Zinc–Histidine as Nucleation Centers for Growth of ZnS Nanocrystals

In this study, water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface with conventional and simple structured amino acid ligands: L-Glycine and L-Alanine. The ZnS:Mn-Gly and ZnS:Mn-Ala nanocrystal powders were characterized by XRD, HR-TEM, EDXS, ICP-AES, and FT-IR spectroscopy. The optical properties were measured by UV-Visible and photoluminescence (PL) spectroscopy. The PL spectra for the ZnS:Mn-Gly and ZnS:Mn-Ala showed broad emission peaks at 599 nm and 607 nm with PL efficiencies of 6.5% and 7.8%, respectively. The measured average particle size from the HR-TEM images were 6.4 ± 0.8 nm (ZnS:Mn-Gly) and 4.1 ± 0.5 nm (ZnS:Mn-Ala), which were also supported by Debye-Scherrer calculations. In addition, the degree of aggregation of the nanocrystals in aqueous solutions were measured by a hydrodynamic light scattering method, which showed formation of sub-micrometer size aggregates for both ZnS:Mn-Gly (273 ± 94 nm) and ZnS:Mn-Ala (233 ± 34 nm) in water due to the intermolecular attraction between the capping amino acids molecules. Finally, the cytotoxic effects of ZnS:Mn-Gly and ZnS:Mn-Ala nanocrsystals over the growth of wild type E. coli were investigated. As a result, no toxicity was shown for the ZnS:Mn-Gly nanocrystal in the colloidal concentration region from 1 µg/mL to 1000 µg/mL, while ZnS:MnAla showed significant toxicity at 100 µg/mL.

Section: Introductionmentioning

confidence: 99%

Biological Toxicities and Aggregation Effects of ʟ-Glycine and ʟ-Alanine Capped ZnS:Mn Nanocrystals in Aqueous Solution

Park¹,

Song²,

Kong³

et al. 2014

“…21 A solution of ZnSO 4 ·5H 2 O (1.44 g, 5 mmol) in 50 mL of water was slowly added to a 50 mL aqueous mixture containing 1.0 mmols of polyethylene oxide molecules at ambient temperature. In another flask, MnSO 4 · H 2 O (0.02 g, 0.1 mmol) and Na 2 S (0.40 g, 5 mmol) were dissolved in 20 mL of DI water.…”

Section: Methodsmentioning

confidence: 99%

Syntheses and Optical Characterizations of ZnS:Mn Nanocrystals Capped by Polyethylene Oxide Molecules of Varying Molecular Weights

Kim¹,

Hwang²

2010

Low-dimensional semiconducting nano-materials have gained significant attention over the past decade.1,2 These materials have found a wide range of applications in non-linear optics or electronic devices, and more recently as some bio-imaging or labeling agents due to their unique physical, chemical and optical properties. [3][4][5] Among the most important characteristics of these semiconducting nanocrystals is their optical properties which can vary greatly with the size of the nanocrystals, because the corresponding band gap energies differ even between materials of identical chemical composition. 6,7 ZnS:Mn nanocrystals (an orange light emitting nanophosphor) have attracted substantial interest on account of their high quantum yields and stability at ambient temperature, essential properties of commercial electro-luminescence devices.8 Considerable progress has been made in the synthetic techniques used to create such nanocrystals including gas, solid, and aqueous solution reactions via the thermal decomposition of organometallic precursors. However, these methods often require high temperatures and pressures and even the use of bio-hazardous substances. 9Water-dispersible semiconducting nanocrystals were developed especially for fluorescent labeling agents in living cells as an advanced bio-imaging technique. [10][11][12] They are expected to replace complicated or hazardous radioactive detection, and have formed the basis of very sensitive biological assays. In addition, semiconducting nanocrystals are much more efficient, sensitive and stable than the organic dyes currently used. Unfortunately, most highly luminescent semiconductor nanocrystals are grown in non-polar media, making them largely incompatible with any biological system. To date, there are several reports of solubilized hydrophobic nanocrystals in water, created by modifying the crystals' surfaces;13-15 however, generating water-dispersible and bio-compatible semiconductor nanocrystals which maintain high quantum efficiency and stability in a biological system still remains a great challenge. Several biocompatible amino acid molecule-capped ZnS:Mn nanocrystals have been synthesized in this laboratory. 16,17 In addition, more recently, we have synthesized mercaptoacetate (MAA) molecules capped water-dispersible ZnS:Mn nanocrystal. The surface capping MAA molecules were characterized by FT-Raman spectroscopy, and the specific coordination mode of the MAA molecule was determined by a DFT calculation. 18This paper describes the synthesis of water-dispersible ZnS: Mn nanocrystals whose surfaces are capped by polyethylene oxide molecules of varying molecular weight. Their physical and optical properties are also investigated. Historically, the abbreviations PEG (polyethylene glycol) and PEO (polyethylene oxide) refer to oligomers or polymers of ethylene oxide molecules. PEG has tended to refer to oligomers and polymers with a molecular mass below 20,000 g/mol, while PEO to polymers with a molecular mass above that. 19 This article refers to all pol...

“…There are several reports of solubilized hydrophobic nanocrystals in water. 7,8 The most common synthetic scheme for the water-dispersible nanocrystal is to use polar surface capping ligands such as mercaptoacetate (MAA) and sulfodiisooctyl succinate (AOT) molecules to form a micelle structure where the negative charges are distributed on the surface. In addition, it was shown that the photoluminescence efficiency for the AOT capped ZnS:Mn nanocrystal increased up several times after the surface modification.…”

Section: Introductionmentioning

confidence: 99%

Syntheses and Characterizations of Serine and Threonine Capped Water-Dispersible ZnS:Mn Nanocrystals and Comparison Study of Toxicity Effects on the growth of E. coli by the Methionine, Serine, Threonine, and Valine Capped ZnS:Mn Nanocrystals

Lim¹,

Park²,

Byun³

et al. 2012

Water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystals with conventional aminoacids ligands: serine and threonine. The aminoacids capped ZnS:Mn nanocrystal powders were characterized by XRD, HR-TEM, EDXS, ICP-AES and FT-IR spectroscopy. The optical properties were also measured by UV/Vis and solution photoluminescence (PL) spectroscopies in aqueous solvents. The solution PL spectra showed broad emission peaks around 600 nm with PL efficiencies of 9.7% (ZnS:Mn-Ser) and 15.4% (ZnS:Mn-Thr) respectively. The measured particle sizes for the aminoacid capped ZnS:Mn nanocrystals by HR-TEM images were about 3.0-4.0 nm, which were also supported by Debye-Scherrer calculations. In addition, cytotoxic effects of four aminoacids capped ZnS:Mn nanocrsystals over the growth of wild type E. coli were investigated. Although toxicity in the form of growth inhibition was observed with all the aminoacids capped ZnS:Mn nanocrystals at higher dose (1 mg/mL), ZnS:Mn-Met and ZnS:Mn-Thr appeared non-toxic at doses less than 100 µg/mL. Low biological toxicities were seen at doses less than 10 µg/ mL for all nanocrystals.