Narrow Results

Some of the fundamental properties of the nanofluids affect not only the transport phenomenon but also enhance the the heat transfer characteristics. The advancement in Rotatory machine technology can also be attributed mainly to a lot of research work that had been done on rotating disk flows with addition of nanoparticles in the base fluid. Taking cue of these developments, we examined the nanofluid (Cu+H₂O) flow over a rotating disk moving upward/ downward with viscous dissipation by reducing the governing Navier–Stokes equations into ordinary differential equations using appropriate transformations and then numerically evaluated them by the BVP Mid-rich scheme in Maple software. The study of velocity and thermal profiles is carried out and examined graphically. The results show that the upward movement of the disk escalates the radial and azimuthal velocity profiles along with the thermal gradient. In contrast, the addition of nanoparticles decreases the heat transfer rate at a constant disk movement.

A self-assembled monolayer (SAM) of octanethiol was vapor-deposited onto the surface of copper (Cu) nanoparticles as a means of preventing oxidation. The presence of octanethiol on the surface of Cu nanoparticles was verified using Fourier transform infrared spectroscopy and transmission electron microscopy. The electrical resistance of copper nanoparticles with deposition of a 12-nm thickness of octanethiol on the surface was found to be 100 times greater than that of uncoated powders, indicating uniform SAM coating of the particles.

Photoabsorption profiles of copper clusters, Cu_N, grown in superfluid helium droplets were studied by beam depletion spectroscopy. For N below ~ 10³ the spectra are characteristic of individual metallic particles, but in larger clusters a strong, broad absorption feature appears in the near-infrared region. This suggests a transition from single- to multicenter condensation: as the arrival frequency of metal atoms exceeds their transport time within the helium matrix, they nucleate into small individual agglomerates which later collect into a noncompact, possibly fractal or percolative assembly. The data, in concert with earlier observations on silver cluster growth, affirm that the formation of cluster–cluster aggregates with unusual optical properties is a general phenomenon achievable with the use of the helium nanodroplet technique.

Copper nanoparticles received much attention due to its high electrical conductivity, high melting point, low electrochemical migration behavior and low cost. Top down (physical methods) and bottom up (chemical and biological) approaches adopted for the synthesis of copper nanoparticles are reported. The property of copper nanoparticles mainly depends on the synthesis route and their process parameters. The influence of process parameters on the morphology, growth and yield of the nanoparticles by adopting various synthesis methods are discussed in detail. From the earlier reports, it is proved that electrochemical and chemical reduction method have received much higher attention due to their simple operation, low cost, faster reaction rate, high yield, environment friendly and low energy consumption. The characterization techniques, advantages and limitations of each synthesis methods are also discussed. The extensive applications of copper nanoparticles in various fields are also highlighted.

Electrolysis is a method used for producing copper (Cu) nanoparticles at faster rate and at low cost in ambient conditions. The property of Cu nanoparticles prepared by electrolysis depends on their process parameters. The influence of selected process parameters such as copper sulfate (CuSo₄) concentration, electrode gap and electrode potential difference on particle size was investigated. To optimize these parameters response surface methodology (RSM) was used. Cu nanoparticles prepared by electrolysis were characterized by using X-ray diffraction (XRD) and scanning electron microscope (SEM). After reviewing the results of analysis of variance (ANOVA), mathematical equation was created and optimized parameters for producing Cu nanoparticles were determined. The results confirm that the average size of Cu particle at the optimum condition was found to be 17nm and they are hexagonal in shape.

A method of synthesis is presented for the rapid preparation of copper, copper oxide and mixed copper oxide-copper nanoparticles employing a conventional home microwave oven. The nanoparticles were characterized by SEM, XRD and UV-visible spectroscopy. The size and the composition of the nanoparticles were controlled by the heating time. Cuprous oxide nanoparticles were obtained at short heating times and copper nanoparticles at longer times, while mixed cuprous oxide-copper nanoparticles where obtained in an in between window of time.

Various methods for the synthesis of copper nanoparticles employing chemical, physical and biological techniques considering bottom-up and top-down methods synthesis have been studied. The properties of copper nanoparticles depend largely on their synthesis procedures. The results from various investigations performed by different scientists using these methods have been summarized. The applications, characterization techniques, advantages and disadvantages of each synthesis method are also the point of discussion. A detailed study of the results reveals that chemical reduction methods are most suitable for the synthesis of copper nanoparticles. Chemical reduction of copper salts using ascorbic acid (Vitamin C) is a new and green approach in which ascorbic acid is used both as the reduction and capping agent. This approach is the most effective and is also economical. Wide applications have been reported in various fields, including heat transfer, catalyst production, electronics and medicine at a commercial scale. This process is nontoxic, environment-friendly and economical. The applications, characterization techniques, advantages and disadvantages of each synthesis method have been presented.

Green nanomaterial synthesis is the process of producing various metallic nanoparticles (MNPs) utilizing bioactive reagents. It attempts to reduce waste and promote environmental sustainability by employing mild reaction conditions and safe materials. Researchers have demonstrated a strong interest in using natural biomolecules extracted from plants to synthesize MNPs. The individual biomolecules in this plant extract function as reducing, capping, and stabilizing substances in the green production of stable MNPs using their related metal ion precursor solution. The advantages of this method are that it is environmentally friendly, does not require energy, and is cheap and quick. Recently, MNPs have been developed in the field of cancer due to various qualities, including their increased reactive surfaces and small specified volume, which make them suited for traditional small pharmaceuticals and pharmaceutical compounds. MNPs, such as gold (AuNPs), silver (AgNPs) and copper (CuNPs), are increasingly being used as anticancer agents. This review describes the synthesis of three MNPs: AuNPs, AgNPs and CuNPs nanoparticles from plant extracts. AgNPs are the most often used synthetic NPs, accounting for more than 25% of all consumer items. AgNPs are generally employed for antibacterial, antifungal and antiviral purposes. Also, the anti-cancer activities of the MNPs were explained. The challenges and predicted developments for future studies are addressed, which are critical for real-world applications. In the future, new types of NPs will be generated employing modern technology, with a wide range of uses in numerous industries.