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Raman crystallinity

Smriti Sahu, Rituraj Sharma, K V Adarsh, Anbarasu Manivannan
Rapid and reversible switching between amorphous and crystalline phases of phase-change material promises to revolutionize the field of information processing with a wide range of applications including electronic, optoelectronics, and photonic memory devices. However, achieving faster crystallization is a key challenge. Here, we demonstrate femtosecond-driven transient inspection of ultrafast crystallization of as-deposited amorphous Ge1Sb2Te4 and Ge1Sb4Te7 thin films induced by a series of 120 fs laser pulses...
January 10, 2018: Applied Optics
Joanna Borowiec, William P Gillin, Maureen A C Willis, Filippo S Boi, Y He, J Q Wen, S L Wang, Leander Schulz
In this study, a direct sulfidation reaction of ammonium perrhenate (NH4ReO4) leading to a synthesis of rhenium disulfide (ReS2) is demonstrated. These findings reveal the first example of a simplistic bottom-up approach to the chemical synthesis of crystalline ReS2. The reaction presented here takes place at room temperature, in an ambient and solvent-free environment and without the necessity of a catalyst. The atomic composition and structure of the as-synthesized product were characterized using several analysis techniques including energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and differential scanning calorimetry...
January 11, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Wenbo Xin, Igor M De Rosa, Peiyi Ye, Joseph Severino, Chao Li, Xunqian Yin, Mark S Goorsky, Larry Carlson, Jenn-Ming Yang
Assembling Au nanocrystals with tunable dimensions and shapes on graphene templates has attracted increasing attention recently. However, directly growing anisotropic Au nanobelts on a graphene support has been rarely reported. Here, a facile, one-pot, and surfactant-free route is demonstrated to synthesize well-defined Au nanobelts with the induction of a multilayer graphene (mlG) template. The obtained Au nanobelts are single-crystalline with a preferable (111) orientation. More importantly, their structural evolution starting from Au clusters is systematically investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM)...
January 11, 2018: Nanoscale
Hong Wang, Yu Chen, Martial Duchamp, Qingsheng Zeng, Xuewen Wang, Siu Hon Tsang, Hongling Li, Lin Jing, Ting Yu, Edwin Hang Tong Teo, Zheng Liu
Layered transition metal (Ti, Ta, Nb, etc.) dichalcogenides are important prototypes for the study of the collective charge density wave (CDW). Reducing the system dimensionality is expected to lead to novel properties, as exemplified by the discovery of enhanced CDW order in ultrathin TiSe2 . However, the syntheses of monolayer and large-area 2D CDW conductors can currently only be achieved by molecular beam epitaxy under ultrahigh vacuum. This study reports the growth of monolayer crystals and up to 5 × 105 µm2 large films of the typical 2D CDW conductor-TiSe2 -by ambient-pressure chemical vapor deposition...
January 10, 2018: Advanced Materials
Felix Rosenburg, Emanuel Ionescu, Norbert Nicoloso, Ralf Riedel
The microstructure of segregated carbon in silicon oxycarbide (SiOC), hot-pressed at T = 1600 °C and p = 50 MPa, has been investigated by VIS Raman spectroscopy (λ = 514 nm) within the temperature range 25-1000 °C in air. The occurrence of the G, D' and D bands at 1590, 1620 and 1350 cm-1, together with a lateral crystal size La < 10 nm and an average distance between lattice defects LD ≈ 8 nm, provides evidence that carbon exists as nano-crystalline phase in SiOC containing 11 and 17 vol % carbon. Both samples show a linear red shift of the G band up to the highest temperature applied, which is in agreement with the description of the anharmonic contribution to the lattice potential by the modified Tersoff potential...
January 9, 2018: Materials
Cheng Li, Ye Wu, Bingchen Deng, Yujun Xie, Qiushi Guo, Shaofan Yuan, Xiaolong Chen, Maruf Bhuiyan, Zishan Wu, Kenji Watanabe, Takashi Taniguchi, Hailiang Wang, Judy J Cha, Michael Snure, Yingwei Fei, Fengnian Xia
Black phosphorus (BP) has recently attracted significant attention due to its exceptional physical properties. Currently, high-quality few-layer and thin-film BP are produced primarily by mechanical exfoliation, limiting their potential in future applications. Here, the synthesis of highly crystalline thin-film BP on 5 mm sapphire substrates by conversion from red to black phosphorus at 700 °C and 1.5 GPa is demonstrated. The synthesized ≈50 nm thick BP thin films are polycrystalline with a crystal domain size ranging from 40 to 70 µm long, as indicated by Raman mapping and infrared extinction spectroscopy...
January 3, 2018: Advanced Materials
Congyan Zhang, Ming Yu
Atomic layers of GaP and InP binary compounds with unique anisotropic structural, electronic, and mechanical properties have been predicted from the first principle molecular dynamics simulations. These new members of phosphide binary compounds family stabilize to a sandwiched two-dimensional (2D) crystalline structure with orthorhombic lattices symmetry and high buckling of 2.14 Å-2.46 Å. Their vibration modes are similar to those of phosphorene with six Raman active modes ranging from ~80 cm-1 to 400 cm-1...
January 9, 2018: Nanotechnology
Gregorio Dal Sasso, Ivana Angelini, Lara Maritan, Gilberto Artioli
Retrieving the pristine chemical or isotopic composition of archaeological bones is of great interest for many studies aiming to reconstruct the past life of ancient populations (i.e. diet, mobility, palaeoenvironment, age). However, from the death of the individual onwards, bones undergo several taphonomic and diagenetic processes that cause the alteration of their microstructure and composition. A detailed study on bone diagenesis has the double purpose to assess the preservation state of archaeological bones and to understand the alteration pathways, thus providing evidence that may contribute to evaluate the reliability of the retrieved information...
March 1, 2018: Talanta
Li Ji, Hsien-Yi Hsu, Jack Lee, Allen J Bard, Edward T Yu
Hybrid organic-inorganic halide perovskites (HOIPs) have recently attracted tremendous attention because of their excellent semiconducting and optoelectronic properties, which exist despite their morphology and crystallinity being far inferior to those of more mature semiconductors, such as silicon and III-V compound semiconductors. Heteroepitaxy can provide a route to achieving high performance HOIP devices when high crystalline quality and smooth morphology are required, but work on heteroepitaxial HOIPs has not previously been reported...
January 5, 2018: Nano Letters
Jinping Fu, Lin Cui, Congbin Yang, Hui Xiong, Guobin Ren, Xingyuan Ma, Qiufang Jing, Fuzheng Ren
The solvent-shift method was used to identify appropriate polymers that inhibit the growth of felodipine crystals by monitoring particle size in supersaturated drug solutions in the presence of different polymers. We speculated that there would be an intermolecular interaction between the selected polymer (zein) and felodipine by extrapolating the inhibitory effect on crystal growth and then used the selected polymer as a carrier to prepare solid dispersions. The formulations were characterized by crystalline properties, thermodynamics of mixing, dissolution behavior, and physical stability...
January 4, 2018: AAPS PharmSciTech
Joanna Borowiec, William P Gillin, Maureen Willis, Filippo Boi, Yi He, Jiqiu Wen, Shanling Wang, Leander Schulz
In this study, a direct sulfidation reaction of ammonium perrhenate (NH<sub>4</sub>ReO<sub>4</sub>) leading to a synthesis of rhenium disulfide (ReS<sub>2</sub>) is demonstrated. These finding reveal the first example of a simplistic bottom-up approach to the chemical synthesis of crystalline ReS<sub>2</sub>. The reaction presented here takes place at room temperature, in an ambient and solvent-free environment and without the necessity of a catalyst. The atomic composition and structure of the as-synthesized product were characterized using several analysis techniques including energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, thermogravimetric analysis (TGA) and differential scannig calorimetry (DSC)...
December 29, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Minoo Tasbihi, Kamila Kočí, Ivana Troppová, Miroslava Edelmannová, Martin Reli, Libor Čapek, Reinhard Schomäcker
The photocatalytic reduction of CO2 with H2O was investigated using Cu/TiO2 photocatalysts in aqueous solution. For this purpose, Cu/TiO2 photocatalysts (with 0.2, 0.9, 2, 4, and 6 wt.% of Cu) have been synthesized via sol-gel method. The photocatalysts were extensively characterized by means of inductively coupled plasma optical emission spectrometry (ICP-OES), N2 physisorption (BET), XRD, UV-vis DRS, FT-IR, Raman spectroscopy, TEM-EDX, and photoelectrochemical measurements. The as-prepared photocatalysts contain anatase as a major crystalline phase with a crystallite size around 13 nm...
December 28, 2017: Environmental Science and Pollution Research International
Leonardo Giorgi, Theodoros Dikonimos, Rossella Giorgi, Francesco Buonocore, Giuliana Faggio, Giacomo Messina, Nicola Lisi
The present work demonstrates that, upon anodic polarization in a aqueous fluoride-containing electrolyte, TiO2 nanotube array films can be formed with a well-defined crystalline phase, rather than an amorphous one. The crystalline phase was obtained avoiding any high temperature annealing. We studied of the nanotubes formation in HF/H2O medium and the development of crystalline grains on the nanotube wall and we found a facile way to achieve crystalline TiO2 nanotube arrays through one-step anodization. The film crystallinity resulted to be influenced by the synthesis parameters and the optimization of the electrolyte composition and anodization conditions (applied voltage and time) has been carried out...
December 28, 2017: Nanotechnology
Karan Kumar Gupta, R M Kadam, N S Dhoble, S P Lochab, S J Dhoble
The present paper reports on the γ-ray and C6+ ion beam induced effect on the structural and luminescence properties of Eu doped LiNaSO4 phosphors synthesized via wet the chemical method. The material was irradiated by 60Co and 137Cs γ-rays and 75 MeV C6+ ions in a fluence range varying from 2 × 1010 to 1 × 1012 ion per cm2. The ion induced modified properties were investigated using X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL), thermoluminescence (TL) and electron paramagnetic resonance (EPR) studies...
December 20, 2017: Physical Chemistry Chemical Physics: PCCP
Yosuke Kuroiwa, Kenjirou Higashi, Keisuke Ueda, Keiji Yamamoto, Kunikazu Moribe
We investigated the formation and stabilization mechanisms of indomethacin (IMC)/poloxamer 407 nanosuspensions. Stable nanosuspensions were prepared via 24 h wet-milling of three IMC forms (γ form, α form, and amorphous) with poloxamer 407. Cryogenic-transmission electron microscopy images of nanoparticles obtained using γ-form IMC indicated a rhombic-plate shape. In contrast, needle-like nanoparticles were observed in the nanosuspensions of α-form and amorphous IMC. Suspended-state cross polarization 13C NMR and Raman measurements directly detected the molecular states of IMC in nanosuspensions...
December 12, 2017: International Journal of Pharmaceutics
Sukanya Ramaraj, Sakthivel Mani, Shen-Ming Chen, Thangavelu Kokulnathan, Bih-Show Lou, M Ajmal Ali, A A Hatamleh, Fahad M A Al-Hemaid
Recently, the multiferroic material has fabulous attention in numerous applications owing to its excellent electronic conductivity, unique mechanical property, and higher electrocatalytic activity, etc. In this paper, we reported that the synthesis of bismuth ferrite (BiFeO3) nanosheets integrated functionalized carbon nanofiber (BiFeO3 NS/F-CNF) nanocomposite using a simple hydrothermal technique. Herein, the structural changes and crystalline property of prepared BiFeO3 NS/F-CNF nanocomposite were characterized using Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS)...
December 6, 2017: Journal of Colloid and Interface Science
D Di Genova, S Kolzenburg, S Wiesmaier, E Dallanave, D R Neuville, K U Hess, D B Dingwell
The most viscous volcanic melts and the largest explosive eruptions on our planet consist of calcalkaline rhyolites. These eruptions have the potential to influence global climate. The eruptive products are commonly very crystal-poor and highly degassed, yet the magma is mostly stored as crystal mushes containing small amounts of interstitial melt with elevated water content. It is unclear how magma mushes are mobilized to create large batches of eruptible crystal-free magma. Further, rhyolitic eruptions can switch repeatedly between effusive and explosive eruption styles and this transition is difficult to attribute to the rheological effects of water content or crystallinity...
December 13, 2017: Nature
Mikhail Chubarov, Tanushree H Choudhury, Xiaotian Zhang, Joan M Redwing
There is significant interest in the growth of single crystal monolayer and few-layer films of transition metal dichalcogenides (TMD) and other 2D materials for scientific exploration and potential applications in optics, electronics, sensing, catalysis and others. The characterization of these materials is crucial in determining the properties and hence the applications. The ultra-thin nature of 2D layers presents a challenge to the use of X-ray diffraction (XRD) analysis with conventional Bragg-Brentano geometry in analyzing the crystallinity and epitaxial orientation of 2D films...
December 14, 2017: Nanotechnology
Nithya Pandiyan, Balaji Murugesan, Jegatheeswaran Sonamuthu, Selvam Samayanan, Sundrarajan Mahalingam
In this study, a typical green synthesis route has approached for CeO2/ZrO2 core metal oxide nanoparticles using ionic liquid mediated Justicia adhatoda extract. This synthesis method is carried out at simple room temperature condition to obtain the core metal oxide nanoparticles. XRD, SEM and TEM studies employed to study the crystalline and surface morphological properties under nucleation, growth, and aggregation processes. CeO2/ZrO2 core metal oxides display agglomerated nano stick-like structure with 20-45nm size...
November 28, 2017: Journal of Photochemistry and Photobiology. B, Biology
Chen Chao, Jinglin Yu, Shuo Wang, Les Copeland, Shujun Wang
This study aimed to reveal the mechanism of formation of complexes between native maize starch (NMS) and different types of lipids, namely palmitic acid (PA), monopalmitate glycerol (MPG), dipalmitate glycerol (DPG) and tripalmitate glycerol (TPG). The complexing index followed the order of MPG (96.3%) > PA (41.8%) > TPG (8.3%) > DPG (1.1%), indicating that MPG formed more complexes with NMS than PA, and that few complexes were formed between NMS and DPG and TPG. The NMS-PA complex presented higher thermal transition temperatures and lower enthalpy change than the NMS-MPG complex, indicating that although MPG formed more starch complexes, they had less stable crystalline structures than the complex between NMS and PA...
December 12, 2017: Journal of Agricultural and Food Chemistry
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