Metal-Enhanced Fluorescence for Alpha-Fetoprotein Detection and for SERS Using Hybrid Nanoparticles of Magnetic Cluster Core—Plasmonic Shell Composite

We demonstrated that the hybrid core–shell nanostructure of Fe3O4 (core) and gold (shell) could be a good substrate candidate both for metal-enhanced fluorescence (MEF) and surface-enhanced Raman spectroscopy (SERS). The magnetic properties of the core material could provide functionalities such as the magnetically induced aggregation/distribution of nanostructures to increase the hot-spot density, while the nano-thickness gold shell allows for the plasmonic enhancement of both fluorescence and SERS. The gold-capped magnetic (Fe3O4) nanoparticles (GMPs) were facilely synthesized using a newly developed chemical method. The relative molar ratio of the constituent materials of the core–shell composite was optimized for tuning the plasmonic resonance wavelengths for MEF and SERS. We employed GMP-based MEF to detect alpha-fetoprotein (AFP), with concentrations ranging from 0.05 to 1000 ng/mL, and obtained a limit of detection (LOD) as low as 3.8 × 10−4 ng/mL. The signal enhancement factor (EF) in the GMP-based MEF was 1.5 at maximum. In addition, the GMPs were used in SERS to detect rhodamine B (RhB). Its LOD was 3.5 × 10−12 M, and the EF was estimated to be about 2 × 108. The hybrid core–shell nanoparticles could find potential applications in diagnostic assays based on MEF and SERS in various fields such as food verification, environmental testing/monitoring, and disease diagnosis

Conversion of bipolar resistive switching and threshold switching by controlling conductivity behavior and porous volumes of UiO-66 thin films

In the age of big data, a memory with cross-bar array architecture is urgently required to facilitate high-density data storage. To eliminate the sneak path current of integrated circuits, threshold switching-based selectors have been utilized simultaneously with resistive switching memories. In this study, the successful absorption of uric acid (UA) into a UiO-66 matrix was realized at room temperature without any disruption of the host crystalline structure. Fourier transform infrared and Raman spectra revealed the presence of UA based on the interaction of its carbonyl group with the UiO-66 matrix, whereas the diffraction peaks in the X-ray diffraction spectra of the (111) and (200) index planes were slightly shifted to the lower 2θ values, demonstrating the interaction of the UA on the system is occupy porous cages and free volume structures. The occupation of UA in the porous volume of the framework has been estimated by the significant vanishing of surface area from 1299 to 950 cm3 g−1 as well as the almost dismission of UiO-66 porous cages of 12.5 Å by BET analysis. The electronic transitions from linkers to metals and intramolecular between nearest linkers of UA absorbed UiO-66 were heavily reduced via the evidence from photoluminescence spectroscopy. These changes in structural and electronic density lead to the change in the electrical conduction mechanism, operating voltage, and resistive switching characteristics from memory switching to threshold switching corresponding to Ag/UiO-66–PVA/Ag and Ag/UA@UiO-66–PVA/Ag device, respectively. The reduction and vanish of porous cages and free volume restrict the formation management of silver conducting filaments through the UA@UiO-66–PVA matrix. This study provides a new approach to controlling the conversion switching behavior between memory and threshold in metal–organic framework materials for high-density cross-bar architecture

An influence of bottom electrode material on electrical conduction and resistance switching of TiO

We investigated the electrical conduction and resistance switching mechanisms of TiOx thin films grown on three kinds of bottom electrode at room temperature (an inert Pt, an active Ti and fluorine tin oxide FTO electrodes). The bottom electrode materials strongly affect the I-V characteristics and switching parameters. The I-V characteristic is explained through the presence of interface states in the metal electrode devices (Pt and Ti) and the work function in the metal oxide device (FTO). The Pt device has the smallest VSET and largest switching ratio, while the Ti device shows the largest VSET and smallest switching ratio. XPS data shows non-lattice oxygen in TiOx films. Therefore, the proposed bipolar resistance switching arises from formation and rupture of filament paths, generated by the movement of oxygen vacancies. All devices depict the same electrical conductions, trap-controlled space-charge-limited, FN tunneling and Ohmic conductions for a high resistance state and a low resistance state, respectively. In this study, the rarely reported FN tunneling conduction in published TiOx-based ReRAM device was found, which can be attributed to an influence of the bottom electrode on the electronic distribution in devices

Optimization of Oligomer Chitosan/Polyvinylpyrrolidone Coating for Enhancing Antibacterial, Hemostatic Effects and Biocompatibility of Nanofibrous Wound Dressing

A synergistic multilayer membrane design is necessary to satisfy a multitude of requirements of an ideal wound dressing. In this study, trilayer dressings with asymmetric wettability, composed of electrospun polycaprolactone (PCL) base membranes coated with oligomer chitosan (COS) in various concentrations of polyvinylpyrrolidone (PVP), are fabricated for wound dressing application. The membranes are expected to synergize the hygroscopic, antibacterial, hemostatic, and biocompatible properties of PCL and COS. The wound dressing was coated by spraying the solution of 3% COS and 6% PVP on the PCL base membrane (PVP6–3) three times, which shows good interaction with biological subjects, including bacterial strains and blood components. PVP6–3 samples confirm the diameter of inhibition zones of 20.0 ± 2.5 and 17.9 ± 2.5 mm against Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The membrane induces hemostasis with a blood clotting index of 74% after 5 min of contact. In the mice model, wounds treated with PVP6–3 closed 95% of the area after 10 days. Histological study determines the progression of skin regeneration with the construction of granulation tissue, new vascular systems, and hair follicles. Furthermore, the newly-growth skin shares structural resemblances to that of native tissue. This study suggests a simple approach to a multi-purpose wound dressing for clinical treatment