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The ability to plasticize Hydroxypropyl Methyl Cellulose/Beeswax (HPMC/BW) composites depends on plasticizers and their concentration. This paper conducted studying on the impacts of plasticizers to HPMC/BW properties. The plasticizers were used in this research included Glycerol (G), Propylene Glycol (PG), and Polyethylene Glycol 400 (PEG 400) which had the concentration changed in range of 1-3%. HPMC/BW composite films incorporated with 2% of plasticizers formed films with the best characteristics among three tested concentration. Tensile strength and elastic modulus of films were decreased when adding plasticizers, whereas elongation at break were increased. Therefore, it caused an increase in oxygen permeability of HPMC/BW films in comparison with the control film. However, Glycerol showed the lowest Oxygen Permeability (OP) values compared to other composite films. The films were evaluated its microstructural quality using method of scanning electron microscopy (SEM) which had the effects of plasticizers and their efficiencies of plasticizing polymer networks.

Ag/Au bimetallic nanostructures have received much attention in surface-enhanced Raman scattering (SERS). However, the synthesis of this nanostructure type still remains a challenge. In the present research, Ag/Au nanoframes were synthesized via a simple room temperature solution phase chemical reduction method using pre-synthesized triangular Ag nanoplates as templates in the presence of appropriate amounts of HAuCl4. Controlling experimental parameters was applied for understanding of the growth mechanism. The galvanic exchange reaction resulted in a uniform deposition of the Au shell on the Ag nanoplates and the Ag core was removed which generated triangular hollow nanoframes. It is found that the amount of HAuCl4 added to the growth solution played a key role in controlling the Ag/Au nanoframes. The resultant silver/gold nanoframes with average size of 50 nm were applied in detecting methyl red (MR) in the solution-phase using an excitation wavelength laser of 532 nm. The SERS signal was greatly enhanced owing to the tunable plasmonic peaks in the visible region (400–650 nm). The limit of detection (LOD) of MR in diluted solution was 10−6 M. The enhancement factor (EF) was about 8 × 104 toward 10−5 M of MR. Interestingly, the linear dependence between the logarithm of the SERS signal intensity (log I) and the logarithm of the MR concentration (log C) occurred in the range from 10−6 to 10−4 M. Our work promises the application of Ag/Au nanoframes as a chemical sensor in detecting MR molecules at low concentration with high performance.

Silver nanodecahedra and nanoplates were successfully fabricated using a simple solution method, where silver nitrate (AgNO3) was reduced with sodium borohydride (NaBH4) at melting ice temperature. Green light-emitting diode (green LED, wavelength λG = 520 nm) was irradiated into the reaction system to control the morphology of the product. The synthetic procedure was a combination of two processes including the formation of silver seeds and subsequent photomediated crystal growth. This article also presents a mechanism study of the photomediated growth of silver nanoplates and nanodecahedra. In these processes, citrate ions were used as a morphology-controlled reagent and polyvinyl pyrrolidone as a capping agent. The growth process was evaluated by dynamic light scattering and ultraviolet/visible spectra measurements. The obtained silver nanoparticles (AgNPs) possessed various shapes, including triangular, truncated triangular, hexagonal and decahedron depending on the time duration of LED irradiation. Triangular nanoplates or decahedral nanoparticles (80–100 nm) were obtained when the silver colloid was exposed to green LED irradiation for different times (30 min—76 h). The average width and thickness of such nanoparticles were estimated to be approximately 80 nm and 20 nm, respectively. The technology uniqueness in this work is that we can change the morphology of silver from plate to decahedron via prolonging the LED illumination period from 140 min to 76 h instead of changing the light wavelength or temperature of the reaction solution. The surface-enhanced Raman scattering (SERS) experiment was carried out to measure Rhodamine 6G (R6G) concentrations plated on the silicon substrates. Silver nanodecahedra can detect the low concentration of R6G (10−8 M), while silver nanoplates can detect a higher R6G concentration of 10−6 M. Silver nanodecahedra could be used as an effective SERS substrate for ultrasensitive detection.

Water quality modeling in a river basin often faces the problem of having a large number of parameters yet limited available data. The important inputs to the water quality model are pollution concentrations and discharge from river tributaries, lateral inflows and related pollution load from different sources along the river. In general, such an extensive data set is rarely available, especially for data scarce basins. This makes water quality modeling more challenging. However, integration of models may be able to fill this data gap. Selection of models should be made based on the data that is available for the river basin. For the case of Cau River basin, the SWAT and QUAL2K models were selected. The outputs of SWAT model for lateral inflows and discharges of ungauged tributaries, and the observed pollutant concentrations data and estimated pollution loads of sub-watersheds were used as inputs to the water quality model QUAL2K. The resulting QUAL2K model was calibrated and validated using recent water quality data for two periods in 2014. Four model performance ratings PBIAS, NSE, RSR and R2 were used to evaluate the model results. PBIAS index was chosen for water quality model evaluation because it more adequately accounted for the large uncertainty inherent in water quality data. In term of PBIAS, the calibration and validation results for Cau River water quality model were in the “very good” performance range with ǀPBIASǀ

Well-crystalline iron oxide (α-Fe2O3) nanospindles have been prepared using a simple hydrothermal process at temperature of 240°C for different durations (24 h, 36 h, 48 h, and 60 h). The products were characterized by x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy, and visible absorption measurements. Detailed characterization of their structure and composition confirmed formation of pure α-Fe2O3 with rhombohedral crystal structure. The photocatalytic activity of the obtained α-Fe2O3 for demineralization of methylene blue (MB) in aqueous solution under ultraviolet (UV) light irradiation was evaluated. Ultraviolet–visible (UV–Vis) spectroscopy indicated a decrease in the absorbance intensity and concentration of the dye. Mechanistic investigation revealed that $$ \cdot {\hbox{OH}} $$ and $$ \cdot {\hbox{O}} $$ radicals played a crucial role in the degradation process of methylene blue. The α-Fe2O3 nanospindles presented high photocatalytic activity towards MB with degradation efficiency of 78% within 6 h of irradiation. These results demonstrate that α-Fe2O3 nanospindles are suitable for treatment of wastewater.

The synthesis of Ag/Au nanoparticles (NPs) in a controlled manner has been a challenge for a long time. The aim of this report is to present a systematic study on the fabrication, characterization of Ag/Au alloy NP-based surface-enhanced Raman spectroscopy (SERS) substrates. Silver (Ag) and gold (Au) colloidal NPs were prepared by chemical reduction route of the corresponding metal salts by trisodium citrate (TSC). Ag/Au alloy nanoparticles with varying molar fractions are prepared in aqueous solution by the simultaneous reduction of AgNO3 and HAuCl4 by TSC. The composition of Ag and Au in the alloy samples was controlled by tuning the molar ratio of Ag+/Au3+ in the mixture solution. The morphologies of the different products were characterized by TEM, and the size of obtained samples was in the range of 40 to 60 nm. The resulting samples were denoted as AgNPs, AuNPs, Ag3Au, AgAu, and AgAu3 NPs. In order to compare the optical property of the Ag/Au alloy and Ag/Au mixture, we mixed the pure Ag and Au NPs with different ratios to obtain the aggregated nanoparticles. Ag/Au alloy NPs were demonstrated as an ultrasensitive SERS substrate for the detection of rhodamine B (RhB) molecules. The concentration of RhB ranged from 10−11 to 10−5 M. The effect of the Au content on the optical and SERS properties of the Ag/Au alloys was studied. The obtained results show that the Au content in the Ag/Au alloys play an important role in the physical properties of Ag/Au alloy NPs. The SERS spectra of RhB from the as-prepared Ag/Au alloy NP substrates indicated the superior enhancement with high reproducibility and sensitivity compared to those of Ag or Au samples. Interestingly, the highest SERS activity was achieved for the Ag3Au sample with an enhancement factor larger than 1010 for 10−11 M RhB and a limit of detection (LOD) at 10−11 M, as well as good long-term stability after storage for 1 year. As far as we know, this is the highest sensitivity record of RhB by SERS detection. Furthermore, the composition-dependent SERS activity was explained in detail. These advantages demonstrated the potential for growing Ag/Au alloy NP-based SERS substrates in food safety and bioanalysis.

The gold nanocrescent (NC) particles possess a strong plasmon resonance which gives them a strong scattering cross section. They can thus be easily tracked using dark-field microscopy. In this study, we improved the optical configuration setup of dark-field video microscope to simultaneously measure the translational and rotational local temperatures within a glycerol medium. The translational and rotational local temperatures have been measured on the same single gold nanocrescent particle when it was excited by green and red laser. The rotational local temperature was measured by the technique of rotational scattering correlation spectroscopy (RSCS) and the translational local temperature was measured by tracking a single nanoparticle technique through the determination of translational diffusion coefficient under Brownian motion. The result showed that the translational local temperature was significant lower than the rotational local temperature for the same single gold nanocrescent. Remarkablely, we can affirm that the heterogeneity of the optical environment leads to the difference between these two temperatures. The obtained results have a great potential to probe the local nanorheology of a material.

The colloidal silver solution was synthesized by reducing silver nitrate () using sodium borohydride () and starch as a stabilizer agent. The size and optical properties of synthesized AgNPs were characterized by UV-Vis spectroscopy, Fourier transform-infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The effects of several parameters on AgNPs were also investigated. The results have shown that the size of synthesized spherical silver nanoparticles was and disperse in water. The synthesized AgNPs of his study exhibited a strong antibacterial activity against Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). The average zones of inhibition of AgNPs were of 7.7 mm for bacteria E. coli and 7.0 mm for S. aureus. In this study, the zone of inhibition of AgNPs was also compared to the reference antibiotics drug.