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.

Dynamic Ultralong Organic Phosphorescence by Photoactivation.

Abstract: Smart materials with ultralong phosphorescence are rarely investigated and reported. Herein we report on a series of molecules with unique dynamic ultralong organic phosphorescence (UOP) features, enabled by manipulating intermolecular interactions through UV light irradiation. Our experimental data reveal that prolonged irradiation of single-component organic phosphors of PCzT, BCzT, and FCzT under ambient conditions can activate UOP with emission lifetimes spanning from 1.8 to 1330 ms. These phosphors can also be deactivated back to their original states with short-lived phosphorescence by UV irradiation for 3 h at room temperature or through thermal treatment. Additionally, the dynamic UOP was applied successfully for a visual anti-counterfeiting application. These findings may provide unique insight into dynamic molecular motion for optical processing and expand the scope of smart-response materials for broader applications.

Rare-Earth Doping in Nanostructured Inorganic Materials.

Abstract: Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials. Moreover, rare-earth doping can control the ultimate electronic and catalytic performance of doped nanomaterials in a tunable and scalable manner, enabling significant improvements in energy harvesting and conversion. A better understanding of the critical role of rare-earth doping is a prerequisite for the development of an extensive repertoire of functional nanomaterials for practical applications. In this review, we highlight recent advances in rare-earth doping in inorganic nanomaterials and the associated applications in many fields. This review covers the key criteria for rare-earth doping, including basic electronic structures, lattice environments, and doping strategies, as well as fundamental design principles that enhance the electrical, optical, catalytic, and magnetic properties of the material. We also discuss future research directions and challenges in controlling rare-earth doping for new applications.

Molecular Design of UV–vis Absorption and Emission Properties in Organic Fluorophores: Toward Larger Bathochromic Shifts, Enhanced Molar Extinction Coefficients, and Greater Stokes Shifts

Abstract: Understanding the molecular origins of the optoelectronic properties of fluorophores provides rational guidelines for chemists to synthesize better-performing dyes. Factors affecting the UV–vis absorption spectral shift, molar extinction coefficients, and Stokes shift of fluorophores are herein examined at the molecular level, via both (time-dependent) density functional theory-based calculations and the empirical harmonic-oscillator-stabilization-energy (HOSE) and bond-length-alternation (BLA) models. The importance of these factors is discussed using six coumarin dyes as exemplars. In particular, a special focus is devoted to the Stokes shift, a critical parameter in fluorophores. It is demonstrated that incorporating a “rotational” substituent in a fluorophore molecule with tailored steric hindrance effects and resonance effects leads to a substantial increase in the Stokes shift, not only in coumarins but also in other chemical dye families: boron-dipyrromethenes (BODIPYs), cyanines, and stilbenes. St...

Gold and Hairpin DNA Functionalization of Upconversion Nanocrystals for Imaging and In Vivo Drug Delivery.

Abstract: Although multifunctional upconversion imaging probes have recently attracted considerable interest in biomedical research, there are currently few methods for stabilizing these luminescent nanoprobes with oligonucleotides in biological systems. Herein, a method to robustly disperse upconversion nanoprobes in physiological buffers based on rational design and synthesis of nanoconjugates comprising hairpin-DNA-modified gold nanoparticles is presented. This approach imparts the upconversion nanoprobes with excellent biocompatibility and circumvents the problem of particle agglomeration. By combining single-band anti-Stokes near-infrared emission and the photothermal effect mediated by the coupling of gold to upconversion nanoparticles, a simple, versatile nanoparticulate system for simultaneous deep-tissue imaging and drug molecule release in vivo is demonstrated.

Arrays of Magnetic Nanoparticles Patterned via “Dip‐Pen” Nanolithography

Abstract: Oxygen saturated, dilute benzene solutions (corresponding to ca. 1 mM monomer units) of the polymers shown in Figure 1 were contained in a microwave cell of internal dimensions 3.5 ” 7.1 ” 24 mm. The solutions were irradiated with 5 or 10 ns pulses of 3 MeV electrons from a Van de Graaff accelerator with a total absorbed dose per pulse, D, of approximately 1 ” 10 J/m which was accurately measured for each experiment. This resulted initially in the formation of a uniform concentration of ca. 0.1 lM of excess electrons and benzene radical cations. The resulting change in the conductivity of the solution was measured as the change in the power of microwaves (26±38 GHz) reflected by the cell. Using only a single pulse the radiation-induced conductivity could be monitored from 10 ns to 1 ms using a pseudo-logarithmic time-base. The experimental methodology and data reduction procedures have been described in detail previously [4,5].

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.