Showing papers by "South China University of Technology published in 2015"

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

Single-junction polymer solar cells with high efficiency and photovoltage

Abstract: Organic solar cells with efficiency greater than 10% are fabricated by incorporating a semiconductor polymer with a deepened valence energy level. Polymer solar cells are an exciting class of next-generation photovoltaics, because they hold promise for the realization of mechanically flexible, lightweight, large-area devices that can be fabricated by room-temperature solution processing1,2. High power conversion efficiencies of ∼10% have already been reported in tandem polymer solar cells3. Here, we report that similar efficiencies are achievable in single-junction devices by reducing the tail state density below the conduction band of the electron acceptor in a high-performance photoactive layer made from a newly developed semiconducting polymer with a deepened valence energy level. Control over band tailing is realized through changes in the composition of the active layer and the structure order of the blend, both of which are known to be important factors in cell operation4,5,6. The approach yields cells with high power conversion efficiencies (∼9.94% certified) and enhanced photovoltage.

Engineering heterogeneous semiconductors for solar water splitting

Abstract: There is a growing interest in the conversion of water and solar energy into clean and renewable H2 fuels using earth-abundant materials due to the depletion of fossil fuel and its serious environmental impact. This critical review highlights some key factors influencing the efficiency of heterogeneous semiconductors for solar water splitting (i.e. improved charge separation and transfer, promoted optical absorption, optimized band gap position, lowered cost and toxicity, and enhanced stability and water splitting kinetics). Moreover, different engineering strategies, such as band structure engineering, micro/nano engineering, bionic engineering, co-catalyst engineering, surface/interface engineering of heterogeneous semiconductors are summarized and discussed thoroughly. The synergistic effects of the different engineering strategies, especially for the combination of co-catalyst loading and other strategies seem to be more promising for the development of highly efficient photocatalysts. A thorough understanding of electron and hole transfer thermodynamics and kinetics at the fundamental level is also important for elucidating the key efficiency-limiting step and designing highly efficient solar-to-fuel conversion systems. In this review, we provide not only a summary of the recent progress in the different engineering strategies of heterogeneous semiconductors for solar water splitting, but also some potential opportunities for designing and optimizing solar cells, photocatalysts for the reduction of CO2 and pollutant degradation, and electrocatalysts for water splitting.

The oral and gut microbiomes are perturbed in rheumatoid arthritis and partly normalized after treatment

Abstract: We carried out metagenomic shotgun sequencing and a metagenome-wide association study (MGWAS) of fecal, dental and salivary samples from a cohort of individuals with rheumatoid arthritis (RA) and healthy controls. Concordance was observed between the gut and oral microbiomes, suggesting overlap in the abundance and function of species at different body sites. Dysbiosis was detected in the gut and oral microbiomes of RA patients, but it was partially resolved after RA treatment. Alterations in the gut, dental or saliva microbiome distinguished individuals with RA from healthy controls, were correlated with clinical measures and could be used to stratify individuals on the basis of their response to therapy. In particular, Haemophilus spp. were depleted in individuals with RA at all three sites and negatively correlated with levels of serum autoantibodies, whereas Lactobacillus salivarius was over-represented in individuals with RA at all three sites and was present in increased amounts in cases of very active RA. Functionally, the redox environment, transport and metabolism of iron, sulfur, zinc and arginine were altered in the microbiota of individuals with RA. Molecular mimicry of human antigens related to RA was also detectable. Our results establish specific alterations in the gut and oral microbiomes in individuals with RA and suggest potential ways of using microbiome composition for prognosis and diagnosis.

Biosensing by Luminogens with Aggregation-induced Emission Characteristics

Abstract: Fluorescent biosensors are powerful analytical tools for studying biological events in living systems. Luminescent materials with aggregation-induced emission (AIE) attributes have attracted much research interest and have been identified as a novel class of luminogens to develop fluorescent turn-on biosensors with superior sensitivity. In this Tutorial Review, we present an overview of the AIE phenomenon and its mechanism. We summarize the structural design and working principle of AIE biosensors developed recently. Typical examples of AIE biosensors are presented.

Gut microbiome development along the colorectal adenoma-carcinoma sequence.

Abstract: Colorectal cancer, a commonly diagnosed cancer in the elderly, often develops slowly from benign polyps called adenoma. The gut microbiota is believed to be directly involved in colorectal carcinogenesis. The identity and functional capacity of the adenoma- or carcinoma-related gut microbe(s), however, have not been surveyed in a comprehensive manner. Here we perform a metagenome-wide association study (MGWAS) on stools from advanced adenoma and carcinoma patients and from healthy subjects, revealing microbial genes, strains and functions enriched in each group. An analysis of potential risk factors indicates that high intake of red meat relative to fruits and vegetables appears to associate with outgrowth of bacteria that might contribute to a more hostile gut environment. These findings suggest that faecal microbiome-based strategies may be useful for early diagnosis and treatment of colorectal adenoma or carcinoma.

A series of simple oligomer-like small molecules based on oligothiophenes for solution-processed solar cells with high efficiency.

Abstract: A series of acceptor-donor-acceptor simple oligomer-like small molecules based on oligothiophenes, namely, DRCN4T-DRCN9T, were designed and synthesized. Their optical, electrical, and thermal properties and photovoltaic performances were systematically investigated. Except for DRCN4T, excellent performances were obtained for DRCN5T-DRCN9T. The devices based on DRCN5T, DRCN7T, and DRCN9T with axisymmetric chemical structures exhibit much higher short-circuit current densities than those based on DRCN6T and DRCN8T with centrosymmetric chemical structures, which is attributed to their well-developed fibrillar network with a feature size less than 20 nm. The devices based on DRCN5T/PC71BM showed a notable certified power conversion efficiency (PCE) of 10.10% under AM 1.5G irradiation (100 mW cm(-2)) using a simple solution spin-coating fabrication process. This is the highest PCE for single-junction small-molecule-based organic photovoltaics (OPVs) reported to date. DRCN5T is a rather simpler molecule compared with all of the other high-performance molecules in OPVs to date, and this might highlight its advantage in the future possible commercialization of OPVs. These results demonstrate that a fine and balanced modification/design of chemical structure can make significant performance differences and that the performance of solution-processed small-molecule-based solar cells can be comparable to or even surpass that of their polymer counterparts.

Small-molecule solar cells with efficiency over 9%

Abstract: Solution-processed small-molecule solar cells with almost 100% internal quantum efficiency and a power conversion efficiency of 9% are reported. The cells make use of a donor molecule called DRCN7T and use PC71BM as an acceptor.

Functionalization of phosphorescent emitters and their host materials by main-group elements for phosphorescent organic light-emitting devices.

Abstract: Phosphorescent organic light-emitting devices (OLEDs) have attracted increased attention from both academic and industrial communities due to their potential practical application in high-resolution full-color displays and energy-saving solid-state lightings. The performance of phosphorescent OLEDs is mainly limited by the phosphorescent transition metal complexes (such as iridium(III), platinum(II), gold(III), ruthenium(II), copper(I) and osmium(II) complexes, etc.) which can play a crucial role in furnishing efficient energy transfer, balanced charge injection/transporting character and high quantum efficiency in the devices. It has been shown that functionalized main-group element (such as boron, silicon, nitrogen, phosphorus, oxygen, sulfur and fluorine, etc.) moieties can be incorporated into phosphorescent emitters and their host materials to tune their triplet energies, frontier molecular orbital energies, charge injection/transporting behavior, photophysical properties and thermal stability and hence bring about highly efficient phosphorescent OLEDs. So, in this review, the recent advances in the phosphorescent emitters and their host materials functionalized with various main-group moieties will be introduced from the point of view of their structure-property relationship. The main emphasis lies on the important role played by the main-group element groups in addressing the key issues of both phosphorescent emitters and their host materials to fulfill high-performance phosphorescent OLEDs.

Specific light-up bioprobes based on AIEgen conjugates

Abstract: Driven by the high demand for sensitive and specific tools for optical sensing and imaging, bioprobes with various working mechanisms and advanced functionalities are flourishing at an incredible speed. Conventional fluorescent probes suffer from the notorious effect of aggregation-caused quenching that imposes limitation on their labelling efficiency or concentration to achieve desired sensitivity. The recently emerged fluorogens with an aggregation-induced emission (AIE) feature offer a timely remedy to tackle the challenge. Utilizing the unique properties of AIE fluorogens (AIEgens), specific light-up probes have been constructed through functionalization with recognition elements, showing advantages such as low background interference, a high signal to noise ratio and superior photostability with activatable therapeutic effects. In this tutorial review, we summarize the recent progress in the development of specific AIEgen-based light-up bioprobes. Through illustration of their operation mechanisms and application examples, we hope to provide guidelines for the design of more advanced AIE sensing and imaging platforms with high selectivity, great sensitivity and wide adaptability to a broad range of biomedical applications.

Removing Rain from a Single Image via Discriminative Sparse Coding

Abstract: Visual distortions on images caused by bad weather conditions can have a negative impact on the performance of many outdoor vision systems. One often seen bad weather is rain which causes significant yet complex local intensity fluctuations in images. The paper aims at developing an effective algorithm to remove visual effects of rain from a single rainy image, i.e. separate the rain layer and the de-rained image layer from an rainy image. Built upon a non-linear generative model of rainy image, namely screen blend mode, we proposed a dictionary learning based algorithm for single image de-raining. The basic idea is to sparsely approximate the patches of two layers by very high discriminative codes over a learned dictionary with strong mutual exclusivity property. Such discriminative sparse codes lead to accurate separation of two layers from their non-linear composite. The experiments showed that the proposed method outperformed the existing single image de-raining methods on tested rain images.

Mesoporous N-Doped Carbons Prepared with Thermally Removable Nanoparticle Templates: An Efficient Electrocatalyst for Oxygen Reduction Reaction

Abstract: Thermally removable nanoparticle templates were used for the fabrication of self-supported N-doped mesoporous carbons with a trace amount of Fe (Fe-N/C). Experimentally Fe-N/C was prepared by pyrolysis of poly(2-fluoroaniline) (P2FANI) containing a number of FeO(OH) nanorods that were prepared by a one-pot hydrothermal synthesis and homogeneously distributed within the polymer matrix. The FeO(OH) nanocrystals acted as rigid templates to prevent the collapse of P2FANI during the carbonization process, where a mesoporous skeleton was formed with a medium surface area of about 400 m2/g. Subsequent thermal treatments at elevated temperatures led to the decomposition and evaporation of the FeO(OH) nanocrystals and the formation of mesoporous carbons with the surface area markedly enhanced to 934.8 m2/g. Electrochemical measurements revealed that the resulting mesoporous carbons exhibited apparent electrocatalytic activity for oxygen reduction reactions (ORR), and the one prepared at 800 °C (Fe-N/C-800) was the...

Synthesis and applications of novel graphitic carbon nitride/metal-organic frameworks mesoporous photocatalyst for dyes removal

Abstract: Metal-organic frameworks (MOFs) have been attracted considerable attention for their applications in gas storage/separation, adsorption as well as catalysis. In this study, a facile solvothermal method was employed to prepare MOFs and graphitic carbon nitride (g-C3N4) hybrids, and a g-C3N4/Ti-benzenedicarboxylate (MIL-125(Ti)) heterostructures photocatalyst was successfully synthesized. The as-obtained materials were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption–desorption isotherm, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflection spectroscopy (UV–vis DRS), and photoluminescence (PL) spectroscopy. It is indicated that the hybrids have large surface area, mesoporous structure, thermal stability, and enhanced visible-light absorption. Compared with pure MIL-125(Ti) and g-C3N4, the composites exhibited more efficient photocatalytic performance for Rhodamine B degradation from aqueous solution under visible-light irradiation. The optimal g-C3N4 content in g-C3N4/MIL-125(Ti) composite was determined to be 7.0 wt%, and the corresponding photodegradation rate for RhB was 0.0624 min−1, about 2.1 and 24 times higher than that of pure g-C3N4 and MIL-125(Ti), respectively. The indirect dye photosensitization, the Ti3+–Ti4+ intervalence electron transfer, and the synergistic effect between MIL-125(Ti) and g-C3N4 were the three reasons for improved photo-degradation performance. Therefore, it is reasonable to believe that metal-free semiconductor/MOFs photocatalysts have great potentiality in environmental remediation.

Data mining for the Internet of Things: literature review and challenges

Abstract: The massive data generated by the Internet of Things (IoT) are considered of high business value, and data mining algorithms can be applied to IoT to extract hidden information from data. In this paper, we give a systematic way to review data mining in knowledge view, technique view, and application view, including classification, clustering, association analysis, time series analysis and outlier analysis. And the latest application cases are also surveyed. As more and more devices connected to IoT, large volume of data should be analyzed, the latest algorithms should be modified to apply to big data. We reviewed these algorithms and discussed challenges and open research issues. At last a suggested big data mining system is proposed.

Aggregation-induced emission of siloles

Abstract: Aggregation-induced emission (AIE) is a unique and significant photophysical phenomenon that differs greatly from the commonly acknowledged aggregation-caused emission quenching observed for many π-conjugated planar chromophores. The mechanistic decipherment of the AIE phenomenon is of high importance for the advance of new AIE systems and exploitation of their potential applications. Propeller-like 2,3,4,5-tetraphenylsiloles are archetypal AIE-active luminogens, and have been adopted as a core part in the design of numerous luminescent materials with diverse functionalities. In this review article, we elucidate the impacts of substituents on the AIE activity and shed light on the structure–property relationship of siloles, with the aim of promoting the judicious design of AIE-active functional materials in the future. Recent representative advances of new silole-based functional materials and their potential applications are reviewed as well.

Transition metal-catalyzed C-H functionalization of N-oxyenamine internal oxidants.

Abstract: The transition metal-catalyzed C–H functionalization with hydroxylamine derivatives serving as both reactants and internal oxidants has attracted a lot of interest. These reactions obviate the need for external oxidants and therefore result in high reactivity and selectivity, as well as excellent functional group tolerance under mild reaction conditions, and moreover, water, methanol or carboxylic acid is generally released as the by-product, thus leading to reduced waste. This review focuses on the transition metal-catalyzed oxidative C–H functionalization of N-oxyenamine internal oxidants, with an emphasis on the scope and limitations, as well as the mechanisms of these reactions.

Quantifying Losses in Open-Circuit Voltage in Solution-Processable Solar Cells

Abstract: To compare and improve solar cells, merely knowing their percent efficiencies is insufficient; we need to be able to understand and quantify their different physical mechanisms of loss. The authors use the reciprocity relation between light absorption and emission to explore theoretical and practical performance limits for emerging technologies based on organics and perovskites, and compare them to state-of-the-art systems based on GaAs, c-Si, and CIGS. This study indicates the potential of the newer technologies, and shows the factors that limit present-day performance.

Specific Light-Up Bioprobe with Aggregation-Induced Emission and Activatable Photoactivity for the Targeted and Image-Guided Photodynamic Ablation of Cancer Cells†

Abstract: Activatable photosensitizers (PSs) have been widely used for the simultaneous fluorescence imaging and photodynamic ablation of cancer cells. However, the ready aggregation of traditional PSs in aqueous media can lead to fluorescence quenching as well as reduced phototoxicity even in the activated form. We have developed a series of PSs that show aggregation-enhanced emission and phototoxicity and thus the exact opposite behavior to that of previously reported PSs. We further developed a dual-targeted enzyme-activatable bioprobe based on the optimized photosensitizer and describe simultaneous light-up fluorescence imaging and activated photodynamic therapy for specific cancer cells. The design of smart probes should thus open new opportunities for targeted and image-guided photodynamic therapy.

Deep Absorbing Porphyrin Small Molecule for High-Performance Organic Solar Cells with Very Low Energy Losses

Abstract: We designed and synthesized the DPPEZnP-TEH molecule, with a porphyrin ring linked to two diketopyrrolopyrrole units by ethynylene bridges. The resulting material exhibits a very low energy band gap of 1.37 eV and a broad light absorption to 907 nm. An open-circuit voltage of 0.78 V was obtained in bulk heterojunction (BHJ) organic solar cells, showing a low energy loss of only 0.59 eV, which is the first report that small molecule solar cells show energy losses <0.6 eV. The optimized solar cells show remarkable external quantum efficiency, short circuit current, and power conversion efficiency up to 65%, 16.76 mA/cm2, and 8.08%, respectively, which are the best values for BHJ solar cells with very low energy losses. Additionally, the morphology of DPPEZnP-TEH neat and blend films with PC61BM was studied thoroughly by grazing incidence X-ray diffraction, resonant soft X-ray scattering, and transmission electron microscopy under different fabrication conditions.

Biocompatible Deep Eutectic Solvents Based on Choline Chloride: Characterization and Application to the Extraction of Rutin from Sophora japonica

Abstract: The development of novel green solvents has been one of the hottest subjects in green chemistry. Deep eutectic solvents (DESs) have logically and naturally emerged in the search for more biocompatible and biodegradable solvents. In this study, some basic physical properties, including viscosity, conductivity, and density, of 20 DESs prepared from choline chloride and various hydrogen-bond donors were investigated systematically. In addition, the biocompatibility of the tested DESs was qualitatively and quantitatively evaluated using two Gram-positive (Staphylococcus aureus and Listeria monocytogenes) and two Gram-negative (Escherichia coli and Salmonella enteritidis) bacteria. A closed bottle test was used to assess the biodegradability of these DESs. The results demonstrated that these choline chloride-based DESs were excellent solvents with extremely low toxicity and favorable biodegradability. Finally, DESs were used to extract a flavonoid (rutin) from the flower buds of Sophora japonica. An extraction...

Uniform yolk–shell Sn4P3@C nanospheres as high-capacity and cycle-stable anode materials for sodium-ion batteries

Abstract: Uniform yolk–shell Sn4P3@C nanospheres were facilely synthesized via a top-down phosphorized route with yolk–shell Sn@C nanospheres as the precursor. As anode materials for Na-ion batteries, they exhibit very high reversible capacity (790 mA h g−1), superior rate capability (reversible capabilities of 720, 651, 581, 505, and 421 mA h g−1 at 0.2C, 0.4C, 0.8C, 1.5C, and 3C, respectively) and stable cycling performance (a high capacity of 360 mA h g−1 at 1.5C after long 400 cycles).

Genome-wide profiling of HPV integration in cervical cancer identifies clustered genomic hot spots and a potential microhomology-mediated integration mechanism

Abstract: Human papillomavirus (HPV) integration is a key genetic event in cervical carcinogenesis. By conducting whole-genome sequencing and high-throughput viral integration detection, we identified 3,667 HPV integration breakpoints in 26 cervical intraepithelial neoplasias, 104 cervical carcinomas and five cell lines. Beyond recalculating frequencies for the previously reported frequent integration sites POU5F1B (9.7%), FHIT (8.7%), KLF12 (7.8%), KLF5 (6.8%), LRP1B (5.8%) and LEPREL1 (4.9%), we discovered new hot spots HMGA2 (7.8%), DLG2 (4.9%) and SEMA3D (4.9%). Protein expression from FHIT and LRP1B was downregulated when HPV integrated in their introns. Protein expression from MYC and HMGA2 was elevated when HPV integrated into flanking regions. Moreover, microhomologous sequence between the human and HPV genomes was significantly enriched near integration breakpoints, indicating that fusion between viral and human DNA may have occurred by microhomology-mediated DNA repair pathways. Our data provide insights into HPV integration-driven cervical carcinogenesis.

Terthiophene-Based D–A Polymer with an Asymmetric Arrangement of Alkyl Chains That Enables Efficient Polymer Solar Cells

Abstract: We report a series of difluorobenzothiadizole (ffBT) and oligothiophene-based polymers with the oligothiophene unit being quaterthiophene (T4), terthiophene (T3), and bithiophene (T2). We demonstrate that a polymer based on ffBT and T3 with an asymmetric arrangement of alkyl chains enables the fabrication of 10.7% efficiency thick-film polymer solar cells (PSCs) without using any processing additives. By decreasing the number of thiophene rings per repeating unit and thus increasing the effective density of the ffBT unit in the polymer backbone, the HOMO and LUMO levels of the T3 polymers are significantly deeper than those of the T4 polymers, and the absorption onset of the T3 polymers is also slightly red-shifted. For the three T3 polymers obtained, the positions and size of the alkyl chains play a critical role in achieving the best PSC performances. The T3 polymer with a commonly known arrangement of alkyl chains (alkyl chains sitting on the first and third thiophenes in a mirror symmetric manner) yie...

Achieving a Significantly Increased Efficiency in Nondoped Pure Blue Fluorescent OLED: A Quasi-Equivalent Hybridized Excited State

Abstract: Excited state characters and components play a decisive role in photoluminescence (PL) and electroluminescence (EL) properties of organic light-emitting materials (OLEDS). Charge-transfer (CT) state is beneficial to enhance the singlet exciton utilizations in fluorescent OLEDs by an activated reverse intersystem crossing process, due to the minimized singlet and triplet energy splitting in CT excitons. However, the dominant CT component in the emissive state significantly reduces the PL efficiency in such materials. Here, the strategy is to carry out a fine excited state modulation, aiming to reach a golden combination of the high PL efficiency locally emissive (LE) component and the high exciton utilizing CT component in one excited state. As a result, a quasi-equivalent hybridization of LE and CT components is obtained in the emissive state upon the addition of only an extra phenyl ring in the newly synthesized material 4-[2-(4′-diphenylamino-biphenyl-4-yl)-phenanthro[9,10-d]imidazol-1-yl]-benzonitrile (TBPMCN), and the nondoped OLED of TBPMCN exhibited a record-setting performance: a pure blue emission with a Commission Internationale de L'Eclairage coordinate of (0.16, 0.16), a high external quantum efficiency of 7.8%, and a high yield of singlet exciton of 97% without delayed fluorescence phenomenon. The excited state modulation could be a practical way to design low-cost, high-efficiency fluorescent OLED materials.

Microfiber-based few-layer black phosphorus saturable absorber for ultra-fast fiber laser

Abstract: Few-layer black phosphorus (BP), as the most alluring graphene analogue owing to its similar structure as graphene and thickness dependent direct band-gap, has now triggered a new wave of research on two-dimensional (2D) materials based photonics and optoelectronics However, a major obstacle of practical applications for few-layer BPs comes from their instabilities of laser-induced optical damage Herein, we demonstrate that, few-layer BPs, fabricated through the liquid exfoliation approach, can be developed as a new and practical saturable absorber (SA) by depositing few-layer BPs with microfiber The saturable absorption property of few-layer BPs had been verified through an open-aperture z-scan measurement at the telecommunication band and the microfiber-based BP device had been found to show a saturable average power of ~45 mW and a modulation depth of 109%, which is further confirmed through a balanced twin detection measurement By further integrating this optical SA device into an erbium-doped fiber laser, it was found that it can deliver the mode-locked pulse with duration down to 940 fs with central wavelength tunable from 1532 nm to 1570 nm The prevention of BP from oxidation through the 'lateral interaction scheme' owing to this microfiber-based few-layer BP SA device might partially mitigate the optical damage problem of BP Our results not only demonstrate that black phosphorus might be another promising SA material for ultrafast photonics, but also provide a practical solution to solve the optical damage problem of black phosphorus by assembling with waveguide structures such as microfiber