Presence Of Light Illumination Research Articles

Light, Copper, Action: Visible-Light Illumination Enhances Bactericidal Activity of Copper Particles.

Bacteria are an old concern to human health, as they are responsible for nosocomial infections, and the number of antibiotic-resistant microorganisms keeps growing. Copper is known for its intrinsic biocidal properties, and therefore, it is a promising material to combat infections when added to surfaces. However, its biocidal properties in the presence of light illumination have not been fully explored, especially regarding the use of microsized particles since nanoparticles have taken over all fields of research and subjugated microparticles despite them being abundant and less expensive. Thus, the present work studied the bactericidal properties of metallic copper particles, in microscale (CuMPs) and nanoscale (CuNPs), in the absence of light and under white LED light illumination. The minimum bactericidal concentration (MBC) of CuMPs against Staphylococcus aureus that achieved a 6-log reduction was 5.0 and 2.5 mg mL-1 for assays conducted in the absence of light and under light illumination, respectively. Similar behavior was observed against Escherichia coli. The bactericidal activity under illumination provided a percentage increase in log reduction values of 65.2% for S. aureus and 166.7% for E. coli when compared to the assays under dark. This assay reproduced the testing CuNPs, which showed superior bactericidal activity since the concentration of 2.5 mg mL-1 promoted a 6-log reduction of both bacteria even under dark. Its superior bactericidal activity, which overcame the effect of illumination, was expected once the nanoscale facilitated the interaction of copper within the surface of bacteria. The results from MBC were supported by fluorescence microscopy and atomic absorption spectroscopy. Therefore, CuMPs and CuNPs proved to have size- and dose-dependent biocidal activity. However, we have shown that CuMPs photoactivity is competitive compared to that of CuNPs, allowing their application as a self-cleaning material for disinfection processes assisted by conventional light sources without additives to contain the spread of pathogens.

Efficient photoelectrochemical water oxidation and electrochemical supercapacitor performance of ZnAl2O4 hexagonal microstructures

ZnAl2O4 hexagonal microstructure (ZAO) was prepared using the co-precipitation assisted hydrothermal technique. The prepared ZAO exhibits a hexagon morphology. Optical properties study reveals the reduction of bandgap (3.05 eV) thank bulk ZAO materials. The photoelectrochemical (PEC) performance was significantly improved in the presence of light illumination and provides the photocurrent density of 1.32 mA/cm2 under the light-on conditions of linear sweep voltammetry (LSV) measurement. The ZAO materials provide very good photostability over the long period of time. A detailed analysis of the electrochemical supercapacitor performance of ZAO electrode materials was analyzed through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies. The ZAO electrode material shows the specific capacity of 255.4 mAh g−1 at the current density of 1A g−1. The ZAO electrode shows rate capability of ～67 % with cycle stability of 70 % at current density of 6 A g−1 over 500 cycles. The columbic efficiency of the electrode was found to be 98 % after 500 GCD cycles. According to the existing literature, this is the first report on ZAO's performance in supercapacitor applications and opens up new avenues for the exploration of other materials in ZAO - based materials for energy storage.

An in-depth study of photocathodic protection of SS304 steel by electrodeposited layers of ZnO nanoparticles

Thin layers of ZnO nanoparticles were deposited potentiostaticly on the surface of stainless steel 304 (SS304) at various potentials (−0.7 V, −1.0 V, −1.3 V, −1.6 V) to study the effect of photo-generated cathodic protection on the substrate. Electrochemical methods of open circuit potential (OCP), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were employed to investigate the electrochemical behaviors of ZnO-covered SS304 system (ZnO/SS304) in 3.5 wt% NaCl solution under the conditions with and without UV illumination. It is found that the ZnO nanoparticles deposited at −1.0 V was in the shape of hexagonal nanorods, which caused a negative shift to lowest OCP upon UV illumination. Polarization curves were also performed on ZnO/ITO glass system to reveal the photoelectrochemical behavior of ZnO nanoparticles only. Possible anodic and cathodic reactions on the ZnO/SS304 and ZnO/ITO systems at the absence and presence of light illumination have been analysed and discussed in detail. It is found that traditional Tafel extrapolation of the polarization curves cannot be used to get the free corrosion current density of ZnO/SS304 system under light illumination due to the superposition of photo-generated current density. The charge transfer resistance obtained from EIS also includes the influence from the photo-generated reactions on the ZnO/SS304 system. Long-term immersion of the ZnO/SS304 in NaCl solution indicates that the ZnO nanorods underwent morphological transitions to nanotubes at 5 days and finally to needles and thin plates at 10 days. Correspondingly, the photocathodic protection of the ZnO layer decreases with the extension of immersion time. The transformation in morphology is postulated to be caused by the attack of Cl− ions on the surface of ZnO nanoparticles.

Photo-assisted peroxymonosulfate activation via 2D/2D heterostructure of Ti3C2/g-C3N4 for degradation of diclofenac

In this paper, a two dimensional/two dimensional (2D/2D) heterostructure of Ti3C2/g-C3N4 (T/CN) was constructed and used to activate peroxymonosulfate (PMS) for the degradation of diclofenac (DCF) in water in the presence of light illumination. Compared with single photocatalytic process by T/CN (0.040/min) and with pure g-C3N4 nanosheets in PMS system (0.071/min), 5.0 and 3.0 times enhanced activities were achieved in the T/CN-PMS system at optimum Ti3C2 (1.0 wt%) loading under light illumination (0.21/min). Moreover, the decomposing processes of DCF in T/CN-PMS system were applicable in a wide initial pH range (3∼14), therefore, overcoming the limitation of pH dependence in traditional PMS system. Based on the synergistic effect of photocatalysis and PMS oxidation processes, the 1O2 was generated as primary reactive species for the removal of DCF in T/CN-PMS system. The DCF degradation mechanism was further proposed through the results of liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) calculations.

Novel gold dendritic nanoflowers deposited on titanium nitride for photoelectrochemical cells

This study demonstrates the elaboration of a novel composite comprising gold dendritic nanoflowers (Au DNFs)/titanium nitride (TiN)/silicon (Si); this composite can be used for methanol oxidation reactions in alkaline electrolytes. Cyclic voltammograms showed that a thick (650 nm) Au DNFs/TiN/Si (L-DNFs-TiN) composite had double the oxidation current density of a thick (800 nm) Au DNFs/Si (L-DNFs-Si) composite in the presence of light illumination, whereas the oxidation current density for a thin (250 nm) Au DNFs/Si (S-DNFs-Si) composite and Au nanoparticles could not be determined. Chronoamperometry (CA) testing indicated that the L-DNFs-TiN could absorb light illumination more effectively than the L-DNFs-Si did. These results correspond to the broadband light absorption of TiN. Testing with continuous cyclic on/off light illumination showed a repeatable performance in CA, indicating that the proposed L-DNFs-TiN composite can be applied in photoelectrochemical cells in the future.

Scaling Analysis of High Gain Monolayer MoS2Photodetector for Its Performance Optimization

Monolayer MoS2 photodetectors are modeled and simulated by self-consistently solving diffusive transport equations in the presence of light illumination and carrier recombination with the 2-D Poisson equation. The simulated results indicate that very high photoresponsivity (PR) of $\sim 1000$ A/W observed in others’ experiments is due to strong electrostatic effect of pile up of optically generated holes, and efficient optical absorption. It is found that the value of PR is sensitive to gate bias voltage, and the photodetector performance can be improved by decreasing hole mobility if side effects of low hole mobility, such as high recombination rate, slow response speed, and more noise, are suppressed. High quality monolayer MoS2 with large electron mobility and less Shockley–Read–Hall recombination defects is desired for achieving high performance. The PR increases as the gate insulator thickness increases. The channel length needs to be carefully designed by considering the carrier recombination behavior in monolayer MoS2. The optimization method of monolayer MoS2 photodetectors proposed here is also applicable to other monolayer transition-metal dichalcogenide materials in general.

Study of the electron–photon interaction on the spin-dependent transport in nano-structures

Transport through a nano device in the presence of light illumination has been studied by using unitary-transformation scheme together with the non-equilibrium Green's function formalism. The non-interacting Hamiltonian is written within the framework of the tight binding model and structureless electrodes are described in wide-band approximation. The interaction between electrons is modeled by the mean-field Hubbard term. Our results indicate that we can tune the "intrinsic magnetization of zigzag edge" and "spin-polarized current" by using light illumination.

New properties of halogen plasma-treated Cu films

Abstract Luminescence activity and structure of halogen plasma-treated Cu films on Si substrate have been investigated. Peculiar photoluminescence signals in the range of 1.6 – 2.0 eV were detected both at low (from 77 to 15 K), and at room temperature. The observed luminescence peaks are not present for stoichiometric CuCl. The exposure of CuCl- and CuBr-containing layers to helium plasma, with UV-illumination, result in the formation of knots of twisted nanowires on the surface of these layers. These wires don't have luminescent activity. The accelerated degradation of luminescence of these samples in air in the presence of light illumination and ozone treatment was studied.

Temperature sensors based on synthetic diamond films

The transport properties of synthetic diamond films were studied and the resulting data were applied to the development of a simple device which was used as a temperature sensor. It has been observed that the electrical resistivity follows the variable range hopping conducting process. The sensibility and reliability of the electrical characteristics presented by the sensor were very good in the investigated range of temperatures (10 to 300 K). The sensor reading was unaffected even in the presence of light illumination or magnetic field.