Wenjing Tian

Bio: Wenjing Tian is an academic researcher from Jilin University. The author has contributed to research in topics: Polymer solar cell & HOMO/LUMO. The author has an hindex of 55, co-authored 295 publications receiving 11365 citations. Previous affiliations of Wenjing Tian include Nanchang University & Chinese Academy of Sciences.

Piezochromic Luminescence Based on the Molecular Aggregation of 9,10-Bis((E)-2-(pyrid-2-yl)vinyl)anthracene†

Abstract: Luminescent materials sensitive to environmental stimuli are of great interest from a scientific viewpoint owing to their potential applications in fluorescent switches and optical devices. Pressure is one of the most common natural external stimuli, and thus piezochromic materials, which show color changes resulting from external pressure or mechanical grinding, can be used as pressure-sensing and optical-recording systems. However, whereas pH-, light-, and temperature-sensitive materials are relatively well understood, studies of piezochromic materials remain inadequate owing to the absence of an effective mechanism to explain the relationship between changes in molecular assembly or packing and the corresponding luminescence properties of the material. Until now, successful systems have generally made use of transformations between monomeric and dimeric/excimeric states through hydrogen-bonding interactions as the mechanism to cause changes in luminescence. It is well-known that in the condensed phase, the luminescence properties of a given molecular system usually undergo significant variation according to the molecular aggregation state or stacking mode, since intermolecular interactions invariably alter photophysical processes. Therefore, an understanding of and the ability to control the molecular aggregation state and the consequent intermolecular interactions are still very important for the development of piezochromic materials. Herein we report an effective mechanism of piezochromic luminescence on the basis of the molecular aggregation state of 9,10-bis((E)-2-(pyrid-2-yl)vinyl)anthracene (BP2VA). BP2VA exhibited spectacular luminescence characteristics: grinding and the exertion of external pressure on the powder led to a change in its photoluminescence color from green to red. Three crystal polymorphs of BP2VA with different stacking modes involving gradually enhanced p–p interactions in the three crystalline states provided further insight into the origin of luminescence changes under the external stimulae. BP2VA was synthesized in a straightforward manner by a one-step Witting–Horner reaction according to a previously reported method, and the purified material was characterized by spectroscopic methods (see the Supporting Information). BP2VA powder exhibited a strong green emission at lmax= 528 nm, in contrast to its weak orange emission at lmax= 583 nm as a solution in THF. The weak orange emission was ascribed to a conformational relaxation in solution, which was reflected by the corresponding photoluminescence (PL) spectrum of BP2VA at low temperature (77 K; see Figure S1 in the Supporting Information). Furthermore, the emission of BP2VA aggregation as a solution in THF/water was blueshifted to lmax= 570 nm (from the value lmax= 583 nm in THF; see Figure S2). Interestingly, after being ground, BP2VA powder showed a strong red shift with a yellow emission (lmax= 561 nm) under UV light with a wavelength of 365 nm, and after being heated above 160 8C, the ground powder recovered its initial green emission (lmax= 528 nm; Figure 1b,c). The interconversion of the two states with their distinct emission colors is completely reversible through grinding and heating. The red shift of 33 nm in fluorescence emission upon grinding and the recovery of the initial state upon heating is a significant piezochromic effect. To gain further understanding of the piezochromic effect, we investigated the influence of applied pressure on the luminescence of BP2VA. The powder was placed in the holes (diameter: 200 mm) of a T301 steel gasket, which was preindented to a thickness of 50 mm. A small ruby chip was inserted into the sample compartment for in situ pressure calibration according to the R1 ruby fluorescence method. A 4:1 mixture of methanol and ethanol was used as a pressuretransmitting medium (PTM). The hydrostatic pressure on the powder was determined by monitoring the widths and separation of the R1 and R2 lines. The photoluminescence measurements under high pressure were performed on a QuantaMaster 40 spectrometer in the reflection mode. The 405 nm line of a violet diode laser with a spot size of 20 mm and a power of 100 mW was used as the excitation source. The diamond anvil cell (DAC) containing the sample was put on a Nikon fluorescence microscope to focus the laser on the sample. The emission spectra were recorded with a monochromator equipped with a photomultiplier. All experiments were conducted at room temperature. [*] Y. J. Dong, Dr. B. Xu, J. B. Zhang, L. J. Wang, J. L. Chen, Dr. H. G. Lv, Dr. S. P. Wen, Dr. B. Li, Dr. L. Ye, Prof. Dr. W. J. Tian State Key Laboratory of Supramolecular Structure and Materials Jilin Unversity Qianjin Street No. 2699, Changchun 130012 (China) E-mail: wjtian@jlu.edu.cn X. Tan, Prof. Dr. B. Zou State Key Laboratory of Superhard Materials Jilin University (China) E-mail: zoubo@jlu.edu.cn [] These authors contributed equally. [**] This research was supported by the 973 program (2009CB623605), the NSFC (Grant No. 20874035, 21074045, 21073071), and the Project of Jilin Province (Grant No.20100704). Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.201204660. . Angewandte Communications

Pressure-induced metallization of dense (H2S)2H2 with high-Tc superconductivity

Abstract: The high pressure structures, metallization and superconductivity of recently synthesized H2-containing compounds (H2S)2H2 are elucidated by ab initio calculations. The ordered crystal structure with P1 symmetry is determined, supported by the good agreement between theoretical and experimental X-ray diffraction data, equation of states and Raman spectra. The Cccm structure is favorable with partial hydrogen bond symmetrization above 37 GPa. Upon further compression, H2 molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180 GPa, respectively. The predicted metallization pressure is 111 GPa, which is approximately one-third of the currently suggested metallization pressure of bulk molecular hydrogen. Application of the Allen-Dynes-modified McMillan equation for the Im-3m structure yields high Tc values of 191 K to 204 K at 200 GPa, which is among the highest values reported for H2-rich van der Waals compounds and MH3 type hydride thus far.

Low-temperature SnO2-based electron selective contact for efficient and stable perovskite solar cells

Abstract: We demonstrated SnO2 films prepared by sinter-less spin-coating processes as an electron selective contact for CH3NH3PbI3-based planar-heterojunction perovskite solar cells (PSCs). A modified sequential deposition method, in which the grain size of PbI2 precursors was controlled by an equivalent solvent vapor annealing (SVA) process, was used to prepare the perovskite layer on SnO2. With this SVA process, the remnant PbI2 nanocrystals can stably occur at the interface of CH3NH3PbI3/SnO2 to carry out a passivation effect. The photovoltaic performance of SnO2-based PSCs is dependent on both the SVA time and the thickness of the perovskite layer. The optimized PSC device achieves the best power conversion efficiency of up to 13% under the AM 1.5 simulated sunlight illumination, which is highly durable over 30 days of storage time with exposure to the ambient air environment.

Solid-State Photoinduced Luminescence Switch for Advanced Anticounterfeiting and Super-Resolution Imaging Applications

Abstract: Solid-state organic photoswitches with reversible luminescence modulation property are highly attractive because of their wide prospects in advanced photonic applications, such as optical data storage, anticounterfeiting and bioimaging. Yet, developing such materials has long been a significant challenge. In this work, we construct an efficient solid-state photoswitch based on a spiropyran-functionalized distyrylanthracene derivative (DSA-2SP) that exhibits exceptional reversible absorption/luminescence modulation ability. Efficient photoswitching between DSA-2SP and its photoisomer DSA-2MC are facilitated by large free volumes induced by nonplanar molecular structures of DSA moieties, as well as the intramolecular hydrogen bonds between the DSA and MC moieties. Consequently, the excellent solid-state photochromic property of DSA-2SP is highly applicable as both anticounterfeiting inks and super-resolution imaging agents.

Conjugated polymer-based organic solar cells

Abstract: The need to develop inexpensive renewable energy sources stimulates scientific research for efficient, low-cost photovoltaic devices.1 The organic, polymer-based photovoltaic elements have introduced at least the potential of obtaining cheap and easy methods to produce energy from light.2 The possibility of chemically manipulating the material properties of polymers (plastics) combined with a variety of easy and cheap processing techniques has made polymer-based materials present in almost every aspect of modern society.3 Organic semiconductors have several advantages: (a) lowcost synthesis, and (b) easy manufacture of thin film devices by vacuum evaporation/sublimation or solution cast or printing technologies. Furthermore, organic semiconductor thin films may show high absorption coefficients4 exceeding 105 cm-1, which makes them good chromophores for optoelectronic applications. The electronic band gap of organic semiconductors can be engineered by chemical synthesis for simple color changing of light emitting diodes (LEDs).5 Charge carrier mobilities as high as 10 cm2/V‚s6 made them competitive with amorphous silicon.7 This review is organized as follows. In the first part, we will give a general introduction to the materials, production techniques, working principles, critical parameters, and stability of the organic solar cells. In the second part, we will focus on conjugated polymer/fullerene bulk heterojunction solar cells, mainly on polyphenylenevinylene (PPV) derivatives/(1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61) (PCBM) fullerene derivatives and poly(3-hexylthiophene) (P3HT)/PCBM systems. In the third part, we will discuss the alternative approaches such as polymer/polymer solar cells and organic/inorganic hybrid solar cells. In the fourth part, we will suggest possible routes for further improvements and finish with some conclusions. The different papers mentioned in the text have been chosen for didactical purposes and cannot reflect the chronology of the research field nor have a claim of completeness. The further interested reader is referred to the vast amount of quality papers published in this field during the past decade.

Aggregation-Induced Emission: Together We Shine, United We Soar!

Abstract: Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

Aggregation-induced emission

Abstract: Luminogenic materials with aggregation-induced emission (AIE) attributes have attracted much interest since the debut of the AIE concept in 2001. In this critical review, recent progress in the area of AIE research is summarized. Typical examples of AIE systems are discussed, from which their structure–property relationships are derived. Through mechanistic decipherment of the photophysical processes, structural design strategies for generating new AIE luminogens are developed. Technological, especially optoelectronic and biological, applications of the AIE systems are exemplified to illustrate how the novel AIE effect can be utilized for high-tech innovations (183 references).

Synthesis of Conjugated Polymers for Organic Solar Cell Applications

Abstract: -phenylenevinylene)s L4. Fluorene-Based Conjugated Polymers L4.1. Fluorene-Based Copolymers ContainingElectron-Rich MoietiesM4.2. Fluorene-Based Copolymers ContainingElectron-Deficient MoietiesN4.3. Fluorene-Based Copolymers ContainingPhosphorescent ComplexesQ5. Carbazole-Based Conjugated Polymers R5.1. Poly(2,7-carbazole)-Based Polymers R5.2. Indolo[3,2-

Principles Of Fluorescence Spectroscopy

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