Molecular spectroscopy provides intrinsic contrast for in situ chemical imaging, linking the physiochemical properties of biomolecules to the functions of living systems. While stimulated Raman imaging has found successes in deciphering biological machinery, many vibrational modes are Raman inactive or weak, limiting the broader impact of the technique. It can potentially be mitigated by the spectral complementarity from infrared (IR) spectroscopy. However, the vastly different optical windows make it challenging to develop such a platform. Here, we introduce in situ pump-probe IR and Raman excitation (INSPIRE) microscopy, a nascent cross-modality spectroscopic imaging approach by encoding the ultrafast Raman and the IR photothermal relaxation into a single probe beam for simultaneous detection. INSPIRE inherits the merits of complementary modalities and demonstrates high-content molecular imaging of chemicals, cells, tissues, and organisms. Furthermore, INSPIRE applies to label-free and molecular tag imaging, offering possibilities for optical sensing and imaging in biomedicine and materials science.
Single-molecular spectroscopy reveals that photoluminescence (PL) of a single quantum dot blinks, randomly switching between bright and dim/dark states under constant photoexcitation, and quantum dots photobleach readily. These facts cast great doubts on potential applications of these promising emitters. After ∼20 years of efforts, synthesis of nonblinking quantum dots is still challenging, with nonblinking quantum dots only available in red-emitting window. Here we report synthesis of nonblinking quantum dots covering most part of the visible window using a new synthetic strategy, i.e., confining the excited-state wave functions of the core/shell quantum dots within the core quantum dot and its inner shells (≤ ∼5 monolayers). For the red-emitting ones, the new synthetic strategy yields nonblinking quantum dots with small sizes (∼8 nm in diameter) and improved nonblinking properties. These new nonblinking quantum dots are found to be antibleaching. Results further imply that the PL blinking and photobleaching of quantum dots are likely related to each other.
TiO 2 /TiOF 2 Z-scheme nanosheets have been successfully synthesized for photocatalytic antibacterial. The antibacterial efficiency of TiO 2 /TiOF 2 against E. coli and S. aureus were 99.90 % and 81.89 % at low material concentration (110 μg/mL), respectively, which are higher than those of pure TiO 2 , TiOF 2 , and Degussa P25. In situ molecular spectroscopy results demonstrate that the microstructure of the synthesized material can be reconstructed and optimized to enhance the exposure of the active sites·H 2 O and O 2 are effectively adsorbed on the catalyst surface and activated to form OH…Ti and O…Ti surface active species. Furthermore, the dense interface formed in TiO 2 /TiOF 2 acts as an efficient transport path for photoexcited electrons from TiO 2 to TiOF 2 , and thus accelerates the formation of reactive oxygen species . Finally, the mechanism of bacterial inactivation is systematically discussed considering the main active substances, cell morphological changes, and activity of antioxidant enzymes.
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