Research Progress----Shanghai Advanced Research Institute,Chinese Academy of Sciences

Scientists Propose a Novel Self-modulation Scheme in Seeded Free-Electron Lasers

The FEL teams at Shanghai Advanced Research Institute and Shanghai Institute of Applied Physics of the Chinese Academy of Sciences collaborated and reported a novel self-modulation method for enhancing laser-induced energy modulation, thereby significantly reducing the requirement of an external laser system.

　　Seeded free-electron lasers (FELs), which use frequency up-conversion of an external seed laser to improve temporal coherence, are regarded ideal for supplying stable, fully coherent, soft X-ray pulses. However, the requirement for an external seed laser with sufficient peak power to modulate the electron beam can hardly be met by the present state-of-the-art laser systems, it remains challenging for seeded FELs to operate at high repetition rate, e.g., MHz repetition rate.
　　Motivated by such a challenge, the FEL teams at Shanghai Advanced Research Institute and Shanghai Institute of Applied Physics of the Chinese Academy of Sciences collaborated and reported a novel self-modulation method for enhancing laser-induced energy modulation, thereby significantly reducing the requirement of an external laser system. The research results were published in Physical Review Letters entitled "Self-Amplification of Coherent Energy Modulation in Seeded Free-Electron Lasers."
　　Based on the Shanghai soft x-ray FEL test facility, the self-amplification of coherent energy modulation in a seeded FEL is experimentally verified. The peak power requirement of an external seed laser is demonstrated to be relaxed by a factor of 10 to 25 when utilizing the proposed scheme.
　　Moreover, the high harmonic generation in a seeded FEL is realized by using an unprecedentedly small energy modulation. A 795 MeV electron beam with a laser-induced energy modulation amplitude as small as 1.8 times the slice energy spread is used for lasing at the 7th harmonic of a 266-nm seed laser in a single-stage high-gain harmonic generation (HGHG) and the 30th harmonic of the seed laser in a two-stage HGHG.The results pave the way for a high-repetition-rate seeded FEL, which is expected to show great promise for multidimensional coherent spectroscopies, far beyond what has been demonstrated to date. Furthermore, the self-modulation scheme proposed in this work is also promising for solving other critical problems of seeded FELs such as reaching shorter wavelengths and improving stability.
　　Figure 1. The self-modulation scheme together with the electron-beam longitudinal phase spaces at various positions (Image by SARI)
　　Contact: DENG Haixiao
　　Shanghai Advanced Research Institute, Chinese Academy of Sciences
　　Email: denghaixiao@zjlab.org.cn

2021-03-10 more+

New Framework Proposed for Analyzing the Fouling/Scaling behavior of MD Membrane

A research team led by Prof. HE Tao proposed a hydrodynamic theory of slippery surface for fouling/scaling resistance of superhydrophobic membranes.The latest result on the hydrodynamic behavior and scaling/fouling resistance of MD membranes was published in Desalination.

　　Membrane distillation (MD) is a thermal driven desalination technology using hydrophobic membranes for separation. In MD, heat is utilized to compensate the latent heat of evaporation, and ultrapure water desired by the industry is produced in the process. MD can treat streams containing high total dissolved solids with nearly complete rejection to non-volatile matters. Since there is abundant low-grade heat available in various industries, MD is a potential technology to reuse wastewater, dewater products before crystallization, so as to manage the energy balance and reduce carbon footprint in many chemical, petrochemical, steel industries.
　　However, the targeted fluids are mostly highly saline and contain complicated organic and inorganic chemicals, which incur fouling and scaling to the hydrophobic membranes. Thus, understanding the fouling/scaling phenomenon of hydrophobic membranes has long been the research focal of MD.
　　Recently, researchers have been attempting to adopt superhydrophobic membranes for improving the scaling and fouling resistance of MD. But discrepancy in results when using different models has been reported. To unravel this puzzle, a research team led by Prof. HE Tao at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences, collaborating with Prof. YIN Huabing at University of Glasgow in the UK and Professor VOLKOV Alexey from A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, proposed a hydrodynamic theory of slippery surface for fouling/scaling resistance of superhydrophobic membranes.
　　To prove the theory, scientists created and implemented a delicate design of a porous membrane with micro-pillar arrays. A superhydrophobic membrane (MP-PVDF) was successfully prepared using a micromolding phase separation (mPS) method. The team further utilized a rheolometry measurement to quantify the slip length of the membrane surface. Simulation of the surface wetting indicated that there is a strong correlation of surface wetting, slip and scaling/fouling resistance. The latest result on the hydrodynamic behavior and scaling/fouling resistance of MD membranes was published in Desalination entitled “Understanding the fouling/scaling resistance of superhydrophobic/omniphobic membranes in membrane distillation.”
　　The new framework for analyzing the fouling/scaling behavior of MD can identify the wetting and hydrodynamic character of the membrane, which is important for hydrophobic membrane design and further development of membrane distillation.
　　Fig.1 Scaling mitigation in membrane distillation (Image by Prof. HE’s group)
　　Contact: HE Tao
　　Shanghai Advanced Research Institute, Chinese Academy of Sciences
　　Email: het@sari.ac.cn
　　

2021-02-22 more+

Researchers Reveal In-situ Manipulation of Active Au-TiO2 Interface

An international joint research team reported an in-situ strategy to manipulate interfacial structure with atomic precision during catalytic reactions. Results were published in the latest issue of Science.

　　An international joint research team from Zhejiang University, Shanghai Advanced Research Institute of the Chinese Academy of Sciences, and Technical University of Denmark, reported an in-situ strategy to manipulate interfacial structure with atomic precision during catalytic reactions. Results were published in the latest issue of Science.
　　The interface between nanoparticles and substrates plays a critical role in heterogeneous catalysis because most active sites are located at the perimeter of the interface. It is generally believed that this interface is immobile and unchangeable, thus can hardly be adjusted in reactive environments. As a result, it has been challenging to promote catalytic activity through precise control of the interfacial structure.
　　In this study, the scientists first used environmental transmission electron microscopy to directly visualize the epitaxial rotation of gold nanoparticles on titanium dioxide (TiO2) surfaces during CO oxidation at the atomic level. A perfect epitaxial relationship was observed between Au nanoparticles and TiO2 (001) surfaces under an O2 environment in real time.
　　Theoretical calculations including density functional theory calculations and thermodynamics analysis were then carried out, indicating that the epitaxial orientation could be induced by changing O2 adsorption coverage at the perimeter interface. The Au nanoparticle was more stable with adsorption of more O2 molecules at the Au-TiO2 interface, but became less stable with the consumption of O2 with CO.
　　To exploit the promoted activity of Au-TiO2 interface, researchers conducted additional top-view observations and found that this configuration remained unchanged when cooling from 500 °C to 20 °C in CO and O2 reactive environments, showing the rotation of the Au nanoparticle was also temperature dependent in reaction conditions.
　　Taking advantage of the reversible and controllable rotation of the Au nanoparticle, the scientists achieved in-situ manipulation of the active Au-TiO2 interface at the atomic level by changing gas and temperature.
　　This study sheds light on real-time manipulation of catalytic interface structure in reaction conditions at the atomic scale, which may inspire future approaches to real-time design of the catalytic interface under operating conditions.
　　Figure 1. Geometric and electronic structure of Au-TiO2 interface under CO/O2 (A, C, E) and O2 environment (B, D, F) (Image adapted from Science)
　　Figure 2. Manipulation of the Au-TiO2 interface using temperature and gas control (Image adapted from Science)
　　Figure 3. Schematic illustration of In-situ manipulation of active Au-TiO2 interface (Credited by Yong Wang, Zhejiang University)
　　Contact: GAO Yi
　　Shanghai Advanced Research Institute, Chinese Academy of Sciences
　　Email: gaoyi@zjlab.org.cn
　　

2021-01-29 more+

Researchers Develop a Novel Donor-Acceptor System for Highly-effective Sunlight-Driven Hydrogen Evolution

a research team reported a novel photoactive 2D COF from donor Py and acceptor Tz building units, which enabled remarkable photogenerated charge separation and efficient charge migration.

　　Sunlight-driven hydrogen production has been considered as one of the most important renewable energy sources, while active photocatalyst is a prerequisite for efficient hydrogen production. 2D covalent organic frameworks (COFs) could have well-defined arrangements of photo- and electro-active units that serve as electron or hole transport channels for solar energy harvesting and conversion, however, their insufficient charge transfer and rapid charge recombination impede the sunlight-driven photocatalytic performance.
　　Motivated by such a challenge, a research team led by Prof. WEN Ke and Prof. YANG Hui at Shanghai Advanced Research Institute (SARI), collaborated with Prof. ZHANG Yue-Biao at ShanghaiTech University reported a novel photoactive 2D COF from donor Py and acceptor Tz building units, which enabled remarkable photogenerated charge separation and efficient charge migration. The research results were featured on front cover of Angewandte Chemie International Edition.
　　Based on physical structural characterizations, scientists conjectured that Thiazolo[5,4-d]Thiazole might help to boost photo-absorbing ability of previously reported TpTz COF and constructed the new donor-acceptor system from the electron-rich pyrene (Py) and electron-deficient thiazolo[5,4-d]thiazole (Tz). The PyTz-COF demonstrated high photocatalytic activitity for sustainable and efficient water splitting with a photocurrent up to 100 uA cm-2 at 0.2 V vs. RHE and could reach a hydrogen evolution rate of 2072.4 umolg-1 h-1, which exceeds the values of many previously reported COFs.
　　This study not only realized the effective separation and migration of photogenerated electrons and holes, but also revealed a new mechanism of COF photocatalysis. More importantly, it would inspire future development of sunlight-driven photocatalysts for solar energy harvesting and conversion.
　　Figure 1. Synthetic route for PyTz-COF (Image by SARI)
　　Figure 2. Photoelectrochemical and photocatalytic performance of PyTz-COF (Image by SARI)
　　Contact: Prof. Wenke
　　Shanghai Advanced Research Institute, Chinese Academy of Sciences
　　Email: wenk@sari.ac.cn
　　

2021-01-22 more+

Scientists Reveal New Tools in Single-cell Infrared Microspectroscopy Based on Synchrotron Radiation

Single-cell technologies are becoming hot topics and key directions of biomedical research due to their abilities to answer the basic question of cellular functional heterogeneity and to interpret the molecular basis of various chronic diseases as well as aging. Among the single cell techniques, single-cell infrared spectroscopy obtains growing attention because of its advantages in simultaneously identifying the characteristics of intracellular metabolites. Recently, research team at Shanghai Advanced Research Institute together with collaborators have successfully revealed new tools to evaluate single-cell infrared data based on synchrotron radiation.

　　Single-cell technologies are becoming hot topics and key directions of biomedical research due to their abilities to answer the basic question of cellular functional heterogeneity and to interpret the molecular basis of various chronic diseases as well as aging. Among the single cell techniques, single-cell infrared spectroscopy obtains growing attention because of its advantages in simultaneously identifying the characteristics of intracellular metabolites.
　　Recently, Professor Lü Junhong’s group at Shanghai Advanced Research Institute (SARI), collaborating with Shanghai Center for Bioinformation Technology, National Engineering Research Center for Nanotechnology, Capital Medical University Tiantan Hospital, Binzhou Medical University and Shanghai Jiao Tong University Ruijin Hospital, have successfully revealed new tools to evaluate single-cell infrared data based on synchrotron radiation.
　　Fourier Transform infrared (FTIR) spectroscopy is a well-established non-destructive and sensitive analytical technique for the study of biological samples. Due to the inevitable technical errors/variation (caused by water vapor, CO2, instrument noise, etc.) or batch effects, a significant number of cells must be analyzed in order to distinguish the measured signal from controls with statistical confidence. Therefore, estimating a reasonable and practical amount for single-cell infrared spectroscopy is particularly necessary.
　　To this end, the group has developed a statistical method and procedure to evaluate single-cell spectral variability among two different cell types and two states. After calculating the similarity distance of the corresponding infrared spectra, they confirmed that 20 cells measured per time is sufficient to control batch effects (CV < 5%).
　　These findings provide a useful tool to evaluate the single-cell spectral quality and an important benchmark for the investigation of cellular heterogeneity.
　　Figure 1 Batch effects on single-cell infrared spectra and the establishment of evaluation methodology (Image adapted from Chemical Communications)
　　Cell phenomics is an emerging field that simultaneously characterizes many phenotypic traits of cells in response to genetic mutation and environmental influences. The group has proposed a label-free phenotypic screening strategy based on the combination of single-cell infrared microspectroscopy and the statistical calculations of the similarity among single cell infrared spectra.
　　This novel approach enables subtle phenotypic changes to be unveiled within individual cells by using comprehensive analysis of spectral similarity in chemical components. Based on this infrared phonemics method, they demonstrate for the first time phytomedicine protopanaxadiol with different concentration induces phenotypical changes of cancer cell HepG2.
　　These findings provide a powerful tool to accurately evaluate the cell stress responses and to largely expand the phenotypic screening toolkit for drug discovery.
　　Figure 2 Single-cell infrared phenomics and drug screening (Image adapted from Chemical Communications)
　　With the rapid technological advances, a variety of single-cell methods are emerging for the promise of unveiling cellular heterogeneity. The demand of a detailed and unbiased approach to simultaneously quantify global biomolecular structure information in a single cell and heterogeneity within cells is urgent.
　　The research group developed a novel strategy to quantitatively evaluate cellular heterogeneity based on single-cell synchrotron FTIR microspectroscopy and computational methods. After calculating the cell-to-cell similarity distance of the infrared spectral data, they confirmed that the statistical analysis of single-cell infrared phenotypes can be used to quantify the heterogeneity in a specific cell population. Based on this method, they revealed the infrared phenotypes have a similar tendency with increasing heterogenicity at the early stage and decreasing heterogenicity at the terminal stage of differentiation toward adipocyte lineage.
　　These findings provide an alternative methodology for dissecting the cellular heterogeneity, and the combination with other single-cell analysis tools will be very helpful for understanding the genotype-to-phenotype relationship in cellular populations.
　　Figure 3 Sing-cell infrared microspectroscopy quantifies dynamic heterogeneity of Mesenchymal stem cells during adipogenic differentiation (Image adapted from Analytical Chemistry)
　　These findings were published on Chemical Communications (2020,26:3773-3776;2020,86:13237-13240) and Analytical Chemistry (2020,10.1021/acs.analchem.0c04110) respectively.
　　These works were supported by the National Natural Science Foundation of China and from the BL01B beamline of the National Facility for Protein Science in Shanghai (NFPS) at Shanghai Synchrotron Radiation Facility.
　　Contact: Lü Junhong
　　Shanghai Advanced Research Institute, Chinese Academy of Sciences
　　Email: lujunhong@zjlab.org.cn

2021-01-05 more+

Novel compound/c-Si passivation contact for p‐Type Crystalline Silicon Solar Cells Achieving 20% Efficiency

Crystalline silicon heterojunction solar cells based on hole-selective MoOX contacts provide obvious merits in terms of the decent passivation and carrier selectivity but face the challenge of long-term stability. With the aim to improve the performance and stability of solar cells with full area MoOX/ metal contacts, a SiOX tunneling layer on silicon surface is intentionally formed by UV/O3 treatment and an indium tin oxide (ITO) film is sputtered as a high-work-function electrode.

　　Efficient separation and collection of photogenerated carriers through the formation of asymmetric electron and hole transport channels is one of the central issues for crystalline silicon (c-Si) solar cells and other types of photovoltaic devices. Silicon heterojunction solar cells based on MoOX (X<3) hole-selective contacts show significant advantages in carrier-selective transport, however, it faces the challenge for long-term stability due to poor thermodynamic stability of MoOX.
　　Motivated by such a challenge, a research team led by Prof. LI Dongdong at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences collaborated with Jinneng Clean Energy Technology Limited reported a novel stacked structure (c-Si/SiOX/MoOX/V2OX/ITO/Ag) to improve the stability of c-Si solar cells. The research results were published in Advanced Functional Materials entitled “Stable MoOX‐Based Heterocontacts for p‐Type Crystalline Silicon Solar Cells Achieving 20% Efficiency”.
　　In this work, the research team introduced a SiO2 tunneling passivation layer at the MoOX/c-Si interface to suppress the redox reaction brought about by the direct contact between MoOX and c-Si, which keeps the work function of MoOX at a relatively high level. An ultra-thin V2OX layer is deposited on the surface of MoOX film to improve the stability of the heterojunction structure in air and its resistance to sputtering damage. At the same time, the ITO layer is fabricated at the V2OX/Ag interface, which effectively inhibits the migration of metal ion, and finally constructs a tandem structure of c-Si/SiOX/MoOX/V2OX/ITO/Ag, with power conversion efficiency (PCE) of 20.0% and significantly improved stability.
　　This work innovatively constructs a stacked thin film structure based on an in-depth understanding of the interfacial evolution of MoOX/c-Si and MoOX/metal electrodes, providing a new approach to the study of compound/c-Si passivated contact heterojunction solar cells, which can be extended as a universal method to improve the efficiency and stability of heterojunction solar cells and other types of optoelectronics.
　　This work was supported by the National Natural Science Foundation of China, the Natural Science Foundation of Shanghai, the Shanxi Science and Technology Department, and the Youthnnovation Promotion Association of the Chinese Academy of Sciences.
　　
　　Figure 1. The device performances as a function of UV/O3 pre-treatment (Image adapted from Advanced Functional Materials)
　　Figure 2. Characterizations of XPS spectra and passivation properties of MoOX films (Image adapted from Advanced Functional Materials)
　　Contact: LI Dongdong
　　Shanghai Advanced Research Institute, Chinese Academy of Sciences
　　Email: lidd@sari.ac.cn
　　

2020-09-22 more+