02057nas a2200301 4500008004100000022001400041245007100055210006900126260009200195300001400287490000600301520105500307653003001362653001401392653001401406653001801420100002201438700001601460700002101476700002301497700001801520700001801538700002301556700001901579700002301598700002901621856010501650 2007 eng d a1533-488000aLow temperature synthesis of magnetite and maghemite nanoparticles0 aLow temperature synthesis of magnetite and maghemite nanoparticl a26650 THE OLD RD, STE 208, VALENCIA, CA 91381-0751 USAbAMER SCIENTIFIC PUBLISHERScDEC a4294-43020 v73 a

We report on the synthesis of iron oxide nanoparticles below 100 degrees C by a simple chemical protocol. The uniqueness of the method lies in the use of Ferrous ammoniurn sulphate (in conjugation with FeCl3) which helps maintain the stability of Fe-2+ state in the reaction sequence thereby controlling the phase formation. Hexamine was added as the stabilizer. The nanoparticles synthesized at three different temperatures viz, 5 degrees, 27 degrees, and 95 degrees C are characterized by several techniques. Generally, when a mixture of Fe3+ and Fe2+ is added to sodium hydroxide, alpha-Fe2O3 (the anti-ferromagnetic phase) is formed after the dehydration process of the hydroxide. In our case however, the phases formed at all the three temperatures were found to be ferro (ferri) magnetic, implying modification of the formation chemistry due to the specifics of our method. The nanoparticles synthesized at the lowest temperature exhibit magnetite phase, while increase in growth temperature to 95 degrees C leads to the maghemite phase.

10alow temperature synthesis10amaghemite10amagnetite10aNanoparticles1 aBhagwat, Shrikant1 aSingh, Hema1 aAthawale, Anjali1 aHannoyer, Beatrice1 aJouen, Samuel1 aLefez, Benoit1 aKundaliya, Darshan1 aPasricha, Renu1 aKulkarni, Shailaja1 aOgale, Satishchandra, B. uhttps://library.ncl.res.in/content/low-temperature-synthesis-magnetite-and-maghemite-nanoparticles-002255nas a2200253 4500008004100000022001400041245010200055210006900157260007100226300001400297490000700311520133300318100002901651700002301680700002301703700001801726700002001744700002301764700001601787700002401803700001801827700002701845856012901872 2008 eng d a0897-475600aChemical inhomogeneity and mixed-state ferromagnetism in diluted magnetic semiconductor Co : TiO20 aChemical inhomogeneity and mixedstate ferromagnetism in diluted  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB a1344-13520 v203 a

Diluted magnetic semiconductors (DMS) are among the most intensely investigated materials in recent times in view of their great application potential. Yet, they are also the most controversial because of the possibility of extrinsic effects attributable to dopant solubility and clustering, point defects, incorporation of unintentional impurities, etc. This has highlighted the central role of materials chemistry in rendering a specific microstate and property response. In this work, we provide a combined window of high-resolution scanning transmission electron microscopy and electron energy-loss spectrometry, X-ray absorption (XAS)/X-ray magnetic circular dichroism (XMCD), and magnetization measurements on epitaxial rutile CoxTi1-xO2 (x = 0-0.06) system (the first discovered oxide-DMS, which continues to be controversial) grown at low temperature (400 degrees C) under different ambient atmospheres. The study brings out a mixed-state scenario of ferromagnetism involving intrinsic DMS (uniform dopant distribution at low dopant concentration) and coupled cluster magnetism, involving cobalt associations within the matrix at higher concentrations. We also show that by matrix valence control during growth, it is possible to realize a uniform embedded cluster state and the related coupled cluster magnetism.

1 aOgale, Satishchandra, B.1 aKundaliya, Darshan1 aMehraeen, Shareghe1 aFu, Lian-feng1 aZhang, Shixiong1 aLussier, Alexandre1 aDvorak, Joe1 aBrowning, Nigel, D.1 aIdzerda, Yves1 aVenkatesan, Thirumalai uhttps://library.ncl.res.in/content/chemical-inhomogeneity-and-mixed-state-ferromagnetism-diluted-magnetic-semiconductor-co-002727nas a2200253 4500008004100000022001400041245013800055210006900193260007100262300001200333490000700345520177100352100002502123700001902148700002202167700002602189700001802215700001902233700002402252700002302276700001802299700002902317856012702346 2008 eng d a0897-475600aCo : CdS diluted magnetic semiconductor nanoparticles: radiation synthesis, dopant-defect complex formation, and unexpected magnetism0 aCo CdS diluted magnetic semiconductor nanoparticles radiation sy a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJAN a440-4460 v203 a

Incorporating a dopant into a nanoparticle is a nontrivial proposition in view of the size dependent surface versus bulk energy considerations and the intrinsic proximity of the surface to the interior, which facilitates migration to the surface. If realized and controlled, however, it can open up new avenues to novel nanomaterials. Some previous studies have shown the dopability of nanosystems but only with specific surface functionalization. Here, we demonstrate the successful dopant incorporation via a new route of pulsed high energy electron induced synthesis. We choose a system Co:CdS (dilutely cobalt doped cadmium sulfide) in view of the well-known application-worthy properties of CdS and the potential possibility of its conversion to a diluted magnetic semiconductor of interest to spintronics. By using various techniques, we show that matrix incorporation and uniform distribution of cobalt are realized in US nanocrystals without the need for additional chemical or physical manipulation. Optical and photoluminescence properties also support dopant incorporation. Interestingly, although magnetism is realized, it is weak, and it decreases at higher cobalt concentration. First principle density functional calculations are performed to understand this counterintuitive behavior. These calculations suggest that the introduction of parent cation or anion vacancies lead to magnetic moment reduction, albeit marginally. However, with some Co impurity fraction in the octahedral interstitial site inside the wurtzite cage, the magnetic moment drops down drastically. This study reveals that defect states may have an interesting role in dopant stabilization in nanosystems, with interesting system dependent consequences for the properties.

1 aBogle, Kashinath, A.1 aGhosh, Saurabh1 aDhole, Sanjay, D.1 aBhoraskar, Vasant, N.1 aFu, Lian-feng1 aChi, Miao-Fang1 aBrowning, Nigel, D.1 aKundaliya, Darshan1 aDas, Gour, P.1 aOgale, Satishchandra, B. uhttps://library.ncl.res.in/content/co-cds-diluted-magnetic-semiconductor-nanoparticles-radiation-synthesis-dopant-defect-0