A nanocomposite of metal nanoclusters/OSTE is fabricated through off-stoichiometric thiol-ene polymerization, incorporating adamantanethiol-protected electrum nanoclusters Au_23-xAg_x(SAdm)₁₅ (where x = 7.44) along with the OSTE monomer. During the photopolymerization, there is a transforfation of the precursor nanoclusters and the nanocomposite achieves a maximum photoluminescence quantum yield of ≈73% at 740 nm and 60% at the 850 nm emission peak. The photophysical characteristics of nanocomposite AuAgNCs@OSTE are examined at both ambient and low temperatures, revealing an improved radiative recombination mechanism through the interactions with polymer radicals. This high photoluminescence quantum yield near-infrared-emitting AuAgNCs@OSTE material, distinguished by a larger Stokes shift, is utilized to fabricate luminescent solar concentrators measuring 5 × 5 × 0.13 cm³. Experimental measurements are conducted to determine the absorption coefficient, reabsorption coefficient, absorption cross-section, and volume concentration of the device. Additionally, theoretical evaluations of waveguiding efficiency and power conversion efficiency are performed and compared with quantum dot-based alternatives. The findings indicate that the metal NCs@OSTE nanocomposite has the potential to function as a highly efficient, heavy-metal-free nanophosphor, demonstrating superior overall performance for semi-transparent luminescent solar concentrator devices and being suitable for a broad range of light conversion applications in the NIR spectrum.

Upconversion nanoparticles (UCNPs) have attracted great interest due to their unique properties such as anti-Stokes shift, high biocompatibility, and photostability compared with other fluorophores. Single UCNP-based studies are important for highly sensitive biosensing and bioimaging. To enhance the photoluminescence (PL) intensity of UCNPs, various plasmonic nanostructures have been investigated in addition to engineering the elements and structures of UCNPs themselves. However, it is crucial but challenging to precisely control the position of a single UCNP relative to plasmonic nanostructures. Herein, gold nanorod dimers (GNRDs) are used to enhance the PL intensity of single UCNPs selectively captured in the gaps of GNRDs. The dimensions of GNRDs are designed with the assistance of COMSOL Multiphysics simulation to have a plasmonic resonance peak around the excitation wavelength for the UCNPs. After lithography-based fabrication of GNRDs and surface passivation, electron-beam induced deposition is used to selectively create carbon nanodomains (CNDs) in the gaps of GNRDs. The CNDs capture UCNPs by benefiting from the strong affinity between streptavidin and biotin. About 12% of the CNDs capture single UCNPs. Photoluminescence imaging shows an overall intensity enhancement by threefold for single UCNPs by GNRDs of 100 nm gap at 4 × 10 6 W / cm 2 power density. This study shows a promising route for single UCNP-based studies, especially when it is needed to control the position of single UCNPs.

We demonstrate that dielectric Mie scatterers, in the form of silicon nanoparticles (SiNPs), can enhance both the performance and esthetics of semitransparent photovoltaic devices. Unlike plasmonic metal counterparts, dielectric SiNPs exhibit lossless, narrow-band, spectral, and spatially tunable scattering in the visible spectral range. Their effect on a luminescent solar concentrator (LSC) with high visible light transparency is analyzed both theoretically and experimentally as a model system. By selectively reflecting a specific spectral band, SiNPs increase the optical path length of solar photons within the active layer, leading to improved absorption and hence device efficiency. Simultaneously, this light management strategy ensures transmitted color neutrality, an important requirement for wider acceptance of semitransparent photovoltaics. Numerical simulations show that in the regime of individual SiNPs with diameters around 160 nm, a submonolayer surface coverage of ∼10% is sufficient to achieve color neutrality, at the same time enhancing photocurrent by 10–15% for an LSC device. Experimentally, such a dispersed SiNP layer on an LSC substrate is realized by depositing NPs with the surface capped by a sacrificial polymer shell. Subsequent etching of the shell by oxygen plasma leads to an LSC device with a functional selective scattering layer in line with theoretical predictions.

Transparent wood biocomposite (TW) is a sustainable optical material that combines high transmittance with mechanical strength but also exhibits pronounced haze. This haze limits applications where high optical transparency is required, and its physical origin remains insufficiently understood. In this study, photon transport in TW and related wood-based scaffolds at different stages of chemical modification, including delignified wood (DW), native wood (NW) and bleached wood (BW) templates is investigated. Time- and space-resolved transmission measurements are used to extract direction-dependent scattering and absorption coefficients. DW, BW, and NW samples exhibit anisotropic light propagation while TW both suppresses scattering and alters the scattering anisotropy, flipping 90° the dominant transport orientation relative to the fibers. Extracted optical parameters confirm low scattering coefficients, up to 2 orders of magnitude lower than the NW, BW, or DW. The main scattering mechanism for TW is identified as in-plane refraction, leading to predominant forward transmission or “snake-like” photon trajectories, marking a transition from diffusive to quasi-ballistic transport. These insights advance the fundamental understanding of light transport in hierarchical biocomposites and offer a framework for designing sustainable optical composites with broad haze control, increasing the functional potential of TW toward “wood glass”.

CuInS2/ZnS (CIS/ZnS) quantum dots (QDs) are extensively employed as fluorophores in luminescent solar concentrators (LSCs), due to their excellent optical properties and low toxicity. However, the power conversion efficiency (PCE) of LSCs employing CIS/ZnS QDs is significantly constrained by the energy losses from the overlap between the absorption and emission spectra. Herein, we propose a novel and facile approach to enlarge the Stokes shift of CIS/ZnS QDs using the off-stoichiometric thiol–ene (OSTE) polymers. Significantly, the photoluminescence (PL) spectrum of CIS/ZnS QDs in OSTE experienced a substantial redshift of 65 nm without compromising the PLQY. This resulted in a remarkably enlarged Stokes shift of 585 meV and a minimal spectral overlap integral of 0.126, marking the first instance of a nanocomposite featuring CIS/ZnS QDs with such an enlarged Stokes shift. Further investigation demonstrates that thiol monomers, characterized by a strong electron-donating property, altered the Cu+ defect energy states in CIS QDs, resulting in a significant redshift in the PL spectrum. Consequently, a certified record PCE of 1.36% was achieved for a large-area (29 × 29 cm2) LSC device with an average visible transmittance (AVT) of 51%, representing the highest PCE value for such devices. Our findings not only present a viable strategy for augmenting the efficiency of CIS/ZnS QD-based LSCs for building-integrated photovoltaics (BIPV) but also establish a new avenue for controlling the optical properties of QD/polymer nanocomposites for other optoelectronic devices.

High-pressure water vapor annealing (HWA) was recently demonstrated as a method that can substantially improve the photoluminescence quantum yield (PLQY) of silicon quantum dots (Si QDs) with the oxide shell. In this Letter, the mechanism of this enhancement is studied optically on a single-dot level. HWA treatment is performed on Si QDs formed on a silicon-on-insulator wafer, and their photoluminescence (PL) properties were examined before and after the treatment. Our experiments show a 2.5 time enhancement in the average blinking duty cycle of Si QDs after 2.6 MPa HWA treatment without changing the average ON-state PL intensity. This observation proves the carrier trapping process is suppressed on the HWA-built Si/SiO2 interface. We also discussed the mechanism behind the PLQY enhancement of HWA-treated Si QDs by comparing single-dot-level data to reported ensemble PL Si QDs results. HWA treatment is found to mainly brighten "grey" (not 100% efficient) QDs, a mechanism different from changing dark (non-emitting) to bright (100% efficient) Si QDs by ligand passivation.

Fluorescence-based single-molecule detection has been widely investigated and applied in biosensing and bioimaging due to its ultrahigh sensitivity and specificity. However, bulky and expensive commercial fluorescence microscopes are usually required. The Stokes shift property of most commonly used fluorophores requires optical sets such as dichroic mirrors and specific filters in the optical pathway before a photodetector to eliminate excitation and scattering lights from the fluorescence signals. The fluorescence signal collected by an objective is further unavoidably attenuated, and the optical resolution is diffraction-limited. Herein, a proof of concept of a lab-on-a-chip compatible molecular sensor is shown by integrating upconversion nanoparticles (UCNPs) and amorphous hydrogen-doped InGaZnO (InGaZnO:H) thin-film phototransistor (IGZO:H TFTs) aiming to alleviate those issues. Upon illumination with a 980 nm infrared light, the phototransistor shows no photocurrent without UCNPs but yields a high photocurrent with UV-visible fluorescent light emitted from the UCNPs. The molecular detection is enabled by further involving the Förster resonance energy transfer (FRET) mechanism, with the UCNPs as donors. The photocurrent falls back to its original low level when biotinylated gold nanoparticles are added to selectively bind and quench the UCNPs via biotin-streptavidin coupling. Each UCNP shows an estimated photocurrent-to-dark current ratio of 10³ and each biotinylated gold nanoparticle causes at least 1 order of magnitude decrease of the photocurrent. Our integrated setup presents a promising platform for further development toward an optoelectronic biosensor capable of single-molecule detection.

Pure organic ultralong room temperature phosphorescent (URTP) materials have garnered significant attention for applications in luminescent materials, biosensing, and information encryption. These materials offer advantages over heavy metal phosphorescent materials, such as lower cost, reduced biological toxicity, and minimal environmental impact. Herein, for the first time, we demonstrate a series of organic RTP materials based on spiro[fluorene-9,9′-xanthene] (SFX) hole-transporting molecules, specifically X59 and X55. Our research presents that incorporating more rigid SFX units significantly extends RTP lifetime and enhances photoluminescence quantum yield (PLQY). The large steric hindrance of the rigid SFX structures suppresses nonradiative molecular motions, thereby prolonging phosphorescence emission. Compared to the baseline molecule X1, experimental results show that molecule X59 extends the phosphorescence lifetime by 230 ms, while X55 achieves an extension of 260 ms. Furthermore, we highlight the potential of this series of RTP molecules for use in transparent, programmable luminescent tags. Our work not only expands the molecular types of organic RTP materials but also provides innovative strategies for designing long-lived, high-quantum-yield RTP molecules. We envision that this will advance the smart device field of organic phosphorescent materials and their practical applications, such as intelligent labels, tags, and optical sensors.

Metal assisted chemical etching is a promising method for fabricating high aspect ratio micro- and nanostructures in silicon. Previous results have suggested that P-type and N-type silicon etches with different degrees of anisotropy, questioning the use of P-type silicon for nanostructures. In this study, we compare processing X-ray zone plate nanostructures in N and P-type silicon through metal assisted chemical etching with a gold catalyst. Fabricated zone plates were cleaved and studied with a focus on resulting verticality, depth and porosity. Results show that for high aspect ratio nanostructures, both N and P-type silicon prove to be viable alternatives exhibiting different etch rates, but similarities regarding porosity and etch direction.