Comparison of two innovative precipitation systems for ZnO and Al-doped ZnO nanoparticle synthesis

This study presents a comparative approach to investigate the potentials of two innovative methods for the synthesis of ZnO and Al-doped ZnO. The first method is a precipitation system working in mild hydrothermal conditions (90°C) using a tubular reactor (Segmented Flow Tubular Reactor, SFTR). The second method is a microwave-assisted hydrothermal process working at 250°C - 38 atmospheres. Nanocrystalline ZnO with a high specific surface area (49–68 m2/g) was obtained with both systems. Smaller equiaxed particles (50–70 nm) were obtained with the SFTR, with an excellent homogeneity in size and morphology, which was attributed to an excellent control of the process parameters (mixing, temperature, volume of reaction). A higher luminescence signal was measured on these samples. The microwave method leads to particles with a higher crystallinity due to the temperature of the reaction. A significant effect of the aluminum was observed, which reduces the crystal growth to produce equiaxed morphologies. This effect was enhanced by adding poly(acrylic) acid (PAA)

Effect of Water Content in Ethylene Glycol Solvent on the Size of ZnO Nanoparticles Prepared Using Microwave Solvothermal Synthesis

Zinc oxide nanoparticles (ZnO NPs) were obtained by the microwave solvothermal synthesis (MSS) method. The precursor of the MSS reaction was a solution of hydrated zinc acetate in ethylene glycol with water addition. It was proved that by controlling the water concentration in the precursor it was possible to control the size of ZnO NPs in a programmed manner. The less the water content in the precursor, the smaller the size of ZnO NPs obtained. The obtained NPs with the average particle size ranging from 25 nm to 50 nm were characterised by homogeneous morphology and a narrow distribution of particle sizes. The following parameters of the obtained ZnO NPs were determined: pycnometric density, specific surface area, phase purity, chemical composition, lattice parameters, average particle size, and particle size distribution. The average size of ZnO NPs was determined using Scherrer’s formula, Nanopowder XRD Processor Demo web application, by converting the results of the specific surface area, and TEM tests using the dark field technique. ZnO morphology and structure were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The test performed by the X-ray powder diffraction (XRD) confirmed that crystalline ZnO, pure in terms of phase, had been obtained

High pressure effects in chemistry, biology and materials science

4th High Pressure School on Chemistry, Biology, Materials Science and Techniques

Delivery of Natural Agents by Means of Mesoporous Silica Nanospheres as a Promising Anticancer Strategy

Natural prodrugs derived from different natural origins (e.g., medicinal plants, microbes, animals) have a long history in traditional medicine. They exhibit a broad range of pharmacological activities, including anticancer effects in vitro and in vivo. They have potential as safe, cost-effective treatments with few side effects, but are lacking in solubility, bioavailability, specific targeting and have short half-lives. These are barriers to clinical application. Nanomedicine has the potential to offer solutions to circumvent these limitations and allow the use of natural pro-drugs in cancer therapy. Mesoporous silica nanoparticles (MSNs) of various morphology have attracted considerable attention in the search for targeted drug delivery systems. MSNs are characterized by chemical stability, easy synthesis and functionalization, large surface area, tunable pore sizes and volumes, good biocompatibility, controlled drug release under different conditions, and high drug-loading capacity, enabling multifunctional purposes. In vivo pre-clinical evaluations, a significant majority of results indicate the safety profile of MSNs if they are synthesized in an optimized way. Here, we present an overview of synthesis methods, possible surface functionalization, cellular uptake, biodistribution, toxicity, loading strategies, delivery designs with controlled release, and cancer targeting and discuss the future of anticancer nanotechnology-based natural prodrug delivery systems

Nanomedicine as an Emerging Technology to Foster Application of Essential Oils to Fight Cancer

Natural prodrugs extracted from plants are increasingly used in many sectors, including the pharmaceutical, cosmetic, and food industries. Among these prodrugs, essential oils (EOs) are of particular importance. These biologically active volatile oily liquids are produced by medicinal and aromatic plants and characterized by a distinctive odor. EOs possess high anticancer, antibacterial, antiviral, and antioxidant potential but often are associated with low stability; high volatility; and a high risk of deterioration with exposure to heat, humidity, light, or oxygen. Furthermore, their bioavailability is limited because they are not soluble in water, and enhancements are needed to increase their potential to target specific cells or tissues, as well as for controlled release. Nanomedicine, the application of nanotechnology in medicine, may offer efficient solutions to these problems. The technology is based on creating nanostructures in which the natural prodrug is connected to or encapsulated in nanoparticles or submicron-sized capsules that ensure their solubility in water and their targeting properties, as well as controlled delivery. The potential of EOs as anticancer prodrugs is considerable but not fully exploited. This review focusses on the recent progress towards the practical application of EOs in cancer therapy based on nanotechnology applications

Spectroscopic Studies of Nanopowder and Nanoceramics La2Hf2O7:PrLa_2 Hf_2 O_7:Pr Scintillator

Sintered nanoceramics of Pr-doped lanthanum hafnate, $La_{2}Hf_{2}O_{7}:Pr$, were prepared by means of a high-pressure sintering technique using nanopowders made by Pechini method. Structure, morphology, and spectroscopic properties of the ceramics compared to the starting powder are presented and discussed. Emission and excitation spectra recorded at room temperature as well as at 7 K using synchrotron radiation are presented together with results of luminescence kinetics measurements. In ceramics, at 7 K, the $Pr^{3+}$ luminescence from $^{3}P_{0}$ (blue-green, green, and red region) and $^{1}D_{2}$ (red) levels is accompanied by a broad-band emission located in the 380–530 nm range of wavelengths, whereas powders gives only the $Pr^{3+}$-related luminescence. Depending on the excitation wavelength, the broad-band emission maximum moves between 430 and 470 nm indicating superposition of at least two components. In sintered nanoceramics, the lifetimes of $Pr^{3+}$ emissions from $^{3}P_{0}$ and $^{1}D_{2}$ levels were by 10%–20% shorter compared to the powder. The existence of different luminescence centers was proved by the selective emission decays examination. The fast 5$\mathit{d}$ $\rightarrow$ 4$\mathit{f}$ luminescence of $Pr^{3+}$ was not observed from either of the two types of $La_{2}Hf_{2}O_{7}:Pr$ materials

Size Control of Cobalt-Doped ZnO Nanoparticles Obtained in Microwave Solvothermal Synthesis

This article presents the method of size control of cobalt-doped zinc oxide nanoparticles (Zn1−xCoxO NPs) obtained by means of the microwave solvothermal synthesis. Zinc acetate dihydrate and cobalt(II) acetate tetrahydrate dissolved in ethylene glycol were used as the precursor. It has been proved by the example of Zn0.9Co0.1O NPs (x = 10 mol %) that by controlling the water quantity in the precursor it is possible to precisely control the size of the obtained Zn1−xCoxO NPs. The following properties of the obtained Zn0.9Co0.1O NPs were tested: skeleton density (helium pycnometry), specific surface area (BET), dopant content (ICP-OES), morphology (SEM), phase purity (XRD), lattice parameter (Rietveld method), average crystallite size (FW1/5/4/5M method and Scherrer’s formula), crystallite size distribution (FW1/5/4/5M method), and average particle size (from TEM and SSA). An increase in the water content in the precursor between 1.5% and 5% resulted in the increase in Zn0.9Co0.1O NPs size between 28 nm and 53 nm. The X-ray diffraction revealed the presence of only one hexagonal phase of ZnO in all samples. Scanning electron microscope images indicated an impact of the increase in water content in the precursor on the change of size and shape of the obtained Zn0.9Co0.1O NPs. The developed method of NPs size control in the microwave solvothermal synthesis was used for the first time for controlling the size of Zn1−xCoxO NPs

Microwave solvothermal synthesis and characterization of manganese-doped ZnO nanoparticles

Mn-doped zinc oxide nanoparticles were prepared by using the microwave solvothermal synthesis (MSS) technique. The nanoparticles were produced from a solution of zinc acetate dihydrate and manganese(II) acetate tetrahydrate using ethylene glycol as solvent. The content of Mn2+ in Zn1−xMnxO ranged from 1 to 25 mol %. The following properties of the nanostructures were investigated: skeleton density, specific surface area (SSA), phase purity (XRD), lattice parameters, dopant content, average particle size, crystallite size distribution, morphology. The average particle size of Zn1−xMnxO was determined using Scherrer’s formula, the Nanopowder XRD Processor Demo web application and by converting the specific surface area results. X-ray diffraction of synthesized samples shows a single-phase wurtzite crystal structure of ZnO without any indication of additional phases. Spherical Zn1−xMnxO particles were obtained with monocrystalline structure and average particle sizes from 17 to 30 nm depending on the content of dopant. SEM images showed an impact of the dopant concentration on the morphology of the nanoparticles

Size-dependent density of zirconia nanoparticles

The correlation between density and specific surface area of ZrO2 nanoparticles (NPs) was studied. The NPs were produced using a hydrothermal process involving microwave heating. The material was annealed at 1100 °C which resulted in an increase in the average grain size of the ZrO2 NPs from 11 to 78 nm and a decrease in the specific surface area from 97 to 15 m2/g. At the same time, the density increased from 5.22 g/m3 to 5.87 g/m3. This effect was interpreted to be the result of the presence of a hydroxide monolayer on the NP surface. A smaller ZrO2 grain size was correlated with a larger contribution of the low density surface layer to the average density. To prove the existence of such a layer, the material was synthesized using 50% heavy water. Fourier transform infrared spectroscopy (FTIR) permitted the identification of the –OD groups created during synthesis. It was found that the –OD groups persisted on the ZrO2 surface even after annealing at 1100 °C. This hydroxide layer is responsible for the decrease in the average density of the NPs as their size decreases. This study of the correlation between particle size and density may be used to assess the quality of the NPs. In most cases, the technological aim is to avoid an amorphous layer and to obtain fully crystalline nanoparticles with the highest density possible. However, due to the effect of the surface layers, there is a maximum density which can be achieved for a given average NP diameter. The effect of the surface layer on the NP density becomes particularly evident for NPs smaller than 50 nm, and thus, the density of nanoparticles is size dependent