Synthesis and Characterization of Hollow Silver Spheres at Room Temperature

Huiyu Chen,Yaqing Liu,Guizhe Zhao 대한금속·재료학회 2011 ELECTRONIC MATERIALS LETTERS Vol.7 No.2

Hollow silver spheres were synthesized at room temperature using sodium borohydride (NaBH4) as the reducing reagent and poly (vinyl pyrrolidone) (PVP) as the surfactant. The size of the synthesized hollow spheres ranged from 120 to 250 nm, and the surface was composed of many smaller silver nanoparticles. The asobtained product was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-vis absorption spectra. The amount of PVP had a significant effect on the morphology of the resultant silver samples. With an increasing concentration of PVP, the silver products possessed rod-like and shuttle-like shapes. The UV-vis spectrum demonstrated that the broad absorption peak centered at 417 nm resulted from the surface plasmon resonance (SPR) excitation of silver.

Formation of Flower-Like Magnesium Hydroxide Microstructure via a Solvothermal Process

Huiyu Chen,Chunju Xu,Yaqing Liu,Guizhe Zhao 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.5

Flower-like magnesium hydroxide (Mg(OH)2) microstructure composed of many sheet-like nanopetals was prepared on a large scale via a solvothermal reaction at 200°C for 24 h. Water and ethanol mixed solution was employed as solvent and no additional surfactant was involved during the synthetic process. The Mg(OH)2microflowers were characterized by XRD, SEM, HRTEM, and UV-vis techniques. The average size of single flower is about 2 μm and the thickness of the petals ranges from 20 to 30 nm. The temperature and volume ratio of water to ethanol were found to be key roles for controlling the morphology of Mg(OH)2 products. The assembled petals of the Mg(OH)2 microflowers became thicker and smoother with the amount of water decreased in the mixed solvent. The present method is low cost, simple handle and environmentally benign,thus, it can be relatively easy to be scaled up for industrial production.

Green Synthesis and Characterization of Se Nanoparticles and Nanorods

Huiyu Chen,Ji-Beom Yoo,Yaqing Liu,Guizhe Zhao 대한금속·재료학회 2011 ELECTRONIC MATERIALS LETTERS Vol.7 No.4

Selenium nanoparticles and nanorods were successfully prepared in a mixed solvent of ethylene glycol and water at a relatively low temperature of 85°C. No other surfactant or template was employed, and glucose was used as a green and mild reducing reagent in the current synthesis. The volume ratio of ethylene glycol to water played an important role for controlling the shapes of selenium products. The obtained selenium samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectra, and UV-vis absorption spectra. The evolution process from amorphous selenium to a trigonal phase complied with a “solid-solution-solid” formation mechanism. HRTEM and SAED results indicate that the trigonal selenium nanorods grow along the [001] direction. This method might provide an environmentally-friendly and low cost route for the synthesis of other related nanomaterials with controlled morphologies.

Three-dimensional CuO nanobundles consisted of nanorods: hydrothermal synthesis, characterization, and formation mechanism.

Chen, Huiyu,Shin, Dong-Wook,Lee, Jong-Hak,Park, Sung-Min,Kwon, Kee-Won,Yoo, Ji-Beom American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.8

<P>Novel monoclinic CuO nanobundles, 0.8-1 microm in size, were synthesized at 130 degrees C in the presence of sodium dodecyl benzenesulfonate (SDBS) by a simple hydrothermal method. Each nanobundle was comprised of many nanorods with one ends growing together to form a center and another ends radiating laterally from this center. The length and the diameter of these assembled nanorods are in the range of 200-300 nm and about 20-30 nm, respectively. HRTEM and SAED results indicated that the CuO nanorods grow along the [010] direction. An investigation of the hydrothermal process revealed that the reaction time, temperature and surfactant play important roles in the formation of the resultant CuO nanostructures. Isolated CuO nanorods were obtained when the temperature was increased to 190 degrees C, and CuO microflowers composed of many nanosheets were produced at 130 degrees C when cetyltrimethylammonium bromide (CTAB) was employed instead of SDBS. The possible mechanism for the formation of these CuO nanostructures was discussed simply on the basis of the experimental results.</P>

Solvothermal Synthesis and Characterization of Chalcopyrite CuInSe ₂ Nanoparticles

Chen, Huiyu,Yu, Seong-Man,Shin, Dong-Wook,Yoo, Ji-Beom Springer 2010 NANOSCALE RESEARCH LETTERS Vol.5 No.1

<P>The ternary I-III-VI<SUB>2</SUB> semiconductor of CuInSe<SUB>2</SUB> nanoparticles with controllable size was synthesized via a simple solvothermal method by the reaction of elemental selenium powder and CuCl as well as InCl<SUB>3</SUB> directly in the presence of anhydrous ethylenediamine as solvent. X-ray diffraction patterns and scanning electron microscopy characterization confirmed that CuInSe<SUB>2</SUB> nanoparticles with high purity were obtained at different temperatures by varying solvothermal time, and the optimal temperature for preparing CuInSe<SUB>2</SUB> nanoparticles was found to be between 180 and 220 °C. Indium selenide was detected as the intermediate state at the initial stage during the formation of pure ternary compound, and the formation of copper-related binary phase was completely deterred in that the more stable complex [Cu(C<SUB>2</SUB>H<SUB>8</SUB>N<SUB>2</SUB>)<SUB>2</SUB>]<SUP>+</SUP> was produced by the strong <I>N</I>-chelation of ethylenediamine with Cu<SUP>+</SUP>. These CuInSe<SUB>2</SUB> nanoparticles possess a band gap of 1.05 eV calculated from UV–vis spectrum, and maybe can be applicable to the solar cell devices.</P>

Metallic copper nanostructures synthesized by a facile hydrothermal method.

Chen, Huiyu,Lee, Jong-Hak,Kim, Yu-Hee,Shin, Dong-Wook,Park, Sang-Cheol,Meng, Xianhui,Yoo, Ji-Beom American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.1

<P>A facile hydrothermal route has been developed for the synthesis of nearly spherical copper nanoparticles, copper nanocubes and ribbon-like network nanostructures. The as-prepared copper nanostructures were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and UV-vis spectrum analysis. These copper products were fabricated in the presence of surfactant sodium dodecyl benzenesulfonate (SDBS) acting not only as stabilizer but also as size and shape controller via hydrothermal reduction process. HRTEM revealed that the surface of the copper nanostructures was packed with a thin layer of impurities such as oxide combined surfactant or amorphous surfactant. The influence of surfactant concentration and temperature on the resultant copper nanostructures was investigated in details. UV-vis spectra indicated that strong red shift existed for the copper ribbon-like network nanostructures due to the novel morphology as well as the presence of impurities on the surface.</P>

Detecting LDoS Attacks based on Abnormal Network Traffic

( Kai Chen ),( Huiyu Liu ),( Xiaosu Chen ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.7

By sending periodically short bursts of traffic to reduce legit transmission control protocol (TCP) traffic, the low-rate denial of service (LDoS) attacks are hard to be detected and may endanger covertly a network for a long period. Traditionally, LDoS detecting methods mainly concentrate on the attack stream with feature matching, and only a limited number of attack patterns can be detected off-line with high cost. Recent researches divert focus from the attack stream to the traffic anomalies induced by LDoS attacks, which can detect more kinds of attacks with higher efficiency. However, the limited number of abnormal characteristics and the inadequacy of judgment rules may cause wrong decision in some particular situations. In this paper, we address the problem of detecting LDoS attacks and present a scheme based on the fluctuant features of legit TCP and acknowledgment (ACK) traffic. In the scheme, we define judgment criteria which used to identify LDoS attacks in real time at an optimal detection cost. We evaluate the performance of our strategy in real-world network topologies. Simulations results clearly demonstrate the superiority of the method proposed in detecting LDoS attacks.

Facile and Effective Preparation of the Lotus Leaf-based Adsorbent by Exposing Cellulose Nanocrystal for Waste Water Treatment and Air Purification

Huiyu Yang,Ke Liu,Xin Liu,Yaling Wang,Keshuai Liu,Fengxiang Chen,Bo Deng,Weilin Xu 한국섬유공학회 2020 Fibers and polymers Vol.21 No.2

One substantial plant waste, lotus leave was fabricated into lotus leave powder with different diameters by ball milling. The surface morphology, chemical composition, particle size, porosity parameters, crystal structure, and wettabilityof lotus leaf powders (LLPs) were analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), laser particle size analysis, N2 adsorption/desorption, X-ray diffraction (XRD) analysis, and water contact angle (WCA) analysis, respectively. The results showed that the micro- and nanoscale waxy papilla structures on the surface of the lotus leaf were gradually destroyed by mechanical forces along with extended balling time. Accompanied re-exposing of -OH affluent cellulose nanocrystals (CNCs) was proved by HR-TEM, XRD, and FTIR. FTIR also revealed a hydroxyl to carboxyl transition on the surface of CNCs. Both the re-exposure of CNCs and thereof chemical structure transition after ball millingmade the LLP a good candidate for pollutant adsorbent for dye, formaldehyde, and heavy metal ions.

The Work Experience of Newly Recruited Male Nurses during COVID-19: A Qualitative Study

Huiyue Zhou,Xin Wang,Ruofei Du,Xiang Cheng,Kexin Zheng,Shiqi Dong,Justin Henri,Changying Chen,Tao Wang 한국간호과학회 2021 Asian Nursing Research Vol.15 No.3

Purpose: This study was to investigate the work experience of newly recruited male nurses during the COVID-19 pandemic. Methods: With a phenomenological approach, this qualitative study was adopted semistructured interviews by phone or video calls. A total of 9 male nurses newly recruited for the COVID-19 wards in Chinese hospitals were interviewed for this study. And Colaizzi's method was applied for evaluation in the data analysis. Results: Based on our findings, three themes were extracted. First, the newly recruited male nurses showed negative emotions at the beginning of COVID-19 epidemic, which was caused by changes in working conditions and content, but also prompted the nurses to change the way of coping with the crisis. Second, they gradually mastered the working skills and psychological training to cope with COVID- 19 and developed a positive attitude toward life and a high sense of professional responsibility. Finally, we learned about their needs to respond to public health emergencies such as the COVID-19 pandemic. Conclusion: COVID-19 is a disaster for all of humanity. The newly recruited male nurses are an important force in emergency rescue. Although they suffered from short-term negative emotions, they quickly adapted to the crisis. In order to better prepare for future emergencies, the disaster response capacity of newly recruited male nurses needs to be further improved. In addition, newly recruited male nurses have a strong demand for timely and personalized career development guidance.

Knowledge Mapping of Robotic Applications in Tourism and Hospitality

Huiyue, Ye,Sirong, Chen,Rob, Law,Lawrence Hoc Nang, Fong Smart Tourism Research Center 2022 Journal of smart tourism Vol.2 No.4

The use of robots in tourism and hospitality contexts have drawn increasing scholarly and practical regard. Although the number of recent robotics related studies continue to grow, a general knowledge map, which is important to point out promising directions for future studies, remains to be made. To understand the application of robotics in tourism and hospitality, this study conducts descriptive and bibliometric analysis to present a holistic knowledge map of this specific field where research trend, key contributors, highly cited references, and popular themes were identified. Collaboration networks among institutes and regions were additionally illustrated. Collaboration across fields, industries, and perspectives were encouraged following the findings and both theoretical and practical implications are accordingly provided.