Surface coordination chemistry of germanium nanocrystals synthesized by microwave-assisted reduction in oleylamine

Comprehensive solution NMR experiments reveal the binding modes of the native ligands to Ge nanocrystals synthesized via microwave-assisted reduction in oleylamine.

Download Full-text

Factors affecting Ge nanocrystal size in co-sputtered Ge+SiO2films

MRS Proceedings ◽

10.1557/proc-638-f14.1.1 ◽

2000 ◽

Vol 638 ◽

Author(s):

WK Choi ◽

V Ng ◽

YW Ho ◽

TB Chen ◽

V Ho

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Raman Spectroscopy ◽

Thermal Processing ◽

Rapid Thermal Processing ◽

Annealing Duration ◽

Factors Affecting ◽

Transmission Electron ◽

Germanium Nanocrystals ◽

Ge Nanocrystals

AbstractThe high resolution transmission electron microscopy and Raman spectroscopy results of germanium nanocrystals embedded in SiO2 synthesized by rapid thermal processing (RTA) have been presented. From the results of samples with different Ge concentrations, it was concluded that there is a narrow window in the Ge concentration that can produce nanocrystals. We also showed that it is possible to vary RTA duration or temperature to produce Ge nanocrystals with varying sizes. Our results therefore suggest that it is possible to utilize (i) annealing duration and; (ii) temperature to tune crystal sizes for optoelectronic applications.

Download Full-text

X-ray absorption spectroscopy studies for the determination of adsorption binding modes of selenium oxoanions onto iron and manganese based nanomaterials

MRS Proceedings ◽

10.1557/opl.2012.1613 ◽

2012 ◽

Vol 1480 ◽

Author(s):

Christina M. Gonzalez ◽

Jason G. Parsons ◽

Jeffrey Hernandez ◽

Jorge L. Gardea-Torresdey

Keyword(s):

Absorption Spectroscopy ◽

Binding Modes ◽

Edge Structure ◽

X Ray ◽

Microwave Assisted ◽

Spectroscopy Studies ◽

X Ray Absorption ◽

Binding Mechanisms ◽

Iron And Manganese

ABSTRACTIncreasing concentrations of selenium oxoanions in the environment are placing many animals at risk for reproduction failure and deformities. The understanding of binding mechanisms of selenium oxoanions to iron and manganese based oxide minerals could lead to enhanced understanding of selenium mobility in the environment. In this study, the binding mechanisms of selenium oxoanions, selenite and selenate, to non microwave-assisted and microwave-assisted synthetic Fe3O4, Mn3O4, and MnFe2O4 nanomaterials were investigated through the use of X-ray absorption spectroscopy. The X-ray absorption near-edge structure (XANES) spectroscopy studies revealed the oxidation state of selenite and selenate remains the same after binding occurs to all nanomaterials in pH 2, 4, or 6 environments. The binding modes of selenite and selenate were determined to be bidentate binuclear through use of Extended x-ray absorption fine structure (EXAFS) and were independent of nanomaterials, synthetic technique, and pH.

Download Full-text

Germanium Nanocrystals Embedded in Sapphire

MRS Proceedings ◽

10.1557/proc-880-bb5.22 ◽

2005 ◽

Vol 880 ◽

Author(s):

Q. Xu ◽

I.D. Sharp ◽

C.Y. Liao ◽

D. O. Yi ◽

J.W. Ager ◽

...

Keyword(s):

Melting Point ◽

Ion Beam ◽

Implantation Dose ◽

In Situ Tem ◽

Transmission Electron ◽

The Matrix ◽

Germanium Nanocrystals ◽

Ge Nanocrystals ◽

Modal Size

Abstract74Ge nanocrystals are formed in a sapphire matrix by ion implantation followed by thermal annealing. Transmission electron microscopy (TEM) of as-grown samples reveals that the nanocrystals are faceted and have a bi-modal size distribution. Notably, the matrix remains crystalline despite the large implantation dose and corresponding damage. Embedded nanocrystals experience large compressive stress relative to bulk, as measured by Raman spectroscopy of the zone center optical phonon. In contrast, ion-beam-synthesized nanocrystals embedded in silica are observed to be spherical and experience considerably lower stresses. Also, in situ TEM reveals that nanocrystals embedded in sapphire melt very close to the bulk melting point (Tm= 936 °C) whereas those embedded in silica exhibit a significant melting point hysteresis around Tm.

Download Full-text

A Practical Perspective on the Roles of Solution NMR Spectroscopy in Drug Discovery

Molecules ◽

10.3390/molecules25132974 ◽

2020 ◽

Vol 25 (13) ◽

pp. 2974

Author(s):

Qingxin Li ◽

CongBao Kang

Keyword(s):

Drug Discovery ◽

Nmr Spectroscopy ◽

Ligand Binding ◽

Conformational Changes ◽

Solution Nmr ◽

Binding Modes ◽

Protein Ligand Interactions ◽

Ligand Interactions ◽

Solution Nmr Spectroscopy ◽

Solution Nuclear Magnetic Resonance

Solution nuclear magnetic resonance (NMR) spectroscopy is a powerful tool to study structures and dynamics of biomolecules under physiological conditions. As there are numerous NMR-derived methods applicable to probe protein–ligand interactions, NMR has been widely utilized in drug discovery, especially in such steps as hit identification and lead optimization. NMR is frequently used to locate ligand-binding sites on a target protein and to determine ligand binding modes. NMR spectroscopy is also a unique tool in fragment-based drug design (FBDD), as it is able to investigate target-ligand interactions with diverse binding affinities. NMR spectroscopy is able to identify fragments that bind weakly to a target, making it valuable for identifying hits targeting undruggable sites. In this review, we summarize the roles of solution NMR spectroscopy in drug discovery. We describe some methods that are used in identifying fragments, understanding the mechanism of action for a ligand, and monitoring the conformational changes of a target induced by ligand binding. A number of studies have proven that 19F-NMR is very powerful in screening fragments and detecting protein conformational changes. In-cell NMR will also play important roles in drug discovery by elucidating protein-ligand interactions in living cells.

Download Full-text

Biological Applications of Thiocarbohydrazones and Their Metal Complexes: A Perspective Review

Pharmaceuticals ◽

10.3390/ph13010004 ◽

2019 ◽

Vol 13 (1) ◽

pp. 4 ◽

Cited By ~ 4

Author(s):

Carmela Bonaccorso ◽

Tiziano Marzo ◽

Diego La Mendola

Keyword(s):

Coordination Chemistry ◽

Metal Complexes ◽

Metal Binding ◽

Structural Diversity ◽

Binding Modes ◽

Main Research ◽

Research Areas ◽

Wide Range ◽

Clinical Drugs ◽

Sulfur Donor Ligands

Although organic compounds account for more than 99% of currently approved clinical drugs, the established clinical use of cisplatin in cancer or auranofin in rheumatoid arthritis have paved the way to several research initiatives to identify metal-based drugs for a wide range of human diseases. Nitrogen and sulfur donor ligands, characterized by different binding motifs, have been the subject in recent years of one of the main research areas in coordination chemistry. Among the nitrogen/sulfur compounds, very little is known about thiocarbohydrazones (TCH), the higher homologues of the well-known thiosemicarbazones (TSC), and their metal complexes. The extra hydrazine moiety provides the ligands of variable metal binding modes, structural diversity and promising biological implications. The interesting coordination chemistry of TCH has mainly been focused on symmetric derivatives, which are relatively simple to synthesize while few examples of asymmetric ligands have been reported. This informative review on TCHs and their metal complexes will be helpful for improving the design of metal-based pharmaceuticals for applications ranging from anticancer to antinfective therapy.

Download Full-text

Plasma Synthesis of Highly Monodisperse Ge Nanocrystals and Self-Assembly of Dense Nanocrystal Layers

MRS Proceedings ◽

10.1557/proc-0974-cc05-08 ◽

2006 ◽

Vol 974 ◽

Cited By ~ 1

Author(s):

Ryan Gresback ◽

Zak Holman ◽

Uwe Kortshagen

Keyword(s):

Size Distribution ◽

Self Assembly ◽

Crystal Size ◽

Nonthermal Plasma ◽

Nanocrystal Size ◽

Plasma Synthesis ◽

Colloidal Solutions ◽

Germanium Nanocrystals ◽

20 Nm ◽

Ge Nanocrystals

ABSTRACTGermanium nanocrystals have been synthesized using a low-pressure, nonthermal plasma approach. The nanocrystal size can be adjusted between 4-20 nm by varying the plasma parame-ters, and the size distribution is relatively narrow with standard deviations of 10-20% of the av-erage crystal size. Stable colloidal solutions of the germanium crystals have been prepared by grafting organic alkene ligands onto the nanocrystal surfaces. When drop-cast from solution onto TEM grids, the nanocrystals form densely packed films.

Download Full-text

Negative Photoconductivity and Memory Effects of Germanium Nanocrystals Embedded in HfO2 Dielectric

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2006.17931 ◽

2006 ◽

Vol 6 (1) ◽

pp. 205-208 ◽

Cited By ~ 7

Author(s):

Shiye Wang ◽

Weili Liu ◽

Miao Zhang ◽

Zhitang Song ◽

Chenglu Lin ◽

...

Keyword(s):

Forward Bias ◽

Electron Beam Evaporation ◽

Flat Band ◽

Mis Structure ◽

Negative Photoconductivity ◽

Transmission Electron ◽

Optimal Annealing Temperature ◽

Tunnel Layer ◽

Germanium Nanocrystals ◽

Ge Nanocrystals

A metal-insulator-semiconductor (MIS) structure containing an HfO2/SiO2 stack tunnel layer, isolated Germanium (Ge) nanocrystals, and an HfO2 capping layer, was obtained by an electron-beam evaporation method. A high-resolution transmission electron microscopy (HRTEM) study revealed that uniform and pronounced Ge nanocrystals had formed after annealing. Raman spectroscopy provided evidence for the formation of Ge–Ge bonds and the optimal annealing temperature for the crystallization ratio of the Ge. The electric properties of the MIS structure were characterized by capacitance-voltage (C-V) and current–voltage (I–V) measurements at room temperature. Negative photoconductivity was observed when the structure was under a forward bias, which screened the bias voltage, resulting in a decrease in the current at a given voltage and a negative shift in flat band voltage. A relatively high stored charge density of 3.27 × 1012 cm−2 was also achieved.

Download Full-text