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.

Organic phosphorescent nanoscintillator for low-dose X-ray-induced photodynamic therapy

Abstract: X-ray-induced photodynamic therapy utilizes penetrating X-rays to activate reactive oxygen species in deep tissues for cancer treatment, which combines the advantages of photodynamic therapy and radiotherapy. Conventional therapy usually requires heavy-metal-containing inorganic scintillators and organic photosensitizers to generate singlet oxygen. Here, we report a more convenient strategy for X-ray-induced photodynamic therapy based on a class of organic phosphorescence nanoscintillators, that act in a dual capacity as scintillators and photosensitizers. The resulting low dose of 0.4 Gy and negligible adverse effects demonstrate the great potential for the treatment of deep tumours. These findings provide an optional route that leverages the optical properties of purely organic scintillators for deep-tissue photodynamic therapy. Furthermore, these organic nanoscintillators offer an opportunity to expand applications in the fields of biomaterials and nanobiotechnology.

Self-optimization of optical confinement in an ultraviolet photonic crystal slab laser.

Abstract: We studied numerically and experimentally the effects of structural disorder on the performance of ultraviolet photonic crystal slab lasers. Optical gain selectively amplifies the high-quality modes of the passive system. For these modes, the in-plane and out-of-plane leakage rates may be automatically balanced in the presence of disorder. The spontaneous optimization of in-plane and out-of-plane confinement of light in a photonic crystal slab may lead to a reduction of the lasing threshold.

Tuning Long-Lived Mn(II) Upconversion Luminescence through Alkaline-Earth Metal Doping and Energy-Level Tailoring

Abstract: DOI: 10.1002/adom.201900519 However, the multicolor integration relies almost exclusively on the manipulation of relative intensity ratios between the emission peaks. Multicolor tuning of UCNPs through modulating the band position of the emission is highly desirable for their applications in biological detection and imaging. Introducing a different type of emission with a long lifetime into conventional UCNPs is particularly attractive for lifetime-based data encoding. Such nanoparticles could allow the ease of access to a library of transient color codes for multiplexing and data encoding.[9,10] Incorporation of Mn2+ upconversion luminescence into lanthanide emission at a single-particle level may provide a much-needed solution for the abovementioned challenge.[11–13] This is because the radiative transition of T1→A1 of Mn2+ is spin-forbidden, allowing the decay lifetime of the optical transition to be much longer than that of lanthanide emitters. Additionally, the emission position and lifetime of Mn2+ ions are likely to be modulated by crystal-site engineering. Our primary design is to change the surrounding of the emitting Mn2+ ions by doping alkaline-earth metal ions (A2+) into the host lattice of hexagonal-phase NaGdF4 (Figure 1a).[14] The added dopants can induce variations in the energy gap between the T1 and A1 energy levels of Mn2+ as well as the ionic distance of Mn2+ or Gd3+, thereby enabling the color tuning of Mn2+ emission (Figure 1b). In our design, the promotion of Mn2+ ions to excited states could be enabled by trapping the excitation energy from the neighboring excited Gd3+ ions that are pumped by an energy migration through a multilayered core– shell nanoparticle (Figure S1, Supporting Information). To validate our hypothesis, we used Ca2+, Mn2+-codoped core–shell nanoparticles as a model system. We first prepared a series of NaGdF4:Ca/Mn (x/30 mol%, x = 0, 5, 20, 40, and 50) core nanoparticles by a hydrothermal method.[11] The results showed that a low Ca2+ doping concentration (<40 mol%) has a negligible impact on the size and morphology of the core nanoparticles. Transmission electron microscopy (TEM) showed that the main products are short nanorods in these cases (Figure S2a–c, Supporting Information). The diameter and length of the nanorods were estimated to be in the regions of 11–13 and 17–20 nm, respectively. Notably, high-level doping of Ca2+ (≈40 mol%) led to a shrinkage in both of the diameter (≈8–9 nm) and length (≈0–12 nm) of the nanorods (Figure S2d, Supporting Information). This morphological change is likely Crystal-site engineering of hexagonal-phase NaGdF4:Mn through alkalineearth metal (A2+) doping is used to tune the upconversion luminescence of the Mn2+ dopants. Experimental and calculated results show the ability of A2+ doping to alter the occupancy site of Mn2+ ion from Na+ to Gd3+, thus enabling an emission change from green (520 nm) to yellow (583 nm) upon excitation at 980 nm. The yellow emission of Mn2+ shows a long emission lifetime of 65 ms, more than three times longer than the green emission of Mn2+ (20 ms). The combination of tunable long-lived Mn2+ emission with lanthanide emission at a single-particle level provides a convenient route to triple transient upconversion color codes upon dynamic excitation, which offers an attractive optical feature particularly suitable for efficient document encoding.

Suppression of charge order and exchange bias effect in Nd0.5Ca0.5MnO3 nanocrystalline

Abstract: An Nd0.5Ca0.5MnO3 (NCMO) sample (average diameter ~45?nm) is synthesized by the sol?gel method. The temperature dependence of magnetization indicates that the charge order state is suppressed and a ferromagnetic (FM) transition occurs at ~100?K. In addition, the magnetic hysteresis loop at 10?K under a cooling field of 10?kOe shifts to both the horizontal and the vertical directions when the measure field is 10?kOe. With an increase in the measure field, both the horizontal and the vertical shifts decrease. When the measure field is 50?kOe, the vertical shift vanishes but the horizontal shift still exists. The observed exchange bias effect is attributed to the exchange coupling between the antiferromagnetic core and the FM shell which embodies spin glass-like surface layers.

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.