02054nas a2200205 4500008004100000022001400041245010900055210006900164260007100233300001400304490000800318520127800326100002001604700001401624700001901638700002501657700002701682700001901709856012001728 2010 eng d a1932-744700aEffect of reduced particle size on the magnetic properties of chemically synthesized BiFeO3 nanocrystals0 aEffect of reduced particle size on the magnetic properties of ch a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB a2108-21150 v1143 a

Here, we report the effect of reduction in particle size on the temperature dependent magnetization of chemically synthesized BiFeO3 nanocrystals with average grain size of 55 nm. The X-ray photoelectron spectroscopy results show a significant broadening of binding energy peaks associated to Fe3+ 2p(3/2) core levels due to the reduced size. Additionally, due to the nanosize effect, the M-H loops show a significant coercivity starting from 390 K with an anomaly located in the vicinity of 150 K in our H-c vs T as well as M-r/M-s(50 kOe) vs T curves. At this temperature, both H-c and M-r/M-s(50 kOe) undergo minima. Additionally, our results for the first time show the evidence of existence of a low temperature anomaly due to spin-glass transition in the range from 40-44 K in the field cooled magnetization curves. In bulk single crystals, this transition is reported to be situated at around 50 K, however, this transition remained so far undiscovered in the recent studies on BiFeO3 nanoparticles due to the insufficient temperature resolution. The significant shift in this transition toward lower temperature can be attributed to size dependent effects. Our results clearly present new information on the size dependent properties of BiFeO3 nanoparticles.

1 aJaiswal, Adhish1 aDas, Raja1 aVivekanand, K.1 aAbraham, Priya, Mary1 aAdyanthaya, Suguna, D.1 aPoddar, Pankaj uhttps://library.ncl.res.in/content/effect-reduced-particle-size-magnetic-properties-chemically-synthesized-bifeo3-003023nas a2200337 4500008004100000022001400041245008600055210006900141260012500210300001100335490000800346520187100354653002202225653002502247653001802272653001802290653002002308653001802328653001702346653001202363653001802375653003102393100002002424700001402444700001902458700001702477700002502494700002702519700001902546856012002565 2010 eng d a0021-897900aMagnetic and dielectric properties and Raman spectroscopy of GdCrO3 nanoparticles0 aMagnetic and dielectric properties and Raman spectroscopy of GdC aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScJAN a0139120 v1073 a

The rare earth orthochromites are extremely interesting due to the richness of their optical, dielectric, and magnetic properties as well as due to their multiferroic properties which make them suitable materials to study in the nanoregime. However, the wet-chemical synthesis of these materials in nanosize is nontrivial. Here, we report for the first time, the detailed Raman spectra as well as magnetic and dielectric properties of chemically synthesized GdCrO3 nanoparticles of size ranging from 40 to 60 nm. The magnetic properties are dictated by competing Cr3+-Cr3+, Gd3+-Cr3+, and Gd3+-Gd3+ superexchange interactions in different temperature regions, resulting into an antiferromagnetic ordering at 167 K due to the Cr3+-Cr3+ followed by weak ferromagnetic ordering due to the onset of Cr3+-Gd3+ interactions. At lower temperature, it shows weak antiferromagnetic ordering due to Gd3+-Gd3+ interaction. Below 95 K, GdCrO3 nanoparticles showed the presence of negative magnetization due to Gd3+ and Cr3+ interactions resulting into weak ferromagnetic coupling. The Raman spectroscopy shows the characteristic Raman shifts indicating that below 450 cm(-1), Gd3+ ions play a dominant role in determining the phonon frequencies of GdCrO3, and above 450 cm(-1), the Cr+3 ions dominate. We also present for the first time the low temperature dielectric constant and loss tangent data for GdCrO3 in a broad temperature and frequency range. The dielectric constant shows a decrease in comparison to the bulk values due to the size dependent effects. It also shows a peak centered at around 320 K above which it shows a sharp decrease. The dielectric loss value in GdCrO3 nanoparticles is quite small and shows an interesting frequency dependent anomaly at lower temperature which might be due to the coupling between magnetic and dielectric order parameters.

10adielectric losses10agadolinium compounds10aMagnetisation10aMultiferroics10ananofabrication10aNanoparticles10apermittivity10aphonons10aRaman spectra10asuperexchange interactions1 aJaiswal, Adhish1 aDas, Raja1 aVivekanand, K.1 aMaity, Tuhin1 aAbraham, Priya, Mary1 aAdyanthaya, Suguna, D.1 aPoddar, Pankaj uhttps://library.ncl.res.in/content/magnetic-and-dielectric-properties-and-raman-spectroscopy-gdcro3-nanoparticles-002225nas a2200169 4500008004100000022001400041245013300055210006900188260007100257300001600328490000800344520150700352100002301859700002501882700001901907856012901926 2012 eng d a1520-610600aTemperature-dependent spectroscopic evidences of curcumin in aqueous medium: a mechanistic study of its solubility and stability0 aTemperaturedependent spectroscopic evidences of curcumin in aque a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC a14533-145400 v1163 a

In curcumin, keto-enol-enolate equilibrium of the heptadiene-dione moiety determines its physiochemical and antioxidant properties. However, its poor solubility in water at neutral pH and room temperature decreases its bioavailability. Potential therapeutic applications have triggered an interest in manipulating the solubility of curcumin in water as its stability and solubility in water remains poorly understood. Here, the mechanism behind its solubility at various temperatures and the influence of interplay of temperature, intramolecular H-bonding, and intermolecular forces is reported, which leads to aggregation-disaggregation at various temperatures. Remarkable change is observed in temperature-dependent electronic transition behavior of curcumin, however, the absorption spectra after cooling and heating cycles remain unchanged, hinting much better thermal stability of curcumin in water than previously thought. This study indicates that it is perhaps the breaking of intramolecular hydrogen bonding which leads to exposure of polar groups and hence responsible for the dissolution of curcumin at higher temperature. The formation of intermolecular aggregates might be responsible behind a better room temperature stability of the molecules after cooling its aqueous suspension from 90 to 25 degrees C. These curcumin solubility studies have great application in biological research with reference to bioavailability and to understand target oriented mode of action of curcumin.

1 aJagannathan, Ramya1 aAbraham, Priya, Mary1 aPoddar, Pankaj uhttps://library.ncl.res.in/content/temperature-dependent-spectroscopic-evidences-curcumin-aqueous-medium-mechanistic-study-002686nas a2200193 4500008004100000022001400041245018200055210006900237260011000306300001400416490000600430520181900436100002302255700002302278700002302301700002502324700001902349856012402368 2013 eng d a2040-336400aIn situ synthesis and surface functionalization of gold nanoparticles with curcumin and their antioxidant properties: an experimental and density functional theory investigation0 aIn situ synthesis and surface functionalization of gold nanopart aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcDEC a1882-18930 v53 a

Curcumin ((1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) is an active component of turmeric; it is responsible for its characteristic yellow color and therapeutic potential, but its poor bioavailability remains a major challenge. In order to improve the bioavailability of curcumin, various approaches have been used. One of the possible approaches to increase the bioavailability of curcumin is its conjugation on the surface of metal nanoparticles. Therefore, in the present study, we report the binding of curcumin on the surface of gold nanoparticles (AuNPs). The AuNPs were synthesized by the direct reduction of HAuCl4 using curcumin in the aqueous phase, without the use of any other reducing agents. We found that curcumin acts both as a reducing and capping agent, stabilizing the gold sol for many months. Moreover, these curcumin-capped AuNPs also show good antioxidant activity which was confirmed by the DPPH (2,2-diphenyl-l-picrylhydrazyl) radical test. Thus, the surface functionalization of AuNPs with curcumin may pave a new way of using the curcuminoids towards possible drug delivery and therapeutics. Apart from the experimental study, a detailed quantum chemical calculation using density functional theory (DFT) has been performed, in order to investigate the formation of a complex of curcumin with Au3+ ions in different possible conformational isomeric forms. Our theoretical calculations indicate the evidence of electron transfer from curcumin into the Au center and essentially indicate that as a consequence of complexation, Au3+ ions are reduced to Au-0. Our theoretical results also propose that it is the breakage of intramolecular H-bonding that probably leads to the increased availability of curcumin in the presence of gold ions and water molecules.

1 aSingh, Dheeraj, K.1 aJagannathan, Ramya1 aKhandelwal, Puneet1 aAbraham, Priya, Mary1 aPoddar, Pankaj uhttps://library.ncl.res.in/content/situ-synthesis-and-surface-functionalization-gold-nanoparticles-curcumin-and-their-0