Current Articles

2020, Volume 18,  Issue 2

Display Method:
2020, 18(2): 0-0.
2020, 18(2): 1-1.
Special Section on Energy, Materials, and Nanotechnology
Rational Design of Colloidal Core/Shell Quantum Dots for Optoelectronic Applications
Xiang-Long Huang, Xin Tong, Zhiming M. Wang
2020, 18(2): 105-118. doi: 10.1016/j.jnlest.2020.100018
Colloidal core/shell quantum dots (QDs) are promising for solar technologies because of their excellent optoelectronic properties including tunable light absorption/emission spectra, high photoluminescence quantum yield (PLQY), suppressed Auger recombination, efficient charge separation/transfer, and outstanding photo-/thermal-/chemical stability. In this review, engineered core/shell QDs with various types of band structures and corresponding device performance in luminescent solar concentrators (LSCs), light-emitting diodes (LEDs), solar-driven photoelectrochemical (PEC) devices, and QDs-sensitized solar cells (QDSCs) are summarized. In particular, the applications of interfacial layer engineering and eco-friendly, heavy metal-free core/shell QDs in optoelectronic devices are highlighted. Finally, strategies towards the developments and practical perspectives of core/shell QDs are briefly mentioned to offer guidelines for achieving prospective high-efficiency and long-term stable QD devices.
Recent Advances of Bismuth Oxychloride Photocatalytic Material: Property, Preparation, and Performance Enhancement
Wen-Wen Liu, Ren-Fu Peng
2020, 18(2): 119-137. doi: 10.1016/j.jnlest.2020.100020
Due to its unique layered structure, bismuth oxychloride (BiOCl) has potential applications as a photocatalytic material in clean energy utilization and environmental purification. In recent years, researchers have carried out a lot of studies and made important progress for the preparation and performance enhancement of BiOCl. In this review, the charge separation property of BiOCl was analyzed based on the crystal structure and electronic structure. Subsequently, the common preparation method of BiOCl was expounded, and the growth mechanism of BiOCl was introduced. Furthermore, the strategies for modulating the photocatalytic performance of BiOCl via doping, vacancy creation, internal electric field tuning, co-catalysts modification, composites construction, and using sensitizers were summarized. Finally, in view of the current research status of the BiOCl photocatalytic material, some problems still need to be addressed including exploring the method of controlled synthesis of BiOCl exposed other high energy surfaces, developing advanced characterization methods to clarify the detailed transfer path of the photogenerated charge, and expanding the photocatalytic application range of BiOCl.
A Green Strategy to Synthesize Ag/Ag3PO4/Chitosan Composite Photocatalysts and Their Photocatalytic Degradation Performance under Visible Light Irradiation
Peng-Cheng Wu, Hui-Li Peng, Yu-Han Wu, Lei Li, Xiao-Rui Hao, Bang-Hua Peng, Gui-Hua Meng, Jian-Ning Wu, Zhi-Yong Liu
2020, 18(2): 138-150. doi: 10.1016/j.jnlest.2020.100019
In this work, the plasmonic Ag/Ag3PO4/chitosan (Ag/Ag3PO4/CS) composite photocatalyst was prepared by a low-temperature strategy. Environmentally friendly CS plays triple vital roles in this composite. First, it was devoted to in situ reducing metallic silver from silver ions of Ag3PO4. Also, as the carrier of Ag/Ag3PO4 nanoparticles, CS can effectively prevent aggregation. Furthermore, benefitting from the settlement of hydrophilic CS, the prepared composite could be easily separated and recovered from the solution system. X-ray diffraction (XRD), the scanning electron microscope, energy-dispersive X-ray spectroscopy (EDS), ultraviolet-visible (UV-vis) diffused reflectance spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to characterize the properties of materials. The results of photo-decomposition testing showed that the Ag/Ag3PO4/CS composite possessed good activity for the decomposition of Rhodamine B (RhB) under visible light.
Synthesis of Octapod Cu-Au Bimetallic Nanocrystal with Concave Structure through Galvanic Replacement Reaction
Zhen-Ni Wang, Qiang Li, Zhen-Huan Zhao, Xiao-Mei Tong
2020, 18(2): 151-158. doi: 10.1016/j.jnlest.2020.100046
We synthesized octapod Cu-Au bimetallic alloy with a concave structure by employing a replacement reaction between AuPPh3Cl and Cu nanocubes. Using the Cu nanocube as sacrificial templates, we have successfully generated high-active sites on alloy nanocrystals by carefully tuning the replacement reaction and growth. The key is to afford the proper concentration of AuPPh3Cl-TOP to the reaction solution. When the Au precursor with high concentration is injected into the galvanic replacement reaction, the growth dominated the process and hollowed octapod Cu-Au alloy was obtained. In contrast, when the concentration of the Au precursor is low, the replacement reaction can only take place at the nanocrystals, leading to generate Cu-Au nanocages. This work provides an effective strategy for the preparation of hollow bimetallic nanocrystals with high-active sites.
Molecular Dynamics Analysis of the Effect of Laser and Defects on the Micro-Structure of Fused Silica
Li Li, Ming-Wen Zhang, Zhe-Zhen Zhao
2020, 18(2): 159-168. doi: 10.1016/j.jnlest.2020.100045
In this work, the classic molecular dynamics simulations are employed to investigate the atomic structural modification of fused silica with defects as laser irradiation. The dynamics evolution of the atomic structure of fused silica is modeled during energy deposition. The structure parameters such as pair distribution functions (PDFs), bond angle distributions (BADs), and the coordination number are given. The calculated results reveal that fused silica undergoes significant changes in terms of Si-O, Si-Si, and O-O bond lengths, Si-O-Si and O-Si-O bond angles, and the Si and O coordination numbers during laser irradiation. The effects of different surface defects on the micro-structure of fused silica are discussed too. The simulation results of molecular dynamics may help to understand the role of defects in the radiation effect of fused silica.
Random Group Recommendation Model Based on Fuzzy Clustering
Zhe Ding, Zhen Qin, Qi-Xu Wang, Zhi-Guang Qin
2020, 18(2): 169-178. doi: 10.1016/j.jnlest.2020.100054
The group recommendation system is a viral requirement for the Internet service provider to provide recommendation services for all the users in a group. Due to the shared or different interests among users in the group, it is difficult for traditional personal recommendation algorithms to predict items that can meet the requirements of all the users in the group. In this paper, a random group recommendation model is proposed to recommend the top K most appealing items for all the users in a random group. By analyzing item ratings of all the users in the group, the recommendation model can abstract the group as a virtual user. Then a personal recommendation algorithm is applied to suggest the top K most appealing items for the virtual user. And the preference score and fuzzy clustering algorithm based on multiclass are applied to optimize the recommendation result of the group recommendation model. Finally, the MovieLens-100K dataset is applied to verify the efficiency of the recommendation model. The experimental results show that the items recommended by the proposed group recommendation model are more popular for all the users in the group than the items recommended by traditional group recommendation algorithms.
Robust Video Watermarking Using a Hybrid DCT-DWT Approach
Jie Sang, Qi Liu, Chun-Lin Song
2020, 18(2): 179-189. doi: 10.1016/j.jnlest.2020.100052
In order to solve the limitations of the digital video watermarking algorithm, this paper proposes a new robust video watermarking algorithm using combining discrete cosine transform (DCT) and discrete wavelet transform (DWT) techniques. First of all, the video frames are randomly selected and then the DCT algorithm is applied to the selected video frames. After that, the first column of the selected video frames is scrambled using the Arnold algorithm. Furthermore, every column with 4 direct current (DC) coefficients is reshaped and transformed into four different sub-bands using the DWT technique. Next, the watermark is embedded into the approximation (LL) sub-band. The proposed algorithm is easy to carry out because it provides random frames with no special requirements for video frames. The experiment results indicate that this algorithm can resist against different kinds of watermarking attacks, such as the Gaussian filter attack and sharpen attack. In addition, it also illustrates that the proposed algorithm has a better result than some other watermarking algorithms.
Consensus Based Least Squares Estimation for Single-Integrator Multi-Agent Systems with a Time-Varying Reference State
Ali Alouache, Qing-He Wu
2020, 18(2): 190-200. doi: 10.1016/j.jnlest.2020.100053
This paper discusses consensus tracking of single-integrator multi-agent systems with a time varying reference state based on the least squares estimation theory to deal with the case of communications disturbance. Since none of the followers can communicate with the leader within the accepted time due to communications disturbance, least squares estimation is applied for online estimation of the time varying reference state and reducing the tracking errors occurred due to communications disturbance. A theoretical proof is provided under some assumptions while the necessary and sufficient conditions are demonstrated for which consensus is reached on the time-varying reference state in case of communications disturbance. Finally, a Matlab example is given to validate the effectiveness of the proposed approach.