Plasmon-exciton couplings in the MoS2/AuNP plasmonic hybrid structure

Photoluminescence of MoS2 on Plasmonic Gold Nanoparticles Depending on the Aggregate Size

Transition metal dichalcogenides (TMDs) are promising candidates for ultrathin functional semiconductor devices. In particular, incorporating plasmonic nanoparticles into TMD-based devices enhances the light-matter interaction for increased absorption efficiency and enables control of device performance such as electronic, electrical, and optical properties. In this heterohybrid structure, manipulating the number of TMD layers and the aggregate size of plasmonic nanoparticles is a straightforward approach to tailoring device performance. In this study, we use photoluminescence (PL) spectroscopy, which is a commonly employed technique for monitoring device performance, to analyze the changes in electronic and optical properties depending on the number of MoS2 layers and the size of the gold nanoparticle (AuNP) aggregate under nonresonant and resonant excitation conditions. The PL intensity in monolayer MoS2/AuNPs increases as the size of aggregates increases irrespective of the excitation conditions. The strain induced by AuNPs causes a red shift, but as the aggregates grow larger, the effect of p-doping increases and the blue shift becomes prominent. In multilayer MoS2/AuNPs, quenched PL intensity is observed under nonresonant excitation, while enhancement is noted under resonant excitation, which is mainly contributed by p-doping and LSPR, respectively. Remarkably, the alteration in the spectral shape due to resonant excitation is evident solely in small aggregates of AuNPs across all layers.

Review of Gold Nanoparticles in Surface Plasmon-Coupled Emission Technology: Effect of Shape, Hollow Nanostructures, Nano-Assembly, Metal-Dielectric and Heterometallic Nanohybrids

Point-of-care (POC) diagnostic platforms are globally employed in modern smart technologies to detect events or changes in the analyte concentration and provide qualitative and quantitative information in biosensing. Surface plasmon-coupled emission (SPCE) technology has emerged as an effective POC diagnostic tool for developing robust biosensing frameworks. The simplicity, robustness and relevance of the technology has attracted researchers in physical, chemical and biological milieu on account of its unique attributes such as high specificity, sensitivity, low background noise, highly polarized, sharply directional, excellent spectral resolution capabilities. In the past decade, numerous nano-fabrication methods have been developed for augmenting the performance of the conventional SPCE technology. Among them the utility of plasmonic gold nanoparticles (AuNPs) has enabled the demonstration of plethora of reliable biosensing platforms. Here, we review the nano-engineering and biosensing applications of AuNPs based on the shape, hollow morphology, metal-dielectric, nano-assembly and heterometallic nanohybrids under optical as well as biosensing competencies. The current review emphasizes the recent past and evaluates the latest advancements in the field to comprehend the futuristic scope and perspectives of exploiting Au nano-antennas for plasmonic hotspot generation in SPCE technology.

Photoluminescence Enhancement of Monolayer WS2 by n-Doping with an Optically Excited Gold Disk

In nanophotonics and quantum optics, we aim to control and manipulate light with tailored nanoscale structures. Hybrid systems of nanostructures and atomically thin materials are of interest here, as they offer rich physics and versatility due to the interaction between photons, plasmons, phonons, and excitons. In this study, we explore the optical and electronic properties of a hybrid system, a naturally n-doped monolayer WS2 covering a gold disk. We demonstrate that the nonresonant excitation of the gold disk in the high absorption regime efficiently generates hot carriers via localized surface plasmon excitation, which n-dope the monolayer WS2 and enhance the photoluminescence emission by regulating the multiexciton population and stabilizing the neutral exciton emission. The results are relevant to the further development of nanotransistors in photonic circuits and optoelectronic applications.

Strong coupling of hybrid states of light and matter in cavity-coupled quantum dot solids

The formation of plasmon-exciton (plexciton) polariton is a direct consequence of strong light-matter interaction, and it happens in a semiconductor-metal hybrid system. Here the formation of plasmon-exciton polaritons was observed from an AgTe/CdTe Quantum Dot (QD) solid system in the strong coupling regime. The strong coupling was achieved by increasing the oscillator strength of the excitons by forming coupled QD solids. The anti-crossing-like behaviour indicates the strong coupling between plasmonic and excitons state in AgTe/CdTe QD solids, resulting in a maximum Rabi splitting value of 225 meV at room temperature. The formation of this hybrid state of matter and its dynamics were studied through absorption, photoluminescence, and femtosecond transient studies.

Influence of Solvents and Adsorption of Organic Molecules on the Properties of CVD Synthesized 2D MoS2

We present a simple method for modification of 2D materials by drop-casting of the organic molecule in solution on the 2D material under ambient conditions. Specifically, we investigated the adsorption of 6-(4,5-Dihydro-1H-imidazol-3-ium-2-yl)-2-(naphthalene-2-yl)benzothiazole methanesulfonate (L63MS) organic molecule on 2D MoS2. To better understand the effect of the organic molecule on the 2D material, we also investigated the impact of solvents alone on the materials' properties. The MoS2 samples were synthesized using ambient pressure chemical vapor deposition. Atomic force microscopy, Raman spectroscopy, photoluminescence spectroscopy and optical microscopy were used to characterize the samples. The measurements were performed after synthesis, after the drop-casting of solvents and after the drop-casting of organic molecule solutions. Our results indicate that the used organic molecule effectively adsorbs on and prompts discernible changes in the (opto)electronic properties of the 2D material. These changes encompass variations in the Raman spectra shape, alterations in the photoluminescence (PL) signal characteristics and modifications in excitonic properties. Such alterations can be linked to various phenomena including doping, bandgap modifications, introduction or healing of defects and that the solvent plays a crucial role in the process. Our study provides insights into the modification of 2D materials under ambient conditions and highlights the importance of solvent selection in the process.