Structural analysis of x-ray irradiated carbon nanostructures

One of the new and promising applications of carbon nanostructures (CNs) are various dosimetry devices. Namely, these devices based on carbon nanostructures can provide the possibility for device miniaturization, lower costs, and high scale manufacturing. So, very important factors for the device processing need a quantitative study of the effects of relatively lower doses of X-ray irradiation on the carbon nanostructures. In this study, we present the effects of relatively low doses of x-ray irradiation on the physical and chemical properties of three carbon-based nanostructures (multiwall carbon nanotubes - MWCNTs, graphene - G, hybrid - G/MWCNTs). We have used a range of characterization techniques including scanning electron microscopy, Raman and FTIR spectroscopy, thermal and particle size analysis. Specifically, it was found that irradiation exposure results in a reduction in the sp2 nature of all three carbon-based nanostructures

Decentralized Coordination of Temperature Control in Multiarea Premises

With local control of a large number of objects that mutually influence each other, the problem of coordinating local control systems to achieve the best overall result arises. If the structure of the system (the number of control objects and the parameters of interaction) can change frequently, then the process of setting up/training a centralized coordinator will take an unacceptably large part of the action time and require a significant amount of resources. In this work, the use of decentralized coordination is proposed to solve the problem. As a basic task for research on decentralized coordination control of objects that mutually influence each other, stabilizing the comfort temperatures was set in multizone rooms using movable heaters. Providing individual thermal comfort is an important problem. In particular, there are many multiarea premises with conflicting requirements for the comfort of habitats. This problem can be solved with the help of movable heaters and air conditioners. However, the presence of heat flows between areas with different specified parameters makes it difficult to adjust them. The work aims to improve the quality of thermal control in multiarea premises with a dynamic structure for the location of movable heaters. To achieve this goal, we proposed the concept of Movable Smart Heaters (MSH). A group of Movable Smart Heaters that could influence each other and exchange information forms a dynamic system with a changing structure since switching on/off or moving one MSH to another area changes the mutual influence and connections in the system. The criteria for control quality are defined and evaluated. The proposed coordination algorithms make it possible to optimize the operating modes of the system automatically when its structure and/or settings are changed. Simulation of the system is performed with the use of a worked-out modelling library in Scilab. The results of comparing the MSH system’s efficiency show an increase in comfort while reducing energy consumption

Effect of non-stoichiometry of initial reagents on morphological and structural properties of perovskites CH3NH3PbI3

Abstract The properties of films of organic-inorganic perovskites CH3NH3PbI2.98Cl0.02 depending on the ratio of starting reagents in solutions (PbI2:{CH3NH3I + CH3NH3Cl}) has been investigated. It was found that the formation of the perovskite structure with the ratio of the initial reagents PbI2: CH3NH3I = 1:1 occurs at 70–80 °C, and with the increase of the temperature of thermal treatment to 120 °C, the thermal destruction of the perovskite begins. When the ratio of the starting reagents PbI2: CH3NH3I = 1:2, the formation of the perovskite structure occurs through the intermediate compound (CH3NH3)2PbI4, and when the ratio is 1:3—(CH3NH3)3PbI5 and (CH3NH3)2PbI4. Independent on the ratio of the initial components (CH3NH3I:PbI2), the ratio between the content of lead and iodine in the films remains unchanged, that is why a significant difference in the film properties could be explained by the anisotropy of the particle shape, which is consistent with the data of electron microscopy and X-ray diffractometry

Additional file 1: of Theoretical and Experimental Study of Phonon Spectra of Bulk and Nano-Sized MoS2 Layer Crystals

Hamiltonian of layer-type crystal. (DOCX 180 kb

Raman and X-ray Photoemission Identification of Colloidal Metal Sulfides as Potential Secondary Phases in Nanocrystalline Cu 2 ZnSnS 4 Photovoltaic Absorbers

The aim of this study is to establish reliable spectroscopic fingerprints of compounds that may form as secondary phases in Cu2ZnSnS4 (CZTS) nanocrystals (NCs) synthesized by “green” colloidal chemistry directly in aqueous solutions or during post-processing of NC films for photovoltaic application. For this purpose, we investigated a series of binary and ternary compound NCs synthesized under the same conditions as the quaternary CZTS NCs. The capabilities of combined Raman and X-ray photoemission (XPS) spectroscopies are used to identify these compounds formed separately and define spectral fingerprints for distinguishing them as possible secondary phases in the spectra of CZTS NCs. Besides the conventional analysis of element ratios and chemical shifts of the core-level peaks in the XPS spectra, the careful analysis of Auger lines and modified Auger parameters are applied to distinguish otherwise similar spectral contributions of different compounds. In the case of CuxS NCs the binding energy separation between the Cu2p3/2 and S2p3/2 core-levels is used as the additional fingerprint. As a criterion of a certain crystal structure in Raman spectroscopy, we rely not only on frequency positions of particular phonon modes but also on selective probing of different compounds at different (resonant) excitation wavelengths. The reasons of controversial previous reports on Raman spectra of CuxS are revealed and characteristic Raman spectra of Sn-poor Cu-Sn-S and Sn-poor Zn-Sn-S are proposed. For Cu-Zn-S, a mixture of CuxS and ZnS is formed under the given mild conditions rather than ternary compounds or alloys

Spectroscopic Study of Phytosynthesized Ag Nanoparticles and Their Activity as SERS Substrate

The affordable and scalable synthesis of noble metal nanoparticles that are biocompatible without additional functionalization steps has been a growing field of research, stimulated by numerous prospective applications of these NPs. In the case of phytosynthesized or biogenic noble metal NPs, the mechanism of NP stabilization by biomolecules contained in each particular plant extract or living organism determines the possible applications of these NPs. In this work, we investigated Ag NPs synthesized in water with plant extracts of common toothwort (Lathraea squamaria) and two species of pepper (Capsicum annuum and Capsicum chinense). From FTIR and XPS, we drew conclusions about the composition of the functional groups and molecules that stabilize NPs in each extract, such as polysaccharide compounds (pectins, cellulose, glycosides and phenolic acids). Distinct characteristic IR features of amide I and amide II proteins were observed, which are common in plant extracts, while features of amide III were not distinctly observed in our extracts. A Raman spectroscopy study revealed weak own-SERS activity of the biomolecules of the extract and high efficiency of the NPs in the enhancement of “external” analytes, such as dyes and antibodies. This is the first report of the efficient SERS application of phytosynthesized Ag NPs

Spectroscopic Study of Phytosynthesized Ag Nanoparticles and Their Activity as SERS Substrate

The affordable and scalable synthesis of noble metal nanoparticles that are biocompatible without additional functionalization steps has been a growing field of research, stimulated by numerous prospective applications of these NPs. In the case of phytosynthesized or biogenic noble metal NPs, the mechanism of NP stabilization by biomolecules contained in each particular plant extract or living organism determines the possible applications of these NPs. In this work, we investigated Ag NPs synthesized in water with plant extracts of common toothwort (Lathraea squamaria) and two species of pepper (Capsicum annuum and Capsicum chinense). From FTIR and XPS, we drew conclusions about the composition of the functional groups and molecules that stabilize NPs in each extract, such as polysaccharide compounds (pectins, cellulose, glycosides and phenolic acids). Distinct characteristic IR features of amide I and amide II proteins were observed, which are common in plant extracts, while features of amide III were not distinctly observed in our extracts. A Raman spectroscopy study revealed weak own-SERS activity of the biomolecules of the extract and high efficiency of the NPs in the enhancement of “external” analytes, such as dyes and antibodies. This is the first report of the efficient SERS application of phytosynthesized Ag NPs

Colloidal Cu-Zn-Sn-Te Nanocrystals: Aqueous Synthesis and Raman Spectroscopy Study

Cu-Zn-Sn-Te (CZTTe) is an inexpensive quaternary semiconductor that has not been investigated so far, unlike its intensively studied CZTS and CZTSe counterparts, although it may potentially have desirable properties for solar energy conversion, thermoelectric, and other applications. Here, we report on the synthesis of CZTTe nanocrystals (NCs) via an original low-cost, low-temperature colloidal synthesis in water, using a small-molecule stabilizer, thioglycolic acid. The absorption edge at about 0.8–0.9 eV agrees well with the value expected for Cu2ZnSnTe4, thus suggesting CZTTe to be an affordable alternative for IR photodetectors and solar cells. As the main method of structural characterization multi-wavelength resonant Raman spectroscopy was used complemented by TEM, XRD, XPS as well as UV-vis and IR absorption spectroscopy. The experimental study is supported by first principles density functional calculations of the electronic structure and phonon spectra. Even though the composition of NCs exhibits a noticeable deviation from the Cu2ZnSnTe4 stoichiometry, a common feature of multinary NCs synthesized in water, the Raman spectra reveal very small widths of the main phonon peak and also multi-phonon scattering processes up to the fourth order. These factors imply a very good crystallinity of the NCs, which is further confirmed by high-resolution TEM