Cu@CuOx/WO3 with photo-regulated singlet oxygen and oxygen adatoms generation for selective photocatalytic aromatic amines to imines.

Photocatalysts can absorb light and activate molecular O2 under mild conditions, but the generation of unsuitable reactive oxygen species often limits their use in synthesizing fine chemicals. To address this issue, we disperse 1 wt% copper on tungsten trioxide (WO3) support to create an efficient catalyst for selective oxidative coupling of aromatic amines to imines under sunlight irradiation at room temperature. Copper consists of a metallic copper core and an oxide shell. Experimental and density functional theory calculations have confirmed that Cu2O is the primary activation site. Under λ < 475 nm, the light excites electrons of the valence bands in Cu2O and WO3, which activate O2 to superoxide radical •O2-. Then rapidly transforms into oxygen adatoms (•O) and oxygen anion radicals (•O-) species on the surface of Cu2O. Simultaneously, it is captured by holes in the WO3 valence band to generate singlet oxygen (1O2). •O bind to 1O2 promoting the coupling reaction of amines. When λ > 475 nm, intense light absorption due to the localized surface plasmon resonance excites numerous electrons in Cu to promote the oxidative coupling with the adsorbed O2. This study presents a promising approach towards the design of high-performance photocatalysts for solar energy conversion and environmentally-friendly oxidative organic synthesis.

Underwater wireless optical communication employing polarization multiplexing modulation and photon counting detection.

Wireless optical communication is a crucial direction for improving the data transmission rate in underwater environments. In order to improve the communication performance over the water channel, this paper studies underwater wireless optical communication (UWOC) employing polarization multiplexing modulation and photon counting detection. The improvements in bit error rates and communication capacities are analyzed theoretically by constructing the communication model of polarization multiplexing modulation UWOC based on photon counting. Under specific conditions, the polarization maintenance characteristics of photons over water channels are demonstrated by measuring the Mueller matrix, the fidelity of quantum states, depolarization ratio, and calculating the ratios of ballistic photons. Based on these results, by designing and developing the experimental system of UWOC with the polarization multiplexing modulation and photon counting detection, the data transmission rates of 14.58Mbps and 7.29Mbps are realized over a water channel of 92 m by using polarization on-off keying multiplexing modulation and polarization 2-pulse-position multiplexing modulation, respectively.

Practical underwater quantum key distribution based on decoy-state BB84 protocol.

Polarization encoding quantum key distribution has been proven to be a reliable method to build a secure communication system. It has already been used in an inter-city fiber channel and near-Earth atmosphere channel, leaving an underwater channel the last barrier to conquer. Here we demonstrate a decoy-state BB84 quantum key distribution system over a water channel with a compact system design for future experiments in the ocean. In the system, a multiple-intensity modulated laser module is designed to produce the light pulses of quantum states, including signal state, decoy state, and vacuum state. Classical communication and synchronization are realized by wireless optical transmission. Multiple filtering techniques and wavelength division multiplexing are further used to avoid cross talk of different lights. We test the performance of the system and obtain a final key rate of 245.6 bps with an average quantum bit error rate of 1.91% over a 2.4 m water channel, in which the channel attenuation is 16.35 dB. Numerical simulation shows that the system can tolerate up to 21.7 dB total channel loss and can still generate secure keys in 277.9 m Jerlov type I ocean channel.

Development of a Sensitive and Fast Determination Method for Trace Carbaryl Residues in Food Samples Based on Magnetic COF (TpPa-NH2)@Fe3O4 Nanoparticles and Fluorescence Detection.

Developing a simple and effective method for measuring carbaryl residues in food is urgent due to its widespread use and the associated health risks in agriculture, as well as various defects in existing detection techniques. The COF (TpPa-NH2)@Fe3O4 nanocomposite (amino modification) was synthesized via a two-step method and used as an adsorbent for the extraction of carbaryl from food samples in this study. The results indicated that COF (TpPa-NH2)@Fe3O4 can rapidly and successfully capture carbaryl directly from samples via π-π stacking and hydrophobic interactions, achieving maximum adsorption within 5 min under a small adsorbent quantity using a fluorescence spectrophotometer. Under the optimized conditions, carbaryl exhibited good linearity in the range of 0.2-120 µg·kg-1, and the limit of detection was 0.012 µg·kg-1. The recoveries of the samples were 96.0-107.4%. This method has broad application prospects for the monitoring of carbaryl in food.

Enhancing the Activity of Carboxymethyl Cellulase Enzyme Using Highly Stable Selenium Nanoparticles Biosynthesized by Bacillus paralicheniformis Y4.

The inorganic selenium is absorbed and utilized inefficiently, and the range between toxicity and demand is narrow, so the application is strictly limited. Selenium nanoparticles have higher bioactivity and biosafety properties, including increased antioxidant and anticancer properties. Thus, producing and applying eco-friendly, non-toxic selenium nanoparticles in feed additives is crucial. Bacillus paralicheniformis Y4 was investigated for its potential ability to produce selenium nanoparticles and the activity of carboxymethyl cellulases. The selenium nanoparticles were characterized using zeta potential analyses, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). Additionally, evaluations of the anti-α-glucosidase activity and the antioxidant activity of the selenium nanoparticles and the ethyl acetate extracts of Y4 were conducted. B. paralicheniformis Y4 exhibited high selenite tolerance of 400 mM and the selenium nanoparticles had an average particle size of 80 nm with a zeta potential value of -35.8 mV at a pH of 7.0, suggesting that the particles are relatively stable against aggregation. After 72 h of incubation with 5 mM selenite, B. paralicheniformis Y4 was able to reduce it by 76.4%, yielding red spherical bio-derived selenium nanoparticles and increasing the carboxymethyl cellulase activity by 1.49 times to 8.96 U/mL. For the first time, this study reports that the carboxymethyl cellulase activity of Bacillus paralicheniforis was greatly enhanced by selenite. The results also indicated that B. paralicheniformis Y4 could be capable of ecologically removing selenite from contaminated sites and has great potential for producing selenium nanoparticles as feed additives to enhance the added value of agricultural products.

Experimental demonstration of underwater decoy-state quantum key distribution with all-optical transmission.

We demonstrate the underwater quantum key distribution (UWQKD) over a 10.4-meter Jerlov type III seawater channel by building a complete UWQKD system with all-optical transmission of quantum signals, a synchronization signal and a classical communication signal. The wavelength division multiplexing and the space-time-wavelength filtering technology are applied to ensure that the optical signals do not interfere with each other. The system is controlled by FPGA and can be easily integrated into watertight cabins to perform the field experiment. By using the decoy-state BB84 protocol with polarization encoding, we obtain a bit rate of secure keys of 1.82 Kbps and an error rate of 1.55% at the attenuation of 13.26 dB. We prove that the system can tolerate the channel loss up to 23.7 dB and therefore may be used in the 300-meter-long Jerlov type I clean seawater channel.

Genetically engineered exosomes display RVG peptide and selectively enrich a neprilysin variant: a potential formulation for the treatment of Alzheimer's disease.

Exosome is a promising next generation nano-based drug delivery vehicle. However, the unknown molecular mechanisms underlying its natural tissue tropism and the relatively low quantity of naturally enriched molecules of therapeutic value hamper exosome's clinical application. The aim of the research was to create a targeted and highly efficacious exosome formulation for the treatment of Alzheimer's disease (AD). Genetic engineering techniques combined with co-transfection of parental cells were employed to create an exosome formulation that displays RVG peptide on its surface targeting α7-nAChR and simultaneously enriches a neprilysin variant with increased specificity and efficacy in degrading ß amyloid peptide (Aß). The exosome formulation was preferentially internalised into cell lines in an α7-nAChR expression level-dependent manner. When incubated with Aß-producing N2a cells, it significantly decreased intracellular and secreted Aß40 levels, a potency that is superior to exosomes derived from adipose-derived stem cell. When systemically administered into mice, the exosome formulation was preferentially targeted to the hippocampus region of the brain and significantly decreased the expression of proinflammatory genes, IL1α, TNFα and NF-κB, and simultaneously increased the expression of anti-inflammatory gene, IL10. Our exosome formulation may be explored as an over-the-counter treatment for AD.

Experimental investigation of quantum key distribution over a water channel.

Quantum key distribution (QKD) has undergone significant development in recent decades, particularly with respect to free-space (air) and optical fiber channels. Here, we report a proof-of-principle experiment for the BB84 protocol QKD over a water channel. First, we demonstrate again the polarization preservation properties of the water channel in optical transmission according to the measured Mueller matrix, which is close to the unit matrix. The reason for the polarization preservation, revealed by Monte Carlo simulation, is that almost all the received photons are unscattered. Then, we performed the first polarization encoding BB84 protocol QKD over a 2.37 m water channel. The results show that QKD can be performed with a low quantum bit error rate, less than 3.5%, with different attenuation coefficients.