Photoacid-Loaded Nanopores of Hollow Mesoporous Organosilica Capsules for Fluorescent Humidity Sensing

Abstract

Humidity sensing has a wide application and receives intense attention from a broad spectrum of research areas. In this work, we demonstrated a robust humidity sensing strategy by loading photoacid HPTS (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt) into nanopores of hollow mesoporous organosilica (HMO) capsules. Taking advantage of the capillary condensation of nanopores, water vapor is enriched, which triggers the fluorescent color change of HPTS through intermolecular excited-state proton transfer (ESPT) for humidity sensing. The ESPT induced fluorescent color change behavior of HPTS loaded in nanopores was comprehensively investigated by using both steady and picosecond time-resolved fluorescence spectroscopy. The fabricated humidity sensors exhibit rapid response and recovery, qualified reversibility, and selectivity, which enable continuous monitoring of human respiration. Notably, the sensing performance, i.e., sensitivity and response range, can be effectively tuned by fabricating HMO capsules with properly sized nanopores, which provides an opportunity to design unique nanostructures of the humidity sensor for specific applications.

Elucidation of a detection mechanism of a fluorescent sensor based on photo-induced electron transfer for water

“…Indeed, the development of fluorescent sensors for the visualization as well as detection and quantification of a trace amount of water in solutions, solids, and gas or on material surfaces has been of considerable scientific and practical concern in recent years, with the objective of not only a fundamental study in analytical chemistry, photochemistry, and photophysics, but also their potential applications to environmental and quality control monitoring systems and industry. [20][21][22][23][24][25][26][27][28] Herein we provide a direction in molecular design toward creating an effective PET-type fluorescent sensor for water as well as a conclusive detection mechanism of the anthracene-AminoMeCNPhenylBPin structure for water.…”

Synthesis of Monodispersed Hollow Mesoporous Organosilica and Silica Nanoparticles with Controllable Shell Thickness Using Soft and Hard Templates

“…Guo et al synthesized photoacid-loaded HMOS, which enabled rapid response humidity sensing within a humidity range of 30−99% by a fluorescence color change of the photoacid loaded in the nanopores. 23 Lee et al optimized the loading efficiency of the perfluorocarbon liquid into HMOS for application as a contrast agent in magnetic resonance imaging. 24 Additionally, the organosilica shell exhibits functionality owing to the presence of organic groups.…”

“…The confinement of PdAg nanoparticles and PEI in the hollow structures of HMOS improved the catalytic activity while allowing the recovery and reuse of the catalyst. Guo et al synthesized photoacid-loaded HMOS, which enabled rapid response humidity sensing within a humidity range of 30–99% by a fluorescence color change of the photoacid loaded in the nanopores . Lee et al optimized the loading efficiency of the perfluorocarbon liquid into HMOS for application as a contrast agent in magnetic resonance imaging .…”

Excited-State Proton Transfer from Embedded Photoacids to Silanols on Mesostructured Surfaces: Role of Structural Heterogeneity

“…In order to confirm this intriguing observation, we further estimated the relative contribution of the ROH* and RO − * emission by multi-Gaussian fitting (Figures 5a and S15) of ps-TRF spectra at each delay times and defined α = I ROH* /I RO − * as an indicator of ESPT progress. According to the measured steady emission spectra of ROH in mesostructured silica (Figure 3d, blue thick line), we employed the sum of areas of the first two peaks (blue) and the last peak (green) to represent I ROH* and I RO − * , 68 respectively. The resulting time-dependent α evolutions at different pH treatment values were further fitted exponentially (Figure S16), and the resulting time constants (t 1 and t 2 ) are summarized in Table 1.…”