Monodisperse Spherical Nanoparticles Research Articles

Green synthesis of selenium nanoparticles capped by Tithonia diversifolia pectin for anti‐inflammation activity

AbstractThis work reports a green method to synthesize pectin‐capped selenium nanoparticles (PT‐SeNPs) using ascorbic acid as a reductant under mild conditions. Pectin was extracted from Tithonia diversifolia (Hemsley) A. Gray plant. Pectin played the role of a capping agent preventing the agglomeration of selenium nanoparticles. The synthesized PT‐SeNPs were characterized by UV–Vis spectrophotometry, EDX spectroscopy, TEM, DLS, FT‐IR, XRD, and TG‐DTA. The TEM and DLS techniques revealed monodispersed spherical selenium nanoparticles with sizes range of 100–200 nm. The amorphous PT‐SeNPs showed a phase transformation of nanostructure at 132 °C and a sublimation at 486 °C. The anti‐inflammatory of the obtained PT‐SeNPs was investigated in ethyl phenylpropiolate (EPP)‐induced rats. Rats treated with PT‐SeNPs exhibited ear edema inhibitions of 34.8%, 43.3%, and 46.7%, respectively at 30, 60 and 90 min after EPP injection.

Biogenic Silver Nanoparticles Produced by Soil Rare Actinomycetes and Their Significant Effect on Aspergillus-derived mycotoxins.

The current investigation addressed the green synthesis of silver nanoparticles (AgNPs) using newly isolated silver-resistant rare actinomycetes, Glutamicibacter nicotianae SNPRA1 and Leucobacter aridicollis SNPRA2, and investigated their impact on the mycotoxigenic fungi Aspergillus flavus ATCC 11498 and Aspergillus ochraceus ATCC 60532. The formation of AgNPs was evidenced by the reaction's color change to brownish and the appearance of the characteristic surface plasmon resonance. The transmission electron microscopy of biogenic AgNPs produced by G. nicotianae SNPRA1 and L. aridicollis SNPRA2 (designated Gn-AgNPs and La-AgNPs, respectively) revealed the generation of monodispersed spherical nanoparticles with average sizes of 8.48 ± 1.72 nm and 9.67 ± 2.64 nm, respectively. Furthermore, the XRD patterns reflected their crystallinity and the FTIR spectra demonstrated the presence of proteins as capping agents. Both bioinspired AgNPs exhibited a remarkable inhibitory effect on the conidial germination of the investigated mycotoxigenic fungi. The bioinspired AgNPs caused an increase in DNA and protein leakage, suggesting the disruption of membrane permeability and integrity. Interestingly, the biogenic AgNPs completely inhibited the production of total aflatoxins and ochratoxin A at concentrations less than 8 μg/mL. At the same time, cytotoxicity investigations revealed the low toxicity of the biogenic AgNPs against the human skin fibroblast (HSF) cell line. Both biogenic AgNPs exhibited feasible biocompatibility with HSF cells at concentrations up to 10 μg/mL and their IC50 values were 31.78 and 25.83 μg/mL for Gn-AgNPs and La-AgNPs, respectively. The present work sheds light on the antifungal prospect of the biogenic AgNPs produced by rare actinomycetes against mycotoxigenic fungi as promising candidates to combat mycotoxin formation in food chains at nontoxic doses.

Biosafety risk assessment of gold and aluminum nanoparticles in tumor-bearing mice.

To improve the biosafety of the nanodelivery system, this study developed novel monodisperse spherical aluminum nanoparticles (Al NPs) and evaluated their cytotoxicity in vitro and distribution and biotoxicity in vivo. Compared with gold nanoparticles of the same size, Al NPs not only had low cytotoxicity in vitro but also did not cause accumulation in major organs in vivo after intravenous injections. No significant abnormalities were observed in the serum biochemical indices of mice injected with Al NPs. Additionally, no substantial changes occurred in the histopathology of major organs, and no apparent biological toxicity was measured after consecutive injections of Al NPs. These results indicate that Al NPs have a good biological safety and provide a new method for developing low-toxicity nanomedicine.

Preparation and anti-tumor activity of selenium nanoparticles based on a polysaccharide from Paeonia lactiflora

The combination of selenium and polysaccharides is one of the significant ways to ameliorate the anti-cancer effects of polysaccharides. PLP50-1, a homogeneous polysaccharide purified from the aqueous extract of Paeonia lactiflora, had a molecular weight of 1.52 × 104 Da and consisted of α-D-Glcp-(1→, →4)-α-D-Glcp-(1→, →6)-α-D-Glcp-(1→, →4,6)-α-D-Glcp-(1→, and →6)-β-D-Fruf-(2→. PLP50-1 showed weak anti-tumor effects against A549 cells. To ameliorate the activity of PLP50-1, the complex nanoparticles combining P. lactiflora polysaccharide with selenium were constructed successfully. Structural properties of the polysaccharide-based selenium nanoparticles (PLP-SeNPs) were clarified using various means. The results displayed that a kind of monodisperse spherical nanoparticles containing high selenium content (39.1 %) with controllable size was constructed and showed satisfactory stability. The cellular anti-tumor assay indicated that PLP-SeNPs had stronger antiproliferative activity against A549 cells than PLP50-1. Additionally, the zebrafish experiments displayed that PLP-SeNPs inhibited the proliferation and migration of A549 cells significantly and blocked the angiogenesis.

Preparation and thermogenic performance of monodisperse ferromagnetic Fe/SiO2 nanoparticles for magnetic hyperthermia and thermal ablation*

Ferromagnetic nanoparticles have great potential to be used in the field of magnetic hyperthermia and thermal ablation due to its high saturation magnetization (Ms) and high heating efficiency. In this paper, monodisperse spherical α-Fe2O3 nanoparticles were prepared by hydrothermal method using FeCl3, NaHCO3 and Na2SO4 as reactants. Then monodisperse Fe/SiO2 nanoparticles with core/shell structure were obtained by coating SiO2 on the surface of α-Fe2O3 nanoparticles and reducing at 500℃ in hydrogen atmosphere. The diameter of Fe core is about 230 nm and the thickness of SiO2 coating is about 75 nm. Magnetic measurements show that Fe/SiO2 nanoparticles exhibit typical ferromagnetic properties with Ms about 132.5 emu/g at 25 ℃. As-obtained Fe/SiO2 nanoparticles have higher heating efficiency than superparamagnetic ferrite nanoparticles. The high heating ability of the Fe/SiO2 nanoparticles is estimated to be related to the hysteresis loss and Brownian relaxation mechanism during alternating magnetization. The results show that Fe/SiO2 nanoparticles are promising for the applications of magnetic hyperthermia and thermal ablation.

Electrochemical Sensing Platform based on Greenly Synthesized Gum Arabic Stabilized Silver Nanoparticles for Hydrogen Peroxide and Glucose

Gum Arabic stabilized silver nanoparticles (GA-Ag NPs) were successfully synthesized by one step green synthesis method. The as-prepared nanoparticles were characterized using XRD, DLS, FTIR, TEM, and UV–vis spectroscopy. XRD data confirmed that the synthesized Ag NPs were face-centred cubic and the crystallite size was calculated to be around 5 nm. TEM image confirmed the successful synthesis of monodispersed spherical nanoparticles with particle sizes in the range of 10–20 nm. Cyclic voltammetry experiment revealed the outstanding electrochemical response and electrocatalytic behaviour of GA-Ag NPs for the sensing of H2O2. Based on the cyclic voltammetry, amperometric, and differential pulse voltammetric (DPV) experiments, it was concluded that strong oxidizing agent H2O2 undergoes through reduction process at the surface of GA-Ag NPs/GCE. Excellent electrocatalytic behaviour of the GA-Ag NPs was exhibited for sensing of glucose also. The limit of detection as calculated from DPV experiments were 0.242 μM and 0.205 μM for H2O2 and glucose respectively. The reported electrochemical sensor has numerous advantages such as simple and green synthesis method, extremely high sensitivity, stability and reproducibility, and extremely good response.

Step-scheme perylenediimide supramolecular nanosheet and TiO2 nanoparticle composites for boosted water splitting performance

Adjusting the band gap of organic-inorganic composites by chemical bonding can effectively construct Step-scheme (S-scheme) heterojunctions, featuring properties of fast photogenerated charge migration and excellent photocatalytic performance. In this work, a novel perylene-3, 4, 9, 10-tetracarboxylicdiimide (PDI)-titanium dioxide (TiO2) heterojunction is elaborately synthesized through simple solvent compounding method. The monodispersed spherical TiO2 nanoparticles was prepared with the capping agents of oleylamine and oleic acid, and suffered by a ligand exchange process with nitrosonium tetrafluoroborate (NOBF4) to remove oleylamine and oleic acid. The NOBF4 ligands were further replaced by PDI super molecular nanosheets to obtain two dimensional (2D)-zero dimensional (0D) PDI-TiO2 composites. TiO2 nanoparticles are evenly anchored on the surface of PDI nanosheets with intimate contact. The PDI-TiO2 composites has emerged considerably superior activity in hydrogen evolution. The highest hydrogen evolution rate for PDI-TiO2composites with the PDI weight percentage of 2.4% was 9766 μmol h−1 g−1 under solar light irradiation, which is 2.56 times of TiO2-NOBF4 catalyst. Moreover, PDI-TiO2 composites possess stoichiometric overall water splitting performance with H2 and O2 release rates of 238.20 and 114.18 μmol h−1 g−1. The superior photocatalytic performance of PDI-TiO2 composites can be attributed to the dramatic increase in visible and NIR light absorption caused by π-π stacking structure of PDI, the prevented charge recombination by the S-scheme heterojunction, and the enhanced oxygen evolution by the stronger oxidation capability of PDI. PDI supramolecular nanosheets may work as a novel functional support for many types of semiconductor nanomaterials as graphene, which will display a wide range of application prospects in the energy and environmental fields.

Enhanced catalytic activity of platinum decorated silica nanocrystals in rapid reduction of organic dyes

Pt decorated silica (Pt/SiO2) nanocrystals (NCs) were synthesized using a chemical route, and their activities were evaluated towards the reduction of Methylene Blue (MB), Rhodamine B (RhB) and p-Nitrophenol (PNP). X-ray diffraction (XRD) analysis confirmed cubic crystal structure of Pt NCs. The formation of monodispersed spherical SiO2 nanoparticles with an average particle size of ∼150 nm was confirmed by Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy. The High Resolution TEM confirmed cubic crystal structure of Pt NCs having lattice fringes with interplaner spacing of ∼0.29 nm, corresponding to (111) plane. The catalytic activities of the Pt/SiO2 NCs towards MB, RhB and PNP were studied using UV-visible spectrophotometer. The Pt/SiO2 NCs showed excellent catalytic activity with pseudo first order rate constant values 0.016 s−1, 0.011 s−1, 0.006 s−1 for MB, RhB and PNP, respectively. The synthetic method used in the present work offers valuable insights for facile preparation of Pt/SiO2 NCs as an efficient and valuable catalyst for environmental remediation.

Preparation, characterization, and antitumor activity of Chaenomeles speciosa polysaccharide-based selenium nanoparticles

Nanoparticles have been found to possess unique advantages in many fields, especially in the field of cancer treatment. Herein, based on the unique physical and chemical properties of natural polysaccharides, the polysaccharide from the edible and medicinal fruits of Chaenomeles speciosa was prepared, and the complex nanoparticles constructed by combining C. speciosa polysaccharide with selenium have been successfully developed by a chemical method. Monodisperse spherical nanoparticles with the particle size of 80.5 nm were characterized by various methods, which exhibited ideal size distribution and prominent stability under physiological conditions and alkaline conditions. Cellular studies demonstrated the nanoparticles significantly inhibited the growth of MCF-7 cells with an IC 50 value of 8.37 ± 0.97 μg/mL through inducing the apoptosis and arresting the cell circle at S phase. Moreover, the zebrafish assays confirmed the antitumor effects of the nanoparticles, which suppressed the proliferation and migration of tumor and blocked the angiogenesis of transgenic zebrafish. Collectively, the results suggested that the nanoparticles may be considered as a candidate agent to treat breast cancer.

Turbulent melting characteristics of hybrid nano-enhanced molten salt phase change material in rectangular enclosure

The turbulent melting characteristics of hybrid nano-enhanced phase change material (HNEPCM) in a three-dimensional rectangular enclosure has been numerically investigated. The lower and upper walls are partially heated and cooled using constant surface temperature boundary condition and the other surfaces are specified with adiabatic boundary condition. The rectangular enclosure is filled with molten salt phase change material (PCM) of potassium nitrate (KNO3) with melting temperature of 334 °C. The transient melting rates of PCM are investigated by dispersing hybrid mono-dispersed spherical nanoparticles of Aluminum oxide (Al2O3) combined with Silicon dioxide (SiO2), Titanium dioxide (TiO2) and Multi-walled carbon nanotubes (MWCNT). The Rayleigh number (Ra) and particle volume fraction (ϕ) are varied in the range of 106≤Ra≤1010 and 2%≤ϕ≤5%. The turbulent phase change process of PCM is modeled using enthalpy–porosity approach with Lam–Bremhorst k−ϵ turbulence model. The three-dimensional governing equations are discretized using Finite difference technique and computations are carried out using Fortran 90 in-house code. The stronger thermal buoyancy force accelerates the melting rate and the melting pattern indicates the accumulation of large quantity of molten metal in the upper regions of the rectangular enclosure. The average melting velocity and turbulent kinetic energy of pure KNO3 PCM is increased by 51.17% and 77.84% by the addition of Al2O3−MWCNT hybrid nanoparticles. The impact of hybrid nanoparticles on the melting rate and thermal performance of PCM is significant in higher Rayleigh number flows than transitional flows. The present results are validated and are in close agreement with the benchmark experimental results.

(Invited, Digital Presentation) Enhancement of Magnetic Dipole Transition of Molecules By Silicon Nanoparticle Nanoantenna

A nanoantenna is a nanodevice that manipulates light propagation and enhances light-matter interaction at the nanoscale. Integration of an emitter into a nanoantenna capable of increasing local density of photonic states at the emission wavelength results in the enhanced spontaneous emission rate (Purcell effect). The most widely studied nanoantennas for the Purcell enhancement are plasmonic nanoantennas made from gold or silver nanostructures supporting surface plasmon resonances. In most cases, nanoantennas have been used for the enhancement of electric dipole-allowed transition of a molecule. In addition, recently, nanoantennas capable of enhancing magnetic dipole transition of a molecule are attracting attention. For the magnetic Purcell enhancement, nanoantennas have to have magnetic resonances at the optical frequency. Although it is possible to achieve magnetic resonances at the optical frequency by plasmonic nanostructures, the inherent absorption loss of noble metals limits the magnetic Purcell enhancement. On the other hand, nanoparticles of high refractive index dielectrics inherently have low-loss magnetic-type Mie resonances at the optical frequency, and thus are potentially more attractive as a material to realize large magnetic Purcell enhancement.We have developed spherical nanoparticles of crystalline silicon (Si) having the magnetic dipole (MD) and quadrupole (MQ) Mie resonances at the optical frequency [1]. In this work, to demonstrate the potential of a Si nanoparticle as a nanoantenna for the magnetic Purcell enhancement, we develop a composite nanoparticle, that is, a Si nanosphere decorated with europium ion (Eu3+) complexes, in which magnetic dipole emission of Eu3+ is efficiently coupled to the magnetic Mie modes of the nanosphere [2]. We systematically investigate the light scattering and photoluminescence spectra of the coupled system by means of single particle spectroscopy. The results are shown in Figure 1. By tuning the MQ Mie resonance of a Si nanosphere to the 5D0-7F1 magnetic dipole transition of Eu3+, the branching ratio between the magnetic and electric dipole (5D0-7F2) transitions is enhanced up to 7 times. The observed large magnetic Purcell enhancement offers an opportunity to develop novel fluorophores with enhanced magnetic dipole emission. Furthermore, the enhanced magnetic field of dielectric Mie resonators enhances otherwise very weak absorption due to magnetic dipole transition, and makes direct excitation of triplet states of a molecule possible [3]. Direct excitation of triplet states reduces photon energy necessary for energy conversion and chemical reactions utilizing a triplet state compared to a conventional process involving singlet-singlet excitation and singlet-triplet intersystem crossing.[1] H. Sugimoto, et. al., "Mie Resonator Color Inks of Monodispersed and Perfectly Spherical Crystalline Silicon Nanoparticles" Advanced Optical Materials, 8 (2020) 2000033.[2] H. Sugimoto, and Minoru Fujii, "Magnetic Purcell Enhancement by Magnetic Quadrupole Resonance of Dielectric Nanosphere Antenna", ACS Photonics, 8 (2021) 1794.[3] H. Sugimoto, et. al., "Direct Excitation of Triplet State of Molecule by Enhanced Magnetic Field of Dielectric Metasurfaces", Small, 2021, DOI: 10.1002/smll.202104458.Figure 1: Photoluminescence (red curves) and scattering (black curves) spectra of single Si naosphere-Eu3+ complex composite nanoparticles with different Si nanosphere diameters. The diameters are shown at the right end of the figure. Figure 1

Biosynthesis of cadmium sulfide nanoparticles using aqueous extract of Lactobacillus acidophilus along with its improvement by response surface methodology

Although the biosynthesis of nanoparticles by microorganisms can overcome problems associated with common synthesis methods, using pathogenic bacteria, isolating nanoparticles from the cell, and having producing agents in broth media are challenging. This research aimed to biosynthesize cadmium sulfide nanoparticles from the aqueous extract of Lactobacillus acidophilus and improve the biosynthesis process by response surface methodology. The biosynthesis process was conducted by the aqueous extract as a producing, stabilizing, and capping agent, accompanied by cadmium chloride and sodium sulfide solutions as cadmium sulfide precursors in a ratio of 1:10:10, respectively, considering pH and temperature as process variables. Ultraviolet–visible spectroscopy of colloidal aqueous solution showed a peak with an average maximum absorbance of 0.161 ± 0.023 after 18 h of incubation in un-optimized conditions which was improved up to 0.204 ± 0.049 under pH 9 and temperature of 50 °C in optimized conditions. Field emission scanning electron microscopy indicated monodispersed spherical nanoparticles with an average size of 19.07 ± 2.54 nm in optimized conditions. X-ray diffraction revealed the formation of cubic/hexagonal crystallites in an amorphous matrix. Fourier transform infra-red spectroscopy determined functional groups involved in the biosynthesis. The findings of this research showed that the bacterium aqueous extract has a good potential for the biosynthesis of nanoparticles.

Azeotropic Distillation-Induced Self-Assembly of Mesostructured Spherical Nanoparticles as Drug Cargos for Controlled Release of Curcumin.

Methods of large-scale controllable production of uniform monodispersed spherical nanoparticles have been one of the research directions of scientists in recent years. In this paper, we report an azeotropic distillation-induced evaporation self-assembly method as a universal method, and monodispersed hydrophobic ordered mesoporous silica nanospheres (MHSs) were successfully synthesized by this method, using triethoxymethylsilane (MTES) as the silica precursor and hexadecyl trimethyl ammonium bromide (CTAB) as the template. SEM and TEM images showed good monodispersity, sphericity, and uniform diameter. Meanwhile, SAXS and N2 adsorption–desorption measurements demonstrated a highly ordered lamellar mesostructure with a large pore volume. The model drug, curcumin was successfully encapsulated in MHSs for drug delivery testing, and their adsorption capacity was 3.45 mg g−1, which greatly improved the stability of curcumin. The release time when net release rate of curcumin reached 50% was extended to 6 days.

Fabrication and characterization of superparamagnetic nickel ferrite ferrofluid

Because of their unique magnetic characteristics, magnetic nanoparticles are being used in various applications. We used a two-step method to create nickel ferrite ferrofluid in this study. The first step included hydrothermal preparation of oleic acid-capped nickel ferrite nanoparticles, followed by surface functionalization of the particles with citric acid, which made the nanoparticles hydrophilic. The materials' phase purity, functional groups, and magnetic behaviour were investigated. The production of mono-dispersed spherical nanoparticles with an average diameter of 9 ± 3.6 nm was shown by TEM images. With a blocking temperature of 53 K, ZFC-FC measurements verified the sample's superparamagnetic properties. The average magnetic moment per particle and the average size of the magnetic particle were calculated using the Langevin function.

Hypericum perforatum L.-Mediated Green Synthesis of Silver Nanoparticles Exhibiting Antioxidant and Anticancer Activities.

This contribution focuses on the green synthesis of silver nanoparticles (AgNPs) with a size < 100 nm for potential medical applications by using silver nitrate solution and Hypericum Perforatum L. (St John’s wort) aqueous extracts. Various synthesis methods were used and compared with regard to their yield and quality of obtained AgNPs. Monodisperse spherical nanoparticles were generated with a size of approximately 20 to 50 nm as elucidated by different techniques (SEM, TEM). XRD measurements showed that metallic silver was formed and the particles possess a face-centered cubic structure (fcc). SEM images and FTIR spectra revealed that the AgNPs are covered by a protective surface layer composed of organic components originating from the plant extract. Ultraviolet-visible spectroscopy, dynamic light scattering, and zeta potential were also measured for biologically synthesized AgNPs. A potential mechanism of reducing silver ions to silver metal and protecting it in the nanoscale form has been proposed based on the obtained results. Moreover, the AgNPs prepared in the present study have been shown to exhibit a high antioxidant activity for 2, 2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation, and super oxide anion radical and 2,2-diphenyl-1-picrylhydrazyl. Synthesized AgNPs showed high cytotoxicity by inhibiting cell viability for Hela, Hep G2, and A549 cells.

Activation of yeast alcohol dehydrogenase in the presence of citrate stabilized gold nanoparticles: An insight into its interaction and modulation mechanism

The presence of nanoparticles in the reaction mixture greatly affects the properties of the bio-macromolecules. Citrate, used as a stabilizing and functionalizing agent assists in forming monodispersed spherical gold nanoparticles (AuNPs). Here, an insight into the role of enzyme:cit-AuNPs ratio in modulating the activity of yeast alcohol dehydrogenase (YADH) is provided in relation with the different levels of agglomerations between cit-AuNPs and YADH. Cit-AuNPs formed were characterized by UV–visible spectrophotometer, transmission electron microscope (TEM), zetasizer, dynamic light scattering (DLS) and energy dispersive x-ray analysis (EDAX). The interaction of YADH with cit-AuNPs was further investigated by absorption, fluorescence and molecular docking analysis, and by using unmodified and thiol-modified YADH. Stable monodispersed cit-AuNPs of size ~10 nm and hydrodynamic radii of 21.2 nm were formed which agglomerated in the presence of higher concentration of YADH. Cit-AuNPs bind to YADH and the activity of the enzyme in their presence depends on the ratio of the enzyme to cit-AuNPs. YADH to cit-AuNPs ratio of 1:5 enhances the activity of the enzyme by 3.1 fold. The nanoparticles are also able to activate YADH in the presence of organic solvents. Thiols of YADH are mainly responsible for the attachment to cit-AuNPs. This provides a different approach of studying industrial, diagnostic and therapeutic applications as well as interactions of bio-macromolecules with nanomaterials.

Surface-modified nanosilica-chitinase (SiNp-Chs)-doped nano enzyme conjugate and its synergistic pesticidal activity with plant extracts against armyworm Spodoptera litura (Fab.) (Lepidoptera: Noctuidae).

A laboratory experiment was conducted to evaluate enhanced pesticidal activity of silica nanoparticles‐doped chitinase nano enzyme conjugate against an economically important insect pest Spodoptera litura (Fab.) (Lepidoptera; Noctuidae). Silica nanoparticles were synthesized by hydrolysis and condensation of precursor tetraethylorthosilicate (TEOS) followed by functionalization with functioning agent 3‐aminopropyltriethoxysilane. Functionalized silica nanoparticles thus acquired were doped with chitinase enzyme produced by Serratia marcescens SU05. Doped nanosilica–chitinase nano enzyme conjugate was loaded with pesticidal plant extracts to study the improved pesticidal activity. Synthesized nano enzyme conjugate revealed high stable, monodisperse spherical nanoparticles and exhibited effective loading with respective plant extracts. Nano enzyme conjugates and plant extracts loaded with nano enzyme conjugate recorded high rate of mortality against the larval instars and brought about a distinct effect on the life stage parameters of S.litura. Non‐target toxic effect of nano enzyme conjugate was carried out by determination of lethality and changes in protein profiling against brine shrimp (Artemia salina) that shows less lethality and no distinct changes in protein profiling which suggest the effective utilization of silica nanoparticles doped chitinase as an insecticidal agent against economically important insect pests associated with various crops.

Investigating the effect of nonionic surfactant on the silica nanoparticles formation and morphology in a microfluidic reactor

The conventional sol-gel method used to synthesize monodispersed spherical silica nanoparticles produces particles with irregular shapes and low monodispersity. Microreactors show a promising new platform to synthesize nanomaterials due to their unique flow and mixing characteristics. In most known shear-based droplet generation microreactors, the effect of the flowing liquid’s physical properties on the reactor performance and product characteristics are not well investigated. Scaling-down the flow system was proven to change the flow behavior which will be dominated by the liquid apparent physical properties that are highly controllable. A new method to synthesize silica nanoparticles adapting the sol-gel approach in a microfluidic chip is proposed and experimentally tested in the present work. This work also analyzes changing the flowing reactants’ physical properties using nonionic surfactants with different concentrations on the reaction performance and nanoparticle size and properties. A custom-made microreactor, made from polydimethylsiloxane, was designed and then fabricated using a direct writing technique. The investigated surfactant concentration was within the range of 1 to 5 vol/vol%, respective to tetraethyl orthosilicate. A traditional bench-scale sole-gel method was also performed with the same reaction properties for comparison purposes. The obtained nanoparticles were characterized using transmission electron microscopy and EDX. The silica nanoparticles synthesized from a bench-scale system showed poor monodispersity and an irregular shape compared to the perfect spherical particles produced from the microflow system. The addition of surfactant reduced the coalescence of the droplet besides reducing the size of the droplets. Increasing the surfactant concentration reduces the silica nanoparticle size. The results showed that highly monodispersed silica nanoparticles with an average size of 5.76 ± 1.27 nm were synthesized using the microflow system comparing to silica nanoparticles with a mean size of 95 ± 4 nm produced from the bench-scale.

Thermally stable high-contrast iridescent structural colours from silica colloidal crystals doped with monodisperse spherical black carbon particles

The saturation of iridescent structural colours of silica colloidal film is significantly improved by addition of a small amount of the monodisperse spherical black carbon nanoparticles which are uniformly dispersed in a colloidal crystal matrix.

Biosynthesized monodispersed spherical Se co-catalyst nanoparticles impregnated over ZnO for 4-chloroguaiacol degradation under solar irradiations

The present study outlines the importance of biosynthesized selenium (Se) nanoparticles as co-catalyst for enhanced photoactivity of Se@ZnO nanocomposites under solar irradiations. The selenium-rich Bacillus sp. bacteria were isolated and used to synthesize extracellular Se nanoparticles (Se NPs), and structural characterization was carried out using various techniques. Different amounts (0.5–2 wt%) of Se NPs were loaded over ZnO followed by calcination at 200 °C for 120 min to form Se@ZnO nanocomposites. The optical absorption of Se@ZnO showed a slight red shift as compared to bare ZnO and a new broadband in 500–700 nm range appeared with increasing the amount of Se. HR-TEM analysis showed spherical shaped, highly monodispersed Se NPs with size less than 100 nm. Further, 1 wt% Se@ZnO nanocomposites exhibited the highest degradation efficiency (93%) of 4-chloroguaiacol (4-CG) as compared to bare ZnO (8%) under natural sunlight. The reaction followed first-order kinetics with an apparent rate constant k = 0.16 min−1. Moreover, the environmental applicability of the synthesized Se@ZnO was also tested for real pharmaceutical industrial effluent degradation. It was observed that the chemical oxygen demand (COD) level decreased from 1140 mgL−1 to 500 mgL−1 after 240 min of sunlight exposure.