Ag nanoparticles enhanced near-IR emission from Er3+ ions doped glasses

Vitreous materials containing rare-earth (RE) ions and metallic nanoparticles (NPs) attract considerable interest because the presence of the NPs may lead to an intensification of luminescence. In this work, the characteristics of 1.54 μm luminescence for the Er³⁺ ions doped bismuthate glasses containing Ag NPs were studied under 980 nm excitation. The surface plasmon resonance (SPR) band of Ag NPs appears from 500 to 1500 nm. Transmission electron microscopic (TEM) image reveals that the Ag NPs are dispersed homogeneously with the size from 2 to 7 nm. The strength parameters Ω_t(t = 2, 4, 6), spontaneous emission probability (A), radiative lifetime (τ) and stimulated emission section (σ_em) of Er³⁺ ions were calculated by the Judd–Ofelt theory. When the glass contains 0.2 wt% AgCl, the 1.54 μm fluorescence intensity of Er³⁺ reaches a maximum value, which is 7.2 times higher than that of glass without Ag NPs. The Ag NPs embedded glasses show significantly fluorescence enhancement of Er³⁺ ions by local field enhancement from SPR.     

Antibacterial activity of silver nanoparticles stabilized on tannin-grafted collagen fiber

Bayberry tannin (BT), a typical plant polyphenol, was grafted on collagen fiber (CF) in different mass ratios. Subsequently, the BT-grafted CF (BT-CF) was used as carrier and stabilizer to prepare BT-CF stabilized silver nanoparticles (BT-CF-AgNPs). Scanning Electron Microscopy image of BT-CF-AgNPs showed that the BT-CF-AgNPs was in ordered fibrous state. X-ray Diffraction patterns and Transmission Electron Microscopy images offered evidence that the Ag nanoparticles were well dispersed on BT-CF. Fourier Transform-Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) investigations revealed that the Ag NPs were stabilized by the phenolic hydroxyls and quinones of BT on CF through electron donation/acception interaction. Antibacterial experiments demonstrated that BT-CF-AgNPs exhibited high antibacterial activity. When cell suspensions of Escherichia coli and Staphylococcus aureus (10⁴–10⁵ cfu/mL) were contacted with BT_0.19-CF-AgNPs (mass ratio of BT to CF = 0.19, conc. of Ag = 8 μg/mL) at 310 K under constant shaking, the number of cells went down to zero within 2 h. In addition, the minimal inhibitory concentration of BT_0.19-CF-AgNPs against Escherichia coli, Staphylococcus aureus, Penicillium glaucum and Saccharomyces cerevisiae was 2 μg/mL, 4 μg/mL, 6 μg/mL and 12 μg/mL Ag, respectively. During recycling use, the antibacterial activity of BT_0.19-CF-AgNPs against Escherichia coli can last for 5 cycles. These facts suggest that BT-CF-AgNPs can be used as a new and effective antibacterial agent.     

Antibacterial effect of sand blasted,large-grit,acid-etched treated Ti–Ag alloys

The purpose of this study was to investigate the antibacterial effect of sand-blasted, large-grit, acid-etched (SLA) treated Ti–Ag alloys. Three different alloys with varying Ag contents (Ti–1Ag, Ti–2Ag, and Ti–4Ag) were SLA treated by grit blasting with 250 μm sized alumina and acid-etching in 7% HCl + 27% H₂SO₄ solution at 110 °C for 5 min. The microporous structures were formed following SLA treatment and Ag particles were identified on Ti–2Ag and Ti–4Ag alloys. And high concentration of Ag released steadily during 7 days from the Ti–4Ag. Higher level of antibacterial effect was evident on SLA treated Ti–Ag alloys compare to commercially pure Ti (p < 0.05) in the antibacterial test using Streptococcus aureus whereas no significant difference in cell viability among the SLA treated Ti–Ag allows and commercially pure Ti was identified. Hence, it was concluded that SLA treated Ti–Ag had an antibacterial effect while being biocompatible.     

Preparation of PMN–PT–BT/Ag nanocomposites by surface modification with MgO sol

Nanocomposites of 0.96(0.91Pb(Mg_1/3Nb_2/3)O₃–0.09PbTiO₃)–0.04BaTiO₃ (PBT) with Ag were prepared via synthesis of low-temperature-sinterable PBT/Ag composite powder and its surface modification with a MgO sol. Dielectric properties and modulus of rupture were investigated as a function of the amount of the MgO sol at sintering temperature in the range from 850 to 1000 °C. The MgO sol seemed to suppress the diffusion and migration of Ag during the heat treatment to give rise to the homogeneous microstructure with 300–80 nm of Ag particles in about 3.5–2.5 μm grains. The proper amount of the MgO sol seemed to be 0.5–1.0 wt.% for the PBT powder with 3.0 mol% Ag. The PBT/Ag nanocomposites showed density >99% T.D., ɛ_rt of 18,000–20,000, tan δ of 1–0.5%, specific resistivity of 10¹² Ω cm, and MOR of 125–145 MPa.     

The applicability of SWCNT on the counter electrode for the dye-sensitized solar cell

In this study, two types of the counter electrode were designed and fabricated for the dye-sensitized solar cell (DSSC): (1) one had a layer of SWCNT/Ag on the FTO-glass (Fluorine doped tin oxide, SnO₂:F) substrate; (2) the other had a layer Ag sandwiched between a layer of SWCNT and the FTO-glass substrate. This study also examined the effects of the mass ratio of SWCNT to Ag-paste, the surfactant (such as TOAB), the type of FTO-glass substrate, and the sintering temperature of preparing the counter electrode on the short-circuit photocurrent and the open-circuit photovoltage of the DSSC. At a fixed sintering temperature of 150 °C and a fixed FTO-glass substrate of 8 Ω/sq, this film of SWCNT markedly increased the short-circuit photocurrent from 227.3 μA (conventional DSSC without a layer of SWCNT) to 1033.5 μA (DSSC with a layer of SWCNT/Ag). Most importantly, at a fixed FTO-glass substrate of 8 Ω/sq, this study shows that the short-circuit photocurrent of the DSSC with a layer Ag sandwiched between a layer of SWCNT and the FTO-glass substrate of the counter electrode (2565 μA) substantially exceeds that of DSSC with a thin film of platinum on the FTO-glass substrate of the counter electrode (1263.7 μA).     

Flow-based method for epinephrine determination using a solid reactor based on molecularly imprinted poly(FePP–MAA–EGDMA)

A solid phase reactor based on molecularly imprinted poly(iron (III) protoporphyrin-methacrylic acid-ethylene glycol dimethacrylate) (MIP–MAA) has been synthesized by bulk method and applied as an selective material for the epinephrine determination in the presence of hydrogen peroxide. In order to prove the selective behaviour of MIP, two blank polymers named non-imprinted polymer (NIP1), non-imprinted polymer in the absence of hemin (NIP2) as well as a poly(iron (III) protoporphyrin-4-vynilpyridine-ethylene glycol dimethacrylate) (MIP–4VPy) were synthesized. The epinephrine-selective MIP–MAA reactor was used in a flow injection system, in which an epinephrine solution (120 μL) at pH 8.0 percolates in the presence of hydrogen peroxide (300 μmol L^? 1) through MIP–MAA. The oxidation of epinephrine by hydrogen peroxide is increased by using MIP–MAA, being the product formed monitored by amperometry at 0.0 V vs. Ag/AgCl. The MIP–MAA showed better selective behaviour than NIP1, NIP2 and MIP–4VPy, demonstrating the effectiveness of molecular imprinting effect. Highly improved response was observed for epinephrine in detriment of similar substances (phenol, ascorbic acid, methyl-l-DOPA, p-aminophenol, catechol, l-DOPA and guaiacol). The method provided a calibration curve ranging from 10 to 500 μmol L^? 1 and a limit of detection of 5.2 μmol L^? 1. Kinetic data indicated a value of maximum rate V_max (0.993 μA) and apparent Michaelis–Menten constant of K_m^app(725.6 μmol L^? 1). The feasibility of biomimetic solid reactor was attested by its successful application for epinephrine determination in pharmaceutical formulation.     

Upgrading of low-grade gold ore samples for improved particle characterisation using Micro-CT and SEM/EDX

There is a considerable challenge in accurate characterisation of gold (Au) particles in low-grade plant ore mineral samples. This is particularly true for automated mineralogical tools such as X-ray micro-computed tomography (Micro-CT) and scanning electron microscopy (SEM), where the need for statistically meaningful numbers of particles requires many sections to be analysed. Whiles the Vertical Gas Stream (VGS) elutriator is suitable for coarse particle upgrading (i.e. >38 μm), the performance is poor for finer particles (i.e. <38 μm). Consequently, the system has been modified to Vertical Water Stream (VWS) elutriator using higher density fluid (i.e. water) to enable analysis of Au particles below 38 μm. In this work, the VGS system was used to upgrade Au particles in the ?53 + 38 μm size fraction (in rougher concentrate, rougher tailings, regrind mill discharge and regrind cyclone underflow) and the VWS system was used to upgrade Au particles in the ?38 μm size fraction of the regrind mill discharge sample. The VWS elutriator was calibrated using galena (specific gravity, S.G. of 7.58) and quartz (S.G. of 2.65) particles of <38 μm size as model minerals. From the calibration tests, partition curves as a function of particle size were generated. Using these measurements, theoretical partition curves for Au (S.G. of 19.3) have been calculated. The VWS concentrate was characterised using Micro-CT and compared with SEM coupled with energy dispersive X-ray (EDX) analysis of ?53 + 38 μm ore size fraction of the VGS concentrate of the four sample streams. The Micro-CT analysis of VWS Au concentrate showed that sufficient particles (Au) can be upgraded. SEM/EDX results indicate that regrind does not affect changes in free Au particle morphology, aspect ratio and frequency of shearing damage in the ?53 + 38 μm size fraction. Cyclone classification of the regrind mill discharge in the ?53 + 38 μm size fraction appears to perform surface cleaning by exposing obscuring silver (Ag) surfaces on Au particles in the mill discharge sample.     

Strength of deformation processed Cu–Fe–Ag in situ composites

Three Cu–Fe–Ag in situ composites, i.e. Cu–14 wt.%Fe–1 wt.%Ag, Cu–14 wt.%Fe–3 wt.%Ag and Cu–11 wt.%Fe–6 wt.%Ag, were prepared by cast and drawn process. Strength of the composites was investigated in detail. The results show that the presence of Ag can refine the primary Fe dendrites, leading to much higher strength of Cu–Fe–Ag composites, which reached 1578 and 1357 MPa for Cu–14Fe–3Ag and Cu–11Fe–6Ag respectively at η = 6.1, however that of the same processed Cu–12 wt.% Fe is only 978 MPa. Strength of Cu–Fe–Ag can be expressed as σ = 1319 × λ^− 1 / 2 + 57 × C_Fe–M^1 / 2 + Δσ_Ag, where λ is filament spacing, C_Fe–M is the Fe content in the matrix and Δσ_Ag is strengthening effect of Ag in the matrix. As Ag content is lower, Δσ_Ag = 100 × C_Ag ^1 / 2 and as it is near or beyond 6 wt.%, Δσ_Ag should be determined by specific experiment due to a second-stage work hardening of the matrix. The calculated strength of Cu–Fe–Ag composites fits the experimental results well.     

Electrochemical oxidation of adenosine-5′-triphosphate on a chitosan–graphene composite modified carbon ionic liquid electrode and its determination

In this paper a new electrochemical method was proposed for the determination of adenosine-5′-triphosphate (ATP) based on a chitosan (CTS) and graphene (GR) composite film modified carbon ionic liquid electrode (CTS–GR/CILE). CILE was fabricated by using ionic liquid 1-butyl-3-methylimidazolium dihydrogen phosphate ([BMIM]H₂PO₄) as the binder, which was further modified by GR and CTS composite. The modified electrode exhibited an excellent electrocatalytic activity toward the oxidation of ATP with the increase of the oxidation peak current and the decrease of the oxidation peak potential. The electrochemical parameters of ATP on CTS–GR/CILE were calculated with the electron transfer coefficient (α) as 0.329, the electron transfer number (n) as 2.15, the apparent heterogeneous electron transfer rate constant (ks) as 3.705 × 10^? 5 s^? 1 and the surface coverage (Γ_T) as 9.33 × 10^? 10 mol cm^? 2. Under the optimal conditions the oxidation peak current was proportional to ATP concentration in the range from 1.0 × 10^? 6 to 1.0 × 10^? 3 M with the detection limit of 0.311 μM (S/N = 3). The proposed electrode showed excellent reproducibility, stability, anti-interference ability and further successfully applied to the ATP injection sample detection.     

Characterization of native microalgal strains for their chromium bioaccumulation potential: Phytoplankton response in polluted habitats

Due to its various uses, Cr contamination has become widespread in a diverse array of environments. The present study was carried out during 2007–2008 to investigate the accumulation potential of metals (Cr, Cu, Fe, Mn, Ni and Zn) and metalloid (As) by green (GA) and blue green (BGA) microalgae growing naturally in selected Cr-contaminated sites in districts Unnao and Kanpur (Uttar Pradesh, India). This investigation is a preliminary work to identify suitable native microalgae for biomonitoring and phytoremediation purposes. A total of 22 GA and 11 BGA were encountered in three seasons (summer, rainy and winter). Among these, the accumulation potential was evaluated in high biomass producing strains of BGA (three) and GA (nine). The maximum accumulation of Cr was shown by Phormedium bohneri (8550 μg g^?1 dw) followed by Oscillatoria tenuis (7354 μg g^?1 dw), Chlamydomonas angulosa (5325 μg g^?1 dw), Ulothrix tenuissima (4564 μg g^?1 dw), and Oscillatoria nigra (1862 μg g^?1 dw); all of which demonstrated a transfer factor of >10% for Cr. The results also indicate that the phytoplankton diversity was modified by Cr pollution. BGA represented the dominant community where Cr concentration was higher (11.84 and 2.27 mg L^?1) (r = 0.695), whereas GA showed negative correlation with respect to Cr concentration (r = ?0.567). In conclusion, different algal species were able to grow in Cr-contaminated sites and to accumulate significant amounts of Cr with a high transfer factor.     

Effect of solidification parameters on the microstructure of Sn-3.7Ag-0.9Zn solder

In this work, Sn–Ag–Zn alloy of eutectic composition (Sn-3.7wt.%Ag-0.9wt.%Zn) was directionally solidified upward at a constant temperature gradient (G = 4.33 K/mm) in a wide range of growth rates (V = 3.38–220.12 μm/s) and a constant growth rate (V = 11.52 μm/s) with different temperature gradients (G = 4.33–12.41 K/mm) using a Bridgman type directional solidification furnace. The microstructure was observed to be a rod Ag₃Sn structure in the matrix of β–Sn from the directionally solidified Sn-3.7wt.%Ag-0.9wt.%Zn samples. The values of eutectic spacing (λ) were measured from transverse section of samples. The dependency of eutectic spacing on the growth rate (V) and temperature gradient (G) were determined with linear regression analysis. The dependency of λ on the values of V and G were found to be λ = 10.42V ^? 0.53 and λ = 0.27G ^? 0.48, respectively. The values of bulk growth were also determined to be λ²V = 86.39 μm³/s by using the measured values of λ and V. The results obtained in present work were compared with the previous similar experimental results obtained for binary and ternary alloys.     

Microstructure and tensile strength of PM304 composite

PM304 composite comprising NiCr (80/20) matrix (60 wt.%) combined with Cr₂O₃ (20 wt.%), Ag (10 wt.%) and eutectic BaF₂/CaF₂ (10 wt.%) as solid self-lubricants additives has been successfully prepared by mechanical alloying and powder metallurgy. The sintered PM304 samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS). The density of PM304 composite sintered at 1100 °C was 7.3 g/cm³, and the mean tensile strength 47 MPa. The size of Cr₂O₃, BaF₂/CaF₂ particles was less than 1 μm, and that of Ag particles below 5 μm. Fracture morphology indicates that the fracture of PM304 is mainly along Ni80Cr20 grains.     

A comparison of Ga:ZnO and Ga:ZnO/Ag/Ga:ZnO source/drain electrodes for In–Ga–Zn–O thin film transistors

We compared the characteristics of single Ga:ZnO (GZO) and GZO/Ag/GZO multilayer electrodes for source/drain (S/D) contacts in amorphous In–Ga–Zn–O (a-IGZO)-based thin film transistors (TFTs). Due to the existence of a Ag metallic layer between the GZO layers, the GZO/Ag/GZO multilayer electrode exhibited low sheet resistance (3.95 ohm/sq.) and resistivity (3.32 × 10^?5 ohm-cm). The saturation mobility (10.2 cm² V^?1 s^?1) of the a-IGZO TFT with GZO/Ag/GZO S/D electrodes is much higher than that attained for the a-IGZO TFT with single GZO S/D electrodes (0.7 cm² V^?1 s^?1) due to the lower resistivity of the GZO/Ag/GZO multilayer S/D electrode. Furthermore, it is expected that the high transparency of the GZO/Ag/GZO multilayer will allow for the possible realization of fully transparent a-IGZO TFTs.     

Single crystal structure determination and infrared fluorescence of the system (K3Sr1−xNdx) (Nd1−xSr1+x) Nb10O30

The μ-pulling down technique has permitted to grow single crystal fibers, of the gross chemical formula K₃Sr₂NdNb₁₀O₃₀, having a sufficient optical quality to carry out spectroscopic studies. The crystal structure has been determined and refined to reliability factors: (i) R₁ = 0.0384 (wR₂ = 0.0665) at room temperature; (ii) R₁ = 0.0334 (wR₂ = 0.0638) at 120 K. Difference in the cationic distribution over the 15- and 12-fold sites was noticed. IR fluorescence spectra investigated under different laser excitation wavelength at 300 K and 77 K show strong emissions at 0.9 and 1.06 μm. Low temperature fluorescence behavior is compatible with Nd³⁺ ions located in both Sr²⁺ and K⁺ sites with 15- and 12-fold coordination, respectively.     

Study on 2.0 μm fluorescence of Ho-doped water-free fluorotellurite glasses

Ho³⁺-doped water-free fluorotellurite glasses with composition of 60TeO₂–30ZnF₂–10NaF (mol%, TZNF60) were made by using specially-designed physical and chemical dehydration technique. 2.04 μm fluorescence (Ho³⁺: ⁵I₇ → ⁵I₈) was observed experimentally and presented in this paper: A broad bandwidth of ∼149 nm, large simulated emission cross-section of 7.2 × 10⁻²¹ cm², and the longest reported fluorescence lifetime of ∼10 ms among all the reported Ho³⁺-doped oxide glasses. Thanks to the absence of OH groups and low phonon energy with the addition fluorides into tellurite oxide glasses, 1.00Ho-TZNF60 glass demonstrates the maximum figure of merit (σ_em × τ_f) of 7.13 × 10⁻²⁷ m² s, thus regarded as a promising optical material for the development of 2.0 μm fiber lasers.     

Development of novel naphthalimide-functionalized magnetic fluorescent nanoparticle for simultaneous determination and removal of Hg2+

Mercury (Hg) commonly found in the global environment poses a serious threat to the environment and human health because of its durability, easy transference and high biological accumulation. So, great attention has been paid to the quantification and removal of mercury. Herein, we present the synthesis and properties of a novel naphthalimide-functionalized magnetic fluorescent nanoparticle for simultaneous determination and removal of Hg²⁺. The proposed nanoparticle showed a good linear relation (Y = −29.12216X + 363.2597, correlation coefficient of R² = 0.9952) between the fluorescence intensity at 540 nm and the concentration of Hg²⁺ varying from 0.1 μmol/L to 4.5 μmol/L. Additionally, our proposed nanoparticle exhibited excellent Hg²⁺-selectivity over other metal ions, which was ascribed to the formation of imide-Hg-imide complexes. The removal of Hg²⁺ from contaminated water samples was achieved by the aggregation-induced sedimentation (AIS) strategy. Moreover, the suspended magnetic nanoparticle could be removed by external magnetic field, and the secondary pollution was avoided.     

Preparation and optical characterization of e-beam deposited cerium oxide films

Cerium oxide films, of 0.3–1 μm thickness, were reactively deposited in the oxygen atmosphere onto quartz plates by the PVD method. An electron gun was used as an evaporation source. Films were characterized with the AFM method, Raman spectroscopy and spectrophotometrically. Optical properties of these films were examined for the wavelength range 0.2–2.5 μm. Films were characterized by high transparency, between 0.38 and 2.5 μm. The complex refractive index, n^*=n − jk, was evaluated. The dispersion characteristics for n(λ) and k(λ) were presented. We found that the refractive index strongly depends on the temperature of substrates (300 K ⩽ T_s ⩽ 673 K) during film deposition. Estimated values of the refractive index (at λ = 0.55 μm) were in the range 1.91–2.34.     

Preparing silver nanoparticles in supercritical water

Silver (Ag) nanoparticles were prepared using Ag microparticles as precursors in supercritical water (SCW). The effect of reaction time on preparing Ag nanoparticles was investigated. The obtained products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The results indicated that, with the increase of reaction time, Ag microparticles prepared by calcination method with the sizes > 2 μm remained after SCW treatment because of their high crystallinity, but those with the sizes < 1 μm were destroyed and formed many Ag nanoparticles due to the destructive effect of SCW.     

An investigation on microstructure and mechanical properties of Al7075 to Ti–6Al–4V Transient Liquid Phase (TLP) bonded joint

Transient Liquid Phase (TLP) bonding of two dissimilar alloys Al7075 and Ti–6Al–4V has been done at 500 °C under 5 × 10⁻⁴ torr. Cu was electrodeposited on Al7075 and Ti–6Al–4V surfaces, 50 μm thick Sn–4Ag–3.5Bi film was used as interlayer and bonding process was carried out at several bonding times. The microstructure of the diffusion bonded joints was evaluated by Light Optical Microscopy (LOM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The eutectic and intermetallic compounds formation along Al7075 grain boundaries and Ti/Al interface such as θ(Al₂Cu), TiAl and Ti₃Al were responsible for joint formation at the aluminum and titanium interfaces. Microhardness and shear strength tests were used to investigate the mechanical properties of the bonds. Hardness of the joints increased with increasing bonding time which can be attributed to the intermetallics formation at the interface. The study showed that the highest bond strength was 36 MPa which was obtained for the samples joined for 60 min.     

The effect of nano-sized stainless steel powder addition on mechanical and physical properties of micropowder injection molded part

Micropowder injection molding (μPIM) is a new technology that has potential in the mass production of microcomponents. A bulk material of nanoparticles possesses completely different properties from those of large-sized particles. The main objective of this study is to study the effects of nano-sized powder addition on the μPIM process of powder-polymer mixtures for the fabrication of miniature parts. The binder systems consist of polyethylene glycol (PEG), polymethyl methacrylate (PMMA), and stearic acid (SA) with different powder loading blended with powders. The results indicate that increasing the nanopowder content to 30 wt.% increased the powder loading and decreased the injection and sintering temperatures. The sintered parts had densities of 96% of the theoretical value. High physical and mechanical properties of the sintered specimen were achieved with the 30 wt.% nano-sized powder sintered at 1200 °C at a heating rate of 5 °C/min under vacuum atmosphere. A significant reduction of the surface roughness of the sintered parts using the nano–microhybrid powder (S_a = 0.365 μm) was observed compared with the sintered parts with only micropowder (S_a = 1.002 μm). Using nanopowders, the hardness also increased from 182 HV to 221 HV with a linear shrinkage of approximately 9%, which is less than that of the micropowders (18%).