1,721,015 research outputs found
Green Synthesis and Analytical Characterization of Core-Shell Copper Sub-Microparticles
No full textThis study demonstrates a simple and reproducible approach to synthesize green core-shell copper sub-microparticles stabilized by poly(n-vinyl)pyrrolidone (PVP). Cu@PVP colloids were here prepared using copper sulfate pentahydrate as precursor and glucose as reducing agent. The presence of PVP in the synthetic medium eliminates the need for an inert atmosphere during the process, thus simplifying the whole method. Both the morphology and the spectroscopic properties of Cu@PVP colloids were investigated by transmission electron microscopy, and infrared, UV-Vis and X-ray photoelectron spectroscopies. Size distributions and average shell thickness were obtained by statistical analysis on TEM micrographs, and spectroscopies demonstrated the formation of a PVP layer around the copper core. The produced colloids were employed in composite thin films for potential antimicrobial application, in association with a highly-recyclable polymer: polycarbonate (4,4’-(1-methylethylidene)bis(phenol))
Electrochemical Synthesis and Analytical Characterization of Hybrid Zinc/Calcium Antimicrobial Nano-Oxides for Cultural Heritage Applications
No full textThe present study proposes the one-step synthesis of Zn/Ca hybrid nano-oxides combining an electrochemical route to ZnO nanostructures (NSs) with the wet chemical production of Ca(OH)2 NSs. ZnO is a known antimicrobial and Ca(OH)2 has consolidating properties, both appealing for stone artwork preservation in the field of cultural heritage. Two concentrations of the electrolytic bath (NaOH 0.1 and 0.4 M) were studied resulting in distinct final nanomaterials (Zn−Ca0.1 and Zn−Ca0.4). Fourier transform infrared, X-ray photoelectron spectroscopies, and transmission electron microscopy demonstrated that Zn−Ca0.1 consisted of lamellar calcium hydroxyzincate NSs, whereas Zn−Ca0.4 showed hexagonal Ca(OH)2 (∼500 nm) and ZnO (∼50 nm) NSs. Nanocoatings prepared with Zn−Ca0.1 exhibited a Zn2+ release increasing up to 1 μmol cm−2 in 24 h. Instead, Zn−Ca0.4-based nanocoatings released a constant value of about 0.35 μmol/cm2. Both types of nanocoatings showed good antimicrobial activity against Bacillus subtilis after 48 h and hydrophilic behavior over 28 days
Spectroscopic characterisation of TiO2 nanoparticles
No full textTiO2 nanoparticles (TiO2 NPs), synthetised by the hydrolysis at room temperature of titanyl oxalate, have been characterised by UV-vis spectroscopy and photoluminescence analysis. The influence of precursor concentration on Ti02 NPs growth and their optical properties have been studied. By the interpretation of absorbance spectra a rapid formation of titania clusters has been suggested and a constant energy onset at 3.59 eV has been found, according to a direct transition calculated for titanum dioxide. No size quantization effects can be addressed for stabilised colloids. Two photoluminescence (PL) peaks have been assigned to direct and indirect transitions, respectively. A third peak has been related to surface oxygen vacancies. Copyright © 2008 American Scientific Publishers All rights reserved
A strategic framework for zinc oxide electrochemical synthesis using design of experiments
Full text linkElectrochemical methods have gained increasing attention for the synthesis of micro- and nanostructured materials such as zinc oxide (ZnO). Traditionally, the development of such syntheses has relied on the One Variable At a Time (OVAT) approach, which systematically changes a single parameter while keeping others constant. However, this method provides only a limited understanding of the multidimensional experimental space. In contrast, a Design of Experiments (DoE) strategy offers a more efficient and statistically robust framework for identifying optimal synthesis conditions. In this work, we propose the application of a Full Factorial Design combined with Response Surface Methodology (RSM) to optimize for the first time the electrochemical synthesis of ZnO structures. The synthetic strategy integrates a hybrid electrochemical–Thermal process: sacrificial zinc electrolysis in a 30 mM sodium hydrogen carbonate solution, followed by thermal annealing that is typically employed in sol–gel methods to gain a final control over stoichiometry and morphology. ZnO microrods (ZnO MRs) were synthesized under galvanostatic conditions using benzalkonium chloride as a cationic surfactant and stabilizer. Its concentration (0.001–0.5 M) and the applied current density (2–20 mA/cm2) were selected as the key variables. A two-factor, three-level Central Composite Design (CCD) was implemented to investigate their combined effects on the electrosynthesis yield and ZnO length. The predictive model derived from the chemometric analysis was successfully validated, demonstrating the method’s potential for rational and efficient optimization of nano- and micromaterial electrosynthesis. Moreover, the proposed model was also validated on a scaled-up system, proving effective not only for laboratory-scale optimization but also for guiding process development toward industrial applications, where control, reproducibility, and efficiency are critical
Ultra-low HIV-1 p24 detection limits with a bioelectronic sensor
Full text linkEarly diagnosis of the infection caused by human immunodeficiency virus type-1 (HIV-1) is vital to achieve efficient therapeutic treatment and limit the disease spreading when the viremia is at its highest level. To this end, a point-of-care HIV-1 detection carried out with label-free, low-cost, and ultra-sensitive screening technologies would be of great relevance. Herein, a label-free single molecule detection of HIV-1 p24 capsid protein with a large (wide-field) single-molecule transistor (SiMoT) sensor is proposed. The system is based on an electrolyte-gated field-effect transistor whose gate is bio-functionalized with the antibody against the HIV-1 p24 capsid protein. The device exhibits a limit of detection of a single protein and a limit of quantification in the 10 molecule range. This study paves the way for a low-cost technology that can quantify, with single-molecule precision, the transition of a biological organism from being “healthy” to being “diseased” by tracking a target biomarker. This can open to the possibility of performing the earliest possible diagnosis
Ag-based synergistic antimicrobial composites. A critical review
No full textThe emerging problem of the antibiotic resistance development and the consequences that the health, food and other sectors face stimulate researchers to find safe and effective alternative methods to fight antimicrobial resistance (AMR) and biofilm formation. One of the most promising and efficient groups of materials known for robust antimicrobial performance is noble metal nanoparticles. Notably, silver nanoparticles (AgNPs) have been already widely investigated and applied as antimicrobial agents. However, it has been proposed to create synergistic composites, because pathogens can find their way to develop resistance against metal nanophases; therefore, it could be important to strengthen and secure their antipathogen potency. These complex materials are comprised of individual components with intrinsic antimicrobial action against a wide range of pathogens. One part consists of inorganic AgNPs, and the other, of active organic molecules with pronounced germicidal effects: both phases complement each other, and the effect might just be the sum of the individual effects, or it can be reinforced by the simultaneous application. Many organic molecules have been proposed as potential candidates and successfully united with inorganic counterparts: polysaccharides, with chitosan being the most used component; phenols and organic acids; and peptides and other agents of animal and synthetic origin. In this review, we overview the available literature and critically discuss the findings, including the mechanisms of action, efficacy and application of the silver-based synergistic antimicrobial composites. Hence, we provide a structured summary of the current state of the research direction and give an opinion on perspectives on the development of hybrid Ag-based nanoantimicrobials (NAMs)
Pros and Cons of Sacrificial Anode Electrolysis for the Preparation of Transition Metal Colloids: A Review
No full textElectrochemical synthesis of transition metal nanoparticles (NPs) and related oxides is highly appealing, as it affords nanomaterials with high purity and dimensional control by properly setting only few experimental parameters. The resurgence of electrochemical routes to NPs can be traced back to seminal works by the Reetz's group, about 25 years ago. Despite many advantages, this method has intrinsic limitations, mainly related to the use of organic solvents, which may limit real-life applications of the as-prepared NPs. Therefore, an important current issue in the electrosynthesis of these systems regards the preparation of aqueous and long-lived colloids. In this Review, we provide an overview of the most promising electrosyntheses of colloidal nanomaterials; real-life applications of electrochemically produced NPs will also be commented on
Assessment of gold bio-functionalization for wide-interface biosensing platforms
Full text linkThe continuous improvement of the technical potential of bioelectronic devices for biosensing applications will provide clinicians with a reliable tool for biomarker quantification down to the single molecule. Eventually, physicians will be able to identify the very moment at which the illness state begins, with a terrific impact on the quality of life along with a reduction of health care expenses. However, in clinical practice, to gather enough information to formulate a diagnosis, multiple biomarkers are normally quantified from the same biological sample simultaneously. Therefore, it is critically important to translate lab-based bioelectronic devices based on electrolyte gated thin-film transistor technology into a cost-effective portable multiplexing array prototype. In this perspective, the assessment of cost-effective manufacturability represents a crucial step, with specific regard to the optimization of the bio-functionalization protocol of the transistor gate module. Hence, we have assessed, using surface plasmon resonance technique, a sustainable and reliable cost-effective process to successfully bio-functionalize a gold surface, suitable as gate electrode for wide-field bioelectronic sensors. The bio-functionalization process herein investigated allows to reduce the biorecognition element concentration to one-tenth, drastically impacting the manufacturing costs while retaining high analytical performance
Ag modified ZnS for photocatalytic water pollutants degradation: Influence of metal loading and preparation method
Full text linkIn this paper, the photocatalytic degradation of organic pollutants was investigated using Ag/ZnS nanoparticles at different noble metal loadings. The photocatalysts were prepared at room temperature by two different methods: photodeposition and chemical reduction. The obtained samples were characterized by Specific surface area measurement, X-ray photoelectron spectroscopy, X-ray Powder diffraction, ultraviolet–visible diffuse reflectance and Raman spectroscopy. The X-ray photoelectron spectroscopy spectra showed that Ag is present on ZnS surface as intermediate state between nanostructured Ag0 and Ag2O. Moreover, the addition of silver caused a significant change of the absorption spectrum of bare ZnS, resulting in higher absorbance in the visible region, due to the Ag surface plasmon band. Methylene blue (MB) was used to evaluate the photocatalytic activity of the prepared samples. The best photocatalytic activity was observed using the sample at 0.1 wt% Ag loading prepared by chemical reduction method. In particular, the almost complete MB degradation was achieved using UV-LEDs as light sources and 6 g L−1 of catalyst dosage. Finally, the optimized photocatalyst was also effective in the degradation of phenol in aqueous solution under UV irradiation
Effect of the surface chemical composition and of added metal cation concentration on the stability of metal nanoparticles synthesized by pulsed laser ablation in water
Full text linkMetal nanoparticles (NPs) made of gold, silver, and platinum have been synthesized by means of pulsed laser ablation in liquid aqueous solution. Independently from the metal nature, all NPs have an average diameter of 10 ± 5 nm. The ζ-potential values are:-62 ± 7 mV for gold,-44 ± 2 mV for silver and-58 ± 3 for platinum. XPS analysis demonstrates the absence of metal oxides in the case of gold and silver NPs. In the case of platinum NPs, 22% of the particle surface is ascribed to platinum oxidized species. This points to a marginal role of the metal oxides in building the negative charge that stabilizes these colloidal suspensions. The investigation of the colloidal stability of gold NPs in the presence of metal cations shows these NPs can be destabilized by trace amounts of selected metal ions. The case of Ag+ is paradigmatic since it is able to reduce the NP ζ-potential and to induce coagulation at concentrations as low as 3 μM, while in the case of K+ the critical coagulation concentration is around 8 mM. It is proposed that such a huge difference in destabilization power between monovalent cations can be accounted for by the difference in the reduction potential
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