in ultrathin films. The subsequent relaxation of thermalized, equilibrium electron gas is faster than in traditional plasmonic metals due to the lower carrier concentration and agrees well with that in a bulk covellite showing no evidence of quantum confinement or hot-hole trapping at the surface states. The excitation of coherent optical phonon modes in a covellite is also demonstrated, revealing coherent lattice dynamics in plasmonic materials, which until now was mainly limited to dielectrics, semiconductors, and semimetals. These findings show advantages of this new mesoscopic plasmonic material for active control of optical processes.
| S-EPMC8408971 | biostudies-literature
Project description:Colloidal nanoparticles (NPs) have been recently spotlighted as building blocks for various nanostructured devices. Their collective properties have been exhibited by arranging them on a substrate to form assembled NPs. In particular, electrophoretic deposition (EPD) is an emerging fabrication method for such nanostructured films. To maximize the benefits of this method, further studies are required to fully elucidate the key parameters that influence the NP deposition. Herein, two key parameters are examined, namely: (i) the aging of colloidal NPs and (ii) the charge formation by surface ligands. The aging of Cu2-xS NPs changes the charge states, thus leading to different NP deposition behaviors. The SEM images of NP films, dynamic light scattering, and zeta potential results demonstrated that the charge control and restoration of interparticle interactions for aged NPs were achieved via simple ligand engineering. The charge control of colloidal NPs was found to be more dominant than the influence of aging, which can alter the surface charges of the NPs. The present results thus reveal that the charge formation on the colloidal NPs, which depends on the surface ligands, is an important controllable parameter in EPD.
| S-EPMC7827911 | biostudies-literature
Project description:Ternary chalcostibite copper antimony sulfide (CuSbS2) is an emerging semiconductor material having applications in photovoltaics, energy storage and optoelectronics due to its high absorption coefficient, suitable bandgap, and it consists of non-toxic and earth abundant elements. CuSbS2 thin films are prepared by combining chemical bath deposition (antimony sulfide (Sb2S3)) and thermal evaporation (copper (Cu)) followed by a heat treatment and their application as visible to near infrared photodetectors is reported. Crystalline structure, elemental composition, chemical state, morphology and optoelectronic properties of the films were characterized by various techniques. The effect of three different Cu thicknesses (CAS 20, CAS 30 and CAS 40 nm) on the photodetection properties are evaluated under illumination using light emitting diodes (LEDs) and a laser. The photodetectors fabricated are successfully tested under different wavelengths, power densities and applied voltage and their photoresponse cyclic stability for each wavelength of illumination was recorded. From the sensitivity calculations, the sample with 20 nm Cu thickness (CAS 20) showed higher detection sensitivity for visible to near infrared wavelengths. Better responsivity results were obtained for CAS 40 because of its improved crystallinity and phase purity. Photodetector properties such as sensitivity and responsivity are evaluated for all the samples. These results are beneficial for cost effective and environment friendly photodetectors and optoelectronic devices based on CuSbS2 thin films.
| S-EPMC9085606 | biostudies-literature
Project description:Phospholipids (PLs) are a major, diverse constituent of cell membranes. PL diversity arises from the nature of the fatty acid chains, as well as the headgroup structure. The headgroup charge is thought to contribute to both the strength and specificity of protein-membrane interactions. Because it has been difficult to measure membrane charge, ascertaining the role charge plays in these interactions has been challenging. Presented here are charge measurements on lipid Nanodiscs at 20°C in 100 mM NaCl, 50 mM Tris, at pH 7.4. Values are also reported for measurements made in the presence of Ca(2+) and Mg(2+) as a function of NaCl concentration, pH, and temperature, and in solvents containing other types of cations and anions. Measurements were made for neutral (phosphatidylcholine and phosphatidylethanolamine) and anionic (phosphatidylserine, phosphatidic acid, cardiolipin, and phosphatidylinositol 4,5-bisphosphate (PIP2)) PLs containing palmitoyl-oleoyl and dimyristoyl fatty acid chains. In addition, charge measurements were made on Nanodiscs containing an Escherichia coli lipid extract. The data collected reveal that 1) POPE is anionic and not neutral at pH 7.4; 2) high-anionic-content Nanodiscs exhibit polyelectrolyte behavior; 3) 3 mM Ca(2+) neutralizes a constant fraction of the charge, but not a constant amount of charge, for POPS and POPC Nanodiscs; 4) in contrast to some previous work, POPC only interacts weakly with Ca(2+); 5) divalent cations interact with lipids in a lipid- and ion-specific manner for POPA and PIP2 lipids; and 6) the monovalent anion type has little influence on the lipid charge. These results should help eliminate inconsistencies among data obtained using different techniques, membrane systems, and experimental conditions, and they provide foundational data for developing an accurate view of membranes and membrane-protein interactions.
| S-EPMC5018125 | biostudies-literature
Project description:Despite their uniform crystallinity, the shape and faceting of semiconducting nanowires (NWs) can give rise to variations in structure and associated electronic properties. Here we develop a hybrid scanning probe-based methodology to investigate local variations in electronic structure across individual n-doped GaN NWs integrated into a transistor device. We perform scanning microwave microscopy (SMM), which we combine with scanning gate microscopy (SGM) to determine the free-carrier SMM signal contribution and image local charge carrier density variations. In particular, we find significant variations in free carriers across NWs, with a higher carrier density at the wire facets. By increasing the local carrier density through tip-gating, we find that the tip injects current into the NW with strongly localized current when positioned over the wire vertices. These results suggest that the strong variations in electronic properties observed within NWs have significant implications for device design and may lead to new paths to optimization.
| S-EPMC10938853 | biostudies-literature
Project description:In this study, we report on the green fluorescence exhibited by nitrobenzofurazan-sulfide derivatives (NBD-Si, i = 1-4). The optical responses of these studied compounds in a polar methanol solvent were simulated by the use of time-dependent density functional theory (TD-DFT) employing the Becke-3-Parameter-Lee-Yang-Parr (B3LYP) functional along with the 6-31G(d,p) basis set. The computed energy and oscillator strength (f) results complement the experimental results. The band gap was calculated as the difference between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). Additionally, the density of states (DOS) was computed, providing a comprehensive understanding of the fundamental properties of these materials and further corroborating the experimental data. When the experimental data derived from ultraviolet/visible (UV/visible) and fluorescence spectroscopic techniques and those from simulated spectra are analyzed, the extracted values match up adequately. In addition, the NBD-sulfide compounds exhibit a large Stokes shift up to 85 nm in a polar methanol solvent. They are hypothesized to represent a novel paradigm of excited-state intramolecular charge transfer (ICT). To understand the intrinsic optical properties of NBD-Si materials, an ICT was identified, and its direction within the molecule was evaluated using the ratio of βvect and βtotal, values extracted from the computed nonlinear optical (NLO) properties. Moreover, the reduced density gradient (RDG)-based noncovalent interactions (NCIs) were employed to characterize the strength and type of NBD-Si interactions. Furthermore, noncovalent interactions were identified and categorized using the Quantum Theory of Atoms in Molecules (QTAIM) analysis. Ultimately, the combination of Hirshfeld surface analysis and DFT calculations was utilized to enhance the characterization and rationalization of these NCIs.
| S-EPMC10694821 | biostudies-literature
Project description:In this work, the synthesis of visible light sensitive copper sulfide (CuS) nanoparticles and their composites with carbon nanotubes (T-CuS) via a solvothermal technique is reported. The synthesized nanoparticles (NPs) and their composites were significantly characterized by powder X-ray diffraction (PXRD), scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, photoluminescence (PL) spectroscopy and thermogravimetric analysis (TGA). The effect of carbon nanotubes (CNTs) on the crystallinity, microstructures, photo-absorption, photo-excitation, thermal stability and surface area of CuS was investigated. The current-voltage (I vs. V) characteristics of both CuS and T-CuS based Schottky diodes were measured to determine the charge transport parameters like photosensitivity, conductivity, mobility of charge carriers, and transit time. The photocatalytic performance of bare CuS and T-CuS in the decomposition of Rhodamine B dye was studied using a solar simulator. The T-CuS composite showed higher photocatalytic activity (94%) compared to bare CuS (58%). The significance of charge carrier mobility in transferring photo-induced charges (holes and electrons) through complex networks of composites and facilitating the photodegradation process is explained. Finally, the reactive species responsible for the Rhodamine B degradation were also identified.
| S-EPMC10334374 | biostudies-literature
Project description:Noncovalent functionalization of single-walled carbon nanotubes (SWCNT) by semiconducting oxides is a majorly sought technique to retain individual properties while creating a synergetic effect for an efficient heterostructure charge transfer. Three types of electronically and optically different SWCNTs: metallic (m), semiconducting (s), and pristine (p) are functionalized by ZnO using a facile sonication method. The physicochemical and morphological properties of the ZnO-functionalized SWCNTs, m-SWCNT+ZnO, s-SWCNT+ZnO, and p-SWCNT+ZnO, are analyzed by advanced characterization techniques. Evidence of charge transfer between SWCNT and ZnO is observed with an increase in charge carrier lifetime from 3.31 ns (ZnO) to 4.76 ns (s-SWCNT+ZnO). To investigate the optimum interaction between SWCNTs and ZnO, critical coagulation concentrations (CCC) are determined using UV-vis absorption spectroscopy for m-SWCNT, s-SWCNT, and p-SWCNT using different molar concentrations of ZnO as the coagulant. The interaction and coagulation mechanisms are described by the modified DLVO theory. Due to the variation in dielectric values and electronic properties of SWCNTs, the CCC values obtained have differed: m-SWCNT (1.9 × 10-4), s-SWCNT (3.4 × 10-4), and p-SWCNT (2 × 10-4). An additional analysis of the aggregates and supernatants of the CCC experiments is also shown to give an insight into the interaction and coagulation processes, explaining the absence of influence exerted by sedimentation and centrifugation.
| S-EPMC9088952 | biostudies-literature
Project description:We have successfully designed the geometry of the microwave cavity and the thin metal electrode, achieving resonance of the microwave cavity with the metal-insulator-semiconductor (MIS) device structure. This very simple MIS device operates in the cavity, where charge carriers are injected quantitatively by an applied bias at the insulator-semiconductor interface. The local motion of the charge carriers was clearly probed through the applied external microwave field, also giving the quantitative responses to the injected charge carrier density and charge/discharge characteristics. By means of the present measurement system named field-induced time-resolved microwave conductivity (FI-TRMC), the pentacene thin film in the MIS device allowed the evaluation of the hole and electron mobility at the insulator-semiconductor interface of 6.3 and 0.34 cm² V⁻¹ s⁻¹, respectively. This is the first report on the direct, intrinsic, non-contact measurement of charge carrier mobility at interfaces that has been fully experimentally verified.
| S-EPMC3822380 | biostudies-literature
Project description:Near-infrared colloidal nanocrystals (NIR-CNCs) have been widely utilized in optoelectronic applications due to their exceptional optical properties and suitability for mass production. However, their practical application is often hindered by poor chemical stability and suboptimal electronic properties. In this work, four different surface ligand systems-insulating ligands, organic molecular linkers, inorganic molecular linkers, and matrix-type ligands-were systematically investigated to evaluate their effects on the transport and recombination behavior of NIR-CNCs via photoinduced carriers. While molecular linkers enhance transport behavior by improving electronic coupling, they tend to induce photoinduced charge carrier accumulation under AM1.5 illumination due to a high degree of Fermi-level pinning caused by unfavorable electronic structures. In contrast, the matrix-type band-like transport ligand significantly reduced dark current and hysteresis characteristics in CNCs, demonstrating superior performance. Impedance and capacitance analyses revealed that the matrix-type ligand, with its multiple carrier separation pathways, enhanced carrier transport through sub-states facilitated by amorphous MoS x and effectively passivated CNC trap states, thereby reducing the Fermi-level pinning effect. This approach dramatically suppressed hot carrier-induced trap state generation, minimized photoinduced recombination, and improved operational stability. Overall, this study presents a significant advancement in developing cost-efficient, chemically stable NIR optoelectronic devices with outstanding electronic properties.
| S-EPMC11865893 | biostudies-literature