Papers by Keyword: Raman Spectroscopy

Abstract: The multilayered AlCrN coating physical vapour deposited (PVD) over the stainless steel (SS) substrate was studied. Raman spectroscopy was used to determine the resistance of the coating under high temperature oxidative conditions (25–800 °C). Static oxidation tests of the AlCrN PVD coating mainly leads to the formation of Cr₂O₃ at temperatures up to 800 °C. The results of the sliding tests indicate the development of oxides layers in the wear tracks on the surface of AlCrN PVD coated samples at the room temperature, which is critically dependant on the sliding speed against Si₃N₄ counter balls. The maximum reliable sliding speeds against Si₃N₄ counter balls under applied normal load of 3 N at 20, 300/500 and 800 °C was determined to be 0.486, 0.162 and 0.054 m·s^-1, respectively.

Abstract: The influence of graphite grinding time on the formation of carbon nanotubes (CNTs), is investigated. Graphite with different grinding time is used for the growth of CNTs by a cost-effective method using a microwave oven. The samples produced using the different grinding time contain nanotubes with an average diameter in the range 31–50 nm as observed by field emission scanning electron microscopy (FESEM). The lowest intensity ratio of D and G bands (ID/IG) and full width at half maximum of G as identified by Raman spectroscopy for grinding time 20 minute indicates the improved crystallinity of CNTs.

Abstract: In this paper, tensile mechanical properties of carbon nanotube (CNT) film under lateral loading are measured. Comparing with works before, it is found that elastic modulus of CNT film under lateral stretch is higher than that under longitudinal stretch, which is an interesting experimental result. With multi-scale experimental methods including SEM and micro-Raman spectroscopy, the change of CNT bundle network of the film under lateral stretch and axial elongation of CNTs in the loading direction are measured. Based on the experimental results, the control mechanism on difference of lateral and longitudinal mechanical properties of CNT film is analyzed.

Abstract: Stainless steel is widely used due to its high resistance to corrosion, rust and stains. However, the surface hardness of stainless steel is not high. This limits its engineering applications. Graphene is a material with a very high intrinsic strength. In order to broaden the range of applications of stainless steel, coating it with graphene is a good choice to enhance its surface hardness. In this report, we have improved the surface hardness of stainless steel by growing graphene on stainless steel surface using thermal chemical vapor deposition. The growth of graphene was also studied. The results show that the growth of graphene on stainless steel can harden the surface of stainless steel.

Abstract: All-dielectric resonant micro-and nanostructures emerge as a promising platform, which can complement the metal-based counterparts in routine biosensing measurements based on surface-enhanced Raman scattering (SERS). However, lack of in-situ temperature control limits performance of nanostructures for precise SERS-based applications. Here, we present an approach for SERS measurement with simultaneous temperature control and employ Raman spectroscopy to mapping of temperature-dependent Raman signal distribution. We attest a chemically inert black silicon (b-Si) substrate for a non-invasive (chemically non-perturbing) SERS identification of the molecular fingerprints at low concentrations. Additional studies of the slow daylight-driven para-aminothiophenol (PATP)-to-4,4'-dimercaptoazobenzene (DMAB) catalytic conversion in the aqueous methanol solution loaded with colloidal silver nanoparticles confirm the non-invasive SERS performance of the all-dielectric crystalline b-Si substrate. Proposed SERS substrates can be fabricated using easy-to-implement scalable technology of plasma etching making such inexpensive all-dielectric substrates promising for routine SERS applications, where the temperature-feedback and the noninvasiveness are of mandatory importance.

Abstract: Percolation networks of electrically connected nanographenes are the promising structures for solving the problem of the transfer of their peculiar quantum properties to the macroscopic level. In this work we report the results of investigations, conducted with using a set of complementary physical methods, on the origin, structural motifs and properties of such networks revealed in thermally reduced graphene oxide films. The presence of zero modes, which may be π-electronic states stabilized at the zigzag edges of network elements, has been established.

Abstract: The aqueous rechargeable zinc ion battery (ARZIB) system has been actively studied in the field of energy storage. Prussian blue analogues (PBAs) are considered effective cathode materials in the ARZIB system. In our previous study, Zn(NO₃)₂ solutions of different concentrations were used as electrolytes in an ARZIB system with a zinc hexacyanoferrate (ZnHCF) electrode. And the effect of electrolyte concentration on the electrochemical performance was studied. In this study, the effect of electrolyte concentration was demonstrated through electrochemical tests and Raman analysis. Charge/discharge tests were conducted at different electrolyte concentrations. And electrochemical performance degradation was observed above a certain electrolyte concentration. This effect was due to the strong interaction between the zinc cations and the nitrate anions, confirmed by the Raman spectroscopy analysis of the Zn(NO₃)₂ electrolyte.

Abstract: Understanding molecular electronics is critical in advance of organic devices. Intermolecular interaction between copper phthalocyanine (CuPc) and multi-walled carbon nanotubes (MWCNT) was studied using infrared spectroscopy and confocal Raman microscope. The organics were prepared using solution processing method at ambient atmosphere. The infrared spectrum showed the signal from the lower wavenumber was largely dominated by broad absorption and the lacking of ‘fingerprints’ peaks provided no information on the MWCNT. Raman absorption spectra under normal (λ = 532 nm) and resonant (λ = 633 nm) were obtained to tackle the disadvantages in the former method. Fingerprint peaks of CuPc in frequency of 600 - 1600 cm^-1 emerged under both excitation wavelengths. New 480 cm^-1, 1100 cm^-1 and 1300 cm^-1 peaks were found in resonant spectra. There were no strong evidence of presence and interaction between CuPc and MWCNT detected in these measurements possibly due to overlapping vibrational states between the two compounds and insufficient quantity of MWCNT in the sample.

Abstract: Green synthesis of nickel oxide nanoparticles (NiO NPs) using Physalis angulata leaf extract (PALE) as weak base sources and stabilizing agents has been reported. Chemical bonding and vibration spectroscopy, crystallographic structure, optical band gap, particle size and microscopic studies of NiO NPs were also investigated. Ni-O vibration modes of NiO NPs were analyzed by FTIR and Raman instrument at ~400 and ~900 cm^-1 wavenumber. XRD pattern of NiO NPs confirmed cubic crystal structure with space group Fm-3m. Optical band gap of NiO NPs determined by using Tauc plot method was about 3.42 eV. Particle size analyzer showed size distribution of NiO NPs was 64.13 nm which confirm NiO formed in nanoscale. Electron microscopic studies of NiO NPs were observed by using scanning electron microscopy and transmission electron microscopy.

Abstract: The oxyhalides Ba₂InO₃F, Ba₂InO₃Cl, and Ba₂InO₃Br were synthesized using the solid state method. It was found that the increasing of halide ion radius leads to the increase of lattice parameters and also caused to redistribution of indium-oxygen bond lengths. The possibility of water uptake was proved by thermogravimetry measurements. The presence of different forms of oxygen-hydrogen groups in the structure of hydrated oxyhalides was indicated by infrared spectroscopy.