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In this study, zinc oxide (ZnO) nanorod arrays were synthesized using a simple hydrothermal reaction on ZnO seeds/n-silicon substrate. Several parameters were studied, including the heat-treatment temperature to produce ZnO seeds, zinc nitrate concentration, pH of hydrothermal reaction solution, and hydrothermal reaction time. The optimum heat-treatment temperature to produce uniform nanosized ZnO seeds was 400°C. The nanorod dimensions depended on the hydrothermal reaction parameters. The optimum hydrothermal reaction parameters to produce blunt tip-like nanorods (770 nm long and 80 nm in top diameter) were 0.1 M zinc nitrate, pH 7, and 4 h of growth duration. Phase analysis studies showed that all ZnO nanorods exhibited a strong (002) peak. Thus, the ZnO nanorods grew in a c-axis preferred orientation. A strong ultraviolet (UV) emission peak was observed for ZnO nanorods grown under optimized parameters with a low, deep-level emission peak, which indicated high optical property and crystallinity of the nanorods. The produced ZnO nanorods were also tested for their UV-sensing properties. All samples responded to UV light but with different sensing characteristics. Such different responses could be attributed to the high surface-to-volume ratio of the nanorods that correlated with the final ZnO nanorods morphology formed at different synthesis parameters. The sample grown using optimum synthesis parameters showed the highest responsivity of 0.024 A/W for UV light at 375 nm under a 3 V bias.

Nanoparticle science is rapidly changing the landscape of various scientific fields and defining new technological platforms. This is perhaps even more evident in the field of nanomedicine whereby nanoparticles have been used as a tool for the treatment and diagnosis of many diseases. However, despite the tremendous benefit conferred, common pitfalls of this technology is its potential short and long-term effects on the human body. To understand these issues, many scientific studies have been carried out. This review attempts to shed light on some of these studies and its outcomes. The topics that were examined in this review include the different possible uptake pathways of nanoparticles and intracellular trafficking routes. Additionally, the effect of physicochemical properties of nanoparticle such as size, shape, charge and surface chemistry in determining the mechanism of uptake and biological function of nanoparticles are also addressed.

The localized surface plasmon resonance (LSPR) effects of nanoparticles (NPs) are effective for enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs). In this study, spiky durian-shaped Au@Ag core-shell NPs were synthesized and embedded in the hole transport layer (HTL) (poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)) of PTB7:PC71BM bulk-heterojunction OSCs. Different volume ratios of PEDOT:PSS-to-Au@Ag NPs (8%, 10%, 12%, 14%, and 16%) were prepared to optimize synthesis conditions for increased efficiency. The size properties and surface morphology of the NPs and HTL were analyzed using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). UV–Vis spectroscopy and current density–voltage (J-V) analysis were used to investigate the electrical performance of the fabricated OSCs. From the results, we observed that the OSC with a volume ratio of 14% (PEDOT:PSS–to–Au@Ag NPs) performed better than others, where the PCE was improved from 2.50% to 4.15%, which is a 66% increase compared to the device without NPs.

A bottom-up approach for synthesizing silver nanoparticles (AgNPs-GA) phytomediated by Garcinia atroviridis leaf extract is described. Under optimized conditions, the AgNPs-GA were synthesized at a concentration of 0.1 M silver salt and 10% (w/v) leaf extract, 1:4 mixing ratio of reactants, pH 3, temperature 32 °C and 72 h reaction time. The AgNPs-GA were characterized by various analytical techniques and their size was determined to be 5–30 nm. FTIR spectroscopy indicates the role of phenolic functional groups in the reduction of silver ions into AgNPs-GA and in supporting their subsequent stability. The UV-Visible spectrum showed an absorption peak at 450 nm which reflects the surface plasmon resonance (SPR) of AgNPs-GA and further supports the stability of these biosynthesized nanoparticles. SEM, TEM and XRD diffractogram analyses indicate that AgNPs-GA were spherical and face-centered-cubic in shape. This study also describes the efficacy of biosynthesized AgNPs-GA as anti-proliferative agent against human breast cancer cell lines, MCF-7 and MCF-7/TAMR-1. Our findings indicate that AgNPs-GA possess significant anti-proliferative effects against both the MCF-7 and MCF-7/TAMR-1 cell lines, with inhibitory concentration at 50% (IC50 values) of 2.0 and 34.0 µg/mL, respectively, after 72 h of treatment. An induction of apoptosis was evidenced by flow cytometry using Annexin V-FITC and propidium iodide staining. Therefore, AgNPs-GA exhibited its anti-proliferative activity via apoptosis on MCF-7 and MCF-7/TAMR-1 breast cancer cells in vitro. Taken together, the leaf extract from Garcinia atroviridis was found to be highly capable of producing AgNPs-GA with favourable physicochemical and biological properties.

Combining iron oxide nanoparticles (Fe3O4 NPs) and gold nanoparticles (Au NPs) in one nanostructure is a promising technique for various applications. Fe3O4 NPs have special supermagnetic attributes that allow them to be applied in different areas, and Au NPs stand out in biomaterials due to their oxidation resistance, chemical stability, and unique optical properties. Recent studies have generally defined the physicochemical properties of nanostructures without concentrating on a particular formation strategy. This detailed review provides a summary of the latest research on the formation strategy and applications of Fe3O4@Au. The diverse methods of synthesis of Fe3O4@Au NPs with different basic organic and inorganic improvements are introduced. The role and applicability of Au coating on the surface of Fe3O4 NPs schemes were explored. The 40 most relevant publications were identified and reviewed. The versatility of combining Fe3O4@Au NPs as an option for medical application is proven in catalysis, hyperthermia, biomedical imaging, drug delivery and protein separation.

One of the most widely used modalities of clinical imaging is computed tomography (CT). Recent reports of new contrast agents toward CT imaging have been numerous. The production of gold nanoparticles (AuNPs) as contrast agents for CT is primarily a topic of intense interest. AuNPs have beneficial features for this application, including excellent X-ray attenuation, flexible sizes and shapes, tailorable surface chemistry, excellent biocompatibility and high levels of contrast generating matter. AuNPs with a size of about 18.5 nm and semi-spherical shape were synthesized using a sonochemical method. The attenuation rate of X-rays as measured in Hounsfield units per unit concentration (HU/mg) was measured. Ultrasound treatment for a duration of five min has been shown to produce highly stable AuNPs in different media (AuNPs in water and phosphate-buffered saline (PBS) was −42.1 mV and −39.5 mV, respectively). The CT value (HU = 395) of the AuNPs increased linearly with an increase in the AuNP dosage. The results confirm the use of ultrasonic treatment for the production of metal nanostructures, particularly highly stable non-toxic AuNPs, with good morphology and high-quality crystal structure using an easy and fast method. Synthesized AuNPs have the potential to be used as a CT contrast agent in medical imaging applications.

Agar have long been used as a growth media for plants. Here, we made agar media with embedded fluidic channels to study the effect of exposure to nutrient solution on root growth and pull-out force. Black Eye bean ( Vigna Unguiculata ) and Mung bean ( Vigna Radiata ) were used in this study due to their rapid root development. Agar media were fabricated using casting process with removable cores to form channels which were subsequently filled with nutrient solution. Upon germination, beans were transplanted onto the agar media and allowed to grow. Pull-out force was determined at 96, 120 and 144 h after germination by applying a force on the hypocotyl above the gel surface. The effect of nutrients was investigated by comparing corresponding data obtained from control plants which have not been exposed to nutrient solution. Pull-out force of Black Eye bean plantlets grown in agar with nutrient solution in channels was greater than those grown in gel without nutrients and was 110% greater after 144 h of germination. Pull-out force of Mung bean plantlets grown in agar with and without nutrient solution was similar. Tap root lengths of Black Eye bean and Mung Bean plantlets grown in agar with nutrient solution are shorter than those grown without nutrient. 

Development of bio-reduction techniques for nanoparticles (NPs) synthesis in medical application remains a challenge to numerous researchers. This work reports a novel technique for the synthesis of gold nanoparticles (AuNP) using palm oil fronds extracts (POFE) in the present of ultrasound radiation. The POFE is a waste material available in abundance in Asia and some African countries. The functional groups in the POFE operate as a persuasive capping and possibly reduced Au3+ to Au0. The prepared AuNPs were characterized by UV-vis spectrophotometry, FTIR, DLS, FESEM, and XRD. The analysis of FTIR validates the coating of alkynes and phenolic composites on the AuNPs. This shows a feasible function of biomolecules for efficient stabilization of the AuNPs. Field emission scanning electron microscopy (FESEM) clearly show the morphology of the prepared AuNPs. The XRD patterns display the peaks of fcc crystal structures at (111), (200), (220), (311) and (222). A physical and photometric detection effect of ten heavy metals (Pb, Zn, Ni, Co, Cu, Hg, As, Cr, Fe, and Mn) were investigated using the biosynthesized AuNPs and only Cr metal was detected by the AuNPs when it concentration increased from 1 ppm to 50 ppm with a rapit decrease of intensity measured using UV-vis spectrocopy at room temperature. While, almost all metals ions are detected at elevated tempeture (45 – 50 °C).

Gold nanoparticles (AuNPs) have numerous usage in various applications, primarily in chemical and biological sensing. There are also various methods of producing AuNPs. However, in some of those methods, removing excess reagents, including ions or residual surfactants, can be difficult and time-consuming, while the functionalization of AuNPs with other types of molecules can only be achieved at lower efficacy. In this report, the AuNPs were produced using a rapid and solvent-free sonochemical and laser ablation methods. Morphology, structure and the colloidal stability of AuNPs produced by the two methods were analyzed and compared. Results have shown that the purity, homogeneity and crystallinity of AuNPs produced using the sonochemical technique showed better characteristics than those acquired by the laser ablation method. AuNPs also demonstrated smaller particle sizes (22 nm), smooth surfaces with higher colloidal stability (50.7 mV). The findings indicate that ultrasound irradiation power improves the crystalline properties of AuNPs and inhibits their agglomeration. The sonochemical approach can, therefore, be used to produce AuNPs with better physicochemical characteristics compared to laser ablation methods.

The optical properties of a spherical gold nanoparticle have become our interest due to its remarkable characteristics when interacting with the light. In this work, the dependence of surface plasmon resonance on the size of the gold nanosphere has been studied with varying diameter from 20 to 100 nm. The optical spectra of the single isolated gold nanoparticles are simulated by employing the versatile MNPBEM toolbox. The wavelength corresponding to the maximum extinction, absorption as well as scattering redshifts (shift to longer wavelengths) were observed as the nanoparticle size increased. The rate of change of scattering (Δsca) and absorption (Δabs) relative to the extinction is calculated to correlate these two properties. For the nanoparticle with size less than 70 nm, Δabs is larger than Δsca, whereas for the diameter of nanoparticles above 70 nm, they show that Δsca is larger than Δabs. Due to this, it is found that absorption efficiency initially increases with nanoparticle size, which eventually reaches a maximum at a size of 70 nm and then begins to decrease with further increase in the nanoparticle diameter. The observed volcano trend of absorption efficiency is the result of electromagnetic retardation and radiative scattering. It can be concluded that the intermediate-size nanoparticle has the highest absorption efficiency with an optimal size of 70 nm for gold nanoparticles.