Quantitative determination of rhamnolipid using HPLC-UV through carboxyl labeling.

Rhamnolipid, as a low-toxic, biodegradable and environmentally friendly biosurfactant, has broad application prospects in many industries. However, the quantitative determination of rhamnolipid is still a challenging task. Here, a new sensitive method for the quantitative analysis of rhamnolipid based on a simple derivatization reaction was developed. In this study, 3-[3'-(l-rhamnopyranosyloxy) decanoyloxy] decanoic acid (Rha-C10-C10) and 3-[3'-(2'-O-α-l-rhamnopyranosyloxy) decanoyloxy] decanoic acid (Rha-Rha-C10-C10) were utilized as the representative rhamnolipids. Liquid chromatography-mass spectrometry and high-performance liquid chromatography-ultra violet results showed that these two compounds were successfully labeled with 1 N1-(4-nitrophenyl)-1,2-ethylenediamine. There was an excellent linear relationship between rhamnolipid concentration and peak area of labeled rhamnolipid. The detection limits of the Rha-C10-C10 and Rha-Rha-C10-C10 were 0.018 mg/L (36 nmol/L) and 0.014 mg/L (22 nmol/L), respectively. The established amidation method was suitable for the accurate analysis of rhamnolipids in the biotechnological process. The method had good reproducibility with the relative standard deviation of 0.96% and 0.79%, respectively, and sufficient accuracy with a recovery of 96%-100%. This method was applied to quantitative analysis of 10 rhamnolipid homologs metabolized by Pseudomonas aeruginosa LJ-8. The single labeling method was used for the quantitative analysis of multiple components, which provided an effective method for the quality evaluation of other glycolipids with carboxyl groups.

A Molten-Salt Method to Synthesize Co9 S8 Embedded, N, S Co-Doped Mesoporous Carbons from Melamine Formaldehyde Resins for Electrocatalytic Hydrogen Evolution Reactions.

We developed a molten salts process to prepare Co9 S8 nanoparticles (NPs) entrapped, S, N co-doped carbons. Cobalt chloride was used as the cobalt source. The melamine-formaldehyde (MF) resin provided the carbon source and nitrogen source, and thiourea provided sulfur source. In addition, common inorganic salts were added as templates to generate pores. The characterization results showed that the prepared materials contained high contents of N, S and Co, and were mesoporous composites. At the same time, the porosity of electrocatalyst depended on the type of salt and the mass ratio of precursor to salt, which further affected the electrocatalytic activity of hydrogen evolution reaction (HER). The best prepared catalyst showed excellent HER performance. The onset overpotential of the catalyst was low (33 mV) and had a small Tafel slope (61.1 mV dec-1 ), in addition to good stability in alkaline media.

2D Material and Perovskite Heterostructure for Optoelectronic Applications.

Optoelectronic devices are key building blocks for sustainable energy, imaging applications, and optical communications in modern society. Two-dimensional materials and perovskites have been considered promising candidates in this research area due to their fascinating material properties. Despite the significant progress achieved in the past decades, challenges still remain to further improve the performance of devices based on 2D materials or perovskites and to solve stability issues for their reliability. Recently, a novel concept of 2D material/perovskite heterostructure has demonstrated remarkable achievements by taking advantage of both materials. The diverse fabrication techniques and large families of 2D materials and perovskites open up great opportunities for structure modification, interface engineering, and composition tuning in state-of-the-art optoelectronics. In this review, we present comprehensive information on the synthesis methods, material properties of 2D materials and perovskites, and the research progress of optoelectronic devices, particularly solar cells and photodetectors which are based on 2D materials, perovskites, and 2D material/perovskite heterostructures with future perspectives.

A solvent-free strategy for synthesis of Co9S8 nanoparticles entrapped, N, S-codoped mesoporous carbon as hydrogen evolution electrocatalyst.

A facile solvent-free method was developed to synthesize Co9S8 nanoparticles entrapped, N, S-codoped mesoporous carbon, which involved two steps, including hand milling and carbonation. This synthetic route did not require any solvent during the entire process. Moreover, no water and/or acid solution were needed to remove the impurity from the calcined samples. The final products had mesoporous structures, as well as high Co, N, and S contents. In details, N and S atoms both doped into the carboneous matrix, and the Co9S8 nanoparticles also dispersed well in the composites. The characterization results revealed that the ratios of the precursors and the calcination temperatures both determined the porosities of the final products, which could further affect the electrocatalytic activities. The optional sample, G2.0T1.0Co0.3-900, revealed excellent electrocatalytic activities for hydrogen evolution reaction (HER) under acidic condition, requiring overpotential of 71 mV to afford a current density of 10 mA cm-2. Additionally, G2.0T1.0Co0.3-900 also showed superior stability and duration.

Bottom-up synthesis of mesoporous germanium as anodes for lithium-ion batteries.

A series of mesoporous germanium materials were synthesized via the self-templating method. Germanium tetrachloride and sodium potassium alloy were utilized as germanium precursor and reducing agent, respectively. The by-products, NaCl and KCl, could be considered as the in-situ templates. The characterization results showed that the mesopores could be obtained, when the salts were removed by water washing. Moreover, the crystalline germanium could also be achieved, when the calcination temperature is as high as 500 °C. However, when the calcination temperatures are 300 °C, the as-received mesoporous germanium materials are amorphous. When evaluated as anode for lithium-ion batteries (LIBs), the obtained mesoporous germanium exhibits outstanding cycling stability, showing a high reversible specific capacity of 803 mA h g-1 after 100 cycles, as well as enhanced rate performance (655 mA h g-1 at 1 C rate).