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Protein immobilization onto electrochemically synthesized CoFe nanowires
Torati, Sri Ramulu,Reddy, Venu,Yoon, Seok Soo,Kim, CheolGi Dove Medical Press 2015 INTERNATIONAL JOURNAL OF NANOMEDICINE Vol.10 No.-
<P>CoFe nanowires have been synthesized by the electrodeposition technique into the pores of a polycarbonate membrane with a nominal pore diameter of 50 nm, and the composition of CoFe nanowires varying by changing the source concentration of iron. The synthesized nanowire surfaces were functionalized with amine groups by treatment with aminopropyltriethoxysilane (APTES) linker, and then conjugated with streptavidin-Cy3 protein via ethyl (dimethylaminopropyl) carbodiimide and <I>N</I>-hydroxysuccinimide coupling chemistry. The oxide surface of CoFe nanowire is easily modified with aminopropyltriethoxysilane to form an amine terminating group, which is covalently bonded to streptavidin-Cy3 protein. The physicochemical properties of the nanowires were analyzed through different characterization techniques such as scanning electron microscope, energy dispersive spectroscopy, and vibrating sample magnetometer. Fluorescence microscopic studies and Fourier transform infrared studies confirmed the immobilization of protein on the nanowire surface. In addition, the transmission electron microscope analysis reveals the thin protein layer which is around 12–15 nm on the nanowire surfaces.</P>
Magnetically Characterized Molecular Lubrication between Biofunctionalized Surfaces
Hu, Xinghao,Torati, Sri Ramulu,Yoon, Jonghwan,Lim, Byeonghwa,Kim, Kunwoo,Kim, CheolGi American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.18
<P>We demonstrate an efficient approach for quantifying frictional forces (sub-piconewton) at nano-bio interfaces by controlled magnetic forces, which is based on simultaneous measurements of critical frequencies for streptavidin-coupled magnetic particles. The maximum phase angle, being corresponded with the critical frequency, is formulated in terms of magnetic, frictional, and viscous forces of the particles on DNA- and SiO<SUB>2</SUB>-functionalized micromagnet arrays. The streptavidin/DNA interface shows lower friction as an enhanced lubrication than the streptavidin/SiO<SUB>2</SUB> interface, which is indicated by the lower transition field of quasi-static motion, the larger ratio of dynamic particles, and also the higher velocity of the particles. The friction coefficients at the streptavidin/DNA and streptavidin/SiO<SUB>2</SUB> interfaces are evaluated numerically as 0.07 and 0.11, respectively, regardless of the vertical force and the velocity. The proposed method would open up new possibilities to study mechanical interactions at biological surfaces.</P> [FIG OMISSION]</BR>
Abbas, Mohamed,Torati, Sri Ramulu,Rao, B. Parvatheeswara,Abdel-Hamed, M.O.,Kim, CheolGi Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.644 No.-
<P><B>Abstract</B></P> <P>Monodisperse Mn<I> <SUB>x</SUB> </I>Zn<SUB>1−</SUB> <I> <SUB>x</SUB> </I>Fe<SUB>2</SUB>O<SUB>4</SUB> (<I>x</I> =0.2, 0.5 and 0.8) nanoparticles have been synthesized using two different routes namely sonochemical and polyol methods, and the shape and size along with physiochemical properties of the nanoparticles were compared in detail. In both the routes, the synthesis was performed in a single reaction without the use of any surfactant and deoxygenated conditions. The reaction kinetics and surface adsorption characteristics of nanoparticles were observed by thermogravimetric analysis and Fourier transform infrared spectroscopy measurements. X-ray diffraction patterns confirmed the formation of a pure ferrite phase with cubic spinel structure, and the patterns further clearly indicate that the sonochemical method produces highly crystalline particles without any post calcination reaction, comparing with the polyol process. Transmission electron microscopy results reveal that the nanoparticles synthesized by polyol method are mostly aggregated and spherical in nature whereas the nanoparticles produced by sonochemical method are monodisperse large particles with cubic like shapes. The overall studies demonstrated that the sonochemical method is facile, reliable, rapid and very attractive for the aqueous synthesis of highly crystalline and high magnetic moment (84.5emu/g) monodisperse superparamagnetic Mn–Zn ferrite nanoparticles which considered as potential materials for various applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mn–Zn ferrite NPs were synthesized by two different methods are polyol and sonochemical. </LI> <LI> The sonochemical method produced NPs with high crystallinity than polyol method. </LI> <LI> The ferrite samples synthesized by sonochemical method showed high magnetization values and superparamagnetic properties. </LI> <LI> XRD, TEM, EDS, TGA, FTIR, and VSM techniques used to characterize the samples. </LI> </UL> </P>
Reddy, Venu,Torati, Ramulu Sri,Oh, Sunjong,Kim, CheolGi American Chemical Society 2013 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.52 No.2
<P>We have presented a biological and eco-friendly method for the synthesis of gold nanoparticles from gold precursor (HAuCl<SUB>4</SUB>) using <I>Sapindus mukorossi</I> Gaertn. fruit pericarp (soapnut shells). We investigate the production of gold nanoparticles as a function of the concentration of HAuCl<SUB>4</SUB> and the amount of soapnut shells. Average nanoparticle sizes of 9, 17, and 19 nm were obtained by using the HAuCl<SUB>4</SUB> concentrations of 1, 5, and 10 mM, respectively, with a fixed amount of soapnut shells extract. The resulted gold nanoparticles are highly crystalline face-centered cubic (fcc) structures. FT–IR analysis suggests that the obtained gold nanoparticles might be stabilized through the interactions of carboxylic groups in the saponins and the carbonyl groups in the flavonoids present in the soapnut shells. These soapnut shells mediated gold nanoparticles were demonstrated to have good catalytic activity for the chemical reduction of <I>p</I>-nitroaniline.</P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ie302037c'>ACS Electronic Supporting Info</A></P>
Satish Kasturi,Sri Ramulu Torati,엄윤지,김철기 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.97 No.-
Recently, miniaturized electrochemical biosensors have the advantage of real-time monitoring and labelfreedetection of biomarkers. However, controlled manipulation of reagent samples for specificimmobilization of biomarkers remains a challenge to attend high-resolution microfluidic biosensor. Here, we designed a microfluidic channel and valves integrated electrochemical biosensor for thedetection of β-amyloid (1–42) biomarker, one of the most neurotoxic peptides present in thecerebrospinalfluid, and a possible marker for the detection of Alzheimer’s disease. The formation of theantibody-antigen complexes on gold microelectrode integrated inside thefluidic chambers waspresented in the developed biosensor, and all the measurements are carefully controlled using pneumaticvalves integrated with the device. The demonstrated microfluidic electrochemical biosensor exhibits alinear response towards various β-amyloid antigen concentrations from 2.2 pM to 22 mM, with anenhanced detection limit of 1.62 pM. The developed technology offers an advantage of minimal reagentsample and suitable environment for miniaturized and sensitive detection of biomarkers, could also beused for the detection of other biomarkers with high efficiency.
NiCo Sensing Layer for Enhanced Signals in Planar Hall Effect Sensors
Jaein Lim,Brajalal Sinha,Torati Sri Ramulu,Kun Woo Kim,Dong-Young Kim,김철기 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.4
NiCo alloy materials have been investigaged as a potential sensing layer for planar Hall effect (PHE) sensors in magnetic multilayer structures. In this study, the magnetoresistive performance of the NiCo alloy is compared with that of the NiFe alloy. With an optimum thickness of 10 nm, the increment of the PHE voltage (Vmax) for the NiCo-based sensor was approximately 1.5 times larger than that of the NiFe-based sensor. The field sensitivity of both sensor types appeared to be nearly equal. However, the dynamic field range for the NiCo sensor was increased by approximately 40% compared with that of the NiFe sensor. The measuring configuration was optimized in order to obtain higher field sensitivity in the sensor. The field sensitivity was measured to be at a maximum at a 20° angle between the easy axis of the sensor and the applied external field, which was approximately three times higher than that in the perpendicular direction.