Efficiency of layered photocatalysts such as graphitic carbon nitride (g-CN) is still too low due to the poor utilization of photoexcited-charge carriers. The major drawback is that the weak van der Waals force among g-CN layers is unfavorable for the charge transfer between the adjacent layers and the intrinsically π-conjugated planes with inefficient random in-plane charge migration. Herein, an atomically dispersed Pd layered photocatalyst with both bridged sites of adjacent layers and surface-sites of g-CN is demonstrated, providing directional charge-transfer channels and targeting active sites for photocatalytic water reduction. Both theoretical prediction and empirical characterizations are conducted to achieve the successful synthesis of single-atom engineered Pd/g-CN hybrid and the excellent separation of charge transfer as well as the efficient photocatalytic hydrogen evolution, much better than that of the optimized Pt/g-CN benchmark. The finding in this work provides a rational way for tailoring the performance and engineering of single-atomic noble metal.

Multivalent protein–carbohydrate interactions initiate the first contacts between virus/bacteria and target cells, which ultimately lead to infection. Understanding the structures and binding modes involved is vital to the design of specific, potent multivalent inhibitors. However, the lack of structural information on such flexible, complex, and multimeric cell surface membrane proteins has often hampered such endeavors. Herein, we report that quantum dots (QDs) displayed with a dense array of mono-/disaccharides are powerful probes for multivalent protein–glycan interactions. Using a pair of closely related tetrameric lectins, DC-SIGN and DC-SIGNR, which bind to the HIV and Ebola virus glycoproteins (EBOV-GP) to augment viral entry and infect target cells, we show that such QDs efficiently dissect the different DC-SIGN/R-glycan binding modes (tetra-/di-/monovalent) through a combination of multimodal readouts: Förster resonance energy transfer (FRET), hydrodynamic size measurement, and transmission electron microscopy imaging. We also report a new QD-FRET method for quantifying QD-DC-SIGN/R binding affinity, revealing that DC-SIGN binds to the QD >100-fold tighter than does DC-SIGNR. This result is consistent with DC-SIGN’s higher trans-infection efficiency of some HIV strains over DC-SIGNR. Finally, we show that the QDs potently inhibit DC-SIGN-mediated enhancement of EBOV-GP-driven transduction of target cells with IC50 values down to 0.7 nM, matching well to their DC-SIGN binding constant (apparent Kd = 0.6 nM) measured by FRET. These results suggest that the glycan-QDs are powerful multifunctional probes for dissecting multivalent protein–ligand recognition and predicting glyconanoparticle inhibition of virus infection at the cellular level.

The photophysical properties of carbon nitride (C 3 N 4 ) are very basic and important in the understanding of its photocatalytic activity. Herein, we measured the UV−vis diffuse reflectance (UVDR) and fluorescence spectra of C 3 N 4 prepared at different temperatures and studied their fluorescence decay kinetics under different wavelengths and different fluences of light excitation. We found, first, that the fluorescence lifetime of C 3 N 4 under visible (465 nm) light excitation is shorter than that under UV (395 nm) light excitation; second, that the fluorescence lifetime of C 3 N 4 under 465 nm light excitation decreases as increasing its processing temperature; and third, that the fluorescence lifetime of C 3 N 4 under 395 nm light excitation decreases with the increase of the light excitation fluence. These findings revealed that the two distinct absorption bands in the UVDR spectrum of C 3 N 4 arise from two different transitions of C 3 N 4 and that the origin of the fluorescence emission of C 3 N 4 arises from its singlet exciton. Besides, the photocatalytic H 2 evolutions of C 3 N 4 synthesized at different temperatures under visible light irradiation were also measured and discussed to correlate with the obtained photophysical properties of C 3 N 4 .

In article number https://doi.org/10.1002/adfm.201802169, Jiaguo Yu, Hao Ming Chen, and co‐workers demonstrate the construction of a single‐atom engineered Pd/g‐CN hybrid with directional charge transfer channels and targeting active sites by interlayer intercalation and a surface anchor of Pd atoms. This unique material shows excellent charge transfer/separation and efficient photocatalytic hydrogen evolution.

Carbon nitrides (CN) have been widely used in photocatalytic applications. However, the charge carrier kinetics of CN after light excitation remains unclear. Herein, we prepared a stable and transparent CN colloid in an aqueous tetraethylammonium hydroxide solution and investigated its carrier kinetics using both femtosecond transient absorption and picosecond time-resolved fluorescence spectroscopy. We found that a new and positive absorption band appears in the femtosecond transient absorption spectrum of the CN colloid, which could be attributed to the absorption of the photogenerated electron/hole pairs (or the electronic excited state) of the CN colloid after light excitation. Moreover, we found that the charge carrier kinetics obtained from the femtosecond transient absorption measurements is dramatically different from that obtained from the picosecond time-resolved fluorescence measurements, indicating that the photophysical process of the CN colloid after light excitation is complicated. With the results obtained from both the femtosecond transient absorption and picosecond time-resolved fluorescence measurements, we proposed a schematic to understand the photophysics and charge carrier kinetics of the CN colloid. We believe that the current study is also significant for researchers to understand the photophysics and charge carrier kinetics of bulk CN.