Electrochemical Growth of Silver Nanobelts in Cylindrical Alumina Nanochannels

Liu, Lichun,Yoo, Sang-Hoon,Lee, Sang A.,Park, Sungho American Chemical Society 2011 Crystal Growth & Design Vol.11 No.9

<P>It is best-known in the nanoscience community that anodic aluminum oxide (AAO) membrane templates have been widely employed in the synthesis of one-dimensional nanomaterials, such as nanowires, nanorods, and nanotubes with cylindrical shapes. In this work, however, we demonstrate that AAO nanochannels can be used to grow silver nanobelts with rectangular shape. The growth method involved an electrochemical reduction of the Tollen’s reagent ([Ag(NH<SUB>3</SUB>)<SUB>2</SUB>]<SUP>+</SUP>) in aqueous solution at room temperature. We found that the concentration of the reagents (Ag<SUB>2</SUB>O and ammonia) and the magnitude of the reduction potential were critical to the growth of silver nanobelts. Significantly, we were able to tailor the dimensions of silver nanobelts. The lengths of silver nanobelts were controllable by the charge transported in the electrochemical reduction, the widths were confined by the diameter of nanochannels, and the thicknesses were dependent on the concentration of ammonia. In addition, crystallographic characterization indicates that silver nanobelts were single crystalline.</P><P>We demonstrate that AAO nanochannels can be used to grow silver nanobelts with rectangular shape. The growth method involved an electrochemical reduction of the Tollen’s reagent ([Ag(NH<SUB>3</SUB>)<SUB>2</SUB>]<SUP>+</SUP>) in aqueous solution at room temperature. The width, thickness, and length of the Ag nanobelt could be systematically controlled.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cgdefu/2011/cgdefu.2011.11.issue-9/cg2007809/production/images/medium/cg-2011-007809_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cg2007809'>ACS Electronic Supporting Info</A></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>

Effective Separation Method for Single-Channel Time-Frequency Overlapped Signals Based on Improved Empirical Wavelet Transform

( Zhipeng Liu ),( Lichun Li ),( Huiqi Li ),( Chang Liu ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.5

To improve the separation performance of time-frequency overlapped radar and communication signals from a single channel, this paper proposes an effective separation method based on an improved empirical wavelet transform (EWT) that introduces a fast boundary detection mechanism. The fast boundary detection mechanism can be regarded as a process of searching, difference optimization, and continuity detection of the important local minima in the Fourier spectrum that enables determination of the sub-band boundary and thus allows multiple signal components to be distinguished. An orthogonal empirical wavelet filter bank that was designed for signal adaptive reconstruction is then used to separate the input time-frequency overlapped signals. The experimental results show that if two source components are completely overlapped within the time domain and the spectrum overlap ratio is less than 60%, the average separation performance is improved by approximately 32.3% when compared with the classic EWT; the proposed method also improves the suitability for multiple frequency shift keying (MFSK) and reduces the algorithm complexity.

Fluorescent Microarrays of <i>in Situ</i> Crystallized Perovskite Nanocomposites Fabricated for Patterned Applications by Using Inkjet Printing

Liu, Yang,Li, Fushan,Qiu, Lichun,Yang, Kaiyu,Li, Qianqian,Zheng, Xin,Hu, Hailong,Guo, Tailiang,Wu, Chaoxing,Kim, Tae Whan American Chemical Society 2019 ACS NANO Vol.13 No.2

<P>Perovskite materials have exhibited promising potential for universal applications including backlighting, color conversion, and anticounterfeiting labels fabricated using solution processes. However, owing to the tendency of those materials to have uncontrollable morphologies and to form large crystals, they cannot be utilized in discontinuous microminiaturization, which is crucial for practical optoelectronic applications. In this research, combining the effects of adding polyvinylpyrrolidone (PVP), precisely controlling the inkjet printing technique, and using a postprocessing procedure, we were able to fabricate <I>in situ</I> crystallized perovskite-PVP nanocomposite microarrays with perfect morphologies. The viscosity of the perovskite precursor increased with the addition of PVP, eliminating the outward capillary flow that induces the coffee-ring effect. In addition, because of the presence of metallic bonds with the C═O groups in PVP and the spatial confinement of such a polymer, we were able to fabricate regulated CsPbBr<SUB>3</SUB> nanocrystals capped with PVP and with a uniform size distribution. The as-printed patterns showed excellent homogeneity on a macroscale and high reproducibility on a microscale; furthermore, those patterns were invisible in the ambient environment, compatible with flexible substrates, and cost-efficient to produce, indicating that this technique holds promising potential for applications such as anticounterfeiting labels.</P> [FIG OMISSION]</BR>

Mixing matrix estimation method for dual‐channel time‐frequency overlapped signals based on interval probability

Zhipeng Liu,Lichun Li,Ziru Zheng 한국전자통신연구원 2019 ETRI Journal Vol.41 No.5

For dual‐channel time‐frequency (TF) overlapped signals with low sparsity in underdetermined blind source separation (UBSS), this paper proposes an effective method based on interval probability to estimate and expand the types of mixing matrices. First, the detection of TF single‐source points (TF‐SSP) is used to improve the TF sparsity of each source. For more distinguishability, as the ratios of the coefficients from different columns of the mixing matrix are close, a local peak‐detection mechanism based on interval probability (LPIP) is proposed. LPIP utilizes uniform subintervals to optimize and classify the TF coefficient ratios of the detected TF‐SSP effectively in the case of a high level of TF overlap among sources and reduces the TF interference points and redundant signal features greatly to enhance the estimation accuracy. The simulation results show that under both noiseless and noisy cases, the proposed method performs better than the selected mainstream traditional methods, has good robustness, and has low algorithm complexity.

Template-Assisted Electrochemical Growth of Hydrous Ruthenium Oxide Nanotubes

조상현,Lichun Liu,유상훈,장호영,박성호 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.5

We demonstrate that ruthenium oxide (RuO2) nanotubes with controlled dimensions can be synthesized using facile electrochemical means and anodic aluminum oxide (AAO) templates. RuO2 nanotubes were formed using a cyclic voltammetric deposition technique and an aqueous plating solution composed of RuCl3. Linear sweep voltammetry (LSV) was used to determine the effective electrochemical oxidation potential of Ru3+ to RuO2. The length and wall thickness of RuO2 nanotubes can be adjusted by varying the range and cycles of the electrochemical cyclic voltammetric potentials. Thick-walled RuO2 nanotubes were obtained using a wide electrochemical potential range (−0.2~1 V). In contrast, an electrochemical deposition potential range from 0.8 to 1 V produced thin-walled and longer RuO2 nanotubes in an identical number of cycles. The dependence of wall thickness and length of RuO2 nanotubes on the range of cyclic voltammetric electrochemical potentials was attributed to the distinct ionic diffusion times. This significantly improves the ratio of surface area to mass of materials synthesized using AAO templates. Furthermore, this study is directive to the controlled synthesis of other metal oxide nanotubes using a similar strategy.

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.

Template-Assisted Electrochemical Growth of Hydrous Ruthenium Oxide Nanotubes

Cho, Sanghyun,Liu, Lichun,Yoo, Sang-Hoon,Jang, Ho-Young,Park, Sungho Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.5

We demonstrate that ruthenium oxide ($RuO_2$) nanotubes with controlled dimensions can be synthesized using facile electrochemical means and anodic aluminum oxide (AAO) templates. $RuO_2$ nanotubes were formed using a cyclic voltammetric deposition technique and an aqueous plating solution composed of $RuCl_3$. Linear sweep voltammetry (LSV) was used to determine the effective electrochemical oxidation potential of $Ru^{3+}$ to $RuO_2$. The length and wall thickness of $RuO_2$ nanotubes can be adjusted by varying the range and cycles of the electrochemical cyclic voltammetric potentials. Thick-walled $RuO_2$ nanotubes were obtained using a wide electrochemical potential range (-0.2~1 V). In contrast, an electrochemical deposition potential range from 0.8 to 1 V produced thin-walled and longer $RuO_2$ nanotubes in an identical number of cycles. The dependence of wall thickness and length of $RuO_2$ nanotubes on the range of cyclic voltammetric electrochemical potentials was attributed to the distinct ionic diffusion times. This significantly improves the ratio of surface area to mass of materials synthesized using AAO templates. Furthermore, this study is directive to the controlled synthesis of other metal oxide nanotubes using a similar strategy.

Surface Plasmon Coupling on Linked Au–Pt Nanorods

Jung, Sujin,Liu, Lichun,Shuford, Kevin L.,Park, Sungho American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.6

<P>This work demonstrates that surface plasmon coupling in linked Au–Pt NRs (NRs) can be controlled by adjusting the relative ratio of material segment lengths. The NRs were synthesized through an anodic aluminum oxide template assisted sequential electrochemical deposition route. Optical spectra of the NRs in solution were acquired in the UV–vis–NIR region to examine surface plasmon coupling. Analysis of the spectra indicated that effective surface plasmon coupling could occur in Au-dominated NRs but not in Pt-dominated ones. The optical properties of Au–Pt–Au three-segment NRs were also examined, and the results provided further clarification regarding the conditions that yield effective coupling of NR segments in these structures. Electrodynamics calculations on two- and three-segment NRs were performed and found to be in good agreement with experiment. These findings regarding surface plasmon coupling of linked, hybrid NRs extend the fundamental knowledge of surface plasmon coupling from single component to hybrid systems and are useful for a variety of applications that necessitate fine controllability of the plasmonic properties.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-6/jp3114804/production/images/medium/jp-2012-114804_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp3114804'>ACS Electronic Supporting Info</A></P>

Galvanically ReplacedHollow Au–Ag Nanospheres:Study of Their Surface Plasmon Resonance

Choi, Yoonjung,Hong, Soonchang,Liu, Lichun,Kim, Seong Kyu,Park, Sungho American ChemicalSociety 2012 Langmuir Vol.28 No.16

<P>We synthesized hollow Au-Ag nanospheres (NSs) by employing a galvanic replacement reaction between HAuCl4 and Ag NSs. Uniform Ag NSs with controllable sizes were synthesized as sacrificial templates by a seed-mediated strategy. The atomic ratio of Au to Ag in Au-Ag NSs was tunable by controlling the reagent concentration. UV-vis extinction spectra acquired from well-dispersed colloidal NS solutions were used to investigate the optical properties of the solutions. In addition to a common dipole mode exhibited on most transition metal nanoparticles, we observed a quadrupole plasmon resonance mode when the diameters of the Ag and Au-Ag NSs were larger than 100 nm. The quadrupole and dipole peaks both shifted to longer wavelengths with increased Au content in Au-Ag NSs. The experimental observation of optical properties of hollow Au-Ag NSs was compared with the theoretical simulation using DDA calculation, showing a good agreement.</P>