Size Reduction Of Nanoparticles Research Articles

Investigating the performance of a novel pH and cathepsin B sensitive, stimulus-responsive nanoparticle for optimised sonodynamic therapy in prostate cancer

Nano-formulations that are responsive to tumour-related and externally-applied stimuli can offer improved, site-specific antitumor effects, and can improve the efficacy of conventional therapeutic agents. Here, we describe the performance of a novel stimulus-responsive nanoparticulate platform for the targeted treatment of prostate cancer using sonodynamic therapy (SDT). The nanoparticles were prepared by self-assembly of poly(L-glutamic acid-L-tyrosine) co-polymer with hematoporphyrin. The nanoparticulate formulation was characterized with respect to particle size, morphology, surface charge and singlet oxygen production during ultrasound exposure. The response of the formulation to the presence of cathepsin B, a proteolytic enzyme that is overexpressed and secreted in the tumour microenvironment of many solid tumours, was assessed. Our results showed that digestion with cathepsin B led to nanoparticle size reduction. In the absence of ultrasound, the formulation exhibited greater toxicity at acidic pH than at physiological pH, using the human prostate cells lines LNCaP and PC3 as targets. Nanoparticle cellular uptake was enhanced at acidic pH – a condition that was also associated with greater cathepsin B production. Nanoparticles exhibited enhanced ultrasound-induced cytotoxicity against both prostate cancer cell lines. Subsequent proof-of-concept in vivo studies demonstrated that, when ectopic human xenograft LNCaP tumours in SCID mice were treated with SDT using the systemically-administered nanoparticulate formulation at a single dose, tumour volumes decreased by up to 64% within 24 h. No adverse effects were observed in the nanoparticle-treated mice and their body weight remained stable. The potential of this novel formulation to deliver safe and effective treatment of prostate cancer is discussed.

Study of Physical Properties of Cadmium Oxide (CdO) and CdO/DNA/RNA Nanostructures Thin Layers Produced by Spray Pyrolysis Technique for Manufacturing Cadmium Oxide (CdO) Nanoparticles and Evaluation of the Effect of DNA/RNA Doping on Their Optical Characteristics

In the current research, Cadmium Oxide (CdO) nanoparticles are produced by ultrasonic waves and the effect of nucleic acids (DNA/RNA) doping on their optical and structural characteristics are investigated. X-ray Diffraction (XRD) analysis confirms extension of peaks and formation of Cadmium Oxide (CdO) nanoparticles. Absorption spectra for the produced samples are shown that addition of DNA/RNA affects the spectrum and absorption edge shifts towards blue region which is due to reduction of nanoparticle size and it confirms by SEM images. In addition, SEM images show the formation of approximately single size ellipsoidal nanostructures for pure Cadmium Oxide (CdO). However, the size, form and distribution of nanoparticles are varied after doping. On the other hand, in the current paper, Cadmium Oxide (CdO) and DNA/RNA/Cadmium Oxide (CdO) nanostructures thin layers are produced using spray pyrolysis technique over a glassy substrate. Annealing of CdO thin layer for half an hour in the air leads to improvement of crystalline structure. Optical characteristics and crystalline structure of samples are studied through X-ray Diffraction (XRD) and UV-Visible spectroscopy. The results of the current study were shown that CdO thin layers are of hexagonal structure. Further, optical gaff of CdO/DNA/RNA/glass thin layer is increased compared to CdO/glass layer.

Thermostability, photostability, and toxicity of clove oil nanoparticles against Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae)

Abstract. Ikawati S, Himawan T, Abadi AL, Tarno H. 2020. Thermostability, photostability, and toxicity of clove oil nanoparticles against Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae). Biodiversitas 21: 4764-4771. Problems related to the essential oils as insecticides are their volatility, poor solubility in water and environmental degradation (such as caused by high temperatures and UV light) which can adversely affect the application. An ideal botanical insecticide formulation would maintain the level of the main compounds adequate for pest control. This study was to evaluate the stability of polyethylene glycol (PEG) coated nanoparticles loaded with clove (Syzygium aromaticum) essential oil to high temperature and UV light also their toxicity to C. ferrugineus. There is a reduction in nanoparticle size after heating from 257 to 173 nm and there is no difference in size distribution. After heating and UV-light treatment, eugenol content in free clove oil decreased significantly, while on nanoparticles there were not significantly changed, that indicated greater stability on the nanoformulation. The median lethal concentration (LC50) of CO-NPs to C. ferrugineus adults value for 72 and 120 hours was 0.734 and 0.676%.

Effects of cold atmospheric plasma treatment on the morphological and optical properties of plasmonic silver nanoparticles

The use of plasma processes in nanomaterial synthesis is limited by a lack of understanding of the effects of plasma treatment on the morphology and other properties. Here, we studied the effects of atmospheric plasma treatment on the morphology and optical properties of Ag nanoparticles. The Ag nanoparticles were deposited on substrates by injecting an aerosol into flowing argon gas and then treated with a low-temperature atmospheric plasma jet. After plasma treatment, the mean Ag nanoparticle diameter reduced to an average of 5 nm, which was accompanied by a blue shift of ∼70 nm in the peak of the surface plasmon resonance; these results are similar to those obtained by thermal treatment at elevated temperatures. The reduction in nanoparticle size is explained by the redox reaction that occurs on the nanoparticle surface, which is evident from the presence of AgO and Ag2O Raman peaks in the treated sample. The surface charge changed as a result of plasma treatment, as indicated by a large change in the zeta potential from +25.1 ± 4 mV for the untreated sample to −25.9 ± 6 mV after 15 min of plasma treatment. Surface-enhanced Raman spectroscopy of the plasma-treated films was carried out with the fluorescent dye Rhodamine 6 G, which showed a ∼120-fold enhancement in the signal intensity relative to the untreated substrates. We, therefore, conclude that cold-plasma treatment modified the surface morphology of the Ag nanoparticles, thereby enhancing their optical properties. This technique could be applied to a wide range of nanoparticle systems used in biosensing applications.

Comparative Evaluation of the Morphological Characteristics of Nanolime Dispersions for the Consolidation of Architectural Monuments

ABSTRACT This work studies the morphological characteristics of four different laboratories synthesized nanolime dispersions, focusing on the characteristics of the polar dispersion medium and the increase of the water content in the final dispersion. An innovation of this research is the incorporation of distilled water that is enriched with O2 nanobubbles (NBs) as an alternative aqueous dispersion medium, with a potential of surfactant action. The evaluation of the dispersions was based on the morphological, chemical and the mineralogical characterization of nanoparticles, their stability and their penetration potential in two porous substrates. The use of the 2-propanol resulted in the reduction of nanoparticle size and the absence of agglomerates. The combined use of 2-propanol and distilled water enriched with O2 NBs was considered also beneficial since it resulted in dispersions with slightly reduced kinetic stability but, with enhanced penetration in the porous substrates.

Caveolin‐1 frame‐shift mutation induce changes in cellular morphology and function

Caveolins, Cav1–3, are oligomeric proteins critical for the formation of membrane caveolae that regulates cell physiology. A frameshift mutation (Cav1F160X) in Cav1 (Cav1M) was described in a patient with a progeria‐like phenotype, which presents nuclear morphology alterations. We hypothesize that Cav1M presents dominant negative function that perturb cellular physiology, particularly nuclear morphology, mitochondrial function, exocytic behavior a plasma membrane structure. Transmission electron microscopy (TEM) of patient‐derived dermal fibroblasts (PCav1M) showed abnormal nuclear shape, increased rough endoplasmic reticulum, abnormal mitochondrial size/shape, increased number of autophagosomes and reduce number of membrane caveolae. Patient‐derive serum shown an increase in exosomes and extracellular vesicles, compared with the unaffected family members. PCav1M fibroblasts showed 4‐fold increase in exosome secretion; PCav1M present also increased exosome secretion compared with Hutchinson‐Gilford progeria patient dermal fibroblasts. Nanotracking and TEM analysis revealed a significant reduction in nanoparticle size in PCav1M‐derived exosomes. Human dermal fibroblasts (HDF) treated to express Cav1M or exogenously exposed to exosomes from PCav1M fibroblasts showed altered nuclear morphology, exosome secretion profile, proteomics, and miRNA analysis. Cellular membrane structure analysis by means of membrane fractions and electron paramagnetic spectroscopy shows an altered localization of proteins commonly found in caveolae fractions and increased membrane fluidity. Our results indicate that mutations in the C‐terminus of Cav1 lead to significant membrane alterations regulating exosome secretion and other cellular morpho‐functional features. Our findings identify a novel role of caveolin in linking plasma and nuclear membrane dynamics that have potential implications for cellular communication, impacting physiology and pathophysiology.Support or Funding InformationNational Institutes of Health (HL091071, AG052722) and Veterans Administration (BX001963).

Enhanced photoelectrocatalytic performance from size effects in pure and La-doped BiFeO3 nanoparticles

Due to the energy crisis, the development of high-performance photoelectrocatalysts is becoming a hot research area in recent years. Among the materials studied, BiFeO3 (BFO) exhibits excellent photoelectrocatalytic performance due to its moderate bandgap and unique band structure. In this paper, both pure BFO and La-doped BFO were synthesized by solgel method. The average size of the BFO nanoparticles was tuned from 65 to 440 nm. For the La-doped BFO, the average size of the nanoparticles was reduced from 95 to 40 nm with the increase in doping level from 0 to 30%. Next, the photoelectrocatalytic performance of the pure BFO nanoparticles were enhanced with the reduction in nanoparticle size, which was possibly caused by increased surface-to-volume ratio. For the increase in doping of La, the corresponding photoelectrocatalytic performance was first enhanced and then degraded. To understand the obtained results, a mechanism was proposed, which can be attributed to the competition between geometric size effects and surface effects. Our findings provided a controlled way to tune the photoelectrocatalytic performance of BFO system, which is crucial for practical applications.

On the Effects of Diluted and Mixed Ionic Liquids as Liquid Substrates for the Sputter Synthesis of Nanoparticles.

The synthesis of nanoparticles by combinatorial sputtering in ionic liquids is a versatile approach for discovering new materials. Whereas the influence on nanoparticle formation of different pure ionic liquids has been addressed, the influence of (I) dilution of ionic liquid with solvents and (II) different mixtures of ionic liquids is less known. Therefore, mixtures of the ionic liquid [Bmim][(Tf)2N] with the organic solvent anisole and other ionic liquids ([Bmim][(Pf)2N], [BmPyr][(Tf)2N]) were used as liquid substrates for the sputter synthesis of nanoparticles, in order to investigate the influence of these mixtures on the size of the nanoparticles. First, mixtures of anisole with a suspension of sputtered Ag nanoparticles in [Bmim][(Tf)2N] were prepared in different volumetric steps to investigate if the stabilization of the NPs by the ionic liquid could be reduced by the solvent. However, a continuous reduction in nanoparticle size and amount with increasing anisole volume was observed. Second, Ag, Au and Cu were sputtered on ionic liquid mixtures. Ag nanoparticles in [Bmim][(Tf)2N]/[Bmim][(Pf)2N] mixtures showed a decrease in size with the increasing volumetric fraction of [Bmim][(Tf)2N], whereas all nanoparticles obtained from [Bmim][(Tf)2N]/[BmPyr][(Tf)2N] mixtures showed increasing size and broadening of the size distribution. Maximum sizes of sputtered Ag and Au NPs were reached in mixtures of [Bmim][(Tf)2N] with 20 vol.% and 40 vol.% [BmPyr][(Tf)2N]. The results indicate that ionic liquid mixtures with different portions of cations and anions have the capability of influencing the ionic liquid stabilization characteristics with respect to, e.g., nanoparticle size and size distribution.

Canted surface spins driven exchange anisotropy in erbium substituted nickel ferrite nanoparticles

Single-phase nickel ferrite nanoparticles doped with rare earth Er3+ ions have been prepared using conventional chemical co-precipitation technique. Existence of pure spinel cubic structure of all samples was confirmed by the X-ray diffraction profiles and Raman modes. Average crystallite sizes ranged from 4 nm to 15 nm were estimated using Williamson-Hall plot. The crystallite size was found to decrease with increasing Er dopants in nanosized nickel ferrites. Compressive microstrain was detected for all the synthesized nanoferrites. Lattice constant increased with the increase of Er concentration due to its large ionic diameter. The crystal symmetry of octahedral sublattices was lowered for higher Er content nanoferrites as detected by the Raman spectra. Indirect optical band gaps increased with Er doping as observed in Tauc plots. Existence of exchange anisotropy in Er content nickel nanoferrites was seen by field cooled (7 T) M(H) plots recorded at 5 K. Both the exchange bias and coercivity were observed to increase at 5 K with the increment of Er percentage. Saturation magnetization also decreased with the increase of Er content. The highest Er content nanoferrites exhibited superparamagnetic nature at room temperature as seen from M(T) plots. The irreversibility temperature as well as blocking temperature was reduced because of mean size reduction of nanoparticles with increasing Er percentage.

Nanoparticle–laser interaction: computation of size reduction and thermal conductance at solid–vapor interface

Laser interaction with a water-immersed metal nanoparticle can bring about a condition such that a bubble is generated and the nanoparticle is evaporated. This phenomenon is strongly dependent on the laser parameters and the nanoparticle size. In this study, we simulate the behavior of a gold nanoparticle and its surrounding medium during interaction with a nanosecond-pulsed laser by considering nanoparticle size reduction, variations in the nanoparticle absorption cross section, and variations in thermal conductance at the nanoparticle–bubble interface. Results show that the bubble dynamics under a low-energy and long-pulse-width laser (so that it does not cause evaporation) strongly depends on the nanoparticle temperature behavior, while under higher laser energy, it is dependent on the amount of nanoparticle size reduction. Moreover, by comparing the nanoparticle thermal behavior with experimental data, we are able to estimate the thermal conductance at the nanoparticle–bubble interface. This simulation not only leads to nanoparticle size control but also helps in understanding the heat transfer processes at nanoscale.

Temperature Variations of Gold Nanoparticle and Dynamics of Plasmonic Bubble in Water Under Nanosecond Pulsed Laser

Suspended gold nanoparticle in water medium starts to warm up under nanosecond laser irradiation and creates a bubble around itself. The present study aims at evaluating the amount of nanoparticle size reduction at boiling temperature, the temperature variations of the nanoparticle, and its medium and finally the bubble formation moment. To this aim, Mie theory was used to calculate the absorption cross section of the nanoparticle in proximity of the bubble. Heat transfer equations were applied to determine the temperature of the nanoparticle and water. In addition, hydrodynamic equations were initiated to evaluate the expansion of the bubble. Then, these three groups of equations were coupled together and solved numerically. Based on the results, the bubble forms at the critical pressure and consequently due to the slow bubble velocity, temperature gradient in the medium is observed. Further, slight pulse width variations play a significant role on the nanoparticle temperature. The calculation of the nanoparticle heating associated with the creation of the bubble helps in controlling nanoparticle size and understanding the nanoscale heat transfer processes.

Strongly confined localized surface plasmon resonance (LSPR) bands of Pt, AgPt, AgAuPt nanoparticles

Multi-metallic alloy nanoparticles (NPs) can enable the advanced applications in the energy, biology, electronics, optics and catalysis due to their multi-functionality, wide tunable range and electronic heterogeneity. In this work, various mono-, bi- and tri-metallic nanostructures composed of Ag, Au and Pt are demonstrated on transparent c-plane sapphire (0001) substrates and the corresponding morphological and optical characteristics are thoroughly investigated. The resulting Pt and AuPt NPs in this study demonstrate much enhanced LSPR responses as compared to the pure Pt NPs from the previous studies, which was contributed by the synergistic effect of Au and Pt and improved surface morphology. These results are sharply distinct in terms of surface morphology and elemental variability from those obtained by the dewetting of monometallic Ag, Au and Pt films under the similar growth conditions, which is due to the distinct dewetting kinetics of the bi-layer and tri-layer films. These NPs exhibit strongly enhanced localized surface plasmon resonance (LSPR) bands in the UV-VIS wavelengths such as dipolar, quadrupolar, multipolar and higher order resonance modes depending upon the size and elemental composition of NPs. The LSPR bands are much stronger with the high Ag content and gradually attenuated with the Ag sublimation. Furthermore, the VIS region LSPR bands are readily blue shifted along with the reduction of NP size. The Ag/Pt bi-layers and Ag/Au/Pt tri-layers are systematically dewetted and transformed into various AgPt and AgAuPt nanostructures such as networked, elongated and semispherical configurations by means of enhanced surface diffusion, intermixing and energy minimization along with the temperature control. The sublimation of Ag atoms plays a significant role in the structural and elemental composition of NPs such that more isolated and semispherical Pt and AuPt NPs are evolved from the AgPt and AgAuPt NPs respectively.

Thermal and chemical reaction performance analyses of solar thermochemical volumetric receiver/reactor with nanofluid

In this paper, a novel solar thermochemical volumetric receiver/reactor with nanofluid is proposed. Thermal and chemical performance analyses of the volumetric receiver/reactor are numerically investigated and compared with those of the conventional surface receiver/reactor. A two-dimensional axisymmetric heat and mass transfer model coupled with reaction kinetics is developed to predict the temperature distribution and reactant conversion ratio. The effects of particle characteristics including size and volume fraction and solar irradiation intensity are discussed. The results indicate that for the nanofluid with a volume fraction greater than 0.005, an optical path depth of 0.015 m is sufficient to absorb almost 100% of the incident solar energy. The volume weighted average temperature of the volumetric receiver/reactor with a volume fraction of 0.05 and particle diameter of 10 nm can reach 506.0 K which is about 8.8 K higher than that of the surface receiver/reactor leading to a 5.2% increase of the outlet methanol conversion ratio from 56.9% to 62.1% under a typical operating condition. The methanol conversion ratio increases with the reduction of nanoparticle size and the increment of the volume fraction and solar irradiation intensity. The thermochemical efficiency has a maximum value of 48.9% when solar irradiation intensity is 600 W/m2.

Effect of gamma irradiation on magnetic gadolinium oxide nanoparticles coated with chitosan (GdNPs-Cs) as contrast agent in magnetic resonance imaging

This study elucidates a gamma irradiation-reduction approach in producing small gadolinium nanoparticles specifically gadolinium oxide nanoparticles coated with chitosan (GdNPs-Cs). Chitosan was used as a natural stabilizer and coating agent, whereas gadolinium (III) chloride hexahydrate (GdCl3.6H2O) was used as a precursor. The gadolinium nanoparticle was synthesized via hydrothermal method prior to chitosan coating and gamma irradiation. The properties of the synthesized GdNPs-Cs were studied in term of molecular conformation, surface plasmon resonance and particle distribution via ultraviolet–visible spectroscopy (UV–Vis), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) characterization. Formation of two new UV–Vis peaks at 260 nm and 290 nm depicts the chemical changes of chitosan post gamma irradiation with visible surface plasmon resonance band correlating the reduction of nanoparticle size. Further analysis via TEM demonstrates that synthesized GdNPs-Cs had an average diameter size in the range of 30–45 nm post gamma irradiation, a reduction of size in comparison with control GdNPs-Cs of 120 nm particle size. Enhancement of T1 image obtained via magnetic resonance imaging (MRI) testing proved the capability of synthesized GdNPs-Cs as a contrast agent. Coherently, gamma irradiation-reduction method may be used in controlling the size of nanoparticle and potentially be applied in all major fields related to gadolinium nanoparticle.

Silver–zinc oxide nanocomposite antiseptic from the extract of Bidens pilosa

Silver nanoparticles (Ag-NPs), zinc oxide (ZnO-NPs) and zinc oxide–silver (ZnO–Ag-NPs) were biosynthesized based on the rich matrix of alkaloids, flavones, tannins capping/stabilizing agents present in Bidens pilosa extract. Different plant parts-root, leaf and seed ware used to prepare the plant extract for synthesis. Also, zinc and silver nitrate salts were used as precursor materials. The surface plasmon peaks (SPR) based on the UV–Vis results for the Ag-NPs, ZnO-NPs were located between 408–411 and 365–450 nm respectively. The SPR peaks for the Ag–ZnO-NPs occurred at 300–450 nm indicating both blue and red shifts. The Ag–ZnO-NPs SPR shifts were associated with possible nanoparticle size reduction and change in dielectric constant of the synthesis medium. Raman measurement peaks at 356, 484, 1350, 1578, 2435 cm−1 associated with OH, –C==C–, –C–O, S=O, =C–H moieties indicated successful capping. Nanoparticle yield was temperature dependent and optimal yield could not be tied to a particular plant part as source of extract. Tunneling electron microscope results showed Ag-NPs and ZnO-NPs were globular/spherical with a diameter range of 2–20 nm. Interestingly, ZnO-NPs TEM displayed isolated miniaturized globular nanoparticles (< 2 nm) which then joined up to form a large donut shaped structure indicating different formation mechanisms for the nanoparticles. XRD results showed the Ag-NPs, ZnO-NPs and the Ag–ZnO-NPs particles were crystalline in nature. The high signal/noise in XRD originated from possible crystalline biomaterials in the extracts. Energy dispersive spectroscopy (EDS) elemental composition results confirmed successful formation of the nanoparticles. Anti-Microbial activity of the synthesized Ag-NPs, ZnO-NPs and ZnO–Ag-NPs were studied against gram negative bacteria Escherichia coli (E. coli), gram positive bacteria Staphylococcus aureus and fungus Candida albicans. Different ZnO: Ag-NPs nanocomposite ratios were used to test for antimicrobial activity. Optimal antimicrobial activity was attained at Ag-NPs:ZnO-NPs ratio of 4:1 which also displayed the least minimum inhibition concentration (MIC) and therefore was used as the active ingredient in formulating a hand sanitizing antiseptic. The formulated antiseptic exhibited good antimicrobial activity.

Design and optimization of PEGylated nanoparticles intended for Berberine Chloride delivery

The pre-formulative screening for polymeric nanoparticles (NPs) manufacture is a very long and laborious process. It is essential however for the selection of the best experimental conditions. The chemical and physical properties of NPs can be affected by different factors and variables during their preparation and thus, the aim of this work is to study the influence of the polymer concentration and the organic to aqueous phase ratio on PLGA-PEG NPs by using a D-optimal Response Surface Methodology (RSM) design. A total of nine formulations were prepared using the nanoprecipitation method, purified and characterized for their size, polydispersity index (PDI) and zeta potential. All formulations were subjected to stability studies after storage over six months under refrigeration. Prediction of the optimal nanosystem was performed using the desirability function targeting the reduction of NPs size and PDI. The optimized NPs formulation (F-1) showed similar theoretical and experimental values, confirming the predictive ability of the mathematical model. The formulation F-1 loaded with Berberine Chloride showed appropriate technological properties for potential intranasal or systemic administration. Our results conclusively demonstrated that RSM is a useful and efficient tool to design new nanoformulation with the least number of experiments.

Pressure dependent ultrasonic characterization of nano-structured w-BN

The work includes evaluation of elastic constants of wurtzite Boron nitride (w-BN) at different particle-size (5–40 nm) and pressure (0–60 GPa) at 300 K using potential model approach. Size and pressure dependent thermo-physical and ultrasonic parameters are also calculated using evaluated elastic constants. It is found that the elastic constants, ultrasonic velocities and Debye temperature of nanostructured w-BN enhance with increase in pressure and reduction in particle size. The size variation of thermal relaxation time resembles the dependency of thermal conductivity with size. The thermal conductivity of nanostructured w-BN is found to increase with reduction in nanoparticle size.

Synthesis of ultra small nanoparticles (&lt; 50 nm) of mesoporous MCM-48 for bio-adsorption

Mono-dispersed spherical MCM-48 mesoporous silica nanoparticles (MSN) with cubic Ia3d mesostructure were synthesized under different stirring conditions using hexadecyltrimethyl ammonium bromide as structure directing agent and EO20PO70EO20 copolymer as particle size control. Results indicated that the EO20PO70EO20 works well in the reduction of nanoparticle size. In addition, increasing the stirring rate transformed mesoporosity from 2-D hexagonal P6mm to 3-D cubic Ia3d. The biomolecule adsorption properties of prepared ultra small nanoparticles of MCM-48 were compared with that of MCM-48 with ten times larger particle sizes. MCM-48 with smaller particle sizes adsorbed much more vitamin B12 compared with MCM-48 with larger particles. In addition, diffusion of vitamin in the intraparticle spaces occurred only for MCM-48 with ultra-small nanoparticles.

Influence of 20 MeV electron irradiation on the optical properties and phase composition of SiOx thin films

Homogeneous films from SiO1.3 (250 nm thick) were deposited on crystalline Si substrates by thermal evaporation of silicon monoxide. A part of the films was further annealed at 700 °C to grow amorphous Si (a-Si) nanoclusters in an oxide matrix, thus producing composite a-Si-SiO1.8 films. Homogeneous as well as composite films were irradiated by 20-MeV electrons at fluences of 7.2 × 1014 and 1.44 × 1015 el/cm2. The film thicknesses and optical constants were explored by spectroscopic ellipsometry. The development of the phase composition of the films caused by the electron-beam irradiation was studied by transmission electron microscopy. The ellipsometric and electron microscopy results have shown that the SiOx films are optically homogeneous and the electron irradiation with a fluence of 7.2 × 1014 el/cm2 has led to small changes in the optical constants and the formation of very small a-Si nanoclusters. The irradiation of the a-Si-SiOx composite films caused a decrease in the effective refractive index and, at the same time, an increase in the refractive index of the oxide matrix. Irradiation induced increase in the optical band gap and decrease in the absorption coefficient of the thermally grown amorphous Si nanoclusters have also been observed. The obtained results are discussed in terms of the formation of small amorphous silicon nanoclusters in the homogeneous layers and electron irradiation induced reduction in the nanocluster size in the composite films. The conclusion for the nanoparticle size reduction is supported by infrared transmittance results.

Solubility measurement and preparation of nanoparticles of an anticancer drug (Letrozole) using rapid expansion of supercritical solutions with solid cosolvent (RESS-SC)

A method of rapid expansion of supercritical solutions with solid cosolvent (RESS-SC) was applied, for the first time, to precipitate nanoparticles of Letrozole (LTZ). Solubility of LTZ, as a poorly water-soluble drug, was measured under various conditions in supercritical CO2 with/without menthol as cosolvent. The solubility of LTZ in ternary system (with solid cosolvent) was increased 7.1 times as large as that of binary system (without solid cosolvent). Then, influences of temperature, pressure, solid cosolvent and spray distance on the size and morphology of the particles were investigated by Taguchi technique. The analysis of variance results showed that, temperature and pressure had the most and least significant impacts on the size-reduction of nanoparticles, respectively. The particles were characterized using SEM, DLS, XRD, FTIR and DSC. Experimental observations revealed that the LTZ particles were nanosized from the original average size of 30μm to the smallest average size of 19nm.