Extended Surface Bands Enabled Lasing Emission and Wavelength Switch from Sulfur Quantum Dots.

The development of a lasing wavelength switch, particularly from a single inorganic gain material, is challenging but highly demanded for advanced photonics. Nonetheless, all current lasing emission of inorganic gain materials arises from band-edge states, and the inherent fixed bandgap limitation of the band-edge system leads to the inaccessibility of lasing wavelength switching from a single inorganic gain material. Here the realization of a single inorganic gain material-based lasing wavelength switch is reported by proposing an alternative lasing emission strategy, that is, lasing emission from surface gain. Previous efforts to achieve surface-gain-enabled lasing emission have been hindered by the limited gain volume provided by surface states due to the broad emission bandwidth and/or low emission efficiency. This challenge is overcome by introducing extended surface bands onto the surface of sulfur quantum dots. The extended surface bands contribute to a high photoluminescence quantum yield and narrow emission bandwidth, thereby providing sufficient gain volume and facilitating stimulated emission. When combined with whispering gallery mode microcavity, surface gain enabled lasing emission manifests an ultralow threshold of 8.3 µJ cm-2. Remarkably, the reconfigurable perturbation to surface gain, facilitated by molecular affinity, allows for the realization of the lasing wavelength switch from a single inorganic gain material.

Increasing antibiotic activity by rapid bioorthogonal conjugation of drug to resistant bacteria using an upconverted light-activated photocatalyst.

Antibiotic vancomycin (Van) is often used as the drug of last resort to treat methicillin resistant Staphylococcus aureus. Due to the emergence of Van-resistant microbes, it is necessary to continuously design strategies to increase the efficacy of Van against resistant cells. In this study, an efficient method of bio-conjugating Van to bacteria is proposed using near-infrared (NIR)-light activation. A Nd3+-sensitized upconversion nanocrystal (UCNC) decorated with toluidine blue O (TB) on its surface undergoes upconverted energy transfer from the UCNC to TB when excited by 808 nm light. The photoexcited TB then catalyses the conversion of the dihydrotetrazine (dHTz) moiety in a Van-dHTz conjugate system to tetrazine which undergoes an efficient inverse electron demand Diels-Alder reaction with prior attached norbornene molecules on bacterial cell walls. The enhanced affinity of Van to bacteria by covalent bonding improves the activity of the drug against drug-resistant Enterococci, and the MIC is reduced by 6- to 7-fold as compared to neat Van. We demonstrate that the mode of action is due to increased inhibition of peptidoglycan cell wall biosynthesis. The findings in this study demonstrate that on-demand NIR-light activated bioorthogonal conjugation of Van to microbes is a viable alternative treatment in combating drug-resistant bacteria.

Lipopolysaccharide-affinity copolymer senses the rapid motility of swarmer bacteria to trigger antimicrobial drug release.

An intelligent drug release system that is triggered into action upon sensing the motion of swarmer P. mirabilis is introduced. The rational design of the drug release system focuses on a pNIPAAm-co-pAEMA copolymer that prevents drug leakage in a tobramycin-loaded mesoporous silica particle by covering its surface via electrostatic attraction. The copolymer chains are also conjugated to peptide ligands YVLWKRKRKFCFI-NH2 that display affinity to Gram-negative bacteria. When swarmer P. mirabilis cells approach and come in contact with the particle, the copolymer-YVLWKRKRKFCFI-NH2 binds to the lipopolysaccharides on the outer membrane of motile P. mirabilis and are stripped off the particle surface when the cells move away; hence releasing tobramycin into the swarmer colony and inhibiting its expansion. The release mechanism is termed Motion-Induced Mechanical Stripping (MIMS). For swarmer B. subtilis, the removal of copolymers from particle surfaces via MIMS is not apparent due to poor adherence between bacteria and copolymer-YVLWKRKRKFCFI-NH2 system.

Photocatalytic CO2 reduction over B4C/C3N4 with internal electric field under visible light irradiation.

Boron carbide/graphitic carbon nitride (B4C/g-C3N4) p-n hetero-junction photocatalyst with an internal electric field was synthesized by a facile solvent evaporation method and characterized by field emission scanning electron microscope (FESEM), UV-Vis diffuse reflectance spectra (UV-Vis DRS), photoluminescence spectra (PL), etc. Photocatalytic activity of the composite B4C/g-C3N4 loaded with Pt co-catalyst was evaluated using CO2 conversion to CH4 with H2 as the hydrogen source and reductant under visible light irradiation. The coupling of p-type B4C with n-type g-C3N4 significantly improved the performance of photocatalytic CO2 reduction; with the optimum B4C mass fraction of 1/6, the composite photocatalyst showed approximately 6 and 8 times higher CH4 generation rate than g-C3N4 and B4C, respectively. The enhancement was attributed to efficient photo-excited electron/hole separation due to the formation of internal electric field at the p-B4C/n-C3N4 interface.

Controllable Synthesis and Photocatalytic Properties Study of Na2Ti3O7 and H2Ti3O7 Nanotubes with High Exposed Facet (010).

The role of replacing Na+ with H+ of titanate in promoting photocatalytic performance was investigated. The experimental results showed that H2Ti3O7 and Na2Ti3O7 catalysts with the same high exposed (010) facet had the similar light absorption capacity, TiO6 octahedral structure, and specific surface area. By comparing to Na2Ti3O7, H2Ti3O7 had longer lifetime and higher separation efficiency of the photo-generated electron-hole pairs, and also had higher density of surface oxygen vacancies, which resulted in the excellent performances for photocatalytic hydrogen production and dye degradation reactions.