ABSTRACT
We report on silicon waveguide distributed Bragg reflector (DBR) cavities hybridized with a tellurium dioxide (TeO2) cladding and coated in plasma functionalized poly (methyl methacrylate) (PMMA) for label free biological sensors. We describe the device structure and fabrication steps, including reactive sputtering of TeO2 and spin coating and plasma functionalization of PMMA on foundry processed Si chips, as well as the characterization of two DBR designs via thermal, water, and bovine serum albumin (BSA) protein sensing. Plasma treatment on the PMMA films was shown to decrease the water droplet contact angle from â¼70 to â¼35°, increasing hydrophilicity for liquid sensing, while adding functional groups on the surface of the sensors intended to assist with immobilization of BSA molecules. Thermal, water and protein sensing were demonstrated on two DBR designs, including waveguide-connected sidewall (SW) and waveguide-adjacent multi-piece (MP) gratings. Limits of detection of 60 and 300 × 10-4 RIU were measured via water sensing, and thermal sensitivities of 0.11 and 0.13â nm/°C were measured from 25-50 °C for SW and MP DBR cavities, respectively. Plasma treatment was shown to enable protein immobilization and sensing of BSA molecules at a concentration of 2 µg/mL diluted in phosphate buffered saline, demonstrating a â¼1.6â nm resonance shift and subsequent full recovery to baseline after stripping the proteins with sodium dodecyl sulfate for a MP DBR device. These results are a promising step towards active and laser-based sensors using rare-earth-doped TeO2 in silicon photonic circuits, which can be subsequently coated in PMMA and functionalized via plasma treatment for label free biological sensing.
ABSTRACT
Nanoparticles provide new opportunities in merging therapeutics and new materials, with current research efforts just beginning to scratch the surface of their diverse benefits and potential applications. One such application, the use of inorganic nanoparticles in antiseptic coatings to prevent pathogen transmission and infection, has seen promising developments. Notably, the high reactive surface area to volume ratio and unique chemical properties of metal-based nanoparticles enables their potent inactivation of viruses. Nanoparticles exert their virucidal action through mechanisms including inhibition of virus-cell receptor binding, reactive oxygen species oxidation and destructive displacement bonding with key viral structures. The prevention of viral outbreaks is one of the foremost challenges to medical science today, emphasizing the importance of research efforts to develop nanoparticles for preventative antiviral applications. In this review, the use of nanoparticles to inactivate other viruses, such as influenza, HIV-1, or norovirus, among others, will be discussed to extrapolate broad-spectrum antiviral mechanisms that could also inhibit SARS-CoV-2 pathogenesis. This review analyzes the published literature to highlight the current state of knowledge regarding the efficacy of metal-based nanoparticles and other antiviral materials for biomedical, sterile polymer, and surface coating applications.
ABSTRACT
A modified set-up for Raman spectroscopy is proposed to utilize an AFM probe in a regime beyond the dependence on near field optics. Possible mechanisms for the observed enhancement have been explored through comparisons to spectra from other enhanced Raman techniques, including surface enhanced Raman, interference enhanced Raman and polarized Raman spectroscopies. The effects of polarization, focusing and interference are heightened when near field effects are diminished, giving rise to spectral enhancement. This technique allows for the characterization of a sub-20 nm monolayer of polystyrene-block-poly(2 vinyl pyridine) reverse micelles and paves the way for a promising method of non-destructive analysis of large self-assembled arrays of colloids.
ABSTRACT
As sustainable energy becomes a major concern for modern society, renewable and clean energy systems need highly active, stable, and low-cost catalysts for the oxygen evolution reaction (OER). Mesoporous materials offer an attractive route for generating efficient electrocatalysts with high mass transport capabilities. Herein, we report an efficient hard templating pathway to design and synthesize three-dimensional (3-D) mesoporous ternary nickel iron nitride (Ni3FeN). The as-synthesized electrocatalyst shows good OER performance in an alkaline solution with low overpotential (259 mV) and a small Tafel slope (54 mV dec-1), giving superior performance to IrO2 and RuO2 catalysts. The highly active contact area, the hierarchical porosity, and the synergistic effect of bimetal atoms contributed to the improved electrocatalytic performance toward OER. In a practical rechargeable Zn-air battery, mesoporous Ni3FeN is also shown to deliver a lower charging voltage and longer lifetime than RuO2. This work opens up a new promising approach to synthesize active OER electrocatalysts for energy-related devices.