The impact of energy transfer processes on the optical profiles of heteroassemblies with quantum dots as a nano-scaffold are highlighted.

The inclusion of inorganic nanoparticles in biological environments has led to the creation of hybrid nanosystems that are employed in a variety of applications. One such system includes quantum dots (QDs) coupled with the photoactive protein, bacteriorhodopsin (BR), which has been explored in developing enhanced photovoltaic devices. In this work, we have discovered that the kinetics of the BR photocycle can be manipulated using CdSe/CdS (core/shell) QDs. The photocycle lifetime of protein samples with varying QD amounts were monitored using time-resolved absorption spectroscopy. Concentration-dependent elongations of the bR and M state lifetimes were observed in the kinetic traces, thus suggesting that excitonic coupling occurs between BR and QDs. We propose that the pairing of BR with QDs has the potential to be utilized in protein-based computing applications, specifically for real-time holographic processors, which depend on the temporal dynamics of the bR and M photointermediates.

Optical data (UV-vis absorption and fluorescence emission spectra, including fluorescence yields and lifetimes) and electrochemical measurements are used to quantify the modulation of the electronic properties of meso-tetrakis(pentafluorophenyl)-chlorin diol and - bacteriochlorin tetraols upon intramolecular chromene-annulation, including the investigation of regio- and stereoisomers. The small modulations of the frontier orbitals of the porphyrinoids are rationalized using DFT computations and can be traced to small electronic effects due to the co-planarized meso-aryl groups in combination with conformational effects.

Hybrid nanostructures comprised of metal nanoparticles (MNPs) and quantum dots (QDs) have been found to exhibit unique, new optical properties due to the interaction that occurs between the MNPs and QDs. The aim of this work is to understand how the exciton-plasmon interaction in these systems is dependent on the excitation wavelength. The nanoassemblies consisted of gold (Au) NPs coated in a silica (SiO2) shell of a controlled thickness and core/shell CdSe/CdS QDs adsorbed onto the SiO2 shells. Our findings show that the photoluminescence lifetimes of the hybrid constructs are dependent on the excitation wavelength relative to the localized surface plasmon resonance (LSPR) of the Au NPs. When the excitation wavelength is closer to the LSPR, the photoluminescence decay of the hybrid structures is faster. We demonstrate that by tuning the excitation wavelength close to the resonance, there is an enhancement in the exciton-plasmon coupling between the Au NPs and QDs resulting in a shortening in the QD photoluminescence lifetime. We then propose a possible mechanism to explain this excitation wavelength-dependent phenomenon.

Gold (Au) nanoparticles of varying sizes were synthesized during an outreach activity to introduce students to the size-dependent optical properties of nanomaterials. For the fabrication of Au nanoparticles of varying sizes, a seeded growth method was employed. In the first part of the activity, students performed the Frens method to obtain Au seeds. Students then used these seeds in the second part to conduct a seed-mediated synthesis, and obtained Au nanoparticles of a wide size range. The size differences in the particles were evident by eyesight due to color changes in the nanoparticle solutions. In addition to observations made about color, the nanoparticles were characterized using UV vis spectroscopy, and a red shift in the peak wavelength of the extinction spectra of the Au nanoparticles was observed when nanoparticles were grown larger in size. This activity demonstrates a straightforward approach to seed-mediated nanoparticle growth and is applicable to both high school and undergraduate students.