Colloidal Solutions In Water Research Articles

Synthesis, morphology and Raman spectroscopy of ZnS/Ag2S heteronanostructures

Sulfide (ZnS)(Ag2S)x heteronanostructures of various composition were obtained by co-deposition from water colloidal solutions of silver and zinc nitrates using sodium sulfide as a sulfidizer and sodium citrate as a stabilizer. The formation of (ZnS)(Ag2S)x heteronanostructures was confirmed using the XRD, HAADF-STEM, SEM, EDX and Raman spectroscopy. The size of ZnS and Ag2S nanoparticles in heteronanostructures (ZnS)(Ag2S)x with x ≤ 0.01 is 2–4 and no more than 3 nm, respectively. Raman spectroscopy showed that addition of silver sulfide nanoparticles into (ZnS)(Ag2S)x heteronanostructures leads to Ag2S deposition onto the surface of ZnS nanoparticles. Doping ZnS with only 1 mol.% of colloidal Ag2S nanoparticles is sufficient to produce a silver sulfide shell on the surface of ZnS nanoparticles.

Chemical structure of steroidal saponin isolated from the leaves of Dracaena draco L.

Saponins are naturally occurring compounds ubiquitously present in various organisms, predominantly in plants. They are noted for forming colloidal solutions in water, which foam on shaking and precipitate cholesterol. Several in vitro and in vivo tests on mixtures and individual saponins have revealed a broad spectrum of biological and pharmacological activities, including cancer-related activity, antiphlogistic and antiallergic, immunomodulating, antihepatotoxic, antiviral, hypoglycemic, antifungal and molluscicidal activities. The Dracaena genus is renowned for an abundance of steroidal saponins utilized in treating digestive and hematological disorders. Previous studies on this genus revealed the presence of steroidal saponins, some of which showed cytotoxic activities against cultured tumor cells and interesting biological activities. This study procured steroidal saponin from the foliage of D. dracoL. using various chromatographic techniques and 1D and 2D nuclear magnetic resonance (NMR) spectroscopic analysis. The structure was deduced as 26-O-β-D-glucopyranosyl-22-O-methylfurosta-5,25(27)-diene-1β,3β,22α,26-tetrol 1-O-{O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl}; a compound previously isolated from the underground parts of Ruscusaculeatus in Japan. Future evaluation of the saponin’s biological activity is imperative to enhance chemotaxonomic data concerning the chemical composition and biological functionality of D. draco L. and, by extension, the Dracaena genus.

Raman, UV-Vis, MS, and IR characterization of molecular-colloidal solution of hydrated fullerenes C60 obtained using vacuum-sublimation cryogenic deposition method. Is the C60 molecule truly highly hydrophobic?

Vacuum-sublimation cryogenic deposition (VS-CD) method is successfully applied to produce fullerene water colloidal solution (FWCS): the melting of the solid phase of the mixture obtained by joint condensation of C60 fullerene and water vapors onto a surface cooled with liquid nitrogen results in formation of a stable colloidal solution. The results of the FWCS characterization by means of Raman, IR, and UV-Vis spectroscopy and their comparison with known literature data on hydrated fullerenes give the authors an opportunity to make conclusion that the FWCS contains C60@{H2O}n complexes of hydrated C60 fullerene. Transmission electron microscopy shows that the VS-CD-produced material contains predominantly small C60 clusters of about 2–5 nm size, while mass spectrometry with laser desorption/ionization has demonstrated the presence of pure fullerene C60 and the absence of any products of its transformation. The performed analysis reveals a close similarity of the stable C60@{H2O}n complexes generated by VS-CD with the previously known highly hydrophilic hydrated fullerene obtained by ultrasonication method.

3,4-Dihydroxiphenylacetic Acid-Based Universal Coating Technique for Magnetic Nanoparticles Stabilization for Biomedical Applications.

Magnetic nanoparticles based on iron oxide attract researchers' attention due to a wide range of possible applications in biomedicine. As synthesized, most of the magnetic nanoparticles do not form the stable colloidal solutions that are required for the evaluation of their interactions with cells or their efficacy on animal models. For further application in biomedicine, magnetic nanoparticles must be further modified with biocompatible coating. Both the size and shape of magnetic nanoparticles and the chemical composition of the coating have an effect on magnetic nanoparticles' interactions with living objects. Thus, a universal method for magnetic nanoparticles' stabilization in water solutions is needed, regardless of how magnetic nanoparticles were initially synthesized. In this paper, we propose the versatile and highly reproducible ligand exchange technique of coating with 3,4-dihydroxiphenylacetic acid (DOPAC), based on the formation of Fe-O bonds with hydroxyl groups of DOPAC leading to the hydrophilization of the magnetic nanoparticles' surfaces following phase transfer from organic solutions to water. The proposed technique allows for obtaining stable water-colloidal solutions of magnetic nanoparticles with sizes from 21 to 307 nm synthesized by thermal decomposition or coprecipitation techniques. Those stabilized by DOPAC nanoparticles were shown to be efficient in the magnetomechanical actuation of DNA duplexes, drug delivery of doxorubicin to cancer cells, and targeted delivery by conjugation with antibodies. Moreover, the diversity of possible biomedical applications of the resulting nanoparticles was presented. This finding is important in terms of nanoparticle design for various biomedical applications and will reduce nanomedicines manufacturing time, along with difficulties related to comparative studies of magnetic nanoparticles with different magnetic core characteristics.

Plasma‐enhanced immobilization of cerium oxide nanoparticles on a fluorocarbon‐based nanofibrous membranes

AbstractFluorocarbon‐based (CF) nanofibrous membrane has been prepared by electrospinning of a source polyvinylidene fluoride and its surface was modified by CeOx nanoparticles by immersion in a water colloidal solution with CeOx nanoparticles (CeOx NPs). Two ways of the deposition of CeOx nanoparticles on the CF nanofiber membrane were used: (1) deposition of CeOx NPs on the pristine electrospun membrane and (2) the immediate deposition CeOx NPs on the plasma treated electrospun membrane. We investigated the effect of plasma treatment on the amount of CeOx NPs deposited on CF nanofiber surfaces and on the Ce3+/Ce4+ ratio in CeOx NPs deposited on CF. The amount of CeOx on nanofiber surfaces was determined by XPS (X‐ray photoelectron spectroscopy) and SEM analysis. Results showed a significant increase of CeOx NPs amount on the plasma treated CF membrane, accompanied by slight decrease of Ce3+/Ce4+ ratio in CeOx NPs adherent on plasma treated CF surface in comparison with pristine CF surface. Detailed analysis of XPS spectra – C1s, O1s, and Ce3d indicated a possibility of the chemical bonding of CeOx NPs on the plasma treated CF surface.

Natural exudate gum from ghatti tree (Anogeissus latifolia): A review on production, processing and marketing

Gum ghatti (GG) is a natural polysaccharide produced from ghatti tree (Anogeissus latifolia). Chemically, the gum is composed of several mono-sugars and uronic acids in the form of calcium and magnesium salts. GG contains soluble and insoluble fractions, which form a thick colloidal solution in water. GG is non-toxic, bio-degradable, and biocompatible to the human digestive system. It finds applications as an emulsifier, stabilizer, binder, thickener, moisture retainer, film-forming agent and a raw material for hydrogel synthesis. The gradual change in the human mindset has increased demand for natural gums like GG to overcome the adverse effects of synthetic additives. As ghatti trees are found in the forest or non-agricultural lands, its gum collection and sales provide an alternate source of sustainable livelihood to the economically backward and resource-constrained population inhabiting forest and sub-forest areas. This review is a unique article covering the literature on production aspects like tree description, importance, GG tapping, production, processing, and marketing. The review of such an important natural product will be useful for researchers, stakeholders, policymakers, and others working in natural resins and gums sector.

Cadmium sulfide quantum dots in water media: Enhanced photoluminescence, dispersion and stability

Within the presented study, we have investigated the effect of the ligand shell on the stability and optical properties of cadmium sulfide (CdS) quantum dots in a water colloidal solution stabilized by 3-mercaptopropyltrimethoxysilane (MPS). The correlation between stability and parameters of nanoparticles, namely, hydrodynamic radius, nucleus size and zeta-potential has been established. The optimal synthesis conditions of stable colloidal solutions shown the luminescence have been found. The mechanism of structural organization of the organic MPS shell, its bonding to the semiconductor nanoparticle surface and influence on the agglomeration have been developed. The mechanism of MPS capped CdS QDs luminescence switch on in water solution by pH control was proposed.

Effect of Nanocoating (CuO Nanoparticles) on the Performance of Solar Evacuated Tube

In domestic solar water heating solar evacuated tubes have been widely used. Enhancement of solar energy absorption is the demand of time and CuO nanoparticles on account of their potential uses mainly in the field of solar energy applications. Cost effective sol-gel method is applied to synthesize CuO nanoparticles on solar evacuated glass tube. The synthesizing initiated from Cupric Acetate with the colloidal solution in water. A thin film has been prepared at room temperature nearly at 30 to 38 °C. The synthesized thin film had been annealed at 300 °C for one hour to give uniform grain structure and good surface morphological properties. For the structural study, the film was characterized by XRD-X-Ray diffraction, SEM-Scanning Electron Microscopy & TEM- Transmission Electron Microscopy. To exhibit the optical behavior of CuO nanoparticles on solar evacuated glass tube, UV-visible spectrum has been performed. By the calculations of an effective mass model, the size of particles determined as 2.26 nm, which supported and justified the TEM analysis. Coated CuO nanoparticles on borosilicate evacuated glass tube has been installed as a domestic solar water heater and working satisfactorily to generate hot water. For solar water heating system (domestic) application of nanotechnology is a novel concept. To develop durable nanocoating on 1800 mm long solar evacuated borosilicate glass tube itself it was a challenge. In this research it is shown that coating is working satisfactorily with energy enhancement. This paper opens the door for new nanocoating developments opportunities.

High electrical conductivity and breakdown current density of individual monolayer Ti3C2Tx MXene flakes

High electrical conductivity and breakdown current density of individual monolayer Ti3C2Tx MXene flakes

Synthesis of Silver Sulfide Colloidal Solutions in Heavy Water D2O

It is for the first time that silver sulfide colloidal solutions were prepared by chemical deposition from silver nitrate and sodium sulfide solutions in heavy water D2O. Sodium citrate served as the stabilizer. The sizes of Ag2S nanoparticles in colloidal solutions were assessed by dynamic light scattering (DLS) measurements and electron microscopy. The silver sulfide nanoparticles in heavy water colloidal solutions prepared from batches having various reagent concentrations had sizes in the range from 3 to 19–20 nm. The increasing silver nitrate concentration and decreasing sodium citrate concentration in the batch only slightly increased the sizes of Ag2S nanoparticles in the prepared colloidal solutions. The silver sulfide colloidal solutions prepared with heavy water D2O retained their stability and unchanged nanoparticle sizes when stored for more than 100 days.

Light converting Yb3+/Er3+ doped YVO4 nanoparticles for biological applications

We have synthesized luminescent YVO4: Yb, Er nanoparticles (NPs) in the size range of 10–700 nm. A bright green luminescence of the dry NPs powder due to Er3+ ions emission centered at 526 and 550 nm was compared for upconverting and downconverting laser excitations at 980 nm and 257 nm, respectively. Moreover, the NPs exhibited bright luminescence in colloidal water solution upon 980 nm laser irradiation. All experiments showed very weak radiative 4F9/2→4I15/2 emission from Er3+ ions at 660 nm that indirectly indicates low efficiency of multiphonon intraionic transitions and insensitivity of the NPs to the luminescence quenchers in the water solution. A broad red band in the luminescence spectrum appearing under intense 257 nm laser excitation can be attributed to emission from crystal lattice defects in the NPs. Based on these facts we propose that YVO4: Yb, Er NPs are promising as efficient upconversion fluorescent nanoprobes for certain biological applications, like optogenetics.

Characterization of the Oxidation of Magnetite Nanoparticles during Their Synthesis by Different Structural Analysis Techniques

Water colloidal solutions of iron oxide nanoparticles coated with tetramethylammonium hydroxide were synthesized by co-precipitation methods. Dimensional analyses were accomplished by transmission electron microscopy (TEM) and the crystalline features of nanoparticles were studied by means of X-ray diffraction (XRD). The iron oxide nanoparticle structure was characterized by the use of the attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectroscopic techniques. For the nanoparticle samples prepared at higher temperatures during synthesis, the Raman spectra demonstrated that magnetic core of iron oxide nanoparticles is composed of a mixture of magnetite (Fe3O4) and maghemite (γ-Fe2O3) phases. We believe that the oxidation of magnetite to maghemite has been occurred during the preparation protocol of nanoparticles performed at higher temperature.

An easy and innovative one-step in situ synthesis strategy of silica nanoparticles decorated by graphene oxide particles through covalent linkages

This research work presents the development of an easy synthesis method for functionalized and covered graphene oxide (GO) nanosheets with silica nanoparticles through one-step in situ sol-gel approach by using two different silane molecules: a tetraethylorthosilane (TEOS) grafted with N (β-aminoethyl)-γ-aminopropyltrimethoxysilane (Z6020) and a TEOS with γ-aminopropyltriethoxy-silane (A1100). Both synthetized GO/SiO2-Z6020 and GO/SiO2-A1100 nanoparticles were characterized and compared in terms of exfoliation level, GO chemical partial reduction and self-condensation efficiency of silica nanoparticles over carbon planes. This way, microstructural and morphological analysis were performed using UV-visible, Fourier Transform InfraRed and Raman spectroscopies, Wide Angle x-rays Scattering, scanning electron microscopy, confocal optical microscopy and thermogravimetric analysis. Laser granulometry and zeta potential measurements on colloidal solutions in water allowed the determination of the particles size distribution and dispersion quality of these nanohybrid materials.

ZnS quantum dots surface-loaded with zinc(II) ions as a viable fluorescent probe for glutathione.

The fluorescence of ZnS quantum dots in colloidal water solution changes very slightly on addition of glutathione (GSH) but is strongly enhanced in the presence of Zn(II) even in concentrations as low as 10μM. The resulting Zn(II)-enhanced fluorescence is found to be quenched by GSH. In contrast to GSH, cysteine does not cause an effect. Response surface methodology was applied to optimize the experimental parameters. The best data can be obtained at 305/427nm as excitation/emission wavelengths. These findings were used to design an indirect method for the fluorometric determination of GSH that has a 0.9μM detection limit and a response that is linear in the 2.0-104.0μM GSH concentration range. The relative standard deviation at a level of 65μM of GSH (for n = 5) is 1.9%. Graphical abstract Schematic presentation of the detection strategy for glutathione and the influence of the mediator (Zn2+). Direct pathway shows that the glutathione cannot cause a change in the bluefluorescence of ZnS QDs. The presence of Zn2+ causes the enhancement of the fluorescence intensity, and thisgenerates the indirect pathway to glutathione detection.

High-throughput laser generation of Si-nanoparticle based surface coatings for antibacterial applications

High-productivity regime of nanosecond IR-laser ablative generation of silicon colloidal solutions in water for anti-bacterial applications was found in terms of GW/cm2-level laser intensity and scanning velocity by measuring multi-shot ablative mass loss and extinction coefficients of the colloids as sub-linear and third-power intensity functions, respectively. This advantageous regime implies sub-linear mass loss versus laser intensity at the simultaneous third-power yield of nanoparticles, resulting from the subcritical-density, opaque ablative plasma regulating the sample ablation rate and the related plasma-mediated dissociation (dispergation) of the ablation products. In contrast, at higher intensities, there is a drastic increase in mass loss with the corresponding increased yield of (sub) micrometer-sized particles owing to intense plasma-driven expulsion of micro-scale melt droplets and the corresponding saturation of the extinction coefficient of the colloidal solutions because of their dynamic local “self-limiting” effect during the high-rate ablation. The optimal low-intensity regime for Si nanoparticle production demonstrates the monotonous correlated increase of mass loss and extinction coefficient in terms of increasing laser scanning velocity, indicating the diminished cumulative effects. Surface coatings prepared from the generated Si nanoparticles exhibit minor surface oxidation, as acquired as their elemental composition via energy-dispersive X-ray spectroscopy, making their contact angle for water droplets (≈51°) close to that of bare Si wafer (≈58°) with its nanometer-thick native oxide layer. Owing to good wetting, the nanoparticle-based surface coatings show strong antibacterial response regarding Gram-negative Pseudomonas auereginosa bacteria even despite their minor oxidative passivation.

Citric acid coated CoFe2O4 nanoparticles transformed through rapid mechanochemical ligand exchange for efficient magnetic hyperthermia applications

Abstract We report the hydrothermal synthesis of uniform size (∼6 nm) oleic acid capped CoFe 2 O 4 (OA-CoFe 2 O 4 ) nanoparticles. These OA-CoFe 2 O 4 nanoparticles were initially hydrophobic and not dispersible in water which were transformed into hydrophilic nanoparticles by modifying their surface with citric acid using a rapid mechanochemical ligand exchange process, which makes CoFe 2 O 4 nanoparticles stable colloidal solution in water. The synthesized citric acid coated CoFe 2 O 4 (CA-CoFe 2 O 4 ) nanoparticles show a high enough and stable zeta potential over 120 days. CA-CoFe 2 O 4 nanoparticles exhibited high biocompatibility under in vitro cell studies. The specific absorption rate (SAR) of the CA-CoFe 2 O 4 nanoparticles was measured by induction heating studies. Upon the exposure of AC external magnetic field, the viability of cancer cells was reduced considerably, suggesting efficient potentiality of these CA-CoFe 2 O 4 nanoparticles for Magnetic Hyperthermia Applications. Present mechanochemical ligand exchange method is proposed as an efficient method for large scale production of biocompatible and water dispersible magnetic oxide nanoparticles for Magnetic Hyperthermia Applications.

Limitations of Self-Regenerative Antioxidant Ability of Nanoceria Imposed by Oxygen Diffusion

Nanoceria (CeO2–x) is a unique antioxidant material with the ability to self-regenerate its properties after interaction with oxidants. In our paper, the dynamics of nanoceria–oxidant interaction accompanied by reversible Ce3+ ↔ Ce4+ transitions of cerium ions was studied for nanoceria water colloidal solutions using conventional spectroscopic techniques. We have shown that interaction of nanoceria with hydrogen peroxide leads to Ce3+ → Ce4+ oxidation, accompanied by quenching of Ce3+ luminescence of nanoceria, and the recovery of initial Ce3+ luminescence intensity occurs with a sufficient time delay (up to few days). The role of oxygen transport within ceria nanoparticles in the regeneration of antioxidant properties of nanoceria after interaction with an oxidant is discussed. Involvement of oxygen diffusion into recovery of nanoceria antioxidant properties hampers the redox activity of ceria nanoparticles making it size- and temperature-dependent.

Decolorization and Degradation of Kraft Lignin Discharged from Pulp and Paper Mill Industry by Axenic and Co-Culture of Bacillus sp.

The aromatic 3-D polymer Lignin, one of the major plant/lignocellulosic biomass, is composed of potentially valuable phenolics monomers (Coumaryl, Guaicyl, Syringyl). Currently lignin and its colloidal solution in water, black liquor, obtained as by-products in many biomass treatment processes, e.g., pulping in paper industry, remain to be considered recalcitrant substrates of a limited commercial value. In developing countries, Kraft lignin (KL) containing Black liquor generated from pulp and paper mill waste water causes severe environmental pollution. This study presents the recent research on bacterial kraft lignin degradation. Kraft lignin degrading bacterium was isolated from the environment of a timber area and further identified by biochemical and 16s rRNA sequencing as Bacillus subtilis. Data of this study revealed that this bacterium reduced lignin (18.66%) and decolorize (25.07%) maximum at 168 h of incubation in axenic condition while in co-culture condition reduced lignin content was reduced to (38%) and 847mg /L (42.89%) respectively. This strain can play key role in remediation of pulp and paper mill effluent as well as degrading material for chemical and biofuel production.

Balance of O2 and H2 content under laser-induced breakdown of aqueous colloidal solutions

Formation of molecular H2 and O2 is experimentally studied under laser exposure of water colloidal solution to radiation of a Nd:YAG laser at pulse duration of 10ns and laser fluence in the liquid of order of 100J/cm2. It is found the partial pressure of both H2 and O2 first increases with laser exposure time and saturates at exposures of order of 1h. The balance between O2 and H2 content depends on the laser energy fluence in the solution and is shifted towards H2 at high fluences. Possible mechanisms of formation of the dissociation products are discussed, from direct dissociation of H2O molecules by electrons of plasma breakdown to emission of laser-induced plasma in liquid.

In English

We investigate the conditions for increase of the photoluminescence of CdS nanocrystals in polyethyleneimine and polyethyleneimine with carbon multiwall nanotubes on macroporous silicon substrates. Macroporous silicon structures are made using the photoelectrochemical etching of n‑Si wafers. Macropores with diameter D p = 2¸5 mm, depth h p = 40¸120 mm and concentration N p = (1¸6)×10 6 cm ‑2 were formed. CdS nanocrystals of 1.8–2 nm in size are synthesized in reaction between Cd 2+ and HS - in a colloidal solution of polyethyleneimine in water. C arbon multiwall high purity nanotubes with submicron length and 20 nm diameter were produced by catalytic pyrolysis of unsaturated hydrocarbons. “Polymer-nanoparticles” coatings are deposited from a colloidal solution in water on single crystalline silicon, macroporous silicon and oxidized macroporous silicon. The maximal photoluminescence intensity of CdS nanocrystals is measured f or the oxidized macroporous silicon substrates with maximal electric field strength at the Si- SiO 2 interface . The photoluminescence quantum yield of CdS nanocrystals on the surface of oxidized macroporous silicon increases with time and reaches 28 %. Photoluminescence of polyethyleneimine with carbon multiwall nanotubes on macroporous silicon with microporous layer is 3–6 times more intense as compared with substrates c-Si, macroporous Si and oxidized macroporous Si due to a non-radiative proton recombination decrease at the silicon matrix boundary with microporous layer and nanocoating.