Gold Nanorods: The Most Versatile Plasmonic Nanoparticles.

Gold nanorods (NRs), pseudo-one-dimensional rod-shaped nanoparticles (NPs), have become one of the burgeoning materials in the recent years due to their anisotropic shape and adjustable plasmonic properties. With the continuous improvement in synthetic methods, a variety of materials have been attached around Au NRs to achieve unexpected or improved plasmonic properties and explore state-of-the-art technologies. In this review, we comprehensively summarize the latest progress on Au NRs, the most versatile anisotropic plasmonic NPs. We present a representative overview of the advances in the synthetic strategies and outline an extensive catalogue of Au-NR-based heterostructures with tailored architectures and special functionalities. The bottom-up assembly of Au NRs into preprogrammed metastructures is then discussed, as well as the design principles. We also provide a systematic elucidation of the different plasmonic properties associated with the Au-NR-based structures, followed by a discussion of the promising applications of Au NRs in various fields. We finally discuss the future research directions and challenges of Au NRs.

Plasmon-Controlled Selective Emission Enhancement of Eu3+ with (Au Core)@(Y(V,P)O4:Eu) Nanostructures.

Plasmonic nanostructures have a capability to control the photoluminescence (PL) emission properties of optical species and thus can dramatically enhance the performances of diverse optical systems and devices. Lanthanide ions typically exhibit multiple PL emission lines. Systematic studies on the plasmon-enabled selective enhancement for the different emission lines of lanthanide ions are still highly desired in order to achieve the fine manipulation on the spectral profile and luminescence intensity ratio (LIR). Herein we report on the synthesis and PL emission properties of monodisperse spherical (Au core)@(Y(V,P)O4:Eu) nanostructures, which integrate the plasmonic and luminescent units into an individual core@shell structure. The localized surface plasmon resonance adjusted through control of the size of the Au nanosphere core enables the systematic modulation of the selective emission enhancement of Eu3+. As revealed by single-particle scattering and PL measurements, the five luminescence emission lines of Eu3+ originating from the 5D0,1 excitation states are affected by the localized plasmon resonance to different extents, which are dependent on both the dipole transition nature and the intrinsic quantum yield of the emission line. Based on the plasmon-enabled tunable LIR, high-level anticounterfeiting and optical temperature measurements for photothermal conversion are further demonstrated. Our architecture design and PL emission tuning results offer many possibilities for constructing multifunctional optical materials by integrating plasmonic and luminescent building blocks into hybrid nanostructures with different configurations.

Titanium Oxynitride Spheres with Broad Plasmon Resonance for Solar Seawater Desalination.

The facile production of hollow and solid nitridized submicrometer titania spheres has been successfully realized, with potential for mass production. The nitridation process gives submicrometer titanium oxynitride spheres, which possess a strong and broadband light absorption property. Interband-transition-induced resonance and plasmon resonance have been found to coexist in titanium oxynitride spheres through single-particle dark-field scattering measurements. Theoretical modeling has further confirmed that the excellent light absorption properties of the oxynitride spheres originate from the supported dual-mode optical resonance. A highly efficient, easy-to-build, and self-sustainable device is rationally designed for solar-driven seawater desalination, where the titanium oxynitride spheres function as photothermal transducers. The hollow spheres possess a higher water evaporation rate than the solid ones as the inner surface of the hollow spheres also provides surface sites for interaction with water molecules. Given the outstanding light absorption capability and the unique morphology of the hollow spheres, a water evaporation rate of ∼1.49 kg m-2 h-1 with a solar-to-thermal conversion efficiency of ∼89.1% has been achieved under the illumination of simulated solar light (1 sun, 1 kW m-2). This marks the record performance among reported plasmon-based solar seawater desalination systems.

Mode-dependent energy exchange between near- and far-field through silicon-supported single silver nanorods.

Optical antenna effects endow plasmonic nanoparticles with the capability to enhance and control various types of light-matter interaction. Most reported plasmonic systems can be regarded as single-channel nanoantennas, which rely only on a bright dipole plasmon mode for energy exchange between near- and far-field. Herein we demonstrate a dual-channel plasmonic system that can separate the excitation and emission processes into two energy exchange pathways mediated by the different plasmon modes, offering a higher degree of freedom for the manipulation of light-matter interaction. Our system, consisting of high-aspect-ratio Ag nanorods and Si substrates, can support a series of bright and dark plasmon modes with distinct near- and far-field properties and generate relatively intensive local field enhancement in the gap region. As a proof-of-principle, we take plasmon-enhanced fluorescence of dye molecules as an example to reveal the energy exchange mechanism in the dual-channel plasmonic system. Such a system is potentially also useful for manipulating other types of light-matter interaction. Our work represents a step toward the utilization of a broader class of plasmon resonance for the development of optical antennas and various on-chip nanophotonic components.

A Schottky-Barrier-Free Plasmonic Semiconductor Photocatalyst for Nitrogen Fixation in a "One-Stone-Two-Birds" Manner.

Plasmonic photocatalysis has received much attention owing to attractive plasmonic enhancement effects in improving the solar-to-chemical conversion efficiency. However, the photocatalytic efficiencies have remained low mainly due to the short carrier lifetime caused by the rapid recombination of plasmon-generated hot charge carriers. Although plasmonic metal-semiconductor heterostructures can improve the separation of hot charge carriers, a large portion of the hot charge carriers are lost when they cross the Schottky barrier. Herein, a Schottky-barrier-free plasmonic semiconductor photocatalyst, MoO3- x , which allows for efficient N2 photofixation in a "one-stone-two-birds" manner, is demonstrated. The oxygen vacancies in MoO3- x serve as the "stone." They "kill two birds" by functioning as the active sites for the chemisorption of N2 molecules and inducing localized surface plasmon resonance for the generation of hot charge carriers. Benefiting from this unique strategy, plasmonic MoO3- x exhibits a remarkable photoreactivity for NH3 production up to the wavelength of 1064 nm with apparent quantum efficiencies over 1%, and a solar-to-ammonia conversion efficiency of 0.057% without any hole scavenger. This work shows the great potential of plasmonic semiconductors to be directly used for photocatalysis. The concept of the Schottky-barrier-free design will pave a new path for the rational design of efficient photocatalysts.

A new cobalt(II) complex nanosheet as an electroactive medium for plasmonic switching on Au nanoparticles.

2D metal-organic complex nanosheets with the merits of high stability and structure tunability are an emerging topic in recent years. To extend the promising ultrathin architectures, a new Co(II) complex nanosheet (Co-nanosheet) is designed and prepared via a readily operated interface-assisted coordination reaction between the ligand 4,4'',4'''-(2,4,6-trimethylbenzene-1,3,5-triyl)tris(2,2':6',2''-terpyridyl) (L) and Co2+ ions. The as-formed Co(II) complex nanosheet exhibits both a uniform layered structure and good thermostability as proposed, which were verified by various chemical and physical analytical methods. Moreover, it is first utilized as an electroresponsive medium to tune the surface plasmon resonance behavior of Au nanoparticles, expanding the applicable fields of this type of 2D materials.

Highly sensitive and uniform surface-enhanced Raman spectroscopy from grating-integrated plasmonic nanograss.

Surface-enhanced Raman scattering (SERS) spectroscopy has found a wide range of applications in biomedicine, food safety and environmental monitoring. However, to date, it is difficult for most SERS substrates to provide an extremely sensitive and highly uniform Raman response simultaneously. Here, we developed a sensitive and uniform SERS sensing strategy based on grating-integrated gold nanograsses (GIGNs), which can amplify the SERS signal up to 10-fold compared to the nanograss without grating (namely on the flat substrate) experimentally. Numerical simulation results show that such an improvement of SERS sensitivity arises from the enhanced hotspots relying on the strong coupling between the localized surface plasmon resonances of individual stripe-regulated gold nanorod assemblies and Wood's anomalies in air and dielectric grating. Importantly, these hotspots on the substrate can be flexibly tailored by adjusting the height and periodicity of the loaded grating. The SERS performances of the GIGNs have further been successfully demonstrated with the label-free detection of adenine and cytosine (DNA bases) molecules at the nanomolar level. Moreover, the GIGNs also presented the uniform spot-to-spot and sample-to-sample SERS signals of the analyte molecules (relative standard deviations down to ∼11% and 13%, respectively). These advantages suggest that our GIGN substrates are of great potential for SERS-related sensing.

[The study of cell biocompatibility of new pattern biphasic calcium phosphate nanocomposite in vitro].

OBJECTIVE: To study the cell biocompatibility of porous biphasic calcium phosphate nanocomposite in vitro. METHODS: Bone marrow mesenchymal cell (BMSCs) obtained from SD rat bone marrow were in vitro induced and proliferated. Afler their osteoblast phenotypes were verified, BMSCs were seeded onto prepared porous biphasic calcium phosphate nanocomposite (Experiment group) and common porous hydroxyapatite (Control group). The cell adhesion was evaluated by scanning electron microscope. Synthesis of alkaline phosphatase enzyme (ALP) and osteocalcin were detected and cell cycle was detected by flow cytometry. RESULTS: BMSCs could fully attach to and extend on the material in experiment and control group, Moreover, experiment group were superior to control group in adhesion, proliferative abilities and osteogenic activity. CONCLUSION: BMSCs can differentiate to osteoblast phenotype; the porous biphasic calcium phosphate nanocomposite as bone tissue engineering scaffold has good cell biocompatibility.