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In this work, we present a quick and simple approach for fabrication of active-surface-enhanced Raman scattering (SERS) substrates based on silver nanoparticles (AgNPs) and porous silicon nanostructures (denoted by Si/Ag substrate). SERS substrates were fabricated by a 3-stage-process including the deposition of Au nanoparticles on Si wafer, etching for porous Si wafer, and coating Ag NPs on porous Si to produce SERS-active layer. To control the uniformity and cleanliness of the SERS substrate, sputtering technique was used to coat Au and AgNPs. The absorption spectra of the Si/Ag substrates exhibited a strong surface plasmon resonance absorption band of AgNPs at 425 nm. Using Si/Ag substrates to detect carbenzadim (CBZ) residue dispersed in acetone has shown that Si/Ag substrates morphology greatly affected the Raman intensity of carbendazim which opens up a promising and potential approach using SERS spectroscopy for food, environment and especially pharmaceutical applications. Keywords: Raman, SERS, plasmon, nanoparticles, carbendazim.

In this report, we present a method to produce active-surface-enhanced Raman scattering (SERS) substrates based on silver nanoparticles (Ag NPs) embedded in SiO2 ordered structures (referred to as Ag/SiO2 substrate) and demonstrate their effectiveness in 0.1 ppm detection of carbenzadim residue in water. The SERS substrates are opal crystals arranged from 260 nm SiO2 nanospheres made by the Stober method. Within these opal crystals, Ag NPs are evenly dispersed as evidenced by field-emission scanning electron microscopy. Raman scattering performed on the Ag/SiO2 substrates showed reflected light in wavelength bands from 470 nm to 570 nm and exhibited the surface plasmon resonance absorption band of Ag NPs, which peaked at 400 nm. The Ag/SiO2 substrates were used to detect carbenzadim (CBZ) residue dispersed in water with CBZ concentration as low as 0.1 ppm. This result opens up prospects of using SERS spectroscopy to quickly determine CBZ pesticide residue on food and in other environments.

In this report, we presented the usage of Stober method to fabricate SiO2 nanospheres and self-assembly method to make SiO2 opal photonic crystals based on the fabricated SiO2 nanospheres. An averaged size of SiO2 nanospheres was controlled by varying concentrations of NH4OH and TEOS. Crystal structure and morphology of particles was investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Experimental results showed that SiO2 nanospheres possess amorphous crystal structure with sizes ranged from 150 to 300 nm. The diffuse reflection spectra show the reflection peaks of the SiO2 opal photonic crystals from 410 nm to 520 nm.

In this paper, we present the results of the study of the effect of residual La on crystal structure, magnetic properties of La1+dFe11.05Si1.95 (d = 0.00; 0.03; 0.06 and 0.09) compounds. The analysis of X-ray diffractions showed that when the La content increases to 9%, the structure still remains cubic in a typical NaZn13 arrangement with unchanged lattice constant (about 0.5%). All compounds exhibit ferromagnetic - paramagnetic phase transitions. The Curie temperature TC increases slightly from 235 to 245 K.

In this work we report a hydrothermal approach for synthesis of zinc stannate (Zn2SnO4–ZTO) nanocrystals. Structural properties and morphology of the samples were investigated in detail. In particular, our research focused on the effect of hydrothermal duration on the phase composition of ZTO nanocrystals. By combining X-ray diffraction analysis, scanning electron microscopy and selected area energy-dispersive X-ray spectroscopy, a crystalline phase transformation during the hydrothermal process was enlightened. The ZTO nanocrystals were doped with europium ions. The room-temperature emission spectra of the undoped ZTO and Eu3+-doped ZTO nanocrystals were recorded. The emission spectra of the undoped ZTO nanocrystals showed two broad bands related to the lattice defects, while the spectra of Eu3+-doped ZTO nanocrystals exhibited the narrow emission peaks, which were assigned to the radiative intra-configurational f–f transitions of Eu3+ ions.

The enhancement and quenching of Eu3+ ion emission were investigated in Zn2SnO4:Eu3+@Au (ZTO:Eu3+@Au) nanocomposites. Under 361 nm excitation we revealed the extinction of the intrinsic defect emission and the enhancement of Eu3+ ion emission when Au content in samples is increased, but under excitation wavelength of 394 nm we observed only the suppression of Eu3+ ion emission. The cause of the observed PL behavior is related to the interaction between surface plasmon induced by gold nanoparticles and luminescence centers in the samples.

The study of electrochromic thin films, which are transparent in the visible range, is significantly important in producing smart doors production and saving energy. This paper reports the results of preparing WO3 thin films on glass substrates and ITO substrates by thermal vacuum evaporation method. The influence of annealing temperature on the properties of thin films was investigated by X-ray diffraction, Raman scattering spectroscopy, X-ray energy dispersive spectroscopy, Atomic force microscopy and absorption and transmittance UV–vis spectroscopy. The results show that WO3 thin films have a high transmittance of about 90% in the visible wavelength from 400 to 900 nm, good substrate adhesion. The WO3 thin films were crystallized at 400 oC and the crystallization of thin films on the ITO substrate better than glass substrate. Electrochromic characteristics of WO3 thin films were investigated by Autolab electrochemical system. The results show the transmittance of WO3 thin film was reduced to around 12 % in visible region when increasing the applied voltage from - 0.1 V to - 0.7 V. The transmittance of the film was completely recovered by using an applied voltage of 2 V.

In the paper, the investigation results of periodical gas-lift flows in vertical pipes using experiment method are presented. The experiment facilities consist of flow measurement equipment, gas and fluid supplier facilities, tubing system. To study the influence of medium physical and dynamical characteristics on the process efficiency, two liquid-gas systems are used, namely, water-air and spindle oil-air. The objects of investigation are to obtain data from tests conducted in some conduits and to analyse the influence of system physical, geometrical and etc. parameters such as: initial liquid height in the conduits, gas injected volume, conduit diameter, conduit configuration and etc. on the considered process.

The paper presents the study results of intermittent gaslift. vertical flows using both experiment and theoretical models. To study the influence of medium thermophysical characteristics on the process efficiency, two gas-liquid systems are used in the experiments. The obtained results show that there is a critical gas injection volume, less than that the liquid slug cannot reach the top of the tubing. Correlations for prediction of liquid entrainment in gas core are also shown for two presented gas-liquid systems. Amodified dynamical model was developed. The model consists of a system of differential equations. The resulting system of equations is numerically solved. The numerical code is verified by using experimental data and calculation data of the other authors. Finally, the effects of system parameters are studied.

This paper presents an experimental facility conducted in Hanoi Institute of Mechanics to investigate multiphase How pattern in the pipes. First and foremost, it is used to define the conditions of water layer formation in the horizontal pipe.Experimental results have been obtained in stainless steel pipes of three different diameters (24.6mm; 30.8mm and 40.5mm) with white spindle oil N° 10 and water. They have been shown in the form of water layer maps.

In this work we report a hydrothermal approach for synthesis of zinc stannate (Zn2SnO4)nanocrystals. Our research focused on the effect of the molar ratio of initial chemicals, reaction temperature and reaction duration on the phase composition and the fluorescence properties.Structural and optical properties of the final products were investigated in detail. X-ray diffractionanalysis indicated that the Zn2SnO4 nanocrystals possess face-centered cubic crystal structure.Raman scattering spectra exhibit two characteristic vibrational modes of Zn2SnO4 crystals. Optical band gap of Eu3+-doped Zn2SnO4 nanocrystals obviously depends on Eu3+content. Theroom-temperature emission spectra of the undoped Zn2SnO4 nanocrystals show two broad bands,while the photoluminescence spectra of Eu3+-doped Zn2SnO4 nanocrystals exhibit the emissionpeaks related to the radiative intra-configurational f-f tr ansitions of Eu3+ions. The absorptiontransitions within Eu3+ions were observed both in the photoluminescence excitation spectra andin the diffuse reflection spectra.

The system receives a pattern sequence, i.e., a time-series of consecutive patterns as an input sequence. The set of input sequences are given as a training set, where a category is attached to each input sequence, and a supervised learning is introduced. First, we introduce a state transition model, AST(Abstract State Transition), where the information of speed of moving objects is added to a state transition model. Next, we extend it to the model including a reinforcement learning, because it will be more powerful to learn the sequence from the start to the goal. Last, we extend it to the model of state including a kind of pushdown tape that represents a knowledge behavior, which we call Pushdown Markov Model. The learning procedure is similar to the learning in MDP(Markov Decision Process) by using DP (Dynamic Programming) matching. As a result, we show a reasonable learning-based recognition of a trajectory for human behavior.

Indium phosphide semiconductor materials (InP) have various applications in the field of semiconductor optoelectronics because of its advantages. But the making of this material is difficult due to the very weak chemical activity of In element. In this report we present a simple method to synthesize InP nanocrystals from inorganic precursors such as indium chloride (InCl 3 ), yellow phosphorus (P 4 ), reduction agent NaBH 4 at low temperature with the aid of ultrasound. Structural, morphological and optical properties of the formed InP nanocrystals were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersed X-ray analysis (EDS), Raman scattering, absorption and photoluminscence (PL) spectroscopy. After the surface treatment of InP nanocrystals with liquid hydrofluoric (HF) acid, the luminescence spectra have an enhanced intensity and consist of the peaks in the region from 500 nm to 700 nm. The intensity of these peaks strongly depends on the concentration and etching time of HF.

Colloidal gold nanoparticles (spheres) have been prepared from HAuCl4 containing aqueous solution by using X-ray irradiation and by chemical reduction method. Gold nanorods were synthesized according to the seed-mediated growth method. The colloidal gold nanoparticles were characterized by using transmission electron microscopy, X-ray diffraction, and UV-VIS absorption spectroscopy. It was found that the concentration of the precursors affects the size of the nanoparticles. In the chemical reduction approach the size of nanoparticles can be controlled by varying amount of trisodium citrate, but in the photochemical method the size of nanoparticles can been controlled by varying the ratio of HAuCl4 to TX-100 and X-ray irradiation duration. Gold nanorods have been synthesized according to the seed-mediated growth method with two steps. The effect of silver acetate and CTAB on formation of gold nanorods has been studied.