ABSTRACT
The application of a liquid crystal (LC) in displays has driven the development of novel LC elements. In this Letter, polarization variable line-space (PVLS) gratings based on photoalignment are fabricated, and their variable-spacing properties are derived using the vector diffraction theory. Both transmissive and reflective PVLS gratings are fabricated to validate the correctness of the derivation. Experimental results indicate that PVLS gratings have a wider wavelength response bandwidth than that of polarization volume grating (PVG). PVLS gratings have angle selectivity, and a large incident angle causes wavelength blueshift. Additionally, the relationship between wavelength and focal length indicates its anomalous dispersion as a diffractive optical element. These results of photoalignment-based PVLS gratings provide valuable insights for the advancement of displays and have the potential to improve visual experiences.
ABSTRACT
The efficiency of CO2 photocatalytic reduction is severely limited by inefficient separation and sluggish transfer. In this study, spin polarization was induced and built-in electric field was strengthened via Co doping in the BiVO4 cell to boost photocatalytic CO2 reduction. Results showed that owing to the generation of spin-polarized electrons upon Co doping, carrier separation and photocurrent production of the Co-doped BiVO4 were enhanced. CO production during CO2 photocatalytic reduction from the Co-BiVO4 was 61.6 times of the BiVO4. Notably, application of an external magnetic field (100 mT) further boosted photocatalytic CO2 reduction from the Co-BiVO4, with 68.25 folds improvement of CO production compared to pristine BiVO4. The existence of a built-in electric field (IEF) was demonstrated through density functional theory (DFT) simulations and kelvin probe force microscopy (KPFM). Mechanism insights could be elucidated as follows: doping of magnetic Co into the BiVO4 resulted in increased the number of spin-polarized photo-excited carriers, and application of a magnetic field led to an augmentation of intrinsic electric field due to a dipole shift, thereby extending carrier lifetime and suppressing charges recombination. Additionally, HCOO- was a crucial intermediate in the process of CO2RR, and possible pathways for CO2 reduction were proposed. This study highlights the significance of built-in electric fields and the important role of spin polarization for promotion of photocatalytic CO2 reduction.
ABSTRACT
Surface defects on photocatalysts could promote carrier separation and generate unsaturated sites for chemisorption and reactant activation. Nevertheless, the inactivation of oxygen vacancies (OVs) would deteriorate catalytic activity and limit the durability of defective materials. Herein, bagasse-derived carbon quantum dots (CQDs) are loaded on the Sn-doped Bi2 O2 CO3 (BOC) via hydrothermal procedure to create BiâOâC chemical bonding at the interface, which not only provides efficient atomic-level interfacial electron channels for accelerating carriers transfer, but also enhances durability. The optimized Sn-BOC/CQDs-2 achieves the highest photocatalytic removal efficiencies for levofloxacin (LEV) (88.7%) and Cr (VI) (99.3%). The elimination efficiency for LEV and Cr (VI) from the Sn-BOC/CQDs-2 is maintained at 55.1% and 77.0% while the Sn-BOC is completely deactivated after four cycle tests. Furthermore, the key role of CQDs in stabilization of OVs is to replace OVs as the active center of H2 O and O2 adsorption and activation, thereby preventing reactant molecules from occupying OVs. Based on theoretical calculations of the Fukui index and intermediates identification, three possible degradation pathways of LEV are inferred. This work provides new insight into improving the stability of defective photocatalysts.
ABSTRACT
Mesoporous silica nanoparticles (MSNs) functionalized with benzimidazole-derived fluorescent molecules (DHBM) are fabricated via a feasible interfacial superassembly strategy for the highly sensitive and selective detection of Cu2+ . DHBM-MSN exhibits an obvious quenching effect on Cu2+ in aqueous solutions, and the detection limit can be as low as 7.69×10-8 â M. The DHBM-MSN solid-state sensor has good recyclability, and the silica framework can simultaneously improve the photostability of DHBM. Two mesoporous silica nanoparticles with different morphologies were specially designed to verify that nanocarriers with different morphologies do not affect the specific detectionability. The detection mechanism of the fluorescent probe was systematically elucidated by combining experimental results and density function theory calculations. Moreover, the detection system was successfully applied to detect Cu2+ in bovine serum, juice, and live cells. These results indicate that the DHBM-MSN fluorescent sensor holds great potential in practical and biomedical applications.
Subject(s)
Nanoparticles , Silicon Dioxide , Benzimidazoles , Copper , Fluorescent DyesABSTRACT
A novel copper ion sensing periodic mesoporous organosilica (SCN-PMO) was obtained by incorporating a Schiff base-based fluorescent receptor into the pore walls of mesoporous silica, which exhibited a well ordered mesoporous structure and excellent optical properties demonstrated by various characterization results. SCN-PMO possessed high selectivity and sensitivity towards Cu2+ based on its specific fluorescence response. The detection limit of SCN-PMO could be as low as 6.7 × 10-7 M. Due to protection of the silica network, SCN chromophores in PMOs exhibited higher photostability and the resulting material possessed great repeatability. Additionally, the fluorescence changes of SCN-PMO towards copper ions in vivo (zebrafish) showed that SCN-PMO has potential application as a nanoprobe in biological fields.
