Universal Plasma Jet for Droplet Manipulation on a PDMS Surface towards Wall-Less Scaffolds.

Droplet manipulation is important in the fields of engineering, biology, chemistry, and medicine. Many techniques, such as electrowetting and magnetic actuation, have been developed for droplet manipulation. However, the fabrication of the manipulation platform often takes a long time and requires well-trained skills. Here we proposed a novel method that can directly generate and manipulate droplets on a polymeric surface using a universal plasma jet. One of its greatest advantages is that the jet can tremendously reduce the time for the platform fabrication while it can still perform stable droplet manipulation with controllable droplet size and motion. There are two steps for the proposed method. First, the universal plasma jet is set in plasma mode for modifying the manipulation path for droplets. Second, the jet is switched to air-jet mode for droplet generation and manipulation. The jetted air separates and pushes droplets along the plasma-treated path for droplet generation and manipulation. According to the experimental results, the size of the droplet can be controlled by the treatment time in the first step, i.e., a shorter treatment time of plasma results in a smaller size of the droplet, and vice versa. The largest and the smallest sizes of the generated droplets in the results are about 6 µL and 0.1 µL, respectively. Infrared spectra of absorption on the PDMS surfaces with and without the plasma treatment are investigated by Fourier-transform infrared spectroscopy. Tests of generating and mixing two droplets on a PDMS surface are successfully achieved. The aging effect of plasma treatment for the proposed method is also discussed. The proposed method provides a simple, fast, and low-cost way to generate and manipulate droplets on a polymeric surface. The method is expected to be applied to droplet-based cell culture by manipulating droplets encapsulating living cells and towards wall-less scaffolds on a polymeric surface.

Achieving an exceptionally high loading of isolated cobalt single atoms on a porous carbon matrix for efficient visible-light-driven photocatalytic hydrogen production.

Single-atom catalysts (SACs) have shown great potential in a wide variety of chemical reactions and become the most active new frontier in catalysis due to the maximum efficiency of metal atom use. The key obstacle in preparing SAs lies in the development of appropriate supports that can avoid aggregation or sintering during synthetic procedures. As such, achieving high loadings of isolated SAs is nontrivial and challenging. Conventional methods usually afford the formation of SAs with extremely low loadings (less than 1.5 wt%). In this work, a new in situ preparation strategy that enables the synthesis of isolated cobalt (Co) SAs with an exceptionally high metal loading, up to 5.9 wt%, is developed. The approach is based on a simple one-step pyrolysis of a nitrogen-enriched molecular carbon precursor (1,4,5,8,9,12-hexaazatriphenylene hexacarbonitrile) and CoCl2. Furthermore, due to the successful electron transfer from carbon nitride to the isolated Co SAs, we demonstrate a high-performance photocatalytic H2 production using Co SAs as a co-catalyst, and the evolution rate is measured to be 1180 µmol g-1 h-1. We anticipate that this new study will inspire the discovery of more isolated SACs with high metal loadings, evidently advancing the development of this emerging type of advanced catalysts.

Cu(OH)2 supported on Fe(OH)3 as a synergistic and highly efficient system for the dehydrogenation of ammonia-borane.

Herein, we first describe the physical mixture of Cu(OH)2/Fe(OH)3 as a composite catalyst precursor for the dehydrogenation of ammonia borane (AB) in methanol. During the initial period of catalytic reaction, Cu nanoparticles were formed in-situ. The catalytic activity of Cu nanoparticles can be significantly enhanced with the assistance of Fe species and OH-. A maximum turnover frequency (TOF) of 50.3 molH2 moltotal metal-1 min-1 (135.6 molH2 molCu-1 min-1) was achieved at ambient temperature, which is superior to those of previously reported Fe or Cu based systems.

Nanostructured Ni2 P as a Robust Catalyst for the Hydrolytic Dehydrogenation of Ammonia-Borane.

Ammonia-borane (AB) is a promising chemical hydrogen-storage material. However, the development of real-time, efficient, controllable, and safe methods for hydrogen release under mild conditions is a challenge in the large-scale use of hydrogen as a long-term solution for future energy security. A new class of low-cost catalytic system is presented that uses nanostructured Ni2 P as catalyst, which exhibits excellent catalytic activity and high sustainability toward hydrolysis of ammonia-borane with the initial turnover frequency of 40.4 mol(H2) mol(Ni2P) (-1) min(-1) under air atmosphere and at ambient temperature. This value is higher than those reported for noble-metal-free catalysts, and the obtained Arrhenius activation energy (Ea =44.6 kJ mol(-1) ) for the hydrolysis reaction is comparable to Ru-based bimetallic catalysts. A clearly mechanistic analysis of the hydrolytic reaction of AB based on experimental results and a density functional theory calculation is presented.