Gold nanoparticles embedded in carbon film: Micromorphology analysis

S¸ tefan T¸a˘lu,Miroslaw Bramowicz,Slawomir Kulesza,Shahram Solaymani,Azizollah Shafikhani,Atefeh Ghaderi,Mohammad Ahmadirad 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.35 No.-

In this paper the sputtered gold nanoparticles (NPs) deposited by Radio Frequency-Plasma EnhancedChemical Vapor Deposition (RF-PECVD) method on the glass substrates in trace of amorphoushydrogenated carbon (Au NPs @ a-C: H) were analyzed to study the three-dimensional (3-D) surfacetexture. The prepared Au NPs @ a-C: H films were used as research materials. The synthesis of sampleswas carried out in different powers from 80 to 120 W while all other parameters were kept constant. TheX-ray diffraction patterns and UV–vis spectra were applied to study the structure and Localized SurfacePlasmon Resonance (LSPR), respectively. An atomic force microscope in a non-contact mode was usedto record the sample surface images then the fractal geometry was studied. The images were numericallyprocessed to calculate the Areal Autocorrelation Function (AACF), which was used to determine theanisotropy ratio Str, and to compute the Structure Function (SF). The log–log plots of the latter were usedto calculate fractal properties of the studied surfaces, such as fractal dimension D, and pseudo-topothesyK. The analysis of 3-D surface texture was helpful in optimizing the functional performance of thethin film.

Ethynylene-analogues of hemicurcuminoids: Synthesis and ground- and excited properties of their boron difluoride complexes

Š,tefane, Bogdan,Pož,gan, Franc,Kim, Eunsun,Choi, Eunyoung,Ribierre, Jean-Charles,Wu, Jeong Weon,Ponce-Vargas, Miguel,Le Guennic, Boris,Jacquemin, Denis,Canard, Gabriel,Zaborova, Elena,Fages Applied Science Publishers 2017 Dyes and pigments Vol.141 No.-

<P><B>Abstract</B></P> <P>The synthesis, characterization and (TD)-DFT calculations of the electrochemical and photophysical properties of novel ethynylene-analogues of hemicurcuminoids are described. These dyes are both emissive in solution and in the solid state. While compounds that emit through an efficient charge transfer (CT) state show solvatochromic behaviour associated with low fluorescence quantum yields, those lacking of donor groups show high fluorescence quantum yields of 70–80%, in solution. The latter dyes also present the advantage to emit in the solid state in the visible region with fluorescence quantum yields up to 23%. Their condensed phase spectrum can be bathochromically shifted to the near infrared region (742 nm) by appending a strong donor group.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of new fluorophores based on hemicurcuminoid boron difluoride. </LI> <LI> Photophysical study reveals strong emission of the dyes not containing charge transfer states. </LI> <LI> Fluorescence properties of dyes in their condensed phase show aggregation induced emission. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Association of Novel Domain in Active Site of Archaic Hyperthermophilic Maltogenic Amylase from<i>Staphylothermus marinus</i>

Jung, Tae-Yang,Li, Dan,Park, Jong-Tae,Yoon, Se-Mi,Tran, Phuong Lan,Oh, Byung-Ha,Janeč,ek, Š,tefan,Park, Sung Goo,Woo, Eui-Jeon,Park, Kwan-Hwa American Society for Biochemistry and Molecular Bi 2012 The Journal of biological chemistry Vol.287 No.11

Microstructure and Micromorphology of Cu/Co Nanoparticles: Surface Texture Analysis

Ştefan Ţălu,Miroslaw Bramowicz,Slawomir Kulesza,Atefeh Ghaderi,Vali Dalouji,Shahram Solaymani,Zahra Khalaj 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.5

This paper analyses the three-dimensional (3-D) surface texture ofCu/Co thin films deposited by DC-Magnetron sputtering methodon the silicon substrates. The prepared Cu/Co nanoparticles wereused as research materials. Three groups of samples were depositedon silicon substrates in the argon atmosphere and gradually cooleddown to room temperature. The crystalline structures and elementalcompositions were analyzed by X-ray diffraction (XRD) spectrumwith conventional Bragg-Brentano geometry. X-ray diffractionprofile indicates that Co and Cu interpenetrating crystallinestructures are formed in these films. The sample surface imageswere recorded using atomic force microscopy (AFM) and analyzedby means of the fractal geometry. Statistical, fractal and functionalsurface properties of prepared samples were computed to describemajor characteristics of the spatial surface texture of Cu/Conanoparticles. Presented deposition method is a versatile, costeffective,and simple method to synthesize nano- and microstructuresof Cu/Co thin films. This type of 3-D morphology allows tounderstand the structure/property relationships and to investigatedefect-related properties of Cu/Co nanoparticles. Presented resultsconfirm the possibility of preparing high-quality Cu/Co nanoparticlesvia DC-Magnetron sputtering method on silicon substrates.

Multifractal Characterization of Water Soluble Copper Phthalocyanine Based Films Surfaces

Ştefan Ţălu,Sebastian Stach,Aman Mahajan,Dinesh Pathak,Tomas Wagner,Anshul Kumar,R. K. Bedi,Mihai Ţălu 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.4

This paper presents a multifractal approach to characterize the structural complexity of 3D surface roughness of CuTsPc films on the glass and quartz substrate, obtained with atomic force microscopy (AFM) analysis. CuTsPc films prepared by drop cast method were investigated. CuTsPc films surface roughness was studied by AFM in tapping-mode™, in an aqueous environment, on square areas of 100 μm2 and 2500 μm2. A detailed methodology for CuTsPc films surface multifractal characterization, which may be applied for AFM data, was also presented. Analysis of surface roughness revealed that CuTsPc films have a multifractal geometry at various magnifications. The generalized dimension Dq and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of CuTsPc films surface morphology at nanometer scale. Multifractal analysis provides different yet complementary information to that offered by traditional surface statistical parameters.

Condition monitoring of engine timing system by using wavelet packet decomposition of a acoustic signal

Tomasz Figlus,Štefan Liščák,Andrzej Wilk,Bogusław Łazarz 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.5

A change in the technical condition of mechanical components of internal combustion engines may not be detected by on-board diagnosticsystems installed in vehicles. In similar cases, measurements and analyses of vibroacoustic signals being recorded prove useful. Since there are certain limitations to vibration measurements, including those related to the vibration transmission and the engine’s hightemperature at measurement points, the authors of this paper have proposed that measurements and analyses of acoustic signals should beapplied for the sake of assessment of the internal combustion engine technical condition. However, such an assessment requires newacoustic signal processing methods to be developed, and so this subject has been elaborated in the paper. The article provides a discussionon the option of applying a wavelet packet decomposition while filtering the internal combustion engine’s acoustic signal in order todiagnose an excessive valve clearance. The authors prepared an algorithm enabling selection of the chosen details and approximation ofthe wavelet analysis to low-frequency components, which constitute the noise, as well as high-frequency components comprising informationon the possible enlarged engine valve clearance. Next, based on the selected high-frequency acoustic signal components, a methodfor automatic detection of enlarged clearance valves was developed, assuming that energy participations of the acoustic signal beingemitted were to be determined while opening and closing individual valves. Under the study discussed, identification tests were conductedusing two 4-cylinder internal combustion engines featuring valves of different clearances to consequently confirm the efficiencyof the algorithm developed for the acoustic signal filtration and automatic detection of enlarged clearance valves.

How morphological surface parameters are correlated with electrocatalytic performance of cobalt-based nanostructures

Naimeh Naseri,Ştefan Ţălu,Slawomir Kulesza,Shervin Qarechalloo,Amine Achour,Miroslaw Bramowicz,Atefeh Ghaderi,Shahram Solaymani 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.57 No.-

To overcome recent energy and environment challenges, developing efficient and low cost photocatalystsare unavoidable. In this context, design of semiconductor nanostructures modified with earth abundantco-catalysts for water splitting reactions requires well engineered and controlled process to optimizesurface interface and maximize nanocomposite system efficiency. Here, TiO2 nanotube were synthesizedelectrochemically and decorated with cobalt based nanostructure co-catalyst for water oxidationreaction using low cost and scalable electro-deposition approach. By changing deposition parametersand complete studying on samples surface morphology and related statistical analysis data, correlationbetween all morphological parameters and photoelectrochamical activity of correspondence photo-anode was illustrated for thefirst time. Based on SEM analysis and surface analysis data as well ascatalytic performance investigation, nanotubes decorated with Co nanoparticles at 0.1 mA cm 2deposited for 2000 s presented the best performance with most isotropic surface. Results suggestedthat by tuning deposition parameters surface structural parameters like fractal dimension, cornerfrequency, roughness and feature shape and size can be engineered completely. Moreover, X-raydiffraction data along with Rietveld method revealed coexistence of anatase, rutile and Ti2O3 phases inthe photoanode while poor crystallinity of grown cobalt based nanostructures was confirmed.

Tensile and Corrosion Properties of Anodized Ultrafine‑Grained Ti–13Nb–13Zr Biomedical Alloy Obtained by High‑Pressure Torsion

Dragana Barjaktarević,Bojan Medjo,Primož Štefane,Nenad Gubeljak,Ivana Cvijović‑Alagić,Veljko Djokić,Marko Rakin 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

Severe plastic deformation (SPD) is a popular group of techniques applied to achieve the nanostructuring of the metallic biomaterials and improvement of their mechanical characteristics. One of the most commonly used SPD methods is the highpressure torsion (HPT) technique which enables the obtainment of the microstructure with small grains and high strength. In the present study, the influence of the plastic deformation and surface modification treatment on the tensile and corrosion properties of the Ti–13Nb–13Zr (wt%) alloy is investigated. In that purpose, the coarse-grained (CG) Ti–13Nb–13Zr (TNZ) alloy was subjected to the HPT processing by applying a pressure of 4.1 GPa with a rotational speed of 0.2 rpm and 5 revolutions at room temperature to obtain the ultrafine-grained (UFG) microstructure. The alloy microstructure before and after HPT processing was analysed using the scanning electron microscopy (SEM) and the X-ray diffraction (XRD). The homogeneity of the UFG TNZ alloy was determined by microhardness testing and microscopic observations. The nanotubular oxide layer on the surface of the TNZ alloy, both in CG and UFG condition, was formed by electrochemical anodization in 1 M H3PO4 + NaF electrolyte for 90 min. SEM analysis was used to characterise the morphology of the anodized surfaces, while energy dispersive spectroscopy was applied to determine the chemical composition of the nanostructured layers formed at the alloy surfaces. Mechanical properties of the TNZ alloy, before and after HPT processing and electrochemical anodization, were determined by tensile testing. After tensile testing, the fractographic analysis was conducted to identify the fracture mechanisms. The potentiodynamic polarization technique was used to determine the corrosion resistance of the alloy before and after plastic deformation and surface modification treatment. The obtained results showed that the alloy is reasonably homogeneous after the HPT processing. The XRD analyses reviled the presence of α′ and β phases in the CG TNZ alloy microstructure, while the additional ω phase was detected in the microstructure of the UFG TNZ alloy. The HPT obtained alloy exhibits higher hardness and improved tensile properties than the alloy in the as-received CG condition, while the electrochemical anodization leads to a decrease of its mechanical properties. Both CG and UFG alloys show excellent corrosion stability in Ringer’s solution. Moreover, electrochemical anodization leads to a decrease or an increase of the corrosion resistance of these materials, depending on the morphology of the formed nanotubular surface layers. The results indicate that the anodized CG TNZ alloy is characterized by a lower modulus of elasticity and better corrosion resistance properties than the anodized UFG TNZ alloy.