Photoinduced Charge Injection from Shallow Point Defects in Diamond into Water.

Thanks to its low or negative surface electron affinity and chemical inertness, diamond is attracting broad attention as a source material of solvated electrons produced by optical excitation of the solid-liquid interface. Unfortunately, its wide bandgap typically imposes the use of wavelengths in the ultraviolet range, hence complicating practical applications. Here, we probe the photocurrent response of water surrounded by single-crystal diamond surfaces engineered to host shallow nitrogen-vacancy (NV) centers.

Probing Correlation of Optical Emission and Defect Sites in Hexagonal Boron Nitride by High-Resolution STEM-EELS.

Optically bright emitters in hexagonal boron nitride (hBN) often acting as a source of a single-photon are mostly attributed to point-defect centers, featuring localized intra-bandgap electronic states. Although vacancies, anti-sites, and impurities have been proposed as candidates, the exact physical and chemical nature of most hBN single-photon emitters (SPEs) within the visible region are still up for debate. Combining site-specific high-angle annular dark-field imaging (HAADF) with electron energy loss spectroscopy (EELS), we resolve and identify a few carbon substitutions among neighboring hBN hexagons, all within the same sample region, from which typical defect emission is observed.

Photo-Induced Charge State Dynamics of the Neutral and Negatively Charged Silicon Vacancy Centers in Room-Temperature Diamond.

The silicon vacancy (SiV) center in diamond is drawing much attention due to its optical and spin properties, attractive for quantum information processing and sensing. Comparatively little is known, however, about the dynamics governing SiV charge state interconversion mainly due to challenges associated with generating, stabilizing, and characterizing all possible charge states, particularly at room temperature. Here, multi-color confocal microscopy and density functional theory are used to examine photo-induced SiV recombination - from neutral, to single-, to double-negatively charged - over a broad spectral window in chemical-vapor-deposition (CVD) diamond under ambient conditions.

Detection of moisture ratio and carotenoid compounds in mamey () fruit during dehydration process using spectroscopic techniques.

This work presents the study of the moisture ratio and carotenoid compounds in dried mamey () using non-invasive spectroscopic techniques. The drying behavior of mamey at 64 °C by a homemade solar dryer is analyzed by fitting the experimental data to four different mathematical drying models. In addition, this result is compared with other drying techniques, namely by heat chamber with natural convection at temperatures of 50 °C and 60 °C.

Room-Temperature Photochromism of Silicon Vacancy Centers in CVD Diamond.

The silicon vacancy (SiV) center in diamond is typically found in three stable charge states, SiV, SiV, and SiV, but studying the processes leading to their formation is challenging, especially at room temperature, due to their starkly different photoluminescence rates. Here, we use confocal fluorescence microscopy to activate and probe charge interconversion between all three charge states under ambient conditions. In particular, we witness the formation of SiV via the two-step capture of diffusing, photogenerated holes, a process we expose both through direct SiV fluorescence measurements at low temperatures and confocal microscopy observations in the presence of externally applied electric fields.

Understanding Proton Transfer in Non-aqueous Biopolymers based on Helical Peptides: A Quantum Mechanical Study.

Histidine (an imidazole-based amino acid) is a promising building block for short aromatic peptides containing a proton donor/acceptor moiety. Previous studies have shown that polyalanine helical peptides substituted at regular intervals with histidine residues exhibit both structural stability as well as high proton affinity and high conductivity. Here, we present first-principle calculations of non-aqueous histidine-containing 3-, α- and π-helices and show that they are able to form hydrogen-bonded networks mimicking proton wires that have the ability to shuttle protons via the Grotthuss shuttling mechanism.

Customized depolarization spatial patterns with dynamic retardance functions.

In this work we demonstrate customized depolarization spatial patterns by imaging a dynamical time-dependent pixelated retarder. A proof-of-concept of the proposed method is presented, where a liquid-crystal spatial light modulator is used as a spatial retarder that emulates a controlled spatially variant depolarizing sample by addressing a time-dependent phase pattern. We apply an imaging Mueller polarimetric system based on a polarization camera to verify the effective depolarization effect.

Generation of unconventional polarization from light scattered by metallic cylinders under conical incidence.

A simple experimental method to generate unconventional polarized states from the conical scattering of light by thin metallic cylinders is presented. Results show that radial and azimuthal polarizations are easily obtained. This opens up the possibility for a broad range of applications, from surgery to industrial and even to remote sensing.