A facile synthesis of silver nanoparticle with SERS and antimicrobial activity using Bacillus subtilis exopolysaccharides

In this study, we report a facile synthesis of silver nanoparticle having SERS and antimicrobial activity using bacterial exopolysaccharide (EPS). Bacillus subtilis (MTCC 2422) was grown in nutrient broth and the extracellular EPS secreted by the organism was extracted and purified. The purified EPS was used for the synthesis of silver nanoparticles. The kinetics of silver nanoparticle synthesis was deduced by varying the exposure time and the concentration of EPS. The rate constant (k) for the synthesis of silver nanoparticle was calculated from the slope of ln(A^∞ ? A^t) versus time plot. The k value was found to be 3.49 × 10^?3, 5.81 × 10^?3 and 5.03 × 10^?3 per min for particle synthesis using 2, 5 and 10 mg/mL EPS, respectively. The nanoparticles synthesised had an average particle size of 5.18 ± 1.49 nm, 1.96 ± 0.77 nm and 2.08 ± 0.88 nm for 2, 5 and 10 mg/mL EPS, respectively. The synthesised particles were characterised using UV-Vis absorbance spectroscopy, high-resolution transmission electron microscopy (HRTEM) attached to EDS (energy dispersive spectroscopy), Fourier transform infrared spectroscopy (FTIR), surface enhanced Raman spectroscopy (SERS) and zeta potential analyser. To our knowledge, this is the first study to report SERS activity of microbial Bacillus subtilis EPS-based synthesis of silver nanoparticle. HRTEM images showed silver nanoparticle entrapped in polysaccharide nanocages. Silver nanoparticle showed higher adherence towards the bacterial surface, with good bactericidal activity against Pseudomonas aeroginosa and Staphylococcus aureus.     

Crosslinking with ammonium zirconium carbonate improves the formation and properties of spruce galactoglucomannan films

Spruce (Picea abies) O-acetyl-galactoglucomannans (GGMs), low-value by-products from the forestry industry were upgraded to sustainable film-forming materials by crosslinking with ammonium zirconium carbonate (AZC). The purpose of crosslinking was to enhance the film formation, reduce the need of polyol plasticizers, and decrease the sensitivity of the film properties to moisture. Tensile testing showed that AZC-crosslinked GGM can be used to prepare strong and stiff films, with tensile strength up to 52 MPa and Young’s modulus of 4.7 GPa. Dynamic mechanical analysis, performed as a function of relative humidity (RH), showed that AZC-crosslinked GGM films retained their stiffness at higher RH than the reference films without AZC. Water vapor sorption and permeability analyses were done to further study the effect of moisture on the film properties, and those showed that the effect of sorbitol as a plasticizer depended greatly on RH. The oxygen permeability of the AZC-crosslinked GGM films was in the range of 4–11 [cm³ μm/(m² day kPa)]. GGM films could offer a bio-based and biodegradable alternative to existing synthetic oxygen barrier materials, on the condition that they are protected from the effects of moisture, e.g., by hydrophobic laminated layers.     

Cheaper membrane materials for microalgae dewatering

Among different strategies to reduce costs in microalgae dewatering process via cross-flow filtration, the one related to membrane material was investigated in order to be decreased. Several materials were tested, starting with the ones commonly used in membrane technology [ceramic, polysulfone (PSf) and polyacrylonitrile (PAN)] to the ones generally employed in packaging industry [acrylonitrile butadiene styrene (ABS), glycol-modified polyethylene terephthalate (PETG) and polylactic acid (PLA)], the latter being considerably cheaper. Experiments carried out showed promising results in terms of permeabilities for PSf–Pluronic^® F127 blended membranes and PAN membranes (11 ± 1 L/h/m²/bar and 22 ± 1 L/h/m²/bar, respectively, instead of 2 ± 2 L/h/m²/bar of PSf membranes), but with high related costs. PLA membranes showed good mechanical properties, biodegradability and price, but low permeability values (5 ± 1 L/h/m²/bar). PETG membranes showed attractive results in terms of costs and permeability, but poor mechanical properties. The polymer that offered the best results was the ABS that reached membrane permeabilities of 19 ± 1 L/h/m²/bar, maintaining good mechanical properties while filtering the microalgae Phaeodactylum tricornutum Bohlin. Thus, a novel functionality was found for these not so common polymers in microalgae dewatering. This indicates that use of these materials could also be considered in other aqueous micro/ultrafiltration applications. In addition, the biodegradable PLA polymer introduces a new concept of cheap and environmental friendly membrane in this application.     

Evaluation and verification of the virgin–recycled mixing ratio of polypropylene plastic

This study has analyzed the properties of blended polypropylene (PP) specimens and employed statistical analysis to develop a method for determining the virgin–recycled mixing ratio of a specimen. Morphological observations and analyses of thermal and mechanical properties were conducted to examine specimen properties. The results were incorporated into regression analysis to create relationship equations. The results revealed that the melt temperature ranged between 167 and 169 °C, melt index (MI) ranged between 7.59 and 18.36 g/10 min, viscosity decreased when the amount of recycled PP and the rotation speed increased, the maximum decomposition temperature decreased with an increase in recycled PP content and increased with the heating rate, activation energy (E_a) ranged between 39.91 and 12.07 kcal/mol, Young’s modulus ranged between 1121.1 and 1910.2 MPa, and impact strength ranged between 37.94and 49.41 J/m (no significant trends). Scanning electron microscopy showed unbroken fibrils distributed on the fracture surface of Specimens 1–3. Additionally, the tensile strain of these specimens was comparatively high. The fracture surfaces of the specimens showed favorable compatibility after undergoing impact tests. The results of regression analysis indicated that the mixing ratio achieved significant correlations with E_a, MI, and Young’s modulus. Thus, regression and multiple regression analysis were performed to create relationship equations.     

Hardness and fracture toughness of thermoelectric La<Subscript>3−<Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>4</Subscript>

Lanthanum telluride (La_3?x Te₄) is a state-of-the-art n-type high temperature thermoelectric material that behaves as a weak and brittle ceramic. Vickers microindentation hardness testing was explored as a rapid analysis technique to characterize the mechanical properties of this material. An indentation size effect was observed with hardness values ranging from 439 ± 31 kgf/mm² (0.01 kgf/10 s contact time) to 335 ± 6 kgf/mm² (0.5 kgf/10 s contact time). The Vickers indentation fracture toughness, K _VIF, based on measurements of crack lengths emanating from the corners of the Vickers indents was 0.70 ± 0.06 MPa m^1/2.     

Preparation and Properties of LiF-doping LiFePO4/C Anode Material

LiFe(PO₄)_1–x F _x /C was successfully composited using a mechanical activation-carbon thermal reduction process using LiF as the doped fluoride source, and x was 0.01, 0.02, 0.03, 0.04. In this article, material testing used scanning electron microscopy, X-ray crystal diffraction analysis, specific surface area analysis, cyclic voltammograms, and the ac impedance test. The results showed that when x = 0.03, LiFe(PO₄)_0.97F_0.03/C material showed good capability in regard to charge and discharge, and cycle performance was good. The specific surface area was 84.27 m²/g, which was created by the mechanical activation-carbon thermal reduction process. The initial discharge of LiFePO₄ synthesized under such conditions was 153.278 mA h/g (0.1C and 2.5–4.2 V). Compared with less doped LiFePO₄/C material, the discharge-specific capacity of the material was 127.351 mA h/g under the same conditions. This increases by 20.34% for the initial time cycle, and after 20 circulations, the capacity was 151.512 mA h/g.     

Crystallographic, thermoelectric, and mechanical properties of polycrystalline type-I Ba8Al16Si30-based clathrates

Crystallographic, thermoelectric, and mechanical properties of polycrystalline Ba₈Al₁₆Si₃₀-based samples with type-I clathrate structure prepared by combining arc melting and spark plasma sintering methods were investigated. The major phase of the samples was a type-I clathrate with an actual Al/Si ratio of ~15/31, strongly suggesting that framework deficiency was absent or was present in very low concentration in the samples. The Hall carrier concentration n of the samples was approximately 1 × 10²¹ cm^?3, which is lower than the values reported so far for the Ba₈Al₁₆Si₃₀ system. Other important material parameters of the samples were as follows: the density-of-states effective mass m* = 2.3m ₀, Hall mobility μ = 7.4 cm² V^?1 s^?1, and the lattice thermal conductivity κ _L = 1.2 W m^?1 K^?1. The thermoelectric figure of merit ZT reached approximately 0.4 (900 K) for a sample with n = 9.7 × 10²⁰ cm^?3. Simulation using the experimentally determined values of material parameters showed that ZT reached values >0.5 if the carrier concentration is optimized at about 3 × 10²⁰ cm^?3. Young’s, shear, and bulk moduli were estimated to be approximately 98, 39, and 117 GPa, respectively, and Poisson’s ratio was found to be 0.25 from the longitudinal and transverse velocities of sound, v _L = 6038 m/s and v _T = 3503 m/s, respectively, for a sample with ZT = 0.4. The coefficient of thermal expansion (CTE) ranged from approximately 8 × 10^?6 K^?1 to 10 × 10^?6 K^?1 (330–690 K), which is smaller than the values reported for Ba₈Ga₁₆Ge₃₀ and Sr₈Ga₁₆Ge₃₀ clathrates.     

Physical and electrical attributes of sintered Ag80–Al20 high temperature die attach material with different organic additives content

In this work, the primary focus was to establish a relationship between the post-sintered physical attributes of the high temperature Ag₈₀–Al₂₀ die attach material and its electrical performance. The post-sintered Ag₈₀–Al₂₀ die attach material depicted the formation of Ag₂Al and Ag₃Al compounds. The melting point and maximum operational temperature for the Ag₈₀–Al₂₀ die attach material was determined to be 518 ± 1 °C and approximately 400 °C respectively, whereby the maximum operational temperature was based on a homologue temperature ratio of 0.85. The die attach material also demonstrated good electrical properties, i.e., an electrical conductivity value of 1.005 × 10⁵ (ohm–cm)^?1, which is higher than or equal to that of most solder systems. By varying the nanoparticle versus organics content between 83.3 and 87.0 %, it was seen that the surface morphology of the die attach material changed and the root-mean-square roughness values reduced to 175.1 nm. A similar observation was seen as the sintering temperature increased between 100 and 380 °C. This reduction in surface roughness proved that there was grain growth and particle coalescence within the die attach material. This translated to a reduction in electrical resistivity. Die attach area and thickness simulations found that smaller and thinner die attach areas are preferred for the Ag₈₀–Al₂₀ die attach material, whereby the highest recorded electrical conductivity value was 1.006 × 10⁵ (ohm–cm)^?1 for an area of 0.2 × 0.2 cm² and thickness of 25.4 μm.     

Investigation the glazability of dimension andesites with glaze coating materials containing boron minerals in construction sector

This study examined the usability of thin plates cut from rocks of volcanic origin as new decorative indoor and outdoor coating material when used instead of ceramic saddle. The study examined the basic material characterization of andesites and the glazability of andesites with glaze coating materials containing boron minerals. The series of characterization tests were conducted on andesite samples. Then, the samples were applied glaze for trial purposes. Analysis indicated that the andesite samples consisted of sanidine, mica and pyroxene minerals and its apparent porosity, density, water absorption, salt crystallization resistance, compressive strength, frost after compressive strength, bending strength and impact resistance values were 15.75 %, 2,640 kg/m³, 7.41 %, 1.06 %, 47.03 MPa, 45.25 MPa, 10.16 MPa and 9.87 kPa respectively. In heat microscope measurements, maximum sintering was recorded at 1,182 °C. Linear expansion coefficient (α) of the andesite at 400 °C was 4.69 × 10^?6 K^?1. Firing performed by using the prepared glaze recipe at approximately 1,055 and 1,000 °C produced good results in terms of body-glaze harmony.     

Effects of annealing process on microstructure and electrical properties of cold-drawn thin layer copper cladding steel wire

The microstructure, mechanical and electrical properties of cold-drawn thin layer copper cladding steel (CCS) wires annealed after different processes were studied by optical microscopy, electron omnipotent material experiment machine, micro hardness machine, SEM and electrical resistivity measurement system. The results indicated that the recovery and recrystallization of steel-core happened in the temperature range 550–750 °C for the holding period of 120 min. When the annealing temperature was higher than 750 °C, grains begun to grow and grain sizes increased gradually with increasing the annealing temperature. The tensile strength and micro hardness were declined with increasing annealing temperature and holding time. The distance of Cu–Fe atoms interfacial diffusion of thin layer CCS wires ranged from 4 µm of cold-drawn wire to 7.5 µm of annealed wire at 850 °C for 120 min. The higher the annealing temperature become, the larger the distance of Cu–Fe atoms interfacial diffusion is. When the annealing temperature was lower than 650 °C, the resistivity was slightly less than 71 × 10^?3 Ω mm² m^?1 which was the resistivity of cold-drawn wire. When the annealing temperature was higher than 650 °C, the resistivity increased with increasing the annealing temperature. Meanwhile, the variation of electrical property of thin layer CCS wires was analyzed and discussed based on microstructure and interfacial diffusion.     

In vitro antimicrobial activity of vancomycin-eluting bioresorbable β-TCP-polylactic acid nanocomposite material for load-bearing bone repair

Release of antimicrobial agents from bone healing devices can dramatically reduce the risk of implant-associated infection. Here we report the fabrication and antimicrobial activity of a multifunctional load-bearing bioresorbable material that can provide mechanical support to the healing bone all while slowly releasing an antibiotic drug. Dense beta-tricalcium phosphate (β-TCP)–40 vol% polylactic acid (PLA) nanocomposite containing 1 wt% vancomycin (VH) was high pressure consolidated at 2.5 GPa, at room temperature, or at 120 °C. Over the course of 5 weeks in TRIS solution, the β-TCP-PLA-VH nanocomposite released approximately 90 % of its drug load. Specimens consolidated at 120 °C had the highest initial mechanical properties and maintained 85 % of their compressive strength and 30 % of their bending strength after 5 weeks release. In vitro growth inhibition study showed significant antimicrobial efficacy of VH-impregnated β-TCP-PLA against methicillin-resistant Staphylococcus aureus when exposed to both high (2 × 10⁵ CFU/mL) and very high (1 × 10⁸ CFU/mL) bacterial concentrations. After 1 week, total eradication of the microorganisms was achieved. The results suggest that the developed high-strength antibiotic-eluting β-TCP-PLA nanocomposite can be a promising material for orthopedic surgical devices.     

Exopolysaccharide produced by Vibrio neocaledonicus sp. as a green corrosion inhibitor: Production and structural characterization

An exopolysaccharide substances produced by Vibrio neocaledonicus sp. was introduced as a novel green inhibitor against the corrosion of carbon steel in artificial seawater and acidic media. The produced extracellular polymeric substance (EPS) is heterogeneous with composition of polysaccharides, nucleic acids and protein and average molecular weight of 29,572 Da. Adsorption of EPS on the metal surfaces and formation of Fe-EPS complexes acted as a barrier to prevent the oxygen penetration and hindered anodic and cathodic reactions. The inhibitory effect increases with increasing EPS concentration and exposure time. The highest corrosion inhibitory effect (95.1%) was observed for 10 g/L of EPS after 5 days of exposure in seawater. This is the highest inhibitory effect ever been reported by EPSs. While, the optimum concentration of EPS with the highest inhibition efficiency in 1 N H₂SO₄ was 1000 ppm. The influence of different parameters, such as initial pH, growth phase, various nitrogen and carbon sources on the production of EPS and its corrosion inhibitory effect were also investigated. According to results, the optimum culture medium for EPS production is contained artificial seawater including 5% mannitol as carbon source and 0.1% (NH₄)₂SO₄ as nitrogen source at pH = 8. This medium could produce 22.24 g/L EPS during 3 days’ incubation at 30 °C. The corrosion inhibitory efficiency of obtained EPS was 95.97%.     

Optimisation of hybridisation effect in graphene reinforced polymer nanocomposites

This article focuses on the optimisation of electrical and mechanical properties of hybrid blends of polyoxymethylene (POM) as primary thermoplastic matrix, polypyrrole (PPY) as secondary conducting polymer and graphene (G) as reinforcement. An initial Taguchi analysis was performed with a focus on improving electrical conductivity (σ) and tensile strength. A mixture analysis using ‘simplex’ statistical design was applied to develop an experimental subset that identified an optimal combination in weight-percentage. Both electrical and mechanical properties were improved by the addition of PPY and graphene particles due to hybridisation mechanism as well as double percolation threshold. The maximum electrical conductivity of 0.95 S cm^?1 was achieved with POM reinforced with 3 wt.% of G and 2.5 wt.% of PPY loading. The mechanical properties were found to be increased with increase in addition of both G and PPY.     

A spectroscopic investigation into the setting and mechanical properties of titanium containing glass polyalkenoate cements

Titanium (Ti) implants are extensively used in a number of biomedical and dental applications. This work introduces Ti into the glass phase of a zinc based glass polyalkenoate cement (GPC) and investigates changes in handling and mechanical properties considering two molecular weight polyacrylic acids (PAA), E9 and E11. Considering the handling properties, the working time (T _w) increased from 50 s_E9, 32 s_E11 (BT 101, Ti-free) to 169 s_E9, 74 s_E11 with TW-Z (highest Ti content), respectively. The setting time (T _s) increased from 76 s_E9, 47 s_E11 (BT 101) to 303 s_E9, 232 s_E11 with TW-Z, respectively. Ti was also found to have a significant increase on both compressive (σ _c) and biaxial flexural strength (σ _f), where σ _c increased from 36 MPa_E9, 56 MPa_E11 (BT 101) to 56 MPa_E9 and 70 MPa_E11 with TW-Z respectfully. σ _f also increased from 11 MPa_E9, 22 MPa_E11 (BT 101) to 22 MPa_E9 and 77 MPa_E11 with TW-Z, respectively. No increase in mechanical properties was evident with respect to maturation. Raman Spectroscopy was employed to investigate changes in glass structure and the setting of the cements with. This revealed increased glass network disruption with increasing TiO₂ content and matured cement setting with TW-Z as compared to the control BT 101. FT-IR was then employed to investigate any additional setting mechanism and changes with time. Spectroscopy determined that Ca²⁺/Sr²⁺PAA complexes are primarily responsible for the setting and mechanical strength with no changes occurring over time.     

Microstructure and mechanical properties of fluorcanasite glass-ceramics for biomedical applications

Four fluorcanasite glass-ceramics were fabricated by controlled heat-treatment of as-cast Glasses A–D. These compositions have been reported previously but essentially, Glass A had the stoichiometric composition (Ca₅Na₄K₂Si₁₂O₃₀F₄) and Glasses B–D were modified by reducing the Na₂O concentration (B), adding excess CaO (C) and P₂O₅ (D). The latter two compositions have been shown to have promising bioactive response in cell culture and simulated body fluid experiments. Devitrification of the stoichiometric composition resulted in poor mechanical properties with crumbling often observed on machining. As a result, no mechanical data could be obtained. In all modified compositions, heat-treatment between 780 °C and 900 °C resulted in measurable indentation fracture toughness (IFT) and biaxial flexural strength (BFS). IFT was optimised in Glass C at 800 °C (2.53 ± 0.02 MPa m^½), but the biaxial flexural strength (BFS) was low, 167 ± 17 MPa, compared to other compositions. For heat- treated Glass D optimum mechanical properties were obtained at 800 °C with BFS and IFT, 249 ± 23 MPa and 1.95 ± 0.01 MPa m^½, respectively. The relationship between the mechanical properties and microstructure is discussed.     

A novel silver–aluminium high-temperature die attach nanopaste system: the effects of organic additives content on post-sintered attributes

An Ag–Al die attach material having a fixed Ag–Al nanoparticles weight percent content (80–20 %), as well as varying organic additives weight percent content was formulated. The total nanoparticle weight percent content was varied between 84.7 and 87.0 %. As the organic additives content in the Ag₈₀–Al₂₀ die attach material decreased from 15.3 to 13.0 %, the nanopaste’s viscosity increased. The die attach material was sintered at 380 °C for 30 min to form Ag₂Al and Ag₃Al compounds. With decreasing organics content from 15.3 to 13.0 %, the porosity of the post-sintered samples also decreased from 30 to 19 %, while the density increased from 2.36 to 6.42 g/cm³. The highest melting point was recorded for the sample with the least organic weight percent content at 519 °C. The coefficient of thermal expansion and electrical conductivity values varied between 6.99–7.74 × 10^?6/ °C and 0.95–1.01 × 10⁵ (ohm-cm)^?1 respectively with decreasing organic content from 15.3 to 13.0 %. The electrical conductivity values recorded were higher than or equal to that of most solder alloy die attach materials. By changing the organic additives content in the Ag₈₀–Al₂₀ die attach material, suitable properties are obtained for high temperature die attach applications.     

Utility of Multivariate Analysis in Modeling the Effects of Raw Material Properties and Operating Parameters on Granule and Ribbon Properties Prepared in Roller Compaction

This article aimed to model the effects of raw material properties and roller compactor operating parameters (OPs) on the properties of roller compacted ribbons and granules with the aid of principal component analysis (PCA) and partial least squares (PLS) projection. A database of raw material properties was established through extensive physical and mechanical characterization of several microcrystalline cellulose (MCC) and lactose grades and their blends. A design of experiment (DoE) was used for ribbon production. PLS models constructed with only OP-modeled roller compaction (RC) responded poorly. Inclusion of raw material properties markedly improved the goodness of fit (R²?=?.897) and model predictability (Q²?=?0.72).     

Impact of different coating processes of microfibrillated cellulose on the mechanical and barrier properties of paper

This study presents a comparison of the mechanical and barrier properties of papers coated with microfibrillated cellulose (MFC) by two different coating processes: (i) bar coating and (ii) size press. Due to the high water content of MFC, water-treated papers were taken as references to highlight the effects of MFC on the properties of papers. Structural, mechanical and barrier properties of the ensued materials were performed respectively with SEM, tensile and stiffness testers, and air and oxygen permeability equipments. The properties of the water-treated papers were considerably damaged compared to those of the base paper that underlined the negative impact of both coating processes on the papers structure. With MFC, the air barrier and the bending stiffness were considerably improved (+90 and +50 % respectively), especially when the bar coating was used, i.e. with 7 g m^?2 of MFC. Size press was indeed not able to considerably improve papers properties as the MFC coat weight barely reached 4 g m^?2 resulting from ten successive MFC layers.     

Preparation and Properties of Porous Composite of Hematite/Magnetite/Carbon with Eucalyptus Wood Biotemplate

By using eucalyptus wood biotemplate, a novel porous composite material of iron oxides and carbon (PC-Fe/C) was manufactured for adsorption of oxoanion pollutants. The material's microstructure and characteristic were investigated by different characterization techniques. The experimental results show that the PC-Fe/C composite mainly consisted of hematite, magnetite, and carbon, and preserved the porous hierarchical texture of the wood with 70 ～ 120 µm macropores, 4.1 ～ 6.4 µm mesopores, and 0.1 ～ 1.3 µm micropores. Its Brunauer-Emmtee-Teller (BET) surface area was 59.2 m² g^?1. The maximum adsorption capacities were 2.49, 2.96, and 0.69 mg g^?1 for arsenic(V), chromium(VI), and phosphorus(V), respectively. The adsorption capacities of the unpulverized material as a novel filtration adsorbent are comparable to fine particles of the pulverized material, natural, and synthetic iron oxides.     

Structural,optical and electrical properties of PbS and PbSe quantum dot thin films

PbS and PbSe were prepared by hot injection method. The powders were used for preparing the corresponding films by using thermal evaporation technique. The structural, optical and electrical properties of PbS and PbSe thin films were investigated. The structural properties of PbS and PbSe were investigated by X-ray diffraction, transmission electron microscopy and energy dispersive X-ray techniques (EDX). PbS and PbSe films were found to have cubic rock salt structure. The particles size ranged from 1.32 to 2.26 nm for PbS and 1.28–2.48 nm for PbSe. EDX results showed that PbS films have rich sulphur content, while PbSe films have rich lead content. The optical constants (absorption coefficient and the refractive index) of the films were determined in the wavelength range 200–2500 nm. The optical energy band gap of PbS and PbSe films was determined as 3.25 and 2.20 eV, respectively. The refractive index, the optical dielectric constant and the ratio of charge carriers concentration to its effective mass were determined. The electrical resistivity, charge carriers concentration and carriers mobility of PbS at room temperature were determined as 0.55 Ω cm, 1.7 × 10¹⁶ cm^?3 and 656 cm² V^?1 s^?1, respectively, and for PbSe films they were determined as 0.4 Ω cm, 9 × 10¹⁵ cm^?3 and 1735 cm² V^?1 s^?1, respectively. These electrical parameters were investigated as a function of temperature.