3353-05-7Relevant articles and documents
Formation of monodisperse and shape-controlled MnO nanocrystals in non-injection synthesis: Self-focusing via ripening
Chen, Yongfen,Johnson, Eric,Peng, Xiaogang
, p. 10937 - 10947 (2007)
Formation of nearly monodiperse MnO nanocrystals by simple heating of Mn stearate in octadecene was studied systematically and quantitatively as a model for non-injection synthesis of nanocrystals. For controlling the shape of the nanocrystals, that is, rice, rods, peanuts, needles, and dots, either an activation reagent (ocadecanol) or an inhibitor (stearic acid) might be added prior to heating. The quantitative results of this typical non-injection system reveal that the formation of nearly monodisperse nanocrystals did not follow the well-known focusing of size distribution mechanism. A new growth mechanism, self-focusing enabled by inter-particle diffusion, is proposed. Different from the traditional focusing of size distribution , self-focusing not only affects the growth process of the nanocrystals, but may also play a role in controlling nucleation. Because of the simplicity of the reaction system, it was possible to also identify the chemical reactions associated with the growth and ripening of MnO nanocrystals with a variety of shapes. Through a recycling reaction path, water was identified as a decisive component in determining the kinetics for both growth and ripening in this system, although the reaction occurred at around 300°C.
Manganese doped fluorescent paramagnetic nanocrystals for dual-modal imaging
Sharma, Vijay Kumar,Gokyar, Sayim,Kelestemur, Yusuf,Erdem, Talha,Unal, Emre,Demir, Hilmi Volkan
, p. 4961 - 4966 (2014)
In this work, dual-modal (fluorescence and magnetic resonance) imaging capabilities of water-soluble, low-toxicity, monodisperse Mn-doped ZnSe nanocrystals (NCs) with a size (6.5 nm) below the optimum kidney cutoff limit (10 nm) are reported. Synthesizing Mn-doped ZnSe NCs with varying Mn2+ concentrations, a systematic investigation of the optical properties of these NCs by using photoluminescence (PL) and time resolved fluorescence are demonstrated. The elemental properties of these NCs using X-ray photoelectron spectroscopy and inductive coupled plasma-mass spectroscopy confirming Mn2+ doping is confined to the core of these NCs are also presented. It is observed that with increasing Mn2+ concentration the PL intensity first increases, reaching a maximum at Mn2+ concentration of 3.2 at% (achieving a PL quantum yield (QY) of 37%), after which it starts to decrease. Here, this high-efficiency sample is demonstrated for applications in dual-modal imaging. These NCs are further made water-soluble by ligand exchange using 3-mercaptopropionic acid, preserving their PL QY as high as 18%. At the same time, these NCs exhibit high relaxivity (≈2.95 mM-1 s-1) to obtain MR contrast at 25°C, 3 T. Therefore, the Mn2+ doping in these water-soluble Cd-free NCs are sufficient to produce contrast for both fluorescence and magnetic resonance imaging techniques.
ANTIFERROMAGNETISM OF QUASI TWO-DIMENSIONAL MANGANESE STEARATE.
Aviram,Pomerantz
, p. 297 - 300 (1982)
The magnetic properties of manganese stearate, a highly two-dimensional magnetic material, are found to change considerably when it is synthesized by a new procedure. Whereas earlier samples behaved like weak-ferromagnets with ordering temperatures about 5 K, the new material is an antiferromagnet with T//n equals 10 K. The reasons may be a change in the crystal structure.
Characterisation of metal carboxylates by Raman and infrared spectroscopy in works of art
Otero, Vanessa,Sanches, Diogo,Montagner, Cristina,Vilarigues, Mrcia,Carlyle, Leslie,Lopes, Joo A.,Melo, Maria J.
, p. 1197 - 1206 (2015/02/19)
This work introduces the complementary use of μ-Raman and μ-Fourier transform infrared (IR) spectroscopy for the detection of specific carbon chains and cations for the identification of metal carboxylates within oil paint microsamples. Metal carboxylates (metal soaps) form naturally when free fatty acids react with metal cations and may also be found as additives or degradation products. Twenty-two metal carboxylates were synthesised, and their spectra assembled in a reference database. Metal salts of cations commonly present in oil paintings were used, including lead, zinc, calcium, cadmium, copper and manganese. The fatty acids selected were the saturated acids palmitic (C1 6:0) and stearic (C18:0) and the polyunsaturated oleic acid (C1 8:1). Azelaic acid (C9 diacid), a product resulting from autoxidation of polyunsaturated acids, was also included. Metal carboxylates were characterised by Raman and IR spectroscopy, and their structures were confirmed by X-ray diffraction. Raman and IR spectroscopy proved to be complementary techniques for a full identification of the metal carboxylates in complex aged paint. Raman enables the differentiation of the carbon chain length in the C-C stretching region (1120-1040 cm-1), and IR distinguishes the metal cation in the COO- stretching absorption region (1650-1380cm-1). Principal component analysis was applied to the spectra in order to facilitate a fast and accurate method to discriminate between the different metal carboxylates and to aide in their identification. Finally, spectra from case studies were successfully projected in the principal component analysis models built, enabling a higher confidence level for the identification of copper palmitate and copper azelate in two 19th-century Portuguese oil paintings.
