Stimulated emission in a CuInS2/ZnS core-shell quantum-dot-doped liquid-core optical fiber.

We fabricated QD liquid-core optical fibers by doping C u I n S 2/Z n S (CIS/ZnS) core/shell QDs with cladding times of 90 and 60 min, respectively, and compared and analyzed their emission properties with those of bare core C u I n S 2 QDs. For CIS/ZnS core/shell QDs (with cladding time of 90 min) doped fibers, their emission transmits the longest distance in the fiber, and the emission intensity is approximately 4.73 times that of bare-core QD-doped fibers. Additionally, the fact that the full-width at half-maximum is narrowing and the spectral intensity is rapidly increasing superlinearly with excitation power indicates that stimulated emission happens in the fiber. The optical performance was compared and showed good agreement with a theoretical two-level system model for the QDs confined in an optical waveguide.

Metagenomic insights into the functions of microbial communities in sulfur-rich sediment of a shallow-water hydrothermal vent off Kueishan Island.

Hydrothermal vent (HTV) systems are important habitats for understanding the biological processes of extremophiles on Earth and their relative contributions to material and energy cycles in the ocean. Current understanding on hydrothermal systems have been primarily focused on deep-sea HTVs, and little is known about the functions and metabolisms of microorganisms in shallow-water HTVs (SW-HTVs), which are distinguished from deep-sea HTVs by a depth limit of 200 m. In this study, we analyzed metagenomes of sulfur-rich sediment samples collected from a SW-HTV of Kueishan Island, located in a marginal sea of the western Pacific Ocean. Comparing with a previously published report of pelagic samples from the nearby sampling site, microbial communities in the SW-HTV sediments enriching with genes of both aerobic and anaerobic respiration inferred variable environments in the tested sediments. Abundant genes of energy metabolism encoding sulfur oxidation, H2 oxidation, and carbon fixation were detected from the sediment samples. Sixty-eight metagenome-assembled-genomes (MAGs) were reconstructed to further understand the metabolism and potential interactions between different microbial taxa in the SW-HTVs sediment. MAGs with the highest abundant were chemolithotrophic sulfur-oxidization bacteria, including Sulfurovum represented Campylobacteria involved sox multienzyme, sulfide oxidation genes and rTCA cycle, and Gammaproteobacteria involved dsr gene and CBB cycle. In addition, Desulfobacterota with the potential to participate in sulfur-disproportionating processes also had higher abundance than the sample's overall mean value. The interaction of these bacterial groups allows the microbial communities to efficiently metabolize a large variety of sulfur compounds. In addition, the potential to use simple organic carbon, such as acetate, was found in chemolithotrophic Campylobacterial MAGs. Collectively, our results revealed the complexity of environmental conditions of the vent sediment and highlight the interactive relationships of the dominant microbial populations in driving sulfur cycles in the SW-HTV sediments off Kueishan Island.

Efficient full-color emitting carbon-dot-based composite phosphors by chemical dispersion.

Realizing full-color emission plays a key role in exploring the luminescence mechanisms of carbon dots (CDots) and promoting the applications of CDots in light-emitting diodes (LEDs). Herein, a synthesis strategy for full-color emitting CDots was developed through the solvothermal reaction of citric acid and urea with a constant mass ratio but varying reactant concentrations in solvent. With the reactant concentrations increasing, a dual regulation mechanism including an enhanced nucleation growth process and subsequently increased C[double bond, length as m-dash]O/C[double bond, length as m-dash]N-related surface states should be responsible for the photoluminescence (PL) shift of CDots from blue to red. Relying on the hydrolyzation and condensation processes of 3-aminopropyltrimethoxysilane, a simple and universal method was developed by chemically dispersing the CDots into a cross-linked silica network on the surface of SiO2 nanoparticles to produce efficient full-color emitting SiO2/CDot composite phosphors with considerable PL quantum yields in the range of 30-60%. It was proved that the full-color emitting SiO2/CDot composite phosphors could be flexibly applied in packaging white LEDs, releasing pure white light at the Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.33) with a color rendering index (CRI) of 80.4 and a high color-rendering white light coming entirely from CDots with the CIE coordinates of (0.34, 0.36) and a CRI of 97.4, indicating promising application of the full-color emitting SiO2/CDot composite phosphors in the LED field.

Towards efficient photoinduced charge separation in carbon nanodots and TiO2 composites in the visible region.

In this work, photoinduced charge separation behaviors in non-long-chain-molecule-functionalized carbon nanodots (CDs) with visible intrinsic absorption (CDs-V) and TiO2 composites were investigated. Efficient photoinduced electron injection from CDs-V to TiO2 with a rate of 8.8 × 10(8) s(-1) and efficiency of 91% was achieved in the CDs-V/TiO2 composites. The CDs-V/TiO2 composites exhibited excellent photocatalytic activity under visible light irradiation, superior to pure TiO2 and the CDs with the main absorption band in the ultraviolet region and TiO2 composites, which indicated that visible photoinduced electrons and holes in such CDs-V/TiO2 composites could be effectively separated. The incident photon-to-current conversion efficiency (IPCE) results for the CD-sensitized TiO2 solar cells also agreed with efficient photoinduced charge separation between CDs-V and the TiO2 electrode in the visible range. These results demonstrate that non-long-chain-molecule-functionlized CDs with a visible intrinsic absorption band could be appropriate candidates for photosensitizers and offer a new possibility for the development of a well performing CD-based photovoltaic system.

Towards efficient solid-state photoluminescence based on carbon-nanodots and starch composites.

A new type of environmentally friendly phosphor based on carbon nanodots (CDs) has been developed through the dispersion of CDs by integrating the CDs with starch particles. The starch particles contain large numbers of hydroxyl groups around the surfaces, which can effectively absorb the CDs, whose surfaces are functionalized by lots of carboxyl and amide groups, through hydrogen bonding. Effective dispersion of CDs on the surfaces of starch particles can suppress the non-radiative decay processes and photoluminescence (PL) quenching induced by aggregation of CDs. The starch matrix neither competes for absorbing excitation light nor absorbs the emissions of CDs, which leads to efficient PL emitting. As a result, the starch/CD phosphors with a quantum yield of ∼50% were obtained. The starch/CD phosphors show great potential in phosphor-based light emitting diodes, temperature sensors, and patterning.

Exploring the effect of band alignment and surface states on photoinduced electron transfer from CuInS2/CdS core/shell quantum dots to TiO2 electrodes.

Photoinduced electron transfer (ET) processes from CuInS2/CdS core/shell quantum dots (QDs) with different core sizes and shell thicknesses to TiO2 electrodes were investigated by time-resolved photoluminescence (PL) spectroscopy. The ET rates and efficiencies from CuInS2/CdS QDs to TiO2 were superior to those of CuInS2/ZnS QDs. An enhanced ET efficiency was surprisingly observed for 2.0 nm CuInS2 core QDs after growth of the CdS shell. On the basis of the experimental and theoretical analysis, the improved performances of CuInS2/CdS QDs were attributed to the passivation of nonradiative traps by overcoating shell and enhanced delocalization of electron wave function from core to CdS shell due to lower conduction band offset. These results indicated that the electron distribution regulated by the band alignment between core and shell of QDs and the passivation of surface defect states could improve ET performance between donor and acceptor.