Simultaneously Broadened Visible Light Absorption and Boosted Intersystem Crossing in Platinum-Doped Graphite Carbon Nitride for Enhanced Photosensitization.

Herein, taking graphite carbon nitride ( g-C3N4) as the example, we demonstrated that the two limiting factors that determine the photosensitization performance, namely, light absorption and intersystem crossing (ISC), could be simultaneously enhanced through Pt2+ doping. Specifically, as a π-conjugated two-dimensional semiconductor, g-C3N4 is capable of absorbing light shorter than 460 nm (2.7 eV). Upon Pt2+ doping that allows metal-to-ligand charge transfer (MLCT) from Pt2+ to the substrate g-C3N4, the light absorption of g-C3N4 was greatly expanded up to 1000 nm. Meanwhile, the large atomic number of Pt2+ ensures promotion of ISC to activate the triplet state of g-C3N4 via heavy atom effect (HAE), which was confirmed via both photosensitization performance and photophysical characterizations. Further, the enhanced light absorption and photosensitization of Pt2+-doped g-C3N4 were harvested for antibiotics removal, a type of environment contaminants that gained global attention because of their worldwide abuse. Compared with its undoped counterpart, Pt2+-doped g-C3N4 featured significantly improved antibiotics removal in the presence of low-power white LED irradiation, which is promising for photosensitized environmental remediation.

In Situ Generation and Consumption of H2O2 by Bienzyme-Quantum Dots Bioconjugates for Improved Chemiluminescence Resonance Energy Transfer.

Exploration of quantum dots (QDs) as energy acceptors revolutionizes the current chemiluminescence resonance energy transfer (CRET), since QDs possess large Stokes shifts and high luminescence efficiency. However, the strong and high concentration of oxidant (typically H2O2) needed for luminol chemiluminescence (CL) reaction could cause oxidative quenching to QDs, thereby decreasing the CRET performance. Here we proposed the use of bienzyme-QDs bioconjugate as the energy acceptor for improved CRET sensing. Two enzymes, one for H2O2 generation (oxidase) and another for H2O2 consumption (horseradish peroxidase, HRP), were bioconjugated onto the surface of QDs. The bienzyme allowed fast in situ cascaded H2O2 generation and consumption, thus alleviating fluorescence quenching of QDs. The nanosized QDs accommodate the two enzymes in a nanometric range, and the CL reaction was confined on the surface of QDs accordingly, thereby amplifying the CL reaction rate and improving CRET efficiency. As a result, CRET efficiency of 30-38% was obtained; the highest CRET efficiency by far was obtained using QDs as the energy acceptor. The proposed CRET system could be explored for ultrasensitive sensing of various oxidase substrates (here exemplified with cholesterol, glucose, and benzylamine), allowing for quantitative measurement of a spectrum of metabolites with high sensitivity and specificity. Limits of detection (LOD, 3σ) for cholesterol, glucose, and benzylamine were found to be 0.8, 3.4, and 10 nM, respectively. Furthermore, multiparametric blood analysis (glucose and cholesterol) is demonstrated.