Enhancement of Visible Light Antibacterial Activities of Cellulose Fibers from Lotus Petiole Decorated ZnO Nanoparticles.

Cellulose/ZnO (CZ) nanocomposites are promising antimicrobial materials known for their antibiotic-free nature, biocompatibility, and environmental friendliness. In this study, cellulose fibers extracted from lotus petioles were utilized as a substrate and decorated with various shapes of ZnO nanoparticles (NPs), including small bean, hexagonal ingot-like, long cylindrical, and hexagonal cylinder-shaped NPs. Increasing zinc salt molar concentration resulted in highly crystalline ZnO NPs forming and enhanced interactions between ZnO NPs and -OH groups of cellulose. The thermal stability and UV-visible absorption properties of the CZ samples were influenced by ZnO concentration. Notably, at a ZnO molar ratio of 0.1, the CZ 0.1 sample demonstrated the lowest weight loss, while the optical band gap gradually decreased from 3.0 to 2.45 eV from the CZ 0.01 to CZ 1.0 samples. The CZ nanocomposites exhibited remarkable antibacterial activity against both Staphylococcus aureus (S. aureus, Gram-positive) and Escherichia coli (E. coli, Gram-negative) bacteria under visible light conditions, with a minimum inhibitory concentration (MIC) of 0.005 mg/mL for both bacterial strains. The bactericidal effects increased with higher concentrations of ZnO NPs, even achieving 100% inhibition. Incorporating ZnO NPs onto cellulose fibers derived from lotus plants presents a promising avenue for developing environmentally friendly materials with broad applications in antibacterial and environmental fields.

Tuned Transport Path of Perovskite MAPbI3 -based Memristor Structure.

In this study, the features of resistive random access memory (RRAM) employing a straightforward Cr/MAPbI3 /FTO three-layer structure have been examined and clarified. The device displays various resistance switching (RS) behavior at various sweep voltages between 0.5 and 5 V. The RS effect has a conversion in the direction of the SET and RESET processes during sweeping for a number of cycles at a specific voltage. The directional change of the RS processes corresponds to the dominant transition between the generation/recombination of iodide ion and vacancy in the MAPbI3 perovskite layer and the electrochemical metallization of the Cr electrode under the influence of an electric field, which results in the conductive filament (CF) formation/rupture. At each stage, these processes are controlled by specific charge conduction mechanisms, including Ohmic conduction, space-charge-limited conduction (SCLC), and variable-range hopping (VRH). By identifying the biased voltage and the quantity of voltage sweep cycles, one can take a new approach to control or modulate the pathways for effective charge transport. This new approach is made possible by an understanding of the RS characteristics and the corresponding mechanisms causing the variation of RS behavior in the structure.

Ultrasensitive biosensors based on waveguide-coupled long-range surface plasmon resonance (WC-LRSPR) for enhanced fluorescence spectroscopy.

We investigated the coupling phenomenon between plasmonic resonance and waveguide modes through theoretical and experimental parametric analyses on the bimetallic waveguide-coupled long-range surface plasmon resonance (Bi-WCLRSPR) structure. The calculation results indicated that the multi-plasmonic coupling gives rise to the enhanced depth-to-width ratio of the reflection dip compared to that of LRSPR excited using a single set of Ag and Teflon. The optimized thickness of Ag(40 nm)/Teflon(700 nm)/Ag(5 nm)/Au(5 nm) was obtained and generated the highest plasmon intensity enhancement, which was 2.38 folds in comparison to the conventional bimetallic surface plasmon resonance (SPR) configuration (Ag/Au). 17ß-Estradiol was used in the fluorescence enhancement experiment by the reflection geometry-based system, wherein the excitation light source was on the side of a WC-LRSPR chip opposite to that of the light detection unit. The phenomenon of surface plasmon-couple emission (SPCE) depends on the number of 17ß-estradiol molecule promoters from female sex steroid hormones, which demonstrated a limit of detection (LOD) of 2 pg mL-1 and 1.47-fold fluorescence improvement as compared to the non-coated material on the surface of pristine glass. This enhanced WC-LRSPR can readily find application in fluorescence escalation needed in cases where a weak fluorescence signal is predicted, such as the small volume of liquid containing fluorescent dyes in biological diagnosis.

Resistive switching effect and magnetic properties of iron oxide nanoparticles embedded-polyvinyl alcohol film.

In this study, the memory device of iron oxide (IO) nanoparticles (NPs) embedded in polyvinyl alcohol (PVA) demonstrates the bipolar resistive switching characteristics under an external electric field. The phase and magnetic properties of iron oxide nanoparticles change corresponding to its resistive states. At the high resistance state (HRS) of device, iron oxide nanoparticles are primarily in Fe2O3 phase and the ferromagnetism behavior is observed. In contrast, the iron oxide nanoparticles clustered by the bridging oxygen vacancies lead to mainly Fe3O4 phase and no hysteresis magnetic curve is observed at the low resistance state (LRS) of device. The results reveal that oxygen vacancies/ions in nanoparticles notably influence the resistance and magnetic behavior of nanocomposite thin films. Our study indicated that the magnetic NPs is high potential of multi-dimensional storage fields.

Correction: Resistive switching effect and magnetic properties of iron oxide nanoparticles embedded-polyvinyl alcohol film.

[This corrects the article DOI: 10.1039/C9RA10101B.].

Thermoelectric Properties of Indium and Gallium Dually Doped ZnO Thin Films.

We investigated the effect of single and multidopants on the thermoelectrical properties of host ZnO films. Incorporation of the single dopant Ga in the ZnO films improved the conductivity and mobility but lowered the Seebeck coefficient. Dual Ga- and In-doped ZnO thin films show slightly decreased electrical conductivity but improved Seebeck coefficient. The variation of thermoelectric properties is discussed in terms of film crystallinity, which is subject to the dopants' radius. Small amounts of In dopants with a large radius may introduce localized regions in the host film, affecting the thermoelectric properties. Consequently, a 1.5 times increase in power factor, three times reduction in thermal conductivity, and 5-fold enhancement in the figure of merit ZT have been achieved at 110 °C. The results also indicate that the balanced control of both electron and lattice thermal conductivities through dopant selection are necessary to attain low total thermal conductivity.