I am a material scientist with interest in developing nano-materials/bio-materials for various biomedical applications. In past, My research interested have been on multi-functional nanoparticles for ovarian cancer targeting and MARS spectral imaging and developing gold nanoparticles based formulation for drug delivery. The current research focus is on dental biomaterials and phospholipid liposome.
Primary Affiliation: University of Minnesota - Minneapolis, MN , United States
Dhiraj Kumar et al 2016 Nanotechnology 27 (35) 355601
Gold nanoparticles (AuNPs) are being studied for several biomedical applications, including drug delivery, biomedical imaging, contrast agents and tumor targeting. The synthesis of nanoparticles with a narrow size distribution is critical for these applications. We report the synthesis of highly mono-dispersed AuNPs by a seed mediated approach, in the presence of tri-sodium citrate and hydroquinone (HQ). AuNPs with an average size of 18 nm were used for the synthesis of highly mono-dispersed nanocrystals of an average size 40 nm, 60 nm, 80 nm and ~100 nm; but the protocol is not limited to these sizes. The colloidal gold was subjected to UV–vis absorbance spectroscopy, showing a red shift in lambda max wavelength, peaks at 518.47 nm, 526.37 nm, 535.73 nm, 546.03 nm and 556.50 nm for AuNPs seed (18 nm), 40 nm, 60 nm, 80 nm and ~100 nm respectively. The analysis was consistent with dynamic light scattering and electron microscopy. Hydrodynamic diameters measured were 17.6 nm, 40.8 nm, 59.8 nm, 74.1 nm, and 91.4 nm (size by dynamic light scattering—volume %); with an average poly dispersity index value of 0.088, suggesting mono-dispersity in the size distribution, which was also confirmed by transmission electron microscopy analysis. The advantage of a seed mediated approach is a multi-step growth of nanoparticle size that enables us to control the number of nanoparticles in the suspension, for size ranging from 24.5 nm to 95.8 nm. In addition, the HQ-based synthesis of colloidal nanocrystals allowed control of the particle size and size distribution by tailoring either the number of seeds, amount of gold precursor or reducing agent (HQ) in the final reaction mixture.
Micro/Nano Materials, Devices, and Systems, SPIE Proceeding
The surface plasmon resonances induced light coupling is widely recognized as a promising way of enhancing the light absorption in photovoltic devices. This is achieved by enhanced localized electromagnetic field in the vicinity of metal surface or the strong light scattering effects from metal nanoparticles integrated on the front surface of as-fabricated solar cells. In this paper, the colloidal gold nanoparticles(Au NPs), synthesized by modified Turkevich and Frens method, were integrated onto the inverted nanopyramid silicon solar cell via a dip coating method. A 7% increase in short-circuit current density of solar cell was observed for 15 minutes dip coating. As a result, a 4.6% increase in overall efficiency was achieved. However,the dense surface coverage of Au NPs resulted in decreased fill factor.
Thiol-terminated polyethylene glycol (PEG) is commonly used to functionalize the surface of gold nanoparticles (AuNPs) in order to improve their in vivo stability and to avoid uptake by the reticular endothelial system. Although it has been reported that AuNPs functionalized with tethered PEG are stable in biological media, the influence of chain density remains unclear. This study investigates the influence of PEG capping density on the stability of washed and dried AuNPs in: water, phosphate-buffered saline solution (PBS), phosphate-buffered saline solution containing bovine serum albumin (PBS/BSA), and dichloromethane (DCM). PEG coating had a dramatic effect on stability enabling stable suspensions to be produced in all the media studied. A linear relationship was observed between capping density and stability in water and DCM with a somewhat lower stability observed in PBS and PBS/BSA. A maximum PEG loading level of ∼14 wt.% was achieved, equivalent to a PEG surface density of ∼1.13 chains/nm2.
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