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Ramasamy, Parthiban,Chandra, Prakash,Rhee, Seog Woo,Kim, Jinkwon RSC Pub 2013 Nanoscale Vol.5 No.18
<P>The visible green and red upconversion emissions in Er(3+)/Yb(3+) doped β-NaGdF4 nanoparticles were enhanced by tridoping with Fe(3+) ions (0-40 mol%). XRD, XPS, ICP-AES and EDS data demonstrated successful incorporation of Fe(3+) ions in NaGdF4:Yb(3+)/Er(3+) nanoparticles. The effect of Fe(3+) tridoping on the upconversion luminescence in NaGdF4:Yb(3+)/Er(3+) NPs was investigated in detail. The green and red emission intensities were enhanced by 34 and 30 times, respectively. The maximum emission was observed in a sample containing 30 mol% Fe(3+) ions. A possible mechanism for the enhanced upconversion emission is proposed. In addition, a layer of silica was coated onto the surface of UCNPs to improve the biocompatibility. Folic acid was covalently linked to the silica coated UCNPs to form UCNP@SiO2-FA nanoprobes, which have been successfully applied to the fluorescent imaging HeLa cells.</P>
Combined plasmonic and upconversion rear reflectors for efficient dye-sensitized solar cells
Ramasamy, Parthiban,Kim, Jinkwon The Royal Society of Chemistry 2014 Chemical communications Vol.50 No.7
<P>A novel rear reflector structure that combines NIR light harvesting β-NaGdF<SUB>4</SUB>:Yb, Er, Fe upconversion nanoparticles (UCNPs) and light reflecting silver particles has been successfully used to improve the performance of dye-sensitized solar cells (DSSCs). The power conversion efficiency of DSSCs with a rear reflector was 7.04%, which is an increase of 21.3% compared to the cell without a rear reflector (5.8%).</P> <P>Graphic Abstract</P><P>The efficiency of dye-sensitized solar cells has been increased using a back reflector structure that combines upconversion nanoparticles (UCNPs) to harvest NIR light and plasmonic silver particles to scatter light. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cc47290f'> </P>
Ramasamy, Mohankandhasamy,Lee, Jin-Hyung,Lee, Jintae Elsevier 2017 Colloids and surfaces. B, Biointerfaces Vol.160 No.-
<P><B>Abstract</B></P> <P>The objective of the present study was to develop a one-pot strategy to synthesis gold nanoparticle complexes using cinnamaldehyde, a potent antibiofilm agent which in its free form, exhibits high volatility and unstable nature. Hence, we developed cinnamaldehyde gold nanoparticles (CGNPs) in a single step to overcome the limitations of free cinnamaldehyde. Furthermore, reduction abilities of cinnamaldehyde under different experimental conditions, that is, varying precursor concentrations of cinnamaldehyde and gold, metal salts, pH, temperature, and light sources, were investigated. UV–vis spectroscopy, transmission electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and dynamic light-scattering measurements revealed that heat influenced the nanoparticle formation in the presence of cinnamaldehyde, and as produced cinnamaldehyde immobilized on gold nanoparticles were spherical, monodispersed, and stable by surface charge. CGNPs containing 0.01% cinnamaldehyde by weight exhibited effective biofilm inhibition of up to >80% against Gram positive bacteria (methicillin-sensitive and -resistant strains of <I>Staphylococcus aureus,</I> MSSA and MRSA, respectively) and Gram negative (<I>Escherichia coli</I> and <I>Pseudomonas aeruginosa</I>) and a fungus <I>Candida albicans</I>. In addition, CGNPs attenuated the virulence of <I>C. albicans</I> by inhibiting hyphae formation. Based on observations of their antibiofilm effects and confocal microscopy findings, CGNPs caused biofilm damage by direct contact. Thus, cinnamaldehyde appears to be a promising reduction material for the eco-friendly, one-pot synthesis of CGNPs with excellent antibiofilm activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> One-pot, cinnamaldehyde gold nanoparticle complexes (CGNPs) were produced. </LI> <LI> Heat plays predominant role in metal salt reduction with cinnamaldehyde. </LI> <LI> CGNPs exhibited antibiofilm activity against pathogens including fungi. </LI> <LI> Cinnamaldehyde is a potent reductant for nanoparticle synthesis. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Ramasamy, Krishnamoorthy,Joe, Manoharan Melvin,Kim, Ki-Yoon,Lee, Seon-Mi,Shagol, Charlotte,Rangasamy, Anandham,Chung, Jong-Bae,Islam, Md. Rashedul,Sa, Tong-Min Korean Society of Soil Science and Fertilizer 2011 한국토양비료학회지 Vol.44 No.4
Soil microorganisms play a major role in improving soil fertility and plant health. Symbiotic arbuscular mycorrhizal fungi (AMF) form a key component of the soil microbial populations. AMF form a mutualistic association with the host plant and exert a positive influence on its growth and nutrient uptake. The establishment of mycorrhizal symbioses with the host plant can positively be influenced by plant growth promoting rhizobacteria through various mechanisms such as increased spore germination and hyphal permeability in plant roots. Though there are evidences that combined interactions between AMF and PGPR can promote the plant growth however mechanisms of these interactions are poorly understood. Better understanding of the interactions between AMF and other microorganisms is necessary for maintaining soil fertility and enhancing crop production. This paper reviews current knowledge concerning the interactions between AMF and PGPR with plants and discusses on enhanced nutrient availability, biocontrol, abiotic stress tolerance and phytoremediation in sustainable agriculture.
Ramasamy Nagarajan,Jayagopal Madhavaraju,John S. Armstrong-Altrin,Raghavendra Nagendra 한국지질과학협의회 2011 Geosciences Journal Vol.15 No.1
Major, trace and rare earth element (REE) geochemistry of carbonate rocks of the Neoproterozoic Shahabad Formation, southern India were studied in order to investigate the depositional environment and source for the REEs. The PAAS (Post Archaean Australian Shale) normalized REE + Y pattern of Shahabad limestones have consistent seawater-like pattern i.e., i) LREE depletion (average (Nd/Yb)_(SN) = 0.64 ± 0.08), ii) negative Ce anomaly, iii) positive Gd anomaly (average Gd_(SN)/Gd^* = 1.05 ± 0.16), iv) superchondritic Y/Ho ratio (average Y/Ho = 38.13 ± 21.35). The depletion of LREE and enrichment of HREE are clearly indicated by the (La/Yb)_(SN), (Dy/Yb)_(SN) and (Nd/Yb)_(SN) ratios, which suggest the retention of seawater characteristics in these limestones. The negative Ce anomaly reflects the incorporation of REE directly from seawater or from the pore water under oxic condition, and also reveals the mixing of two-component systems with terrigenous clay (detrital) in the marine sediments. The terrigenous input in these limestones is confirmed by positive correlation of REE with Al_2O_3, negative correlation of REE with CaO and differences in Y/Ho ratios. V, Cr, and Sc, are positively correlated with Ti, and strong positive correlation of REE with Fe_2O_3, Ni, Cr, Sc, and Y also indicate the presence of terrigenous materials in the Shahabad limestones.
Ramasamy, Mohankandhasamy,Kim, Sanghyo,Lee, Su Seong,Yi, Dong Kee American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.1
<P>We describe the nucleophilic hybridization technique for fabricating magnetic nanoparticle (MNP) around gold nanorod (AuNR) for desired photo-thermal lysis on pathogenic bacteria. From the electromagnetic energy conversion into heat to the surrounding medium, a significant and quicker temperature rise was noted after light absorption on nanohybrids, at a controlled laser light output and optimum nanoparticle concentration. We observed a similar photo-thermal pattern for more than three times for the same material up on repeated magnetic separation. Regardless of the cell wall nature, superior pathogenic cell lysis has been observed for the bacteria suspensions of individual and mixed samples of Salmonella typhi (S.typhi) and Bacillus subtilis (B.subtilis) by the photo-heated nanoparticles. The synthesis of short gold nanorod, conjugation with magnetic nanoparticle and its subsequent laser exposure provides a rapid and reiterated photo-thermal effect with enhanced magnetic separation for efficient bactericidal application in water samples. Resultant novel properties of the nano-aggregates makes them a candidate to be used for a rapid, effective, and re-iterated photo-thermal agent against a wide variety of pathogens to attain microbe free water.</P>
Ramasamy, E.,Chun, J.,Lee, J. Pergamon Press ; Elsevier Science Ltd 2010 Carbon Vol.48 No.15
Ordered mesoporous carbon (OMC) with a high surface area (∼1575m<SUP>2</SUP>/g) and bimodal pores (2.5 and 6.1nm) was synthesized using a soft-template method employing triblock copolymer F127 as the structure directing agent and then applied as a low-temperature processable counter electrode for dye-sensitized solar cell (DSSC). The OMC counter electrode-based DSSC shows an energy conversion efficiency of 7.46%, whereas that of a Vulcan counter electrode is 4.30%. Electrochemical impedance spectroscopy analysis reveals decreased charge transfer resistance at the OMC counter electrode-electrolyte interface, thus improved fill factor and energy conversion efficiency.
Ramasamy, Mohankandhasamy,Lee, Jin-Hyung,Lee, Jintae SAGE Publications 2016 Journal of biomaterials applications Vol.31 No.3
<P>The objective of this study was to develop a bimetallic nanoparticle with enhanced antibacterial activity that would improve the therapeutic efficacy against bacterial biofilms. Bimetallic gold-silver nanoparticles were bacteriogenically synthesized using -proteobacterium, Shewanella oneidensis MR-1. The antibacterial activities of gold-silver nanoparticles were assessed on the planktonic and biofilm phases of individual and mixed multi-cultures of pathogenic Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive bacteria (Enterococcus faecalis and Staphylococcus aureus), respectively. The minimum inhibitory concentration of gold-silver nanoparticles was 30-50 mu M than that of other nanoparticles (>100 mu M) for the tested bacteria. Interestingly, gold-silver nanoparticles were more effective in inhibiting bacterial biofilm formation at 10 mu M concentration. Both scanning and transmission electron microscopy results further accounted the impact of gold-silver nanoparticles on biocompatibility and bactericidal effect that the small size and bio-organic materials covering on gold-silver nanoparticles improves the internalization and thus caused bacterial inactivation. Thus, bacteriogenically synthesized gold-silver nanoparticles appear to be a promising nanoantibiotic for overcoming the bacterial resistance in the established bacterial biofilms.</P>