Light-driven H generation using semiconductor nanocrystal heterostructures has attracted intense recent interest because of the ability to rationally improve their performance by tailoring their size, composition, and morphology. In zero- and one-dimensional nanomaterials, the lifetime of the photoinduced charge-separated state is still too short for H evolution reaction, limiting the solar-to-H conversion efficiency. Here we report that using two-dimensional (2D) CdS nanoplatelet (NPL)-Pt heterostructures, H generation internal quantum efficiency (IQE) can exceed 40% at pH 8.8-13 and approach unity at pH 14.7. The near unity IQE at pH 14.7 is similar to those reported for 1D nanorods and can be attributed to the irreversible hole removal by OH. At pH < 13, the IQE of 2D NPL-Pt is significantly higher than those in 1D nanorods. Detailed time-resolved spectroscopic studies and modeling of the elementary charge separation and recombination processes show that, compared to 1D nanorods, 2D morphology extends charge-separated state lifetime and may play a dominant role in enhancing the H generation efficiency. This work provides a new approach for designing nanostructures for efficient light-driven H generation.

NATMs). [1,3,[7][8][9][10][11][12][13][14][15][16][17][18] Such NATMs with extremely high permeance and selectivity [3,4,7,8,[12][13][14][15][16][17][18][19][20] are expected to offer significant advances over current state-of-the-art polymer membranes, specifically for diffusion-based separation processes such as dialysis. [9] However, i) large-area membrane quality graphene synthesis [1,21,22] and transfer to suitable porous supports (without polymer residue or other contamination from transfer), [1,9,21,[23][24][25][26] ii) mitigation of nonselective leakage by plugging tears/ damages to graphene from transfer and subsequent processing during membrane fabrication, [1,9,13,26] and most importantly iii) the formation of nanopores with a high density and narrow size distribution using cost-effective, scalable processes [1,9,13,27,28] are some of the major challenges that need to be collectively addressed to realize NATMs for practical applications. [22,29] Here, we note that large-area monolayer graphene synthesis has been demonstrated via roll-to-roll chemical vapor deposition (CVD) processes. [22,30] Further, graphene transfer at large scale has also been shown [30,31] (although complete elimination of polymer residue remains nontrivial) [17,32,33] and widely used scalable membrane manufacturing techniques such as interfacial polymerization have been adapted to effectively plug leakage across tears/damage in graphene. [13] However, facile, cost-effective processes to form nanoscale defects in Direct synthesis of graphene with well-defined nanoscale pores over large areas can transform the fabrication of nanoporous atomically thin membranes (NATMs) and greatly enhance their potential for practical applications. However, scalable bottom-up synthesis of continuous sheets of nanoporous graphene that maintain integrity over large areas has not been demonstrated. Here, it is shown that a simple reduction in temperature during chemical vapor deposition (CVD) on Cu induces in-situ formation of nanoscale defects (≤2-3 nm) in the graphene lattice, enabling direct and scalable synthesis of nanoporous monolayer graphene. By solution-casting of hierarchically porous polyether sulfone supports on the as-grown nanoporous CVD graphene, large-area (>5 cm2 ) NATMs for dialysis applications are demonstrated. The synthesized NATMs show size-selective diffusive transport and effective separation of small molecules and salts from a model protein, with ≈2-100× increase in permeance along with selectivity better than or comparable to state-of-the-art commercially available polymeric dialysis membranes. The membranes constitute the largest fully functional NATMs fabricated via bottom-up nanopore formation, and can be easily scaled up to larger sizes permitted by CVD synthesis. The results highlight synergistic benefits in blending traditional membrane casting with bottom-up pore creation during graphene CVD for advancing NATMs toward practical applications.

Quantum-sized metallic clusters protected by biological ligands represent a new class of luminescent materials; yet the understanding of structural information and photoluminescence origin of these ultra-small clusters remains a challenge. Herein we systematically study the surface ligand dynamics and and ligand-metal core interactions of peptide-protected gold nanoclusters (AuNCs) with combined experimental characterizations and theoretical molecular simulations. We propose that the emission brightness of the resultant nanoclusters is determined by the surface peptide structuring, interfacial water dynamics and ligand-Au core interaction, which can be tailored by controlling peptide acetylation, constituent amino acid electron donating/withdrawing capacity, aromaticity/hydrophobicity and by adjusting environmental pH. Specifically, emission enhancement is achieved through increasing the electron density of surface ligands in proximity to the Au core, discouraging photo-induced quenching, and by reducing the amount of surface-bound water molecules. These findings provide key design principles for maximizing the photoluminescence of metallic clusters through the exploitation of biologically relevant ligand properties.

At present, deep ultraviolet (DUV) lasers at the wavelength of fourth harmonics of 1 µm (266 nm/258 nm) and at the wavelength of 193 nm are widely utilized in science and industry. We review the generation of these DUV lasers by nonlinear frequency conversion processes using solid-state/fiber lasers as the fundamental frequency. A DUV laser at 258 nm by fourth harmonics generation (FHG) could achieve an average power of 10 W with a beam quality of M 2 < 1.5. Moreover, 1 W of average power at 193 nm was obtained by sum-frequency generation (SFG). A new concept of 193-nm DUV laser generation by use of the diamond Raman laser is also introduced. A proof-of-principle experiment of the diamond Raman laser is reported with the conversion efficiency of 23% from the pump to the second Stokes wavelength, which implies the potential to generate a higher power 193 nm DUV laser in the future.Yb:YAG laser at 1030 nm using the CLBO crystal [13]. This laser would lead to a better laser machining result compared to the previous DUV lasers with larger M 2 .