KEYWORDS: Fluorescence, Silver, Matrices, Time correlated single photon counting, Temperature metrology, Solids, Metals, Solid state physics, Photoluminescence, Thin films
Ligand-protected metal nanoclusters (NCs) have emerged as prospective less-toxic luminescent materials which can be beneficial for numerous applications, such as bioimaging, biosensing, photo-induced catalytic process, and optoelectronics. The most intriguing properties of NCs are long photoluminescence (PL) lifetime with broadband PL emission, making them more attractive to be developed. However, low PL Quantum Yield (PLQY) and unclear excitonic dynamics mechanism strongly hinder their practical utilization in daily basis. Therefore, to address these issues, gold-doped silver nanoclusters were synthesized using one-pot synthesis method, and were covalently bonded in a solid matrix, polyvinylpyrrolidone (PVP). The fabricated gold-doped silver nanoclusters embedded in PVP matrix (AuAgNCs@PVP) have bright red emission centered at approximately 650 nm with microseconds PL lifetime. By probing the nanosecond time resolution, it was revealed that two distinct decay profile (nano- and micro-seconds) exist in AuAgNCs@PVP, showing the occurrence of Thermally Activated Delayed Fluorescence (TADF). We also found that after the absorption of photons, thermal equilibrium between singlet and triplet states were quickly reached due to fast intersystem crossing and reverse intersystem crossing (ISC/RISC) process owing to the small singlet triplet energy splitting. Hence, we proposed the mechanism behind broadband PL emission with long PL lifetime was due to Thermally Equilibrated Delayed Fluorescence (TEDF).
Graphene quantum dots (GQDs) are one kind of carbon-based nanomaterials which can be used for numerous applications, such as energy conservation, luminescent solar concentrators, bioimaging, and biosensing. It has low toxicity, high conductivity and it shows exceptional optical properties, including photoluminescence (PL) emission which could be adjusted from blue to red emission depending on the solvent. Another interesting properties found in GQDs is anti-Stokes photoluminescence (ASPL). However, the mechanism of ASPL in GQDs was still unclear. In this study, GQDs were prepared with 1,3,6-trinitropyrene as the precursor, then dissolved in toluene (GQDs@TL). The results show that GQDs@TL has PL emission peak at ~595 nm when excited at ~530 nm and ~700 nm. It showed that GQDs@TL has large energy gain (~310 meV). To further understand the mechanism of ASPL, additional temperature-dependent measurements were done. We found that the large energy gain could be gained owing to the contribution of phonon energy and hot-band absorption energy (EHBA) coming from molecular and lattice vibration. Therefore, this study will conclude the mechanism of ASPL.
Heavy-metal-containing quantum dots (QDs), such as CdSe-based quantum dots (QDs) have been applied to lightconversion nano-phosphors due to tunable emission and pure colors. Unfortunately, those QDs involve toxic elements and synthesize in a hazardous halogenated solvent. Therefore, Eco-friendly gold nano-clusters (AuNCs@GSH) in solution phase have gained much attention for promising applications in biophotonics. For the first time, we explore the feasibility of aqueous-solution-processed AuNCs@GSH as luminescent species for promising applications in "green" luminescent solar concentrators (LSCs) by investigating their photophysical properties. Due to ligand-to-metal chargetransfer (LMCT) state, we found that such "green" LSCs formed by Zn-AuNCs@GSH dispersed in a polymer matrix exhibit large Stokes shift and small scattering losses. Compared to AuNCs@GSH, the Zn-AuNCs@GSH dispersed in a polymer matrix could suppress non-radiative recombination rates, inducing the enhancement of luminescence and the increase of PL-QY from 2% to 40%.
The CdSe-based quantum dots (QDs) have been applied to light-conversion nano-phosphors due to tunable emission and pure colors. However, these cadmium-containing QDs was strongly toxic and synthesized in a hazardous solvent. In addition, conventional QD nano-phosphors with a small Stokes shift suffered from reabsorption losses and aggregation-induced photoluminescence (PL) quenching in the solid state. Therefore, there is a need to develop nanophosphors with a large Stokes shift. Here, we demonstrate one-pot synthesis of gold nanoclusters (AuNCs) using 3- aminopropyltrimethoxysilane (APS) and glutathione as protection ligand with a large Stokes shift. The gold nanoclusters with a large Stokes shift can mitigate the aggregation-induced PL quenching and reabsorption losses, which would be potential candidates for "green" nano-phosphors.
The photoluminescence (PL) properties in GaN epilayers were investigated after depositing graphene quantum
dots (GQDs) on the GaN surface. A seven-fold enhancement of the PL intensity in GaN was observed in the GQD/GaN
composite. On the basis of the PL dynamics, the enhancement of PL in GaN is attributed to the carrier transfer from
GQDs to GaN. Such a carrier transfer is caused by the work function difference between GQDs and GaN, evidencing by
Kelvin probe measurement. The improved PL is promising toward applications in the GaN-based optoelectronic devices.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.