Room Temperature Electroluminescence from n-ZnO:Ga/i-ZnO/p-GaN:Mg Heterojunction Device Grown by PLD

Lichun Zhang,Qingshan Li,Feifei Wang,Chong Qu,Fengzhou Zhao 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.3

The n-ZnO:Ga/p-GaN:Mg and n-ZnO:Ga/i-ZnO/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated by the pulsed laser deposition (PLD) technique. The blue electroluminescence (EL) of the n-ZnO:Ga/ p-GaN:Mg heterojunction LEDs is emitted mainly from the p-GaN layer instead of the n-ZnO:Ga layer, for the reason that the electron injection from n-ZnO:Ga prevailed over the hole injection from p-GaN:Mg due to the higher carrier concentration and carrier mobility in n-ZnO:Ga. On the other hand, the n-ZnO:Ga/i-ZnO/p- GaN:Mg heterojunction LEDs exhibited dominant ultraviolet-blue emission. The reason for this difference is attributed to the inserted undoped i-ZnO layer between n-ZnO:Ga and p-GaN:Mg, in which the holes from p- GaN:Mg and the electrons from n-ZnO:Ga are recombined.

Synthesis of octahedral gold tip-blobbed nanoparticles and their dielectric sensing properties

Zhang, Liqiu,Jang, Hee-Jeong,Yoo, Sungjae,Cho, Sanghyun,Won, Ji Hye,Liu, Lichun,Park, Sungho IOP 2018 Nanotechnology Vol.29 No.37

<P>Site-selective synthesis of nanostructures is an important topic in the nanoscience community. Normally, the difference between seeds and deposition atoms in terms of crystallinity triggers the deposition atoms to grow initially at the specific site of nucleation. It is more challenging to control the deposition site of atoms that have the same composition as the seeds because the atoms tend to grow epitaxially, covering the whole surface of the seed nanoparticles. Gold (Au) nano-octahedrons used as seeds in this study possess obvious hierarchical surface energies depending on whether they are at vertices, edges, or terraces. Although vertices of Au nano-octahedrons have the highest surface energy, it remains a challenge to selectively deposit Au atoms at the vertices but not at the edges and faces; this selectivity is required to meet the ever-increasing demands of engineered nanomaterial properties. This work demonstrates an easy and robust method to precisely deposit Au nanoparticles at the vertices of Au nano-octahedrons via wet-chemical seed-mediated growth. The successful synthesis of octahedral Au tip-blobbed nanoparticles (Oh Au TBPs) benefited from the cooperative use of thin silver (Ag) layers at the surface of Au nano-octahedron seeds and iodide ions in the Au growth solution. As-synthesized Au nanostructures (i.e., Au TBPs) gave rise to hybrid optical properties, as evidenced from the UV–vis-NIR extinction spectra, in which a new extinction peak appeared after Au nanoparticles were formed at the vertices of Au nano-octahedrons. A sensitivity evaluation toward dielectric media of a mixture of dimethyl sulfoxide and water suggested that Au TBPs were more optically sensitive compared to the original Au nano-octahedrons. The method demonstrated in this work is promising in the synthesis of advanced Au nanostructures with hybrid optical properties for versatile applications, by engineering the surface energy of vertex-bearing Au nanostructures to trigger site-selective overgrowth of congener Au atoms.</P>

Helical metallic micro- and nanostructures: fabrication and application.

Liu, Lichun,Zhang, Liqiu,Kim, Sang Min,Park, Sungho RSC Pub 2014 Nanoscale Vol.6 No.16

<P>Metal elements occupy more than 70% of the positions in the periodic table, and their use has accelerated human civilization due to their invaluable chemical and physical characteristics. With the rapid development of metals, various structures of microscopic metal particles have been fabricated and investigated as functional materials in scientific research and practical applications. The phrase 'structure determines properties' has been widely acknowledged as a golden rule in chemistry and materials science, especially when the size of small particles is in the micro- or nanoscale dimension. Helical metallic micro- and nanostructures with complex shapes have recently emerged and may be used for various useful applications such as photonics, sensors, actuators, micro-/nanorobotics, and micro-/nanoelectronics, based on their unique mechanical, electrical, and electromagnetic properties. This review paper specifically focuses on the fabrication and application of helical metallic structures with a size ranging from the micro- to nanoscale. The unusual spatial distribution of active atoms in helical metallic micro- and nanostructures and their helical morphology could offer new opportunities for applications beyond those of other conventional metallic and nonmetallic micro- and nanostructures.</P>

Computerized bone age estimation system based on China-05 standard

Yin, Chuangao,Zhang, Miao,Wang, Chang,Lin, Huihui,Li, Gengwu,Zhu, Lichun,Fei, Weimin,Wang, Xiaoyu Techno-Press 2022 Advances in nano research Vol.12 No.2

The purpose of this study is to develop an automatic software system for bone age evaluation and to evaluate its accuracy in testing and feasibility in clinical practice. 20394 left-hand radiographs of healthy children (2-18 years old) were collected from China Skeletal Development Survey data of 1998 and China Skeletal Development Survey data of 2005. Three experienced radiologists and China-05 standard maker jointly evaluate the stages of bone development and the reference bone age was determined by consensus. 1020 from 20394 radiographs were picked randomly as test set and the remaining 19374 radiographs as training set and validation set. Accuracy of the automatic software system for bone age assessment is evaluated in test set and two clinical test sets. Compared with the reference standard, the automatic software system based on RUS-CHN for bone age assessment has a 0.04 years old mean difference, ±0.40 years old in 95% confidence interval by single reading, a 85.6% percentage agreement of ratings, a 93.7% bone age accuracy rate, 0.17 years old of MAD, 0.29 years old of RMS; Compared with the reference standard, the automatic software system based on TW3-C RUS has a 0.04 years old mean difference, a ±0.38 years old in 95% confidence interval by single reading, a 90.9% percentage agreement of ratings, a 93.2% bone age accuracy rate, a 0.16 years of MAD, and a 0.28 years of RMS. Automatic software system, AI-China-05 showed reliably accuracy in bone age estimation and steady determination in different clinical test sets.

Optoelectronic Characteristics of UV Photodetector Based on GaN/ZnO Nanorods p-i-n Heterostructures

Qingshan Li,Lichun Zhang,Fengzhou Zhao,Caifeng Wang,Feifei Wang,Ruizhi Huang 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4

We demonstrate an efficient ultraviolet (UV) photodetector operating at room temperature based on n-ZnO nanorods/i-ZnO/p-GaN heterojunctions. We employ x-ray diffraction and field-emission scanning electron microscopy to confirm the high quality of the ZnO nanorods using an undoped ZnO film as the interlayer. Then, we investigate the photoelectric properties of the fabricated photodetector with UV light illumination under a different reverse bias. Based on the current-voltage curve, the photocurrent to dark current ratio is approximately 73.3 at −4 V. At zerobias voltage, the peak responsivity was 138.9 mA/W at 362 nm under front-illumination conditions. Time-varying measurements indicate the reproducibility and stability of the heterojunction photodetector.

Synthesis of edge-rich vertical multilayer graphene nanotube arrays towards high-performance supercapacitors

Cho, Sanghyun,Jung, Insub,Zhang, Liqiu,Yoo, Sungjae,Won, Ji Hye,Jung, Sang Baek,Liu, Lichun,Park, Sungho IOP 2019 Nanotechnology Vol.30 No.42

<P>In this work, we demonstrate the synthesis of edge-rich vertical multilayer graphene nanotube arrays and edge density-dependent capacitance in a supercapacitor application. We employ Ni-Au multi-block vertical nanotubes fabricated by anodic aluminum oxide template-assisted electrodeposition as a designer substrate for multilayer graphene growth. This edge generation of graphene relies on the distinct carbon solubility of Au and Ni under chemical vapor deposition. Therefore the graphene edge density is tailorable by controlling the total number of bimetallic interfaces of alternating electrodeposited Ni and Au blocks. In supercapacitor applications, we found that the capacitance heavily correlates to the graphene edge densities. Multilayer graphene nanotubes with 18 bimetallic interfaces exhibit 8.4 times higher capacitance than those without interfaces. This experimental evaluation shows great promise to significantly enhance the supercapacitor capacitance by creating high-density edges on multilayer graphene.</P>

Appraisal of Guidelines for the Management of Blood Pressure in Patients with Diabetes Mellitus: The Consensuses, Controversies and Gaps

Menghui Liu,Shaozhao Zhang,Xiaohong Chen,Yue Guo,Xiangbin Zhong,Zhenyu Xiong,Yifen Lin,Huimin Zhou,Yiquan Huang,Zhengzhipeng Zhang,Lichun Wang,Xiaodong Zhuang,Xinxue Liao 대한당뇨병학회 2021 Diabetes and Metabolism Journal Vol.45 No.5

Background: Currently available guidelines contain conflicting recommendations on the management of blood pressure (BP) in patients with diabetes mellitus (DM). Therefore, it is necessary to appraise the guidelines and summarize the agreements and differences among recommendations.Methods: Four databases and the websites of guideline organizations were searched for guidelines regarding BP targets and thresholds for pharmacologic therapy in DM patients, and the included guidelines were appraised with the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument.Results: In 6,498 records identified, 20 guidelines met our inclusion criteria with 64.0% AGREE II scores (interquartile range, 48.5% to 72.0%). The scores of the European and American guidelines were superior to those of the Asian guidelines (both adjusted P<0.001). Most of the guidelines advocated systolic BP targets <130 mm Hg (12 guidelines, 60%) and diastolic BP targets <80 mm Hg (14 guidelines, 70%) in DM patients. Approximately half of the guidelines supported systolic BP thresholds >140 mm Hg (10 guidelines, 50%) and diastolic BP thresholds >90 mm Hg (nine guidelines, 45%). The tiny minority of the guidelines provided the relevant recommendations regarding the lower limit of official BP targets and the ambulatory BP monitoring (ABPM)/home BP monitoring (HBPM) targets and thresholds in DM patients.Conclusion: The lower official BP targets (<130/80 mm Hg) in patients with DM are advocated by most of the guidelines, but they contain conflicting recommendations on the official BP thresholds. Moreover, the gaps regarding the lower limit of official BP targets and the ABPM/HBPM targets and thresholds need to be considered by future study.

Fabrication of Hollow Polymer Microchannels Using the MIMIC Technique with Subsequent Heat Treatment

Weiren Li,Wenqiang Xing,Fengzhou Zhao,Lichun Zhang,Yupeng Huang,Jinxiu Li,Linwei Zhu,Zheng Xu,Dengying Zhang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.8

The hollow polymer microchannels with different shapes and dimensions have been fabricated by the MIMIC method and the heating process for the first time. The smallest cross-sectional dimensions of hollow polymer microchannels were about 2.6 μm in the vertical direction and 3.5 μm in the horizontal direction. The length of hollow polymer microchannels increased parabolically with the heating temperature in the range of 30–135 °C. And the influence of the PDMS mold crosssectional areas on the length of the microchannels was invetigated. Furthermore, the forming mechanism of hollow polymer microchannels was disscussed in detail. This technique provides a cheap, simple and controllable way for the preparation of microchannels.

3D PtAu nanoframe superstructure as a high-performance carbon-free electrocatalyst

Yoo, Sungjae,Cho, Sanghyun,Kim, Dajeong,Ih, Seongkeun,Lee, Sungwoo,Zhang, Liqiu,Li, Hao,Lee, Jin Yong,Liu, Lichun,Park, Sungho The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.6

<P>In this work, we demonstrate how to synthesize a three-dimensional (3D) ordered PtAu nanoframe superstructure and evaluated its performance as an electrocatalyst. Compared to carbon supported platinum (Pt) nanocrystal electrocatalysts (wherein the aggregation- and carbon corrosion-induced fast degradation is a well-known drawback), the 3D PtAu nanoframe superstructure is free from aggregation and carbon corrosion. The 3D superstructure was self-assembled<I>via</I>drop-casting and evaporation using truncated octahedral PtAu nanoframes (TOh PtAu NFs) as building blocks that were produced by controlled wet-chemical etching of a TOh Au core whose edges and vertexes were selectively deposited with Pt atoms. Density functional theory calculations revealed that the surface alloy state of PtAu gave rise to an enhanced catalytic activity compared to pure Pt. Experimental investigations showed that such 3D superstructure electrocatalysts exhibited excellent mass transfer efficiency, higher catalytic activity and stability towards the methanol oxidation reaction (MOR) compared to a commercial Pt/C catalyst. The demonstrated 3D nanoframe superstructure shows great potential for practical catalytic application due to its high structural stability, high catalytic activity, high surface area and ease of fabrication.</P>