The efficiency of heterogeneous photocatalysis for converting solar to chemical energy is low on a per photon basis mainly because of the difficulty of capturing and utilizing light across the entire solar spectral wavelength range. This challenge is addressed herein with a plasmonic superstructure, fashioned as an array of nanoscale needles comprising cobalt nanocrystals assembled within a sheath of porous silica grown on a fluorine tin oxide substrate. This plasmonic superstructure can strongly absorb sunlight through different mechanisms including enhanced plasmonic excitation by the hybridization of Co nanoparticles in close proximity, as well as inter‐ and intra‐band transitions. With nearly 100% sunlight harvesting ability, it drives the photothermal hydrogenation of carbon dioxide with a 20‐fold rate increase from the silica‐supported cobalt catalyst. The present work bridges the gap between strong light‐absorbing plasmonic superstructures with photothermal CO2 catalysis toward the complete utilization of the solar energy.
Addition of a trace quantity of cationic triphenylmethane (TPM+) dyes to isolated Ag nanoparticles in an aqueous solution yielded Ag flocculates composed of a few closely adjacent suspended nanoparticles. This change was evidenced by coupled LSP peaks emerged at 600−800 nm. However, neutral para-rosaniline (p-RA) molecules as well as neutral rhodamine 123 did not cause the Ag flocculation in contrast to their cations, indicating a crucial role of electrostatic interaction between cationic dyes and negatively charged Ag surfaces for the flocculation. Accordingly, cationic dye molecules are located in the nanogap between closely adjacent Ag nanoparticles which evoked enormous SERS intensity. The formation of the Ag flocculates was insensitive to steric hindrance by different amino groups −NH2, −N(CH3)2, and −N(C2H5)2 in TPM dyes. This observation is consistent with dominant role of the electrostatic interaction. Nevertheless, distinct red shifts of fluorescence peaks were observed depending on the molecular structures such as coplanar and propeller phenyl rings, suggesting perturbed electronic states of TPM dyes upon adsorption through the amino groups.
Addition of neutral R123 molecules (10(-7) M) to an as-prepared gold nanoparticles (AuNPs) suspension generated flocculates that are a small number of closely adjacent particles. Formation of AuNP flocculates was evidenced by the coupled localized plasmon peak at 720-750 nm. The AuNP flocculates provided pronounced SERS spectra of adsorbed neutral R123 molecules (SERS-A) as anticipated by FDTD (Finite Difference Time Domain) simulations. The observed SERS spectra are significantly different from those of cationic R123(+) molecules (SERS-B), which electrostatically adsorbed on Cl(-)-treated AuNPs. The difference is not simply due to deprotonation but reflects a distinct difference in adsorption nature between neutral R123 and cationic R123(+) molecules. Indeed neutral R123 molecules exclusively gave an Au-N stretching band at 202 cm(-1), showing the chemisorption on Au surfaces through lone pair electrons at the amino groups. The different adsorption nature is further evidenced by the observation that cationic R123(+) molecules adsorbed on as-prepared (without NaCl addition) AuNP flocculates gave both SERS-A and SERS-B spectra. Thus, the cationic R123(+) molecules form the flocculates both by chemisorption and electrostatic adsorption owing to modest surface charge on as-prepared AuNPs.
This paper presents the use of high spatial resolution silver nanoparticle based near-infrared surface enhanced Raman scattering (SERS) from rat pancreatic tissue to obtain biochrmical information about the tissue. A high quality SERS signal from a mixture of pancreatic tissues and silver nanoparticles can be obtained within 10 s using a Renishaw micro-Raman system. Prominent SERS bands of pancreatic tissue were assigned to known molecular vibrations, such as the vibrations of DNA bases, RNA bases, proteins and lipids. Different tissue structures of diabetic and normal rat pancreatic tissues have characteristic features in SERS spectra. This exploratory study demonstrated great potential for using SERS imaging to distinguish diabetic and normal pancreatic tissues on frozen sections without using dye labeling of functionalized binding sites.
A strong sunlight-absorptive ability and high dispersity are considered as two key requirements of supported metal catalysts for efficient photothermal CO 2 conversions. The former can be improved by increasing the metal loading but often at the expense of decreasing the latter. Here we develop an ion-exchange route to supported Ru nanoparticles with both high loadings and dispersity that exhibit enhanced activity and relatively good stability in photothermal CO 2 catalysis. This strategy involves an ionexchange reaction between Ru 3+ and Mg(OH) 2 to form uniformly distributed and chemically bonded Ru precursors on Mg(OH) 2 supports. The subsequent lowtemperature reduction by H 2 produces highly dispersed Ru nanoparticles whose sizes barely change as the loading increases. Our study provides an avenue for the preparation of strongly light-absorptive and highly dispersed metal catalysts for efficient conversion of carbon dioxide into solar fuels.
Amplification of the intensity and dissymmetry factors (glum) of circularly polarized light is desired to broaden the range of applications of circularly polarized luminescence (CPL) because of the small glum values commonly observed for CPL materials and the loss of intensity resulting from circular polarization. In this study, enhanced CPL produced by metal‐enhanced fluorescence is successfully achieved by the self‐assembly of Au@SiO2 triangular nanoprisms (Au@SiO2TNPs) and fluorophores (sulforhodamine 101 and methylene blue) in chiral cellulose nanocrystal films. By overlapping the plasmon bands of Au@SiO2TNPs and the excitation–emission spectra of fluorophores, both the fluorescence intensity and glum value of CPL are significantly enhanced. For sulforhodamine 101 in the metal‐enhanced CPL system, a 52‐fold fluorescence enhancement is achieved, and the glum value increased from −0.038 to −0.126. For methylene blue in the metal‐enhanced CPL system, a 201‐fold enhancement of fluorescence is obtained, and the glum value is enhanced from −0.055 to −0.085. This metal‐enhanced CPL film is expected to generate superior circularly polarized light for extensive CPL applications because of its outstanding enhanced CPL, fluorescence amplification, and feasibility for different fluorophores.
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