Silver coated bioactive glass particles for wound healing applications

Bioactive glass particles (0.42SiO₂–0.15CaO–0.23Na₂O–0.20ZnO) of varying size (<90 μm and 425–850 μm) were synthesized and coated with silver (Ag) to produce Ag coated particles (PAg). These were compared against the uncoated analogous particles (Pcon.). Surface area analysis determined that Ag coating of the glass particles resulted in increased the surface area from 2.90 to 9.12 m²/g (90 μm) and 1.09–7.71 m²/g (425–850 μm). Scanning electron microscopy determined that the Ag coating remained at the surface and there was little diffusion through the bulk. Antibacterial (Escherichia coli—13 mm and Staphylococcus epidermidis—12 mm) and antifungal testing (Candida albicans—7.7 mm) determined that small Ag-coated glass particles exhibited the largest inhibition zones compared to uncoated particles. pH analysis determined an overall higher pH consider in the smaller particles, where after 24 h the large uncoated and Ag coated particles were 8.27 and 8.74 respectively, while the smaller uncoated and Ag coated particles attained pH values of 9.63 and 9.35 respectively.     

Cathodoluminescence properties of SiO<Subscript>2</Subscript>:Pr<Superscript>3+</Superscript>and ZnO·SiO<Subscript>2</Subscript>:Pr<Superscript>3+</Superscript> phosphor nanopowders

The successful incorporation of ZnO nanoparticles in Pr³⁺-doped SiO₂ using a sol–gel process is reported. SiO₂:Pr³⁺ gels, with or without ZnO nanoparticles, were dried at room temperature and annealed at 600 °C. On the basis of the X-ray Diffraction (XRD) results, the SiO₂ was amorphous regardless of the incorporation of Pr³⁺ and nanocrystalline ZnO or annealing at 600 °C. The particles were mostly spherical and agglomerated as confirmed by Field Emission Scanning Electron Microscopy. Thermogravimetric analysis of dried gels performed in an N₂ atmosphere indicated that stable phases were formed at ≥900 °C. Absorption bands ascribed to ³H₄-³P_{(J = 0,1,2)}, ¹I₆ and ¹D₂ in the UV–VIS region were observed from SiO₂:Pr³⁺ colloids. The red cathodoluminescent (CL) emission corresponding to the ³P₀ → ³H₆ transition of Pr³⁺ was observed at 614 nm from dried and annealed SiO₂:Pr³⁺ powder samples. This emission was increased considerably when ZnO nanoparticles were incorporated. The CL intensity was measured at an accelerating voltage of 1-5 keV and a fixed beam current of 8.5 μA. The effects of accelerating voltage on the CL intensity and the CL degradation of SiO₂:Pr³⁺ and ZnO·SiO₂:Pr³⁺ were also investigated using Auger electron spectroscopy coupled with an Ocean Optics S2000 spectrometer.     

Structured ZnO-based contacts deposited by non-reactive rf magnetron sputtering on ultra-thin SiO2/Si through a stencil mask

In this paper, we study the localized deposition of ZnO micro and nanostructures deposited by non-reactive rf-magnetron sputtering through a stencil mask on ultra-thin (10 nm) SiO₂ layers containing a single plane of silicon nanocrystals (NCs), synthetized by ultra-low energy ion implantation followed by thermal annealing. The localized ZnO-deposited areas are reproducing the exact stencil mask patterns. A resistivity of around 5 × 10^− 3 Ω cm is measured on ZnO layer. The as-deposited ZnO material is 97% transparent above the wavelength at 400 nm. ZnO nanostructures can thus be used as transparent electrodes for Si NCs embedded in the gate-oxide of MOS devices.     

Nucleation and growth mechanism of apatite on a bioactive and degradable ceramic/polymer composite with a thick polymer layer

Nucleation and growth mechanism of apatite on a bioactive and degradable PLLA/SiO₂–CaO composite with a thick PLLA surface layer were investigated compared to that on a bioactive but non-degradable polyurethane (PU)/SiO₂–CaO composite with a thick PU surface layer. The bioactive SiO₂–CaO particles were made by a sol–gel method from tetraethyl orthosilicate and calcium nitrate tetrahydrate under acidic condition followed by heat treatment at 600 °C for 2 h. The PLLA/SiO₂–CaO and PU/SiO₂–CaO composites were then prepared by a solvent casting method which resulted in thick PLLA and PU surface layers, respectively, due to precipitation of SiO₂–CaO particles during the casting process. Two composites were exposed to SBF for 1 week and this exposure led to form uniform and complete apatite coating layer on the PLLA/SiO₂–CaO composite but not on the PU/SiO₂-CaO composite. These results were interpreted in terms of the degradability of the polymers. A practical implication of the results is that a post-surface grinding or cutting processes to expose bioactive ceramics to the surface of a composite with a thick biodegradable polymer layer is not required for providing apatite forming ability, which has been considered as one of the pragmatic obstacles for the application as a bone grafting material.     

Structure and photoluminescence of SiC/ZnO nanocomposites prepared by radio frequency alternate sputtering

SiC/ZnO nanocomposites were prepared by radio frequency alternate sputtering followed by annealing in N₂ ambient. Well-crystallized ZnO matrix was obtained after annealed at 750 °C according to X-ray diffractometer patterns. Transmission electron microscopy analyses indicated that the SiC thin layer aggregated to form SiC nanoclusters with the average size of 7.2 nm when the annealing temperature was 600 °C. When the annealing temperatures increased above 900 °C, some of the SiC nanoclusters changed into SiC nanocrystals and surfacial atoms of the SiC nanoparticles were surrounded by a layer of SiO _x (x ≤ 2) according to the Fourier transform infrared spectrums. The SiC/ZnO nanocomposites annealed at 750 °C exhibit strong photoluminescence bands ranging from 250 to 600 nm. UV light originates from the near band edge emission of ZnO and the blue emission peaked at around 465 nm (2.7 eV) may be due to the formation of emission centers caused by the defects in Si–O network, while the green-emission peak at around 550 nm (2.3 eV) may be attributed to the deep level recombination luminescence caused by the vacancies of oxygen and zinc.     

Photoresponse of n -ZnO/ p -Si heterojunction towards ultraviolet/visible lights: thickness dependent behavior

A series of n-ZnO/p-Si thin film heterojunctions have been fabricated by a low cost sol–gel technique for different ZnO film thicknesses and the dark as well as photo current–voltage (I–V) characteristics have been investigated in details. The heterojunction with ZnO thickness of 0.46 μm shows the best diode characteristics in terms of rectification ratio, I _F/I _R = 5.7 × 10³ at 5 V and reverse leakage current density, J _R = 7.6 × 10⁻⁵ A cm⁻² at −5 V. From the photo I–V curves and wavelength dependent photocurrent of the heterojunctions, it is found that the junction with 0.46 μm ZnO thickness shows the highest sensitivity towards both UV and visible lights.     

RF sputtered piezoelectric zinc oxide thin film for transducer applications

This paper demonstrates the substrate dependency of the c-axis zinc oxide growth in radio-frequency sputtering system. Different deposition conditions were designed to study the influences of Si, SiO₂/Si, Au/Ti/Si, and Au/Ti/SiO₂/Si substrates on the piezoelectric and crystalline qualities of the ZnO thin films. Experimental results showed that the multilayer of Au/Ti/SiO₂/Si-coated silicon substrate provided a surface that facilitated the growth of ZnO thin film with the most preferred crystalline orientation. The 1.5 μm-thick thermally grown amorphous silicon dioxide layer effectively masked the crystalline surface of the silicon substrate, thus allowing the depositions of high-quality 20 nm-thick titanium adhesion layer followed by 150 nm-thick of gold thin film. The gold-coated surface allowed deposition of highly columnar ZnO polycrystalline structures. It was also demonstrated that by lowering the deposition rate at the start of sputtering by lowering RF power to less than one-third of the targeted RF power, a fine ZnO seed layer could be created for subsequent higher-rate deposition. This two-step deposition method resulted in substantially enhanced ZnO film quality compared to single-step approach. The influence of stress relaxation by annealing was also investigated and was found to be effective in releasing most of the residual stress in this layered structure.     

A sol–gel-derived α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> crystal interlayer modified 316L porous stainless steel to support TiO<Subscript>2</Subscript>, SiO<Subscript>2</Subscript>, and TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> hybrid membranes

A homogeneous α-Al₂O₃ crystal membrane was fabricated by the sol–gel technique on 316L porous stainless steel (PSS) substrate with an average pore size of 1.0 μm. The preparation process was optimized by carefully choosing the binder, the concentrations of the casting solutions and the sintering temperatures of the membranes. Compared to methylcellulose and polyethylene glycol 20000, polyvinyl alcohol 1750 was found to be the most effective binder to fabricate a homogeneously structured Al₂O₃ membrane without defects. The concentration to prepare an uniform coverage membrane with a thickness of ~10 μm was 0.032 mol/L. When sintered at 1000 °C, γ-Al₂O₃ membrane with ~3 μm grains was obtained. When sintered at 1200 °C, γ-Al₂O₃ completely transformed into α-Al₂O₃ and the grains grew to ~5 μm. Accordingly, the process was applied to a bigger pore-sized PSS with an average pore size of 1.5 μm to fabricate an α-Al₂O₃ intermediate layer to initially modify its surface. A single α-Al₂O₃ crystal layer with a thickness of ~5 μm and an average pore size of 0.7 μm was achieved. Subsequently, TiO₂, SiO₂, and TiO₂–SiO₂ hybrid membranes were tried on the modified PSS. Defect-free microfiltration membranes with average pore sizes of ~0.3 μm were readily fabricated. The results indicate that the sol–gel method is promising to initially modify the PSS substrates and the sol–gel-derived α-Al₂O₃ crystal layer is an appropriate intermediate layer to modify the PSS and to support smaller grain-sized top membranes.     

The ferroelectric properties and residual stress analysis of Bi<Subscript>3.15</Subscript>Nd<Subscript>0.85</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> thin films with a LaNiO<Subscript>3</Subscript> buffer layer

Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) thin film with a thin LaNiO₃ film as buffer layer was fabricated by sol–gel method on Pt/TiO₂/SiO₂/Si substrate. The BNT thin films have a perovskite phase with a dense microstructure. The P _r and V _c value are 25.5 μc/cm² and 3.7 V, respectively under the applied voltage of 15 V. After the switching of 2 × 10⁹ cycles, the P _r value decreases to 86% of its pre-fatigue value. The leakage current density of the BNT thin films with LaNiO₃ buffer layer were generally in the order of 10⁻⁸ to 10⁻⁶ A/cm². The fatigue and leakage current properties were improved dramatically compared with the BNT film without a LaNiO₃ buffer layer that we prepared before. The measured residual stress was tensile stress and its value was 176 MPa.     

Influence of seed layers on the vertical growth of ZnO nanowires

We synthesized vertically aligned ZnO nanowires on SiO₂ wafer <100> using the Au, ZnO and Au/ZnO seed layers through the physical vapor deposition process. The growth direction of ZnO nanowire was controlled by using the three different seed layers. From the XRD results, we observed the highest intensity of the (002) peak on the Au/ZnO seed layer among the three seed layers. The SEM images show that all of the ZnO nanowires have an average diameter of about 100 ~ 200 nm and a length of about 5 μm, and the nanowires grown on the Au/ZnO seed layer are oriented the most perpendicularly to the substrate surface. From the PL analysis, we observed that the intensity of broad emissions at 400-600 nm relating the green emission for the ZnO nanowires on the Au/ZnO seed layer was much weaker than that for the ZnO nanowires on the ZnO seed layer. The experiment results indicate that the selection of seed layers is important to grow nanowires vertically for the application of nanoscale devices.     

Effect of oxygen pressure of SiOx buffer layer on the electrical properties of GZO film deposited on PET substrate

The present work was made to investigate the effect of oxygen pressure of SiO_x layer on the electrical properties of Ga-doped ZnO (GZO) films deposited on poly-ethylene telephthalate (PET) substrate by utilizing the pulsed-laser deposition at ambient temperature. For this purpose, the SiO_x buffer layers were deposited at various oxygen pressures ranging from 13.3 to 46.7 Pa. With increasing oxygen pressure during the deposition of SiO_x layer as a buffer, the electrical resistivity of GZO/SiO_x/PET films gradually decreased from 7.6 × 10^− 3 to 6.8 × 10^− 4 Ω·cm, due to the enhanced mobility of GZO films. It was mainly due to the grain size of GZO films related to the roughened surface of the SiO_x buffer layers. In addition, the average optical transmittance of GZO/SiO_x/PET films in a visible regime was estimated to be ~ 90% comparable to that of GZO deposited onto a glass substrate.     

The effect of NiO on the phase formation,thermo-physical properties and sealing behaviour of lithium zinc silicate glass–ceramics

We have prepared lithium zinc silicate (LZS) glasses of compositions (mol%) 17.83Li₂O–17.73ZnO–(53.52 − x)SiO₂–5.25Na₂O–1.25P₂O₅–4.31B₂O₃–x-NiO, where 0.5 ≤ x ≤ 2.0, by the melt quench technique. The effect of NiO on the phase formation, thermo-physical properties and sealing behaviour of LZS glass–ceramics was studied using X-Ray diffraction (XRD), thermo-mechanical analysis (TMA) and microhardness (MH) measurements. It is found that NiO incorporation leads to a change in the role of ZnO from network modifier to intermediate oxide. The intermediate network forming Zn²⁺ ions would find it more difficult to diffuse and initiate the transformation of Li₃Zn_0.5SiO₄ to Li₂ZnSiO₄. Thus Li₃Zn_0.5SiO₄ is formed instead of Li₂ZnSiO₄ on addition of 2 mol% NiO. Scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) measurements at the glass–ceramic-to-metal interface reveal a change in the microstructure commensurate with the changing role of ZnO. Addition of NiO favoured interdiffusion of species at the interface leading to better sealing.     

Preparation and antibacterial activities of Ag-doped SiO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> composite films by liquid phase deposition (LPD) method

In the present study, Ag/SiO₂–TiO₂ thin films on ceramic tiles with glazed surface were successfully prepared by a liquid phase deposition method (LPD) at a low temperature. The Ag/SiO₂–TiO₂ thin films obtained were homogenous, well adhered and colored by interference of reflected light. The films were characterized by scanning electron microscopy and X-ray diffraction. From these analysis data, it was found that silver (Ag) nanoparticles were trapped in SiO₂–TiO₂ matrix. The antibacterial effects of Ag/SiO₂–TiO₂ thin films against S. aureus and E. coli were examined by the so-called antibacterial-drop test. The bactericidal activity for the above bacteria cells was estimated by relative number of bacteria survived calculated from the number of viable cells which form colonies on the nutrient agar plates. The Ag/SiO₂–TiO₂ thin films had an excellent antibacterial performance. Atomic absorption spectroscopy (AAS) was used for the quantitative determination of the Ag ion concentration releasing from the Ag/SiO₂–TiO₂ thin film. The releasing rate of Ag ions from the Ag/SiO₂–TiO₂ film is 0.123 μg/mL during 192 h. The antibacterial effect of Ag/SiO₂–TiO₂ thin film before and after aging in a weathering chamber for 48 h was compared and the results show that the antibacterial activity is not compromised after weathering.     

Fabrication and comparative study of top-gate and bottom-gate ZnO–TFTs with various insulator layers

Transparent ZnO thin film transistors (ZnO–TFTs) with different structures and dielectric layers were fabricated by rf magnetron sputtering. The PbTiO₃, AlO _x , SiN _x and SiO _x films were attempted to serve as the gate dielectric layers in the devices, respectively, and XRD was employed to investigate the crystal structure of ZnO films deposited on these dielectric layers. The optical properties of transparent TFTs were measured and revealed the average transmittance ranged from 60 to 80% in the visible part of the spectrum. Electrical measurement shows the properties of the ZnO–TFTs have great relations with the device structure. The bottom-gate TFTs have better behaviors than top-gate ones with the mobility, threshold voltage and the current on/off ratio of 18.4 cm² V⁻¹ s⁻¹, −0.7 V and 10⁴, respectively. The electrical difference of the devices may be due to different character of the interface between the channel and dielectric layers.     

Preparation of monodisperse ZnO/SiO2 composite particles using spray drying with an anionic surfactant template and their photoluminescence characteristics

The photoluminescence (PL) characteristics of ZnO/SiO₂ composite particles were investigated. ZnO/SiO₂ composite particles were synthesized utilizing the consecutive sol–gel spray drying method by incorporating sodium lauryl sulfate (SLS) as a particle morphology control agent. The effect of SLS concentration and ZnO ratio on precursors was studied further on the composite particle morphology and PL performance. Elevating the SLS concentration exhibited a reduction in the particle diameter and an increase in particle uniformity. The particle diameter without SLS was 6.18 µm and reduced to 2.6 µm with the addition of SLS at 3 critical micelle concentrations (CMC). The decrease in ZnO concentration also reduced the particle diameter of the ZnO/SiO₂ composite to 1.74 µm at a ZnO concentration of 25% mol. In addition, the increase in the excitation wavelength from 230 nm to 320 nm indicates a shift in the peak emission intensity at higher wavelengths from 467 nm to 645 nm. The excitation wavelength-dependent photoluminescence phenomenon was exhibited by incorporating silica into the ZnO precursor pre- and post-drying to deliver composite particles. The addition of silica to the composite particles can augment the PL emission intensity without causing a shift in the PL emission peaks when excited at the same wavelength. The 25% mol ZnO composite particles with the addition of SLS 3 CMC had the highest PL emission intensity. The amount of silica nanoparticles sufficient to trap the ZnO nanoparticles in the droplet is an important factor besides the size and uniformity of the particles, which causes the high intensity of PL emission.     

Fabrication and growth mechanism of hexagonal zinc oxide nanorods via solution process

This article presents, the fabrication of perfectly hexagonal zinc oxide nanorods performed via solution process using zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine (HMT) at various concentrations of i.e. 1 × 10⁻³ to 10 × 10⁻² M in 50 mL distilled water and refluxed at 100 °C for 1 h. We used HMT because it acts as a template for the nucleation and growth of zinc oxide nanorods, and it also works as a surfactant for the zinc oxide structures. The X-ray diffraction patterns clearly reveal that the grown product is pure zinc oxide. The diameters and lengths of the synthesized nanorods lie in the range of 200–800 nm and 2–4 μm, respectively as observed from the field emission scanning electron microscopy (FESEM). The morphological observation was also confirmed by the transmission electron microscopy (TEM) and clearly consistent with the FESEM observations. The chemical composition was analyzed by the FTIR spectroscopy, and it shows the ZnO band at 405 cm⁻¹. On the basis of these observations, the growth mechanism of ZnO nanostructures was also proposed.     

Preparation and ferroelectric properties of predominantly (100)-oriented SrBi4Ti4O15 ferroelectric thin film on Pt(111)/TiO2/SiO2/Si(100) substrate

A predominantly (100)-oriented SrBi₄Ti₄O₁₅ (SBTi) ferroelectric thin film (orientation factor f ₍₁₀₀₎ = 68%) was formed on Pt(111)/TiO₂/SiO₂/Si(100) substrate using a metal organic decomposition process combined with a sequential layer annealing method. The film exhibits a well saturated hysteresis loop with a remanent polarization of 25 μC/cm². Furthermore, the coercive field (E _c ) is as low as 80 kV/cm. The values of the dielectric constant (ε _r ) and dissipation factor (tan δ) at 100 kHz are estimated to be 380 and 0.08, respectively. 15% loss of P _r was observed after 10⁹ switching cycles in the predominantly (100)-oriented SBTi film. The growth mode of the predominantly (100)-oriented SBTi film is discussed based on the sequential layer annealing process and the anisotropic structure of SBTi.     

Magnetic properties of Fe78.4Si9.5B9Cu0.6Nb2.5 nanocrystalline alloy powder cores

The microstructure and morphology of nanocrystalline Fe_78.4Si_9.5B₉Cu_0.6Nb_2.5 alloy powders prepared by ball milling technique were characterized by X-ray diffraction and scanning electron microscopy studies. The effective permeability (μ_e), quality factor (Q), DC bias property, and core losses of the corresponding powder cores were tested using low capacitance resonator meter and B–H analyzer in the range of 1–1000 kHz. The results show that the relative density and compression strength of the powder cores increased with increasing particle size. Powder cores from large size particles (150–300 μm) were found to exhibit higher μ_e and core loss, but lower Q level when compared to samples of small size ones (5–40 μm). Moreover, the μ_e of powder cores with large particles reached a peak value with the addition of 2 wt% glass binder. The Q value was also found to be proportional to the binder content except 10 wt%, while its peak position was shifted toward higher frequency.     

Self-Formation of a Ru/ZnO Multifunctional Bilayer for the Next-Generation Interconnect Technology via Area-Selective Atomic Layer Deposition

This study suggests a Ru/ZnO bilayer grown using area-selective atomic layer deposition (AS-ALD) as a multifunctional layer for advanced Cu metallization. As a diffusion barrier and glue layer, ZnO is selectively grown on SiO₂, excluding Cu, where Ru, as a liner and seed layer, is grown on both surfaces. Dodecanethiol (DDT) is used as an inhibitor for the AS-ALD of ZnO using diethylzinc and H₂O at 120 °C. H₂ plasma treatment removes the DDT adsorbed on Cu, forming inhibitor-free surfaces. The ALD-Ru film is then successfully deposited at 220 °C using tricarbonyl(trimethylenemethane)ruthenium and O₂. The Cu/bilayer/Si structural and electrical properties are investigated to determine the diffusion barrier performance of the bilayer film. Copper silicide is not formed without the conductivity degradation of the Cu/bilayer/Si structure, even after annealing at 700 °C. The effect of ZnO on the Ru/SiO₂ structure interfacial adhesion energy is investigated using a double-cantilever-beam test and is found to increase with ZnO between Ru and SiO₂. Consequently, the Ru/ZnO bilayer can be a multifunctional layer for advanced Cu interconnects. Additionally, the formation of a bottomless barrier by eliminating ZnO on the via bottom, or Cu, is expected to decrease the via resistance for the ever-shrinking Cu lines.     

High-speed preparation and dielectric properties of BaTi<Subscript>4</Subscript>O<Subscript>9</Subscript> film by laser chemical vapor deposition

BaTi₄O₉ film was prepared on Pt/Ti/SiO₂/Si substrate by laser chemical vapor deposition. The microstructure and dielectric properties were investigated. The single-phase BaTi₄O₉ film with random orientation was obtained. The surface consisted of round and rectangular grains, and the cross-section was columnar microstructure. The deposition rate (R _dep) was 135 μm h⁻¹. The dielectric constant (ε _r) and loss (tanδ) were 35 and 0.01, respectively, at 1 MHz. With increasing temperature, ε _r increased and showed a broad peak around 736 K, which indicated there might be a phase transition.