Nanoscale Confinement and Fluorescence Effects of Bacterial Light Harvesting Complex LH2 in Mesoporous Silicas

Many key chemical and biochemical reactions, particularly in living cells, take place in confined space at the mesoscopic scale. Toward understanding of physicochemical nature of biomacromolecules confined in nanoscale space, in this work we have elucidated fluorescence effects of a light harvesting complex LH2 in nanoscale chemical environments. Mesoporous silicas (SBA-15 family) with different shapes and pore sizes were synthesized and used to create nanoscale biomimetic environments for molecular confinement of LH2. A combination of UV–vis absorption, wide-field fluorescence microscopy, and in situ ellipsometry supports that the LH2 complexes are located inside the silica nanopores. Systematic fluorescence effects were observed and depend on degree of space confinement. In particular, the temperature dependence of the steady-state fluorescence spectra was analyzed in detail using condensed matter band shape theories. Systematic electronic-vibrational coupling differences in the LH2 transitions between the free and confined states are found, most likely responsible for the fluorescence effects experimentally observed

Surface Engineering of Quantum Dots for Remarkably High Detectivity Photodetectors

Ternary alloyed CdSe_<i>x</i>Te_1–<i>x</i> colloidal QDs trap-passivated by iodide-based ligands (TBAI) are developed as building blocks for UV–NIR photodetectors. Both the few surface traps and high loading of QDs are obtained by in situ ligand exchange with TBAI. The device is sensitive to a broad wavelength range covering the UV–NIR region (300–850 nm), showing an excellent photoresponsivity of 53 mA/W, a fast response time of ≪0.02s, and remarkably high detectivity values of 8 × 10¹³ Jones at 450 nm and 1 × 10¹³ Jones at 800 nm without an external bias voltage. Such performance is superior to what has been reported earlier for QD-based photodetectors. The photodetector exhibits excellent stability, keeping 98% of photoelectric responsivity after 2 months of illumination in air even without encapsulation. In addition, the semitransparent device is successfully fabricated using a Ag nanowires/polyimide transparent substrate. Such self-powered photodetectors with fast response speed and a stable, broad-band response are expected to function under a broad range of environmental conditions