In the field of synthesis and processing of noble metal nanoparticles, the study of the bottom-up method, called Ultrasonic Spray Pyrolysis (USP), is becoming increasingly important. This review ...analyses briefly the features of USP, to underline the physical, chemical and technological characteristics for producing nanoparticles and nanoparticle composites with Au and Ag. The main aim is to understand USP parameters, which are responsible for nanoparticle formation. There are two nanoparticle formation mechanisms in USP: Droplet-To-Particle (DTP) and Gas-To-Particle (GTP). This review shows how the USP process is able to produce Au, Ag/TiO2, Au/TiO2, Au/Fe2O3 and Ag/(Y0.95 Eu0.05)2O3 nanoparticles, and presents the mechanisms of formation for a particular type of nanoparticle. Namely, the presented Au and Ag nanoparticles are intended for use in nanomedicine, sensing applications, electrochemical devices and catalysis, in order to benefit from their properties, which cannot be achieved with identical bulk materials. The development of new noble metal nanoparticles with USP is a constant goal in Nanotechnology, with the objective to obtain increasingly predictable final properties of nanoparticles.
To monitor the progress and prevent the spread of the COVID-19 pandemic in real time and outside laboratories, it is essential to develop effective tests that can ensure rapid, selective, and ...reliable diagnosis of infected persons in different environments. Key in this regard is the lateral flow immunoassays (LFIAs) that can detect the presence of the SARS-CoV-2 virus quickly, with the aid of nanoparticles (NPs) and specific proteins. We report the use of gold (Au) NPs AuNPs synthesised from a gold(
) chloride tetrahydrate precursor in a USP device and collected in a suspension composed of deionised water with polyvinylpyrrolidone as a stabiliser and cryoprotectant. In combination with freeze-drying of the AuNPs’ suspension to achieve water elimination, improved stability, and the target concentration, they exhibit the necessary properties for use as markers in LFIA rapid diagnostic tests. This was confirmed by complementary characterisation determined by using the techniques including inductively coupled plasma-optical emission spectrometry, dynamic light scattering method and zeta-potential, ultraviolet-visible spectroscopy, X-ray diffraction, scanning electron microscopy with energy dispersion spectrometer, and transmission electron microscopy, as well as with the preparation of a prototype LFIA test strip with AuNPs. Thus, such AuNPs, as well as the USP method, show promise for the development of new markers for use in LFIA.
Cobalt-chromium (CoCr) alloys have been used in dentistry for dental bridges, crowns and implants for decades. When using CoCr alloys, a number of fractures have occurred in the Dental Laboratory, ...both when handling the castings and after they have been placed in the patient’s mouth. It is assumed that the key cause of the resulting fractures of CoCr dental bridges is the casting process, which includes the preparation and mixing of the basic components of the CoCr dental alloy, unstable solidification and the final treatment of the tooth casting surface. The aim of this study was, therefore, to examine three castings differently prepared from the CoCr alloy. For the initial CoCr alloy, we selected the one supplied directly from the manufacturer; three test samples were CoCr alloy remelted four times in the same crucible, while the fourth sample was the remaining solidified alloy from the crucible, taken at the last remelting. Characterisation of the microstructure of all four samples was performed by optical and scanning electron microscopy equipped with an energy dispersive X-ray spectroscope and X-ray diffractometry. Microhardness measurements were also performed. The investigation revealed that the microstructure of the castings is composed of a CoCr alloy matrix with a eutectic interdendritic composition and interdendritic precipitates, which were rich in W and Mo. The two oxides were identified as chromium oxide with silicon content and chromium oxide, which originated from the CoCr alloy as casting residue. The high content of silicon in the chromium oxide can be attributed to the silicon oxide from the ceramic melting crucible, mixed in with the remains from the CoCr alloy melting. The second oxide showed a more regular elemental content for chromium oxide, mixed with a small quantity of impurities and the casting CoCr alloy. Based on this research, some recommendations were made for working with CoCr alloys in the Dental Laboratory, with the aim of reducing the risk of dental bridge fractures in the future.
A complex concentrated noble alloy (CCNA) of equiatomic composition (Ag20Pd20Pt20Cu20Ni20–20 at. %) was studied as a potential high—performance material. The equiatomic composition was used so that ...this alloy could be classified in the subgroup of high—entropy alloys (HEA). The alloy was prepared by induction melting at atmospheric pressure, using high purity elements. The degree of metastability of the cast state was estimated on the basis of changes in the microstructure during annealing at high temperatures in a protective atmosphere of argon. Characterisation of the metallographically prepared samples was performed using a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), differential scanning calorimetry (DSC), and X–ray diffraction (XRD). Observation shows that the microstructure of the CCNA is in a very metastable state and multiphase, consisting of a continuous base of dendritic solidification—a matrix with an interdendritic region without other microstructural components and complex spheres. A model of the probable flow of metastable solidification of the studied alloy was proposed, based on the separation of L—melts into L1 (rich in Ni) and L2 (rich in Ag). The phenomenon of liquid phase separation in the considered CCNA is based on the monotectic reaction in the Ag−Ni system.
Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes. Wasted and unused rapid antigen lateral flow immunoassays represent mass waste that needs to be ...broken down and recycled into new material components. The aim of this study was to recover gold nanoparticles that are used as markers in lateral flow immunoassays. For this purpose, a dissolution process with aqua regia was utilised, where gold nanoparticles were released from the lateral flow immunoassay conjugate pads. The obtained solution was then concentrated further with gold chloride salt (HAuCl4) so that it could be used for the synthesis of new gold nanoparticles in the process of ultrasonic spray pyrolysis (USP). Various characterisation methods including scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and optical emission spectrometry with inductively coupled plasma were used during this study. The results of this study showed that the recovery of gold nanoparticles from lateral flow immunoassays is possible, and the newly synthesised gold nanoparticles represent the possibility for incorporation into new products.
Gold nanoparticles (AuNPs) have now been used in skin care creams for several years, with marketed anti-aging, moisturizing, and regenerative properties. Information on the harmful effects of these ...nanoparticles is lacking, a concern for the use of AuNPs as cosmetic ingredients. Testing AuNPs without the medium of a cosmetic product is a typical method for obtaining this information, which is mainly dependent on their size, shape, surface charge, and dose. As these properties depend on the surrounding medium, nanoparticles should be characterized in a skin cream without extraction from the cream's complex medium as it may alter their physicochemical properties. The current study compares the sizes, morphology, and surface changes of produced dried AuNPs with a polyvinylpyrrolidone (PVP) stabilizer and AuNPs embedded in a cosmetic cream using a variety of characterization techniques (TEM, SEM, DLS, zeta potential, BET, UV-vis). The results show no observable differences in their shapes and sizes (spherical and irregular, average size of 28 nm) while their surface charges changed in the cream, indicating no major modification of their primary sizes, morphology, and the corresponding functional properties. They were present as individually dispersed nanoparticles and as groups or clusters of physically separated primary nanoparticles in both dry form and cream medium, showing suitable stability. Examination of AuNPs in a cosmetic cream is challenging due to the required conditions of various characterization techniques but necessary for obtaining a clear understanding of the AuNPs' properties in cosmetic products as the surrounding medium is a critical factor for determining their beneficial or harmful effects in cosmetic products.
This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They ...were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3% strain at the break, when compared to the base PLA. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in injection moulding applications and warrant further exploration of their properties and new applications in various fields.
Due to the unique functional properties of shape memory alloys (SMAs) and current scientific interest in Cu-containing biomaterials, a continuously cast Cu-Al-Ni alloy in the form of rods has been ...investigated as a potential candidate for biomedical application. Additionally, the fact that Cu- complexes have an antitumour effect served as a cornerstone to develop more efficient drugs based on trace element complexes. In line with that, our study aimed to analyse the basic properties of the Cu-Al-Ni alloy, along with its anticancer properties. The detailed chemical analysis of the Cu-Al-Ni alloy was performed using XRF and SEM/EDX analyses. Furthermore, a microstructural and structure investigation was carried out, combined with hardness measurements using the static Vickers method. Observations have shown that the Cu-Al-Ni microstructure is homogeneous, with the presence of typical martensitic laths. XRD analysis confirmed the presence of two phases, β' (monoclinic) and γ' (orthorhombic). The viability of osteosarcoma cells in contact with the Cu-Al-Ni alloy was evaluated using epifluorescence microscopy, while their morphology and attachment pattern were observed and analysed using a high-resolution SEM microscope. Biocompatibility testing showed that the Cu-Al-Ni alloy exerted a considerable antineoplastic effect.
In modern times, more and more different materials (including alloys) are in direct contact with human electrolytes (sweat, saliva, lymph, blood, etc.). One of the most important properties for the ...use of these materials is therefore their chemical inertness or resistance to corrosion when they are in contact with human electrolytes. Consequently, during the development of such new materials, it is necessary to study and understand their basic electrochemical behaviour in a given environment. The purpose of this research was to monitor the electrochemical behaviour of the new Au-Ge alloy in artificial sweat and artificial saliva solutions, depending on the electrolyte composition and exposure time. This new alloy represents a potential material for use in dentistry or for jewellery. The obtained results of the study show that the immersion time and the pH value have a significantly greater influence on the corrosion resistance of the new Au-Ge alloy than the composition of the electrolyte solution. The results of the SEM/EDX analysis additionally confirm the main results of the electrochemical measurements.
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