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2023 Vol. 53, No. 6

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2023-6 Contents
2023, 53(6): 1-2.
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2023-6 Abstract
2023, 53(6): 1-2.
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Chemistry; Life Sciences
Recent progress on diaCEST MRI for tumor imaging
Qin Yu, Zian Yu, Lijiao Yang, Yue Yuan
2023, 53(6): 0601. doi: 10.52396/JUSTC-2023-0027
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Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is an advanced imaging method that probes the chemical exchange between bulk water protons and exchangeable solute protons. This chemical exchange decreases the MR signal of water and reveals the distribution and concentration of certain endogenous biomolecules or extrogenous contrast agents in organisms with high sensitivity and spatial resolution. The CEST signal depends not only on the concentration of the CEST contrast agent and external magnetic field but also on the surrounding environments of the contrast agent, such as pH and temperature, thus enabling CEST MRI to monitor pH, temperature, metabolic level, and enzyme activity in vivo. In this review, we discuss the principle of CEST MRI and mainly summarize the recent progress of diamagnetic CEST (diaCEST) contrast agents on tumor imaging, diagnosis, and therapy effect evaluation.
Polymerized small molecular dyes providing nanoparticles with stable photosensitivity for eradicating cancer cells
Xu Chen, Feng Gao, Lihua Yang
2023, 53(6): 0607. doi: 10.52396/JUSTC-2023-0056
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To make small molecular photosensitizer-based nanoparticles photostable, we polymerized such photosensitizers via emulsion polymerization, and the resulting nanoparticles exhibited sustained absorption of the excitation wavelength in the near-infrared region, generated stable photothermal and photodynamic effects upon repeated irradiation with an near-infrared laser, and efficiently eradicated cancerous cells even after prior irradiation exposure.
Perspective
The mystery of Li2O2 formation pathways in aprotic Li–O2 batteries
Zhuojun Zhang, Xu Xiao, Peng Tan
2023, 53(6): 0602. doi: 10.52396/JUSTC-2022-0155
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The solid-state discharge product Li2O2 is closely related to the performance of Li–O2 batteries, which exacerbates the concentration polarization and charge transfer resistance, leading to sudden death and poor cyclability. Although previous theories of the Li2O2 formation pathway help to guide battery design, it is still difficult to explain the full observed Li2O2 behaviors, especially for those with unconventional morphologies. Thus, the pathways of Li2O2 formation remain mysterious. Herein, the evolution of the understanding of Li2O2 formation over the past decades is traced, including the variable Li2O2 morphologies, the corresponding reaction pathways, and the reaction interfaces. This perspective proposes that some Li2O2 particles are strongly dependent on the electrode surface as a result of the dynamic coupling of solution and surface pathways and emphasizes a possible mechanism based on previous experimental results and theories. Further methods are expected to be developed to reveal complex Li2O2 formation pathways and spearhead advanced Li–O2 batteries.
Chemistry
Mercaptopropane-assisted synthesis of graphitic carbon-supported Pt nanoparticles for enhancing fuel cell start-stop performance
Qian-Qian Yang, Tian-Wei Song, Shuai Li, Le Zhang, Xiu-Yuan Ma, Lei Tong, Hai-Wei Liang
2023, 53(6): 0603. doi: 10.52396/JUSTC-2023-0051
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Although graphitic carbons, as a support for the cathode catalyst in proton exchange membrane fuel cells, have significant advantages in enhancing the corrosion resistance of the catalyst, the preparation of small-sized Pt particles on the graphitic carbon support often faces challenges due to its low porosity and lack of defect structures. Here, we report a mercaptopropane-assisted impregnation method to achieve size control of Pt nanoparticles on graphitic carbon. We show that mercaptopropane can coordinate with Pt during the impregnation process and transform into sulfur-doped carbon coatings through the subsequent thermal reduction process, which ensures the formation of small-sized Pt nanoparticles on graphitic carbon. Due to effective size control, the prepared cathode catalyst exhibited enhanced fuel cell performance compared to the catalyst prepared by the traditional impregnation method. We performed the accelerated stress test on the synthesized catalyst using the durability protocol recommended by the U.S. Department of Energy (DOE). After 5000 voltage cycles in the range of 1.0–1.5 V, the catalyst showed a negligible voltage loss of only 10 mV at a current density of 1.5 A·cm−2, meeting the DOE support durability target (30 mV).
Amorphous TiO2 ultrathin nanosheet for stable high-rate lithium storage
Zhongda Chen, Wenqi Zhan, Zhihao Liu, Hang Wang, Liang Wu, Zhixin Sun, Min Zhou
2023, 53(6): 0605. doi: 10.52396/JUSTC-2023-0057
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The use of intercalation-type metal oxides as anode materials in rechargeable lithium-ion batteries is appealing due to their reduced risk of Li plating at low voltages. However, their implementation for fast-charging applications is limited by their lower energy and power density, as well as cycling instability. Herein, we present an amorphous TiO2 nanosheet that exhibits exceptional cycling stability with a high capacity of 231 mA · h · g−1 after 200 cycles at 500 mA · g−1 and 156.7 mA · h · g−1 after 1000 cycles at a high current density of 6 A · g−1. We attribute the enhanced rate performance to the amorphous nature with high isotropy, which facilitates low energy migration paths and ion availability and can accommodate large changes in volume. This work suggests that amorphization represents a promising strategy for developing unconventional metal oxide electrode materials with high-rate performance.
Mechanism of nickel-catalyzed hydroalkylation of branched 1,3-dienes
Mingqiang Liu, Deguang Liu, Zheyuan Xu, Haizhu Yu, Yao Fu
2023, 53(6): 0606. doi: 10.52396/JUSTC-2023-0031
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Abstract:
With the development of algorithms and theoretical chemistry, quantum chemical calculations have been used to explain and predict various chemical experiments. The hydroalkylation of conjugated olefins catalyzed by nickel is an important type of organic chemical reaction, and its mechanism has always been the focus of organic chemists. In this paper, a hydroalkylation reaction developed by the Mazet research group was studied in detail by means of density functional theory (DFT), and a possible mechanism model of the reaction was obtained. In this context, the attractive regioselectivity of the reaction was explored and rationally explained.
Chemistry; Engineering & Materials
Magnetic modification of lanthanide-based upconversion nanocrystals for fingerprint information recognition
Yafei Bi, Fu Zhang, Yu Bai, Yao Wang, Nan Zheng, Sheng Wang, Ning Zhang, Ran Long, Xinglong Gong, Yujie Xiong
2023, 53(6): 0604. doi: 10.52396/JUSTC-2022-0147
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Abstract:
The development of new magnetic fluorescent materials is of great significance for identification and criminal investigation. Since the photosensitive elements used in conventional cameras have exhibited the highest quantum efficiency in the range of 500–700 nm, lanthanide-based upconversion nanoparticles (UCNPs) with main emission peaks at 507–533 nm, 533–568 nm and 637–683 nm are suitable for constructing magnetic fluorescent materials. In this work, we demonstrate a type of magnetic upconversion nanoparticle (MUCNP) of NaGdF4:Yb,Er-Fe3O4 by a ligand-linked method. After optimizing the reaction parameters, the composite particles possess remarkable magnetic properties and upconversion fluorescence intensity and achieve high contrast for latent fingerprint recognition on various substrates. The combination of upconversion luminescence and magnetism contributes to good fingerprint recognition sensitivity and universality.

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