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Microbubbles coated by visco-elastic shells are important for ultrasound diagnosis using contrast agents, and the dynamics of single coated bubbles has been investigated in the literature. However, although a high number of contrast agents are used in practical situations, there has long been an absence of a nonlinear acoustic theory for multiple coated bubbles, except for our recent work by Kikuchi and Kanagawa ["Weakly nonlinear theory on ultrasound propagation in liquids containing many microbubbles encapsulated by visco-elastic shell," Jpn. J. Appl. Phys. 60, SDDD14 (2021)], under several assumptions to be excluded. Aiming for generalization, in this study, we theoretically investigate weakly nonlinear propagation of ultrasound in liquid containing multiple bubbles coated by a visco-elastic shell with compressibility. Leveraging the method of multiple scales, both the Korteweg–de Vries–Burgers (KdVB) equation for a low-frequency long wave and nonlinear Schrödinger (NLS) equation for a high-frequency short wave are derived from the volumetric averaged equations for bubbly liquids based on a two-fluid model and the up-to-date model for single coated bubbles with shell compressibility. Neglected factors in our previous paper, i.e., compressibility of the shell and liquid, drag force acting on bubbles, bubble translation, and thermal conduction, are incorporated in the present KdVB and NLS equations; the proposed model will be regarded as a generic physico-mathematical model. The results show that shell compressibility attenuated ultrasound strongly and decreased nonlinearity of ultrasound. Finally, we compared the magnitudes of six dissipation factors (shell compressibility, shell viscosity, liquid compressibility, liquid viscosity, thermal effect, and drag force) for five typical ultrasound contrast agents, and a similar tendency between KdVB and NLS equations was revealed. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) photocatalysis can harness the energy from sunlight, providing a solution to many green- and energy-related problems. In this study, we aimed to produce Cu doped TiO2 (Cu-TiO2) structures at a low temperature (~70 °C) under atmospheric pressure based on liquid phase deposition. The products prepared with Cu nitrate exhibited anatase-phase TiO2 with the presence of Cu, and the particles showed a waxberry-like structure. Changing the Cu nitrate concentration allowed control of the atomic concentration; we confirmed ~1.3 atm.% of Cu ions in the product when we applied 10 mM in the precursor solution. By doping Cu, the light absorption edge shifted to 440 nm (~2.9 eV), and we proved the photocatalytic reaction through action spectral measurement. We observed the decomposition of acetaldehyde into CO2 on Cu-TiO2 photocatalysts, which produced optimized improvements in photocatalytic activity at Cu dopant levels between 0.2 and 0.4 atm.%. This study demonstrates that the liquid phase deposition technique can be used for doping metallic ions into TiO2, which shows promise for preparing novel and unique nanomaterials as visible light photocatalysts. [ABSTRACT FROM AUTHOR]

In this study, nanomaterials prepared via laser ablation of tin in water are systematically studied and compared. Tin targets were ablated by both millisecond and nanosecond pulsed lasers, resulting in core@shell product nanostructures with different chemistries and morphologies. Depending on laser fluence, the obtained core@shell nanoparticles had either Sn or SnO cores and SnOx shells with varied surface hydration degree. Optical emission spectra of laser-generated plasmas were taken, giving additional support to nanoparticle formation mechanisms. Finally, gas sensing at room temperature is demonstrated as one of the potential applications for such nanostructures. [ABSTRACT FROM AUTHOR]

• ZnS nanoparticles doped with Cu were prepared by pulsed laser ablation of metallic Zn in mercaptoethanol. • Doping level of Cu was controlled via concentration of Cu(NO 3) 2 dissolved in mercaptoethanol. • Prepared ZnS nanoparticles were hexagonal wurtzite ZnS. • Cu-doped ZnS demonstrated higher photocatalytic effect in comparison with undoped ZnS. Nanoparticles of ZnS doped with Cu were prepared by means of pulsed laser ablation in liquid medium containing Cu ions. Nanosecond pulsed laser was focused on Zn target immersed in mercaptoethanol with copper nitrate dissolved as a source of Cu ions. X-ray diffraction and X-ray photoelectron spectroscopy confirmed formation of wurtzite ZnS structures as the main product, while up to ~5% of Zn atoms were substituted by Cu when ≤1.0 mM Cu(NO 3) 2 in mercaproethanol was used as liquid medium. Elemental mapping revealed that dopant Cu atoms were uniformly distributed in the produced nanoparticles. Photoluminescence recorded from the doped nanomaterial exhibited an additional green emission, indicating the presence of interband states resulted from doping with Cu2+. Compared with undoped ZnS nanoparticles, their Cu-doped counterparts demonstrated more efficient photocatalytic behavior toward the decomposition of methylene blue (as model organic compound), which is believed to be caused either by more efficient light absorption extended into the visible region or by the carriers based on the Cu2+ state. The present study demonstrates that the technique used has the capacity of producing doped nanomaterials in one step by incorporating dopants from the liquid phase, which may be promising for preparing novel unique nanomaterials with complex composition. [ABSTRACT FROM AUTHOR]

Nowadays, environmental problems are increasingly varied and the development of various diseases. Due to its ability to create defect in band gap energy and strong antibacterial activity against a variety of microorganisms, ZnO is used to solve both issues. However, ZnO has a large band gap energy, so it is necessary to decrease band gap by doping. In this study, the synthesis of ZnO and ZnO doped materials (N- and (Mg,B,N)-doped ZnO) through the solid-state was carried out. The phases of doped ZnOs are hexagonal wurtzite, according to the results of the characterization using XRD, Raman spectroscopy, and HR-TEM. Surface morphology for N-doped ZnO does not form agglomeration, while in (Mg,B,N)-doped ZnO, agglomeration occurs due to the difference in charge of B with Zn. The existence of dopant in ZnO lattice was confirmed by EDS and XPS. (Mg,B,N)-doped ZnO has the highest specific surface area (14.388 m2/g) according to the BET analysis. The formation of peaks in 358 nm, 520 nm, and 650 nm during PL examination indicates a reduction in the rate of electron-hole recombination and defects. The recombination rate was confirmed by EIS Nyquist spectra result. The band gap energy owing to doping decreased from 3.13 eV to 3.10 eV and 3.12 eV for N- and (Mg,B,N)-doped ZnO, respectively. The lifetime of undoped ZnO, N-doped ZnO, and (Mg,B,N)-doped ZnO is 0.526, 0.610, and 0.695 ns, respectively. Photocatalyst test results showed that N-doped ZnO and (Mg,B,N)-doped ZnO materials were optimum for degradation of methyl violet for under visible light with degradation efficiency of 89.28 % and 93.24 %, respectively. N-doped ZnO and (Mg,B,N)-doped ZnO produce inhibition zone of 7.18 mm and 14.15 mm for Escherichia coli bacteria and 7.50 mm and 11.80 mm for Staphylococcus aureus bacteria. Additionally, molecular docking studies were used to explain a potential mechanism for in vitro bacterial activity. [ABSTRACT FROM AUTHOR]

So far, poly(L-lactic acid), PLLA nanosheets proved to be promising for wound healing. Such biodegradable materials are easy to prepare, bio-friendly, cost-effective, simple to apply and were shown to protect burn wounds and facilitate their healing. At the same time, certain metal ions are known to be essential for wound healing, which is why this study was motivated by the idea of incorporating PLLA nanosheets with Zn2+ ion containing nanoparticles. Upon being applied on wound, such polymer nanosheets should release Zn2+ ions, which is expected to improve wound healing. The work thus focused on preparing PLLA nanosheets embedded with several kinds of Zn-containing nanoparticles, their characterization and ion-release behavior. ZnCl2 and ZnO nanoparticles were chosen because of their different solubility in water, with the intention to see the dynamics of their Zn2+ ion release in liquid medium with pH around 7.4. Interestingly, the prepared PLLA nanosheets demonstrated quit similar ion release rates, reaching the maximum concentration after about 10 h. This finding implies that such polymer materials can be promising as they are expected to release ions within several hours after their application on skin. [ABSTRACT FROM AUTHOR]

ZnO semiconductors are widely known to have benefits in photocatalytic and antibacterial applications. In this study, (Mg/B)–ZnO and (Mg/Cu)–ZnO were synthesized using the combustion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The XRD results confirmed a decrease in the crystal size and an increase in the crystallinity of the doped ZnO samples. SEM analysis confirmed the morphological changes in the structure from rod-shaped to spherical, and the particle size decreased in the doped ZnO samples. EDS analysis validated the nanoparticle composition of Zn, O, Mg, B, and Cu without impurities. Raman spectra confirmed the formation of defects due to the substitution of dopants in the ZnO lattice. All samples for FTIR analysis showed functional chemical group vibrations from Zn–O, C–H, and O–H stretching. The existence of dopant bonds with oxygen was also validated from this analysis. The change in band gap energy was observed from 3.13 to 3.10 eV in Mg/Cu–ZnO and 3.12 eV in Mg/B–ZnO sample due to the influence of the addition of dopant ions. The XPS spectra show the chemical composition of the nanoparticle samples and the oxidation numbers that correlate with the results of EDS and XRD analyses. A decrease in the emission intensity in the PL measurement was observed in the green emission region in the Mg/B–ZnO sample, which correlated with the decrease in electron recombination. The Photocatalytic application was performed by measuring its ability to degrade methyl violet dye under visible-light irradiation. The maximum deterioration after 120 min of irradiation was obtained for the Mg/Cu–ZnO, Mg/B–ZnO, and ZnO samples at 92.62 %, 92.20 %, and 80.89 %, respectively. Antibacterial activity increased against S. aureus bacteria in co-doped ZnO samples with inhibition zones of 12.15 mm, 8.15 mm, and 6.45 mm for Mg/B–ZnO, Mg/Cu–ZnO, and ZnO samples, respectively. • Undoped ZnO, Mg/B–ZnO, and Mg/Cu–ZnO were synthesized by using solid-state method. • The addition of dual dopant Mg/B and Mg/Cu increase the photoatalytic and antibacterial activity of ZnO. • Undoped ZnO, Mg/B–ZnO, and Mg/Cu–ZnO can degrade 80.89 %, 92.20 %, and 92.62 % MV solutions under visible light for 120 min. • Zones of inhibition against S. aureus were 6.45, 8.15, and 12.15 mm for undoped ZnO, Mg/Cu–ZnO, and Mg/B–ZnO, respectively. [ABSTRACT FROM AUTHOR]

Due to the growing worries about environmental issues, dye degradation is substantial. Besides that, it is essential to prevent illness development by creating cutting-edge antibacterial agents that can inhibit bacterial activities. Herein, we report a novel photocatalyst exhibiting visible light responsivity for the degradation of methyl violet dye and possessing antibacterial properties to mitigating the emergence of drug resistance. It is triple-doped ZnO (Mg, Cu, N-doped ZnO, and Mg, Cu, B-doped ZnO), successfully synthesized by the solid-state method. The structure crystal is hexagonal wurtzite, and the crystal size is 34.68, 30.22, and 29.47 nm for undoped ZnO, (Mg, Cu, N)-doped ZnO, and (Mg, Cu, B)-doped ZnO, respectively, according to the study of X-ray diffraction (XRD), Raman, and SEM results. The (Mg, Cu, N)- and (Mg, Cu, B)-doped ZnO have smaller particle sizes than undoped ZnO. FTIR spectra show Zn-O, Cu-O, Mg-O,and B-O stretching for synthesized samples. The formation of (Mg, Cu, N)-doped ZnO and (Mg, Cu, B)-doped ZnO also were confirmed by EDAX. PL shows the formation of peaks in UV emission (∼350 nm) and visible emission (513–519 nm and ∼646 nm) that indicate the inhibition of electron-hole recombination and oxygen vacancies in the ZnO lattice. The effective photocatalytic activity of undoped ZnO, (Mg, Cu, N)-doped ZnO, and (Mg, Cu, B)-doped ZnO achieves 80.89 %, 93.41 %, and 92.18 % decolorization of water pollutant methyl violet. The antibacterial activities of the three samples are 6.45, 6.00, and 11.90 mm, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphene Oxide Quantum Dots (GOQD) have attracted considerable research interest owing to their use in photocatalysis and antibacterial applications. In this study, pyrolysis and hydrothermal methods were used to prepare GOQD (p-GOQD and h-GOQD) sheets with different characteristics that affect the photocatalytic and antibacterial activities of GOQD/ZnO. The synthesized p-GOQD/ZnO and h-GOQD/ZnO were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy. As a result, we found that p-GOQD/ZnO (18–20 nm) exhibited better photocatalytic activity than h-GOQD/ZnO (20–22 nm), with degradation percentages of 97.6 % and 93.04 %, respectively, at 60 min. The degradation rate constants are found to be 0.0498 min−1 for p-GOQD/ZnO and 0.0335 min−1 for h-GOQD/ZnO. In addition, the antibacterial activity of p-GOQD/ZnO was better than that of h-GOQD/ZnO against Escherichia coli and Staphylococcus aureus , with inhibition zone diameters of 10.40 mm and 9.75 mm, respectively. The outstanding photocatalytic and antibacterial performance of p-GOQD/ZnO suggests that p-GOQDs provide better characteristics and applications for ZnO semiconductor composites. The advantages of p-GOQD/ZnO are synergistic effects, low dislocation density, large surface area, and defects, which demonstrate its potential for practical applications in environmental remediation. [Display omitted] • GOQD was synthesized using pyrolysis (p-GOQD) and hydrothermal (h-GOQD) methods. • GOQD was made composite with ZnO using a simple liquid-solid dispersion method. • p-GOQD/ZnO has better photocatalytic and antibacterial activities than h-GOQD/ZnO. • The dye degradation percentage photocatalyzed by p-GOQD/ZnO was 97.6 % for 1 h. • p-GOQD/ZnO inhibits the activity of E. coli better than amoxicillin as control (+). [ABSTRACT FROM AUTHOR]

We demonstrate a multi-purpose plasmonic sensor based on a nanovoid array fabricated via inexpensive and highly-reproducible direct femtosecond laser patterning of thin glass-supported Au films. The proposed nanovoid array exhibits near-IR surface plasmon (SP) resonances, which can be excited under normal incidence and optimised for specific applications by tailoring the array periodicity, as well as the nanovoid geometric shape. The fabricated SP sensor offers competitive sensitivity of ≈ 1600 nm/RIU at a figure of merit of 12 in bulk refractive index tests, as well as allows for identification of gases and ultra-thin analyte layers, making the sensor particularly useful for common bioassay experiments. Moreover, isolated nanovoids support strong electromagnetic field enhancement at lattice SP resonance wavelength, allowing for label-free molecular identification via surface-enhanced vibration spectroscopy. [ABSTRACT FROM AUTHOR]

Mixed oxides of Zn and Sn are of interest for gas sensing and diverse optoelectronic applications, and therefore new approaches to prepare such nanomaterials are anticipated. This study reports, for the first time, on the use of laser ablation in liquid applied to a Sn-Zn alloy and describes obtained products. Core@shell Sn@SnO and ZnO nanoparticles are shown to be produced by millisecond pulsed laser upon ablating eutectic Sn-Zn alloy in water. The as-prepared materials were found to contain surface hydroxide layers which were dehydrated to SnO x and ZnO when higher laser energy fluence was applied or when the products were post-treated at 200C in air. The morphology, shape and size distribution, phase and chemical composition of prepared nanoparticles were studied as a function of laser parameters used during their preparation. Increase in pulse energy was found to result in fabrication of finer particles. It was found that while both metallic Sn and SnO x were presented in the product, zinc was always oxidized to its oxide ZnO. In addition, when properly annealed, the produced nanomaterial demonstrated gas sensing response towards ammonia at room temperature. [ABSTRACT FROM AUTHOR]

Water treatment plants generate vast amounts of sludge and its disposal is one of the most expensive and environmentally problematic challenges worldwide. As sludge from water treatment plants contains a considerable amount of titanium, both can create serious environmental concerns. In this study, the potential to recover titanium from drinking water treatment residue was explored through acid leaching technique. Statistical design for the optimization of titanium recovery was proposed using response surface methodology (RSM) based on a five-level central composite design (CCD). Three independent variables were investigated, namely the acid concentration (3 M–7 M), temperature (40 °C – 80 °C) and solid/liquid ratio (0.005–0.02 g/mL). According to the analysis of variance (ANOVA), the p-value (<0.0001) indicated the designed model was highly significant. Optimization using RSM gave the best fit between validated and predicted data as elucidated by the coefficient of determination with R2 values of 0.9965. However, acid concentration and solid/liquid ratio showed an initial increase in titanium recovery followed by recovery reduction with increasing concentration and ratio. Quadratic RSM predicted the maximum recovery of titanium to be 67.73% at optimal conditions of 5.5 M acid concentration, at a temperature of 62 °C with a solid/liquid ratio of 0.01 g/mL. The verification experiments gave an average of 66.23% recovery of titanium, thus indicating that the successfully developed model to predict the response. This process development has significant importance to reduce the cost of waste disposal, environmental protection, and recovery of economically valuable products. Image 1 • Effect of acid concentration, solid to liquid ratio, and temperature was evaluated using RSM. • Quadratic RSM predicted the maximum recovery of titanium to be 67.73%. • Optimal conditions are 5.5 M acid concentration, 62 °C temperature, and 0.01 g/mL solid/liquid ratio. • At optimum condition, 76.5% of titanium recovery was obtained. • F-value and p-value were 32.08 and <0.0001 which implies the significance of the model. [ABSTRACT FROM AUTHOR]