Catechin-capped gold nanoparticles: green synthesis, characterization, and catalytic activity toward 4-nitrophenol reduction

An eco-friendly approach is described for the green synthesis of gold nanoparticles using catechin as a reducing and capping agent. The reaction occurred at room temperature within 1 h without the use of any external energy and an excellent yield (99%) was obtained, as determined by inductively coupled plasma mass spectrometry. Various shapes of gold nanoparticles with an estimated diameter of 16.6 nm were green-synthesized. Notably, the capping of freshly synthesized gold nanoparticles by catechin was clearly visualized with the aid of microscopic techniques, including high-resolution transmission electron microscopy, atomic force microscopy, and field emission scanning electron microscopy. Strong peaks in the X-ray diffraction pattern of the as-prepared gold nanoparticles confirmed their crystalline nature. The catalytic activity of the as-prepared gold nanoparticles was observed in the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH(4). The results suggest that the newly prepared gold nanoparticles have potential uses in catalysis

Design sensitivity analysis and optimization of nonlinear transient dynamics Part I*sizing design.

SUMMARY For con"guration design of non-linear dynamic structures, such as crashworthiness design, a continuumbased con"guration design sensitivity analysis (DSA) and optimization methods are developed. The same transient dynamic analysis method used in Part I of this paper is employed here. The elastic}plastic material and "nite strain and rotation e!ect are considered. The "rst-order variations of the energy forms, load form and kinematic and structural responses with respect to con"guration design variables are derived. For the con"guration design, both the shape and orientation variations contribute to the "rst-order variation of the equations of motion. The angular design velocity "eld associated with Euler angles is used to represent the orientation variation to obtain accurate design sensitivity results. Like Part I of the paper, the updated Lagrangian formulation and direct di!erentiation method are used for DSA for the path-dependent problem. For the updated Lagrangian formulation, the design velocity "eld that de"nes the mapping between the initial and perturbed designs should also be updated at each con"guration. Numerical implementation of con"guration DSA and optimization is carried out for "xed time steps using DYNA3D and the modi"ed feasible direction (MFD) method. It is observed that the proposed DSA method yields better sensitivity results than the "nite di!erence method for the highly non-linear problem. Design optimization is carried out using the design sensitivity informatio

Numerical method for shape optimization using T-spline based isogeometric method

Numerical methods for shape design sensitivity analysis and optimization have been developed for several decades. However, the finite-element-based shape design sensitivity analysis and optimization have experienced some bottleneck problems such as design parameterization and design remodeling during optimization. In this paper, as a remedy for these problems, an isogeometric-based shape design sensitivity analysis and optimization methods are developed incorporating with T-spline basis. In the shape design sensitivity analysis and optimization procedure using a standard finite element approach, the design boundary should be parameterized for the smooth variation of the boundary using a separate geometric modeler, such as a CAD system. Otherwise, the optimal design usually tends to fall into an undesirable irregular shape. In an isogeometric approach, the NURBS basis function that is used in representing the geometric model in the CAD system is directly used in the response analysis, and the design boundary is expressed by the same NURBS function as used in the analysis. Moreover, the smoothness of the NURBS can allow the large perturbation of the design boundary without a severe mesh distortion. Thus, the isogeometric shape design sensitivity analysis is free from remeshing during the optimization process. In addition, the use of T-spline basis instead of NURBS can reduce the number of degrees of freedom, so that the optimal solution can be obtained more efficiently while yielding the same optimum design shape.Cho S, 2009, STRUCT MULTIDISCIP O, V38, P53, DOI 10.1007/s00158-008-0266-zBazilevs Y, 2008, COMPUT MECH, V43, P143, DOI 10.1007/s00466-008-0277-zUhm TK, 2008, STRUCT ENG MECH, V30, P225Yang HP, 2008, VISUAL COMPUT, V24, P435, DOI 10.1007/s00371-008-0222-3DORFEL MR, 2008, COMPUT METHODS APPL, V199, P264Gomez H, 2008, COMPUT METHOD APPL M, V197, P4333, DOI 10.1016/j.cma.2008.05.003Wall WA, 2008, COMPUT METHOD APPL M, V197, P2976, DOI 10.1016/j.cma.2008.01.025Yang HP, 2007, VISUAL COMPUT, V23, P1015, DOI 10.1007/s00371-007-0168-xHsu SY, 2007, INT J NUMER METH ENG, V72, P606, DOI 10.1002/nme.2027Silva CAC, 2007, STRUCT MULTIDISCIP O, V33, P147, DOI [10.1007/s00158-006-0046-6, 10.1007/s00158-006-0046-06]Bazilevs Y, 2007, COMPUT FLUIDS, V36, P12, DOI 10.1016/j.compfluid.2005.07.012CHO S, 2007, 9 US NAT C COMP MECHCottrell JA, 2007, COMPUT METHOD APPL M, V196, P4160, DOI 10.1016/j.cma.2007.04.007HA SH, 2007, 7 WORLD C STRUCT MULZhang YJ, 2007, COMPUT METHOD APPL M, V196, P2943, DOI 10.1016/j.cma.2007.02.009Bazilevs Y, 2006, COMPUT MECH, V38, P310, DOI 10.1007/s00466-006-0084-3Cottrell JA, 2006, COMPUT METHOD APPL M, V195, P5257, DOI 10.1016/j.cma.2005.09.027Cervera E, 2005, COMPUT STRUCT, V83, P1902, DOI 10.1016/j.compstruc.2005.02.016Roh HY, 2005, INT J NUMER METH ENG, V62, P1927, DOI 10.1002/nme.1254Hughes TJR, 2005, COMPUT METHOD APPL M, V194, P4135, DOI 10.1016/j.cma.2004.10.008Sederberg TW, 2004, ACM T GRAPHIC, V23, P276, DOI 10.1145/1015706.1015715CHOI KK, 2004, STRUCTURAL SENSITIVIRoh HY, 2004, COMPUT METHOD APPL M, V193, P2261, DOI 10.1016/j.cma.2004.01.019Sederberg TN, 2003, ACM T GRAPHIC, V22, P477, DOI 10.1145/882262.882295Kim NH, 2003, STRUCT MULTIDISCIP O, V24, P418, DOI 10.1007/s00158-002-0255-6Cho M, 2003, INT J NUMER METH ENG, V56, P81, DOI 10.1002/nme.546Grindeanu L, 2002, CONCURRENT ENG-RES A, V10, P55, DOI 10.1106/106329302024056FARIN G, 2002, CURVES SURFACES CAGDROGERS DF, 2001, INTRO NURBS HIST PERHUGHES TJR, 2000, FINITE ELEMENT METHOAnnicchiarico W, 1999, FINITE ELEM ANAL DES, V33, P125Hardee E, 1999, ADV ENG SOFTW, V30, P185AZEGAMI H, 1997, P INT C COMP AID OPT, P309PIEGL LA, 1997, MONOGRAPHS VISUAL COCHANG KH, 1995, COMPUT SYST ENG, V6, P151CHOI KK, 1994, FINITE ELEM ANAL DES, V15, P317GU Y, 1990, STRUCT OPTIMIZATION, V2, P23HAUG EJ, 1986, DESIGN SENSITIVITY ABENNETT JA, 1985, AIAA J, V23, P458BRAIBANT V, 1984, COMPUT METHOD APPL M, V44, P247

Shape design optimization of SPH fluid-structure interactions considering geometrically exact interfaces

Fluid-structure interaction problems are solved by applying a smoothed particle hydrodynamics method to a weakly compressible Navier-Stokes equation as well as an equilibrium equation for geometrically nonlinear structures in updated Lagrangian formulation. The geometrically exact interface, consisting of B-spline basis functions and the corresponding control points, includes the high order geometric information such as tangent, normal, and curvature. The exactness of interface is kept by updating the control points according to the kinematics obtained from response analysis. Under the scheme of explicit time integration and updated Lagrangian formulation, the required shape design velocity should be updated at every single step. The update scheme of design velocity is developed using the sensitivity of physical velocity. The developed sensitivity analysis method is further utilized in gradient-based shape optimization problems and turns out to be very efficient since the interaction pairs of particles determined in the response analysis can be directly utilized.Ha YD, 2010, STRUCT MULTIDISCIP O, V40, P307, DOI 10.1007/s00158-009-0363-7Bazilevs Y, 2008, COMPUT MECH, V43, P3, DOI 10.1007/s00466-008-0315-xAntoci C, 2007, COMPUT STRUCT, V85, P879, DOI 10.1016/j.compstruc.2007.01.002LIU GR, 2003, SMOOTH PARTICLE HYDRGray JP, 2001, COMPUT METHOD APPL M, V190, P6641LUND E, 2001, 20011624 AIAATALLEC L, 2001, COMPUT METH APPL MEC, V190, P3039*VAND RES DEV INC, 1999, DOT DES OPT TOOLS USFarhat C, 1998, COMPUT METHOD APPL M, V157, P95Morris JP, 1997, J COMPUT PHYS, V136, P214PIEGL L, 1997, NURBS BOOK MONOGRAPHGHATTAS O, 1995, J COMPUT PHYS, V121, P347SWEGLE JW, 1995, J COMPUT PHYS, V116, P123RHOADES CE, 1992, COMPUT PHYS COMMUN, V70, P478HERNQUIST L, 1989, ASTROPHYS J SUPPL S, V70, P419HAUG EJ, 1986, DESIGN SENSITIVITY AMONAGHAN JJ, 1983, J COMPUT PHYS, V52, P374LIU WK, 1982, COMPUT METHOD APPL M, V31, P129GINGOLD RA, 1977, MON NOT R ASTRON SOC, V181, P375LUCY LB, 1977, ASTRON J, V82, P1013

A Simple Low-Cost Common Mode Active EMI Filter Using a push-pull Amplifier

A simple low-cost active EMI filter (AEF) without transformers is proposed. The equivalent circuit model of the proposed AEF is built, and a block diagram is extracted for efficient feedback analysis. The feedback loop gain and the performance of the AEF are calculated and validated by comparison with SPICE simulations. The proposed AEF enlarges the effective value of Y-capacitors. The AEF is manufactured for the application of a 2.2kW resonant inverter, and the performance is demonstrated by measurements of the conducted emissions

Diallyl disulphide-loaded spherical gold nanoparticles and acorn-like silver nanoparticles synthesised using onion extract: catalytic activity and cytotoxicity

AbstractOnion (Allium cepa) extract was used for the green synthesis of gold and silver nanoparticles. Each colloidal solution exhibited surface plasmon resonance, with a peak at 532 nm for gold nanoparticles and 391 nm for silver nanoparticles. Microscopic results confirmed the presence of spherical shapes. The X-ray diffraction pattern demonstrated a face-centered cubic structure. Both nanoparticles had negative zeta potentials and retained colloidal stability in cell culture medium. Catalytic applications were evaluated for 4-nitrophenol reduction and methyl orange degradation reactions by monitoring with UV-visible spectrophotometry. Furthermore, the nanoparticles demonstrated no significant cytotoxicity against human pancreas ductal adenocarcinoma cells (PANC-1) and human colorectal adenocarcinoma cells (HT-29). PEGylation and diallyl disulphide loading of the gold and silver nanoparticles meaningfully reduced the cell viability of both cell lines. Furthermore, diallyl disulphide loading resulted in more cytotoxicity against PANC-1 cells than against HT-29 cells. Additionally, the gold nanoparticles were more cytotoxic than the silver nanoparticles upon diallyl disulphide loading. Interestingly, after PEGylation and diallyl disulphide loading, the silver nanoparticles exhibited acorn-like shapes, while the gold nanoparticles retained spherical shapes. This result suggested that nanoparticles green-synthesised by onion extract have possibilities as nanocatalysts and drug delivery nanocarriers for catalytic and nanomedicine applications

Sesquiterpenoids from Tussilago farfara Flower Bud Extract for the Eco-Friendly Synthesis of Silver and Gold Nanoparticles Possessing Antibacterial and Anticancer Activities

Sesquiterpenoids from the flower bud extract of Tussilago farfara were effectively utilized as a reducing agent for eco-friendly synthesis of silver and gold nanoparticles. The silver and gold nanoparticles had a characteristic surface plasmon resonance at 416 nm and 538 nm, respectively. Microscopic images revealed that both nanoparticles were spherical, and their size was measured to be 13.57 ± 3.26 nm for the silver nanoparticles and 18.20 ± 4.11 nm for the gold nanoparticles. The crystal structure was determined to be face-centered cubic by X-ray diffraction. Colloidal stability of the nanoparticle solution was retained in a full medium, which was used in the cell culture experiment. The antibacterial activity result demonstrated that the silver nanoparticles showed better activity (two- to four-fold enhancement) than the extract alone on both Gram-positive and Gram-negative bacteria. Interestingly, the highest antibacterial activity was obtained against vancomycin-resistant Enterococci Van-A type Enterococcus faecium. Cytotoxicity on cancer cell lines confirmed that gold nanoparticles were more cytotoxic than silver nanoparticles. The highest cytotoxicity was observed on human pancreas ductal adenocarcinoma cells. Therefore, both nanoparticles synthesized with the sesquiterpenoids from T. farfara flower bud extract can be applicable as drug delivery vehicles of anticancer or antibacterial agents for future nanomedicine applications

Concentration Effect of Reducing Agents on Green Synthesis of Gold Nanoparticles: Size, Morphology, and Growth Mechanism

Under various concentration conditions of reducing agents during the green synthesis of gold nanoparticles (AuNPs), we obtain the various geometry (morphology and size) of AuNPs that play a crucial role in their catalytic properties. Through both theoretical and experimental approaches, we studied the relationship between the concentration of reducing agent (caffeic acid) and the geometry of AuNPs. As the concentration of caffeic acid increases, the sizes of AuNPs were decreased due to the adsorption and stabilizing effect of oxidized caffeic acids (OXCAs). Thus, it turns out that optimal concentration exists for the desired geometry of AuNPs. Furthermore, we investigated the growth mechanism for the green synthesis of AuNPs. As the caffeic acid is added and adsorbed on the surface of AuNPs, the aggregation mechanism and surface free energy are changed and consequently resulted in the AuNPs of various geometry.11Nsciescopu