Recently, Professor Chen Feng’s group has made new progress in the research fields of ion beam synthesized metal nanoparticles for optical applications and ion beam modification of two-dimensional materials for biomedical applications. Two relevant papers have been published in Small, a famous journal in the field of nano research (IF=11.459).

Nonlinear optical materials (NOMs) have attracted great attention in the fields of optical frequency comb generation, optical modulation, and all-optical switching, etc. Recently, metallic nanoparticles (NPs) have been proved to be a novel 0D material for nonlinear optical response enhancement of NOMs owing to the localized surface plasmon resonance (LSPR) effect. Nevertheless, the development of NP-modified NOMs still faces some obstacles such as poor stability and integration.

Cooperating with the research groups from Shanghai Institute of Optics and Fine Mechanics of Chinese Academy of Sciences and Wuhan University, Chen’s group proposed a noveldouble-layer nanostructurewith heterogeneous nanoparticles to achieve enhanced third-order optical nonlinearity of NOMs byscattering-induced energy transfer between adjacent NPs layers.The novel double-layer nanostructurewith embedded Ag NPs layer and Cu NPs layer in LiNbO₃crystal has been fabricated by sequential ion implantation. Both of the elastic collision and thermolysis contribute to the formation of double-layer nanostructure. The embedded NPs possess high stability and integration owing to the protection of surrounding dielectrics. The LSPR effect of Cu NPs is well preserved and the near field intensity is enhanced by the scattering effect of Ag NPs., which leads to the enhancement of third-order nonlinearity of Cu NPs. Compared with Cu NPs layer, the saturation intensity of double-layer nanostructure is reduced by one order of magnitude, and the near-field enhancement factor and modulation depth are enhanced by two folds.Utilizingthe enhanced nonlinearity of Ag/Cu double-layer nanostructure as a saturable absorber,1 μm mode-locked pulsed laser with a repetition rate of 6.55 GHz has been implemented with pulse duration decreased by 32.7%.

This work is published online in Small with title of " A novel hierarchical nanostructure for enhanced optical nonlinearity based on scattering mechanism " (https://doi.org/10.1002/smll.202003172).

The discovery of antibiotics has brought us into a period of infection control to overcome the menace by bacteria, however, the use of antibiotics also brings problems like the production of drug-resistant bacteria. Innovative strategies are required to control infection in the resistance era owing to the widespread antibiotic-resistant microbes and the slow development in antibiotics. A new method is proposed to endow the transition metal sulfides (XS₂, X=W/Mo) quantum dots (QDs) with the antibacterial ability by sulfur vacancies. The ion irradiation process bombed the sulfur away from the top atomic layer of WS₂leaving sulfur vacancies, which makes WS_2–yQDs highly oxidizing and strong antibacterial activities via tailoring electron transport between WS_2–yQDs and membrane. The sterilization efficiency of Gram-positive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus more than 99.9% within 20 min is realized with the concentration of 140 μg mL^-1of XS_2–0.1quantum dots. In addition, it is observed that the occurrence of severe clinical manifestation such as ocular perforation can be prevented efficiently. This work demonstrates the ion irradiation as a novel, simple, and effective strategy to modify the antibacterial activity of WS₂QDs, and provides a candidate way to cure bacterial keratitis.

This work is published in Small with title of "Vacancy - induced antibacterial activity of XS₂-yquantum dots against drug-resistant bacteria for treatment of bacterial keratitis" (https://doi.org/10.1002/smll.202004677).

Written by：Liu Yang

Edited by：Che huiqing