This study shows that coupling to designed plasmonic nanoparticles can modulate the electrophysiological function of proteins in living mammalian cells. Nanostar-shaped particles, that are robust to biological noise, are designed to enable near-field-coupling to plasma membrane-localized mutated Archaerhodopsin proteins in live cells. The coupled rhodopsins exhibit enhanced fluorescence and an increased response speed to membrane voltage. Incorporating this plasmonic enhancement into a Markov chain photocycle model of the Archaerhodopsin mutant QuasAr6a, shows an increased fluorescence emission rate and manipulation of the protein dynamics through a combination of photocycle transition rate enhancements. The results show an improvement in fluorescence and voltage-response dynamics of the functional QuasAr6a Archaerhodopsin mutant, beyond what has been achievable through genetic engineering. This opens up possibilities for engineering the biological functionality of proteins through plasmonics: manipulating protein photocycles could improve light sensitivity, change optogenetic applications, and lead to fluorescent biosensors with enhanced dynamics.

This research aims to investigate the potential of utilizing particle-based luminescent coatings for light management in greenhouses. Light management includes solar spectral conversion, transmittance, and scattering. Phosphor materials perform energy conversion from high-energy radiation to low-energy radiation through photoluminescent mechanisms. These phosphor materials are applied in the form of a sprayable coating intended to be employed on greenhouse roofing. Through energy conversion, a luminescent phosphor coating can achieve spectral conversion, adding light for crop growth, and will at the same time affect both light transmittance and scattering in greenhouse roofing. The application of phosphors as luminescent coatings on greenhouse roofing is a young research topic with very few published results; therefore, it presents several research challenges. The first is the lack of practical work on luminescent greenhouse coatings, demonstrating what type of spectral conversion is beneficial to plants and even the general feasibility of phosphors for greenhouse applications. The second challenge is to define clear and standardized measurable quantities that determine the success of a greenhouse coating, for example, the coating’s UV-to-PAR conversion efficiency. The third challenge is to design and build a measuring system that can characterize these quantities, especially the hemispherical light transmittance of small-scale luminescent coating samples…

Spectral conversion films and coatings based on photoluminescent materials have attracted increasing attention for greenhouse applications and are reported to provide a net benefit through spectral control. However, there is little experimental data on spectral conversion coating that quantifies their optical properties, including absorption, transmittance, scattering loss, and the influence of the phosphor intrinsic parameters. In this work, UV-to-PAR spectral conversion coatings based on two commercial phosphors ZnS:Ag and BaMgAl10O17:Eu2+ (BAM:Eu), with different particle loading and thickness, were fabricated and assessed by direct transmittance, hemispherical light transmittance (THEM), and diffuse reflectance. Transmittance decreased with increasing coating thickness and particle loading, whereas backward scattering showed the opposite trend. Performance indicators derived from direct transmittance revealed that host-absorption ZnS:Ag coatings exhibited greater UV absorption and higher PAR Enhancement than activator-absorption BAM:Eu coatings, resulting from their higher absorption coefficient. Quantum yield had a minimal impact because both phosphors displayed close PLQY values. However, the backward scattering of ZnS:Ag coatings was more pronounced than that of BAM:Eu coating due to the high refractive index of ZnS:Ag (n ≈ 2.3), as confirmed by diffuse reflectance measurements. The 18 mass%, 200 μm ZnS:Ag coating showed the highest 1.3% PAR Enhancement, but its THEM was reduced by about 45%, demonstrating that backward scattering can counteract the benefits of spectral conversion. A general discussion for phosphor selection in greenhouse applications is also provided in this work.

Greenhouse owners highly value the hemispherical light transmittance (THEM) of roofing materials because sunlight rarely projects at a perpendicular angle, especially in high-latitude regions. With growing interest in research of advanced multi-functional greenhouse roofing, a compact and efficient THEM characterization system for lab-scale samples is needed to promote research in the horticulture field. In this study, we developed a tabletop system capable of characterizing THEM of lab-scale samples with a size one-third of that required by the current characterization system. Key designing parameters, such as the beam cross-section area, port area, and port edge thickness were systematically varied to evaluate their impact on THEM characterization. The results indicated that the total port area should be limited to under 1% of the sphere surface area with minimized edge thickness since reflection from the edge area can not be corrected by a double-beam measurement. Furthermore, the collimated beam cross-section area should exceed the port area by a factor of 1.5 to ensure that THEM remains unaffected by the sphere rotation center. The system provides a consistent and reliable method for THEM measurement and offers essential guidelines for future users to construct a similar setup.

Solar spectral conversion by a low-cost luminescent coating for greenhouse applications increases crop yield and can contribute to addressing the food crisis. A luminescent coating based on cheap SiO2 particles doped with Eu2+ and Al3+ demonstrated extra photosynthetic active radiation (PAR) in this work. To optimize the efficiency of this phosphor for greenhouse applications, three phosphor series with varying Al/Eu content in SiO2 were synthesized via a sol–gel approach and characterized by luminescence decay time, absorption, luminescent excitation, emission, and quantum yield measurements. With increasing the Eu%, at a fixed Al%, the decay time and quantum yield decreased while the emission shifted to the red. The effect can be explained by a more and more efficient resonance energy transfer to lower energy Eu2+ ions and quenching sites. While increasing the Al% at a fixed Eu%, the decay time and quantum yield increased, and the red-shift was reduced. Both effects can be explained by an enhanced Eu2+ solubility (reduced Eu clustering) through the Al3+ co-doping, causing the average Eu2+-Eu2+ distance to be longer and the onset of concentration quenching to shift to a higher Eu%. Specifically, we found that for 1 mol% Eu2+, a minimum of 4 mol% Al3+ was required to avoid concentration quenching. Two indicators were developed to quantify the UV to PAR converting efficiency and to quantify the PAR transmission enhancement. Both indicators were determined in a real coating sample based on the optimized phosphor. The result showed an additional PAR was provided by our luminescent coating. A general discussion about all factors that can bring the conversion efficiency of a phosphor coating closer to the theoretical maximum will be presented.