Analysis of the electron transfer properties of carbon quantum dots on gold nanorod surfaces via plasmonic resonance scattering spectroscopy

Carbon dot/inorganic nanomaterial composites

The preparation methods, formation mechanism, properties and applications of carbon dot/inorganic nanohybrid materials are reported.

Photoinduced electron transfer dynamics of AuNPs and Au@PdNPs supported on graphene oxide probed by dark-field hyperspectral microscopy

The time scale for interfacial photoinduced electron transfer (PeT) in plasmonic nanoparticles is not well established and the details are still under debate. This has renewed the interest in studying the electron transfer effect from both experimental and theoretical points of view. We present a quantitative analysis of PeT in single spherical gold (Au) and gold@palladium core@shell (Au@Pd) nanoparticles supported on reduced graphene oxide (RGO) using dark-field hyperspectral microscopy (DFHM) and electrochemical impedance spectroscopy (EIS). By studying the plasmon bandwidth in the scattering spectra of single particles and by correlating it to the plasmon damping processes we showed that PeT occurs from the AuNPs to RGO in a 10 fs time scale with a quantum efficiency of 35%. The introduction of a Pd shell on the AuNPs decreases the PeT time, with transfer occurring in as little as 1.7 fs with quantum yield higher than 74%. Furthermore, EIS showed a smaller resistance for PeT on RGO/Au@PdNPs under green light illumination. Our results can improve the understanding of the chemical interface damping process due to PeT in plasmonic nanomaterials and can enable the design of more efficient plasmon enhanced photocatalysts.

An approach to the photocatalytic mechanism in the TiO2-nanomaterials microorganism interface for the control of infectious processes

The approach of this timely review considers the current literature that is focused on the interface nanostructure/cell-wall microorganism to understand the annihilation mechanism. Morphological studies use optical and electronic microscopes to determine the physical damage on the cell-wall and the possible cell lysis that confirms the viability and microorganism death. The key parameters of the tailoring the surface of the photoactive nanostructures such as the metal functionalization with bacteriostatic properties, hydrophilicity, textural porosity, morphology and the formation of heterojunction systems, can achieve the effective eradication of the microorganisms under natural conditions, ranging from practical to applications in environment, agriculture, and so on. However, to our knowledge, a comprehensive review of the microorganism/nanomaterial interface approach has rarely been conducted. The final remarks point the ideal photocatalytic way for the effective prevention/eradication of microorganisms, considering the resistance that the microorganism could develop without the appropriate regulatory aspects for human and ecosystem safety.

pH and Glutathione Synergistically Triggered Release and Self-Assembly of Au Nanospheres for Tumor Theranostics

Theranostic agents based on near-infrared absorption which integrate both imaging and therapeutic functions have attracted considerable attention. However, because of the interference signal, indiscriminate treatment usually causes side effects on normal tissues during tumor treatment. To address this limitation, we propose a new synergistically triggered mechanism, release and self-assembly of Au nanospheres, for tumor theranostics based on the synergistic effect of H⁺ and glutathione on the tumor microenvironment. In vitro experiments reveal that Au nanospheres release from Au@ZIF-8 at a high concentration of H⁺ or glutathione. Importantly, Au aggregation only appears in the synergistic effect of glutathione and lower pH and exhibits strong coupling plasmonic resonance absorption in the near-infrared region and can be used as the theranostics agent. This statement was further verified by biological transmission electron microscopy and in vivo imaging. Au@ZIF-8 is stable and produces no photoacoustic signal in normal tissue; in contrast, in the presence of overexpressed glutathione and H⁺, Au nanospheres release from Au@ZIF-8, assemble to aggregates, and exhibit a strong signal at the tumor site for imaging and efficient photothermal therapy. This work provides a new strategy for designing theranostic agents with sequentially responsive steps to avoid interference diagnosis signals from normal tissues and reduce damage to normal tissue during treatment.

Facile fabrication of configuration controllable self-assembled Al nanostructures as UV SERS substrates

The resonantly enhanced near-surface electromagnetic field of Al nanostructures (NSs) excited with UV light offers an effective and precise approach to obtain vibration information in complex mixtures up to a single-molecule magnitude. In this work, we propose a facile, cost-effective and large-scale way to fabricate self-assembled Al NSs with systematically controllable configuration and size for the preparation of SERS substrates. The stalagmite-shaped Al nanoparticles (NPs) are directly utilized based on the Volmer-Weber model and drastically develop as a function of the annealing temperature with tunable optical properties, resulting in a maximum enhancement factor of the vibrational Raman signal from adenine molecules up to 3.49 × 10⁷. With a variation of the deposition thickness at an identical temperature, the self-assembled Al NSs sensitively evolve from stalagmite-shaped NPs to worm-like nano-mounds with increased light consumption induced by scattering, which inherently leads to a noticeable reduction in the EF due to the reduced plasmon coupling between NSs with the sparse distribution. The enhancement effect of the SERS substrates is theoretically discussed with the FDTD simulation, providing an instructive reference for promising applications in the bio-sensing technique.

Effect of Nitrogen Doping Level on the Performance of N-Doped Carbon Quantum Dot/TiO2 Composites for Photocatalytic Hydrogen Evolution

Carbon quantum dots (CQDs) have attracted widespread interest for photocatalytic applications, owing to their low cost and excellent electron donor/acceptor properties. However, their advancement as visible-light photosensitizers in CQDs/semiconductor nanocomposites is currently impaired by their poor quantum yields (QYs). Herein, we describe the successful fabrication of a series of nitrogen-doped CQDs (NCDs) with N/C atomic ratios ranging from 0.14-0.30. NCDs with the highest N-doping level afforded a remarkable external QY of 66.8 % at 360 nm, and outstanding electron transfer properties and photosensitization efficiencies when physically adsorbed on P25 TiO₂ . A NCDs/P25-TiO₂ hybrid demonstrated excellent performance for hydrogen evolution in aqueous methanol under both UV and visible-light illumination relative to pristine P25 TiO₂ . Controlled nitrogen doping of CQDs therefore represents a very effective strategy for optimizing the performance of CQDs/semiconductor hybrid photocatalysts.