Xiaogang Liu

Bio: Xiaogang Liu is an academic researcher from National University of Singapore. The author has contributed to research in topics: Medicine & Photon upconversion. The author has an hindex of 94, co-authored 425 publications receiving 41825 citations. Previous affiliations of Xiaogang Liu include Heilongjiang University & Massachusetts Institute of Technology.

Lanthanide-doped nanoparticles in photovoltaics – more than just upconversion

Abstract: Development of photon conversion nanomaterials could principally leverage unutilized portions of the solar spectrum to address the increasing demand for renewable energy. However, improving photovoltaic performance using lanthanide-doped, spectral-converting nanomaterials remains a challenge. For photon upconversion, the most significant issues lie in their low quantum efficiencies and the need for high-power laser excitation. Despite these constraints, lanthanide-doped upconversion nanomaterials hold great promise to enhance the light-harvesting capacity and the conversion efficiency of existing solar cell modules. In this review, we highlight recent advances in developing high-efficiency upconversion nanoparticles for photovoltaic application. Special attention will be paid to fundamental energy transfer mechanisms, the survey of strategies for nanoparticle synthesis and surface modification, and various schemes of nanoparticle integration into photovoltaic devices. We also discuss future research directions and practical challenges in coupling upconversion nanomaterials with existing photovoltaic technologies.

Recent Advances in C—S Bond Formation via C—H Bond Functionalization and Decarboxylation

Abstract: The development of mild and general methods for C–S bond formation has received significant attention because the C–S bond is indispensable in many important biological and pharmaceutical compounds. Early examples for the synthesis of C–S bonds are generally limited to the condensation reaction between a metal thiolate and an organic halide. Recent chemical approaches for C–S bond formation, based upon direct C–H bond functionalization and decarboxylative reactions, not only provide new insights into the mechanistic understanding of C–S coupling reactions but also allow the synthesis of sulfur-containing compounds from more effective synthetic routes with high atom economy. This review intends to explore recent advances in C–S bond formation via C–H functionalization and decarboxylation, and the growing opportunities they present to the construction of complex chemical scaffolds for applications encompassing natural product synthesis, synthetic methodology development, and functional materials as well as nanotechnology.

A unified fluorescence quenching mechanism of tetrazine-based fluorogenic dyes: energy transfer to a dark state

Abstract: Tetrazine-based fluorogenic probes are powerful tools for bioimaging, biosensing, and medical diagnostic applications. In these probes, the attachment of a tetrazine moiety generates a non-fluorescent precursor; upon the bio-orthogonal reaction of the tetrazine fragment, a strong fluorescence signal is released from the fluorophore, resulting in significant fluorescence turn-on responses. To rationally design tetrazine-based probes with enhanced turn-on ratios, one fundamental challenge is to understand their fluorescence quenching mechanism. Herein, utilizing quantum chemistry calculations, we investigated and described a generalized fluorescence quenching mechanism, coined as “energy transfer to a dark state” (ETDS). With the aid of the ETDS mechanism, we demonstrated how a large excited-state energy gap and a short distance between a tetrazine group and a fluorophore are essential for increasing the rate of energy transfer and improving turn-on ratios of tetrazine-based fluorophores. We further proposed two strategies in the rational design of highly desirable fluorogenic probes that exhibit longer emission wavelengths and higher turn-on ratios, including (1) shortening the fluorophore–tetrazine distance via “face-to-face” stacking; and (2) modulating the UV-vis absorption wavelengths. Our calculation results could provide invaluable insights into the rational design of a new generation of tetrazine-based fluorogenic probes.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Room-temperature ultraviolet nanowire nanolasers

Abstract: Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated The self-organized, oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process These wide band-gap semiconductor nanowires form natural laser cavities with diameters varying from 20 to 150 nanometers and lengths up to 10 micrometers Under optical excitation, surface-emitting lasing action was observed at 385 nanometers, with an emission linewidth less than 03 nanometer The chemical flexibility and the one-dimensionality of the nanowires make them ideal miniaturized laser light sources These short-wavelength nanolasers could have myriad applications, including optical computing, information storage, and microanalysis

Structural absorption by barbule microstructures of super black bird of paradise feathers

Abstract: Many studies have shown how pigments and internal nanostructures generate color in nature. External surface structures can also influence appearance, such as by causing multiple scattering of light (structural absorption) to produce a velvety, super black appearance. Here we show that feathers from five species of birds of paradise (Aves: Paradisaeidae) structurally absorb incident light to produce extremely low-reflectance, super black plumages. Directional reflectance of these feathers (0.05-0.31%) approaches that of man-made ultra-absorbent materials. SEM, nano-CT, and ray-tracing simulations show that super black feathers have titled arrays of highly modified barbules, which cause more multiple scattering, resulting in more structural absorption, than normal black feathers. Super black feathers have an extreme directional reflectance bias and appear darkest when viewed from the distal direction. We hypothesize that structurally absorbing, super black plumage evolved through sensory bias to enhance the perceived brilliance of adjacent color patches during courtship display.