Nano Colloids Research Articles

Performance repair of building materials using alumina and silica composite nanomaterials with electrodynamic properties

Abstract In recent years, the service life of building materials has become the focus of attention. Among them, the service life of concrete and steel bars is particularly affected by the corrosion of external ions (such as Cl−) in the environment. To solve this problem, a new type of composite nanocolloid was prepared through a controllable preparation method. The composite nanocolloid is prepared from aluminum chloride sol and silica sol as raw materials. The prepared colloidal particles have a particle size distribution between 10.5 and 17.5 nm, exhibiting excellent stability and dispersibility. In order to verify the improvement effect of the composite nanocolloid on the properties of building materials, the influence of it on the porosity of concrete and the anti-corrosion performance of steel bars was experimentally studied. The results indicate that the moisture absorption and dehumidification speed of concrete treated with composite nano colloids is slower, and the pore size distribution is mainly concentrated in 100–1,000 nm, indicating that the colloids can effectively optimize the pore structure of concrete. In addition, the processed steel plate samples showed high AC impedance values and low corrosion current logarithmic values in electrochemical testing, indicating that composite nanocolloids have a significant protective effect on the corrosion of steel bars, which can effectively improve the performance of building materials and extend their service life.

Unraveling the role of chitosan for nasal drug delivery systems: A review

The discipline of nanoscience has made enormous strides in the recent two decades. The researchers in the field of nanomedicine have been looking into using natural biodegradable polymeric nano-colloids for targeted drug delivery, due to their high levels of bioavailability, biocompatibility, enhanced permeability, better retention time, safety, and less toxicity. The nasal cavity has been considered as an efficient route with great potential for the management of local and systemic diseases like asthma, pneumonia, Alzheimer's disease, etc. Chitosan (CS), a natural polymer, along with its greater efficacy and less toxicity, makes it an attractive candidate for nasal administration. This review has focused on the limitations that might arise when using the nasal route and how CS can play a mechanistic role in helping with these complications when using the nasal drug delivery system. The major revelation from this article is to summarize the various formulations and innovation of CS-loaded nano colloids, such as nanoparticles, liposomes, hydrogels, in situ gel, etc. The preclinical study and various patents published also concluded that the intranasal delivery of CS-loaded nanocolloids have wide potential to manage various neurodegenerative, respiratory, cardiovascular, etc. disorders.

Concentration-dependent enhancement of nonlinear optical properties in Ge-Te-Bi nano colloidal solutions

ABSTRACT We have investigated the preparation and nonlinear optical characterization of Ge20Te75Bi5 (GTB) nano colloidal solutions using the z-scan technique for three different concentrations. The transmission spectra of GTB nano colloid films have been investigated. FTIR spectra have been measured to confirm the presence of amines in nano colloidal solutions. Z-scan traces at 78 × 1012 W/cm2 laser intensity were used to study the nonlinearity of the samples. The nonlinear absorption coefficient increases with an increase in the concentration of nano colloids. The reported high nonlinear response is useful for optical limiting applications. The optical limiting behavior is also studied against different concentrations.

The Influence of Ablation Speed on the Synthesis of Carbon Nanostructures Via Pulsed Laser Ablation of Asphalt in Ethanol

Pulsed liquid laser ablation is considered a green method for the synthesis of nanostructures because there are no byproducts formed after the ablation. In this paper, a fiber laser of wavelength 1.064 µm, peak power of 1 mJ, pulse duration of 120 ns, and repetition rate of 20 kHz, was used to produce carbon nanostructures including carbon nanospheres and carbon nanorods from the ablation of asphalt in ethanol at ablation speeds of (100, 75, 50, 10 mm/s). The morphology, composition and optical properties of the synthesized samples were studied experimentally using FESEM, HRTEM, EDS, and UV-vis spectrophotometer. Results showed that the band gap energy decreased with decreasing the ablation speed (increasing the ablation time), the minimum mean particle size of the synthesized samples was 76 nm at an ablation speed of 100mm/s, while the maximum mean particle size was 98 nm at ablation speed of 50 mm/s, the nanospheres were agglomerated to form larger spherical nanoshapes. All the synthesized carbon nano colloids exhibited a blue-green PL emission. It was concluded that the presence of carbon nanorods has an effect on the optical properties of the synthesized nanospheres.

Synthesis, characterization and investigation on synergistic antibacterial activity and cytotoxicity in vitro of Ag-CuSn nanocolloids

Ag or Cu NPs are typical antibacterial agents, and the pursuit of the strong efficacy under the low dosage makes them towards bimetallic or trimetallic exploration. In this study, Ag-(CuSn) nanocolloids (NCs) based on Cu, Sn and next Ag have been prepared by two steps of the chemical reduction. Phases, morphologies, structure relationships were characterized, the elements releasing behaviors in deionized water, the antibacterial performance over S. aureus, E. coli and C. albicans and the toxicity on L929 cells were also investigated. Results showed Cu, Sn were first reduced into Cu6.26Sn5 alloy, Ag was further deposited on CuSn nanoparticles to form Ag-(CuSn) NCs, the NCs showed a sphere-like morphology with average size less than 30 nm, the structure changed from Ag decorated CuSn to Ag coated one as Ag amounts increased. Ag-(CuSn) NCs displayed lower MIC/MBC than those of Ag or CuSn NPs under the synergistic effect. The suppression on Cu and Ag releasing made Ag0.2-(CuSn) NCs and Ag0.8-(CuSn) NCs perform nontoxic, both good antibacterial ability and biosafety to cells offered them a potential clinical application.

Nano and fine colloids suspended in the soil solution regulate phosphorus desorption and lability in organic fertiliser-amended soils

Mobile colloids impact phosphorus (P) binding and transport in agroecosystems. However, their relationship to P-lability and their relative importance to P-bioavailability is unclear. In soils amended with organic fertilisers, we investigated the effects of nano (NC; 1–20 nm), fine (FC; 20–220 nm), and medium (MC; 220–450 nm) colloids suspended in soil solution on soil P-desorption and lability. The underlying hypothesis is that mobile colloids of different sizes, i.e., NC, FC, and MC, may contribute differently to P-lability in soils enriched with organic fertiliser. NC- and FC-bound Pcoll were positively correlated with P-lability parameters from diffusive gradient in thin films (DGTA-labile P concentration, r ≥ 0.88; and DGTA-effective P concentration, r ≥ 0.87). The corresponding relations with MC-bound Pcoll are weaker (r values of 0.50 and 0.51). NC- and FC-bound Pcoll were also strongly correlated with soil P-resupply (r ≥ 0.64) and desorption (r ≥ 0.79) parameters during DGTA deployment, and the mobility of these colloids was corroborated by electron microscopy of DGTA gels. MC-bound Pcoll was negatively correlated with the solid-to-solution distribution coefficient (r = −0.42), indicating this fraction is unlikely to be the source of P-release from the solid phase after P-depletion from the soil solution. We conclude that NC and FC mainly contribute to regulating soil desorbable-P supply to the soil solution in the DGTA depletion zone (in vitro proxy for plant rhizosphere), and consequently may act as critical conditioners of P-bioavailability, whereas MC tends to form complexes that lead to P-occlusion rather than lability.

Exciton-mediated surface-enhanced Raman studies of Aluminum doped platinum nano colloids

In this article, we report the fabrication of Aluminum doped Platinum bimetallic nanoparticles (NPs) by ultrafast laser ablation (using femtosecond laser pulses of duration ∼50 fs, central maximum 800 nm) of Aluminum (Al) target immersed in Platinum (Pt) colloidal solutions in Isopropanol. Colloidal solutions of Pt NPs at a concentration of 0.5 mM, 1 mM, 3 mM, and 7 mM were prepared in Isopropyl alcohol and exhibited localized surface plasmon resonances (LSPR) at ∼292 nm. However, the LSPRs of Al-doped Pt colloids were modified to ∼283 nm (0.5 mM Pt), ∼226 nm (1 mM Pt) ∼226 nm (3 mM Pt) ∼228 (7 mM Pt). Average sizes of Al-doped Pt colloidal NPs synthesized by the ablation of Al metal targets immersed in 0.5 mM Pt, 1 mM Pt, 3 mM Pt, and 7 mM Pt colloids were estimated to be ∼19.5 nm, ∼11 nm, ∼12 nm, and ∼13.5 nm, respectively. These Al-doped Pt NPs are employed in surface-enhanced Raman scattering (SERS) studies of Methylene Blue (MB) dissolved in IPA at 0.5 μM, 5 μM, and 50 μM concentrations. Although the SPR strength of Pt and Al are moderate, the annihilation of the excitons created in Al-doped Pt NPs might lead to the formation of the charge carriers, enhancing the population in the conduction band and strengthening the SPR, finally leading to a significant SERS enhancement. The estimated enhancement factors for the mode 1623 cm−1 correspond to MB's highly elevated vibrational mode are ∼105. This article is the first report of its kind on SERS of Al-doped Pt NPs to the best of our knowledge.

Tunable luminescence and nonlinear optical properties of nano colloidal Ge20Te75Bi5 chalcogenide glass

In this article, we report spectral studies and optical nonlinearities of optical grade thin films fabricated from nano colloidal solutions of Ge20Te75Bi5 chalcogenide glass. Emission peaks of varying concentrations of Ge20Te75Bi5 nanocomposites shift from 426 nm to 492 nm. Bandgap Eg also varies in the proportion tunable to emission peaks depending on the grain size of the films. The existence of reverse saturable absorption (RSA) is confirmed by the open aperture z-scan traces of nanocomposites with a valley-like pattern. Enhancement of third-order optical nonlinearities in Ge20Te75Bi5 chalcogenide nano colloids studied using the z-scan technique can be exploited to improve the desirable features for usage in nonlinear optical systems.

Investigation on structural and spectral properties of solution-processed GeTeBi chalcogenide glasses

We report structural investigation and optical nonlinearities of optical grade thin films made from Ge20Te75Bi5 chalcogenide glass nano colloidal solutions in this paper. The presence of reverse saturable absorption is demonstrated by the valley-like open aperture z-scan spectra of nano colloids (RSA). Third-order optical nonlinearities in Ge20Te75Bi5 chalcogenide nano colloids were investigated using the z-scan method to enhance the desired features for usage in nonlinear optics.

Understanding the nano colloid-protein interaction in crowded milieu

Unique properties of nano colloids make them diverse molecules of biological applications. The antimicrobial activity of nano colloids prepared from Cymbopogon citratus extract has been well documented. However, for the development of nano colloid-based products for human use, in-depth knowledge of the interactions between proteins and nano colloids is essential. Therefore, in this study, the interactions between the nano colloid synthesized using Cymbopogon citrates extract and holo alpha-lactalbumin (h-α-LA) in a crowded milieu was investigated using several techniques. Trp-fluorescence and far-UV CD measurements were carried out under different pH conditions, which showed significant perturbations in the tertiary and alpha-helical and β-sheet structural content of h-α-LA in the presence of nano colloid, P10. Presence of nano colloid in crowded milieu destabilized the protein in terms of midpoint of thermal denaturation (Tm) and Gibbs free energy (ΔGDo). In this manuscript, the effect of nano colloids on protein structure and stability under crowded cellular conditions was investigated. The CcNc in the presence of P10 has significant detrimental effect on protein’s native conformation which leads to decrease in its stability. This study hypothesised that P10 can be used for improving the efficacy of CcNc as antimicrobial agent.

Green Synthesis and Characterization of Antimicrobial Synergistic AgCl/BAC Nanocolloids.

All over the world, one of the major challenges is the green synthesis of potential materials against antimicrobial resistance and viruses. This study demonstrates a simple method like chemistry lab titration to synthesize green, facile, scalable, reproducible, and stable synergistic silver chloride/benzyldimethylhexadecyl-ammonium chloride (AgCl/BAC) colloidal Nanoantimicrobials (NAMs). Nanocolloidal dispersions of AgCl in an aqueous medium are prepared by using silver nitrate (AgNO3) as precursor and BAC as both sources of chloride and stabilizer, holding an asymmetric molecular structure. The synthetic approach is scalable and green. Both the morphology and stability of AgCl/BAC nanocolloids (NCs) were investigated as a function of different molar fractions of the reagents. AgCl/BAC NCs were characterized by transmission electron microscopy (TEM) and X-ray photoelectron and UV–vis spectroscopies. Zeta potential measurements revealed increasing positive potential values at every stage of the synthesis. Size distribution and hydrodynamic diameter of the particles were measured by dynamic light scattering (DLS), which predicted the formation of BAC layered structures associated with the AgCl nanoparticles (NPs). Small-angle X-ray scattering (SAXS) experiments verify the thickness of the BAC bilayer around AgCl. The produced AgCl/BAC NCs probably have synergistic antimicrobial properties from the AgCl core and the biocide BAC shell. AgCl/BAC NCs stability over months was investigated. The experimental evidence supports the morphological stability of the AgCl/BAC NCs, while higher positive zeta potential values anticipate a long-term antimicrobial effect: a higher surface charge causes NPs to be potentially more lethal to bacteria. AgCl/BAC antimicrobial aqueous colloidal suspensions will be used as additives for the industrial production of antimicrobial coatings.

Nano and Fine Colloids Suspended in the Soil Solution Regulate Phosphorus Desorption and Lability in Organic Fertiliser-Amended Soils

Nano and Fine Colloids Suspended in the Soil Solution Regulate Phosphorus Desorption and Lability in Organic Fertiliser-Amended Soils

Gamma radiation on silver nano colloid for anti-fungal activity

Soft gamma ray irradiation is done on Silver nano colloids prepared using Pepper Nigrum as reducing and stabilizing agent. Change in surface morphology and the structure of the colloid is obtained from Transmission Electron Microscope images and Selected area Electron Diffractogram. Morphology of the gamma irradiated sample is devoid of nano particle clusters and the Selected Area Electron Diffraction pattern confirms the crystal nature as face centered cubic structure of nano silver. UV–visible spectroscopic analysis gives the absorption peaks in the green region. Gamma irradiation results in the reduction in peak intensity without any change in wavelength. A statistical approach is done on treating the gamma irradiated colloidal sample with the as prepared silver nano colloid for measuring the area of affecting fungal infection on a potato-agar medium. It is found that the fungal growth is declined rapidly with the introduction of gamma irradiated silver nano colloid than the as prepared colloid.

Structural and optical studies of colloidal silver nano particles

Colloidal silver nano particles are prepared by biosynthesis using medicinal plants like Ocimum Sanctum and AdhaThodaVasica. Soft gamma ray irradiation is done on the samples. Transmission electron microscopic image of before irradiated silver nano colloid shows the agglomeration of spherical nano clusters while the irradiation results in the reduction of particle size with well defined grains. Selected area electron diffraction studies can explain both the polycrystalline pattern of silver nano colloids. Further, the crystal structure is identified as Face Centered Cubic pattern. The formation and stability of silver nano particles in the colloidal solutions are monitored using uv–visible absorption spectra. Gamma irradiation does not change the band gap value of nano silver. Here the plant extracts served not only as reducing agents but also a good stabilizing agent, which prevents the aggregation of silver nano particles. Gamma ray irradiation helps a better confined morphology for silver nano particle without affecting the structural parameters and optical band gap values.

Anti Fungal Studies of Tea Leaf mediated Silver Nano Colloid

Silver nano colloids are prepared using Tea leaf as reducing and stabilizing agent. Samples with different concentrations of the reducing agents are irradiated with gamma rays of various doses. Transmission Electron Microscope images of the samples show agglomerated clusters of nano particles before irradiation while the images of after irradiation show chain free individual nano particles with reduced size and spherical morphology. The Selected Area Electron Diffraction pattern confirms the crystal nature and face centred cubic structure of nano silver. UV-Visible spectroscopy gives absorption peaks in the blue region. Gamma irradiation results in the reduction in peak intensity without any change in wavelength. A statistical approach is done on treating the gamma irradiated colloidal sample with the as prepared silver nano colloid for measuring the affected area of fungal infection on a potato-agar medium. It is found that the fungal growth is declined rapidly with the introduction of gamma irradiated silver nano colloid than the as prepared colloid.

Optical Density Optimization of Malaria Pan Rapid Diagnostic Test Strips for Improved Test Zone Band Intensity.

For the last few decades, the immunochromatographic assay has been used for the rapid detection of biological markers in infectious diseases in humans and animals The assay, also known as lateral flow assay, is utilized for the detection of antigen or antibody in human infectious diseases. There are a series of steps involved in the development of these immuno-chromatographic test kits, from gold nano colloids preparation to nitrocellulose membrane coating (NCM). These tests are mostly used for qualitative assays by a visual interpretation of results. For the interpretation of the results, the color intensity of the test zone is therefore very significant. Herein, the study was performed on a malaria antigen test kit. Several studies have reported the use of gold nanoparticles (AuNPs) with varying diameters and its binding with various concentrations of protein in order to optimize tests. However, none of these studies have reported how to fix (improve) test zone band intensity (color), if different sized AuNPs were synthesized during a reaction and when conjugated equally with same amount of protein. Herein, different AuNPs with average diameter ranging from 10 nm to 50 nm were prepared and conjugated equally with protein concentration of 150 µg/mL with KD = 1.0 × 10−3. Afterwards, the developed kits’ test zone band intensity for all different sizes AuNPs was fixed to the same band level (high) by utilization of an ultraviolet-visible spectrophotometer. The study found that the same optical density (OD) has the same test zone band intensity irrespective of AuNP size. This study also illustrates the use of absorption maxima (λ max) techniques to characterize AuNPs and to prevent wastage of protein while developing immunochromatographic test kits.

Triboelectric Characterization of Colloidal TiO2 for Energy Harvesting Applications.

Nowadays, energy-related issues are of paramount importance. Every energy transformation process results in the production of waste heat that can be harvested and reused, representing an ecological and economic opportunity. Waste heat to power (WHP) is the process of converting the waste heat into electricity. A novel approach is proposed based on the employment of liquid nano colloids. In this work, the triboelectric characterization of TiO2 nanoparticles dispersed in pure water and flowing in a fluorinated ethylene propylene (FEP) pipe was conducted. The idea is to exploit the waste heat to generate the motion of colloidal TiO2 through a FEP pipe. By placing an Al ring electrode in contact with the pipe, it was possible to accumulate electrostatic charges due to the triboelectric effect between the fluid and the inner pipe walls. A peristaltic pump was used to drive and control the flow in order to evaluate the performances in a broad fluid dynamic spectrum. The system generated as output relatively high voltages and low currents, resulting in extracted power ranging between 0.4 and 0.6 nW. By comparing the power of pressure loss due to friction with the extracted power, the electro-kinetic efficiency was estimated to be 20%.

Triphala green nano colloids: synthesis, characterization and screening biomarkers

Silver nanocolloids are synthesized using the extract of Triphala which is a compound formulation consisting of three different mixtures of plants (Emblica officinalis, Terminalia belerica, Terminalia chebula) (Tp). Formulating the Triphala extracts into silver nanocolloids (TpAgNc) can cure harmful diseases and can bring remarkable changes in the medicinal field because of the synergistic effect of silver and extract. Biophysical characterization of TpAgNc was performed using UV–visible spectroscopy, FT-IR, FESEM, EDAX, Particle size distribution and zeta potential. Antimicrobial activity of TpAgNc was evaluated against biofilm-forming clinical strains of Klebsiella pneumoniae. minimum susceptibility concentration, minimum bactericidal concentration, growth and biofilm inhibition assays were performed. TpAgNc showed potential antibacterial and antibiofilm activity against biofilm-forming K. pneumoniae. Further, the expression of antibiotic-resistant gene CTXM-15 and Amp C was analysed in TpAgNc treated and control. The expressions of both CTXM-15 and Amp C were downregulated in TpAgNc-treated pathogenic K. pneumonia when compared to control. Our results suggest that there is a strong correlation between biofilm formation, virulence and CTXM-15 expression in clinical strains of K. pneumoniae. The present research work revealed that TpAgNc can be incorporated in different formulations to control pathogenic bacteria causing life-threatening infections in humans and animals.

Laser ablation assisted preparation of MnO2 nanocolloids from waste battery cell powder: Evaluation of physico-chemical, electrical and biological properties

The synthesis of nanocolloids (NCs) have been investigated extensively, different techniques were developed for the fabrication of NCs. Fabrication and modification of material using pulse laser ablation/irradiation in liquid (PLAL) has recently gained a much attention of scientific community in view of various advantages (no need of chemical precursors, purity of product, the eco-friendly nature and the cost/unit mass of materials produced). A single-step PLAL technique was adopted for the preparation of MnO2 NCs from waste battery cell powder (WBCP). The laser radiation (1064 nm) for 5 ns at 103 mJ cm−2 was used to prepare the MnO2 NCs. The MnO2 NCs was characterized by XRD, SEM, EDX and UV–vis techniques. The electrical properties were also evaluated of MnO2 NCs at different energy levels and changes in conductance and specific capacitance were significant at low frequency (<200 Hz). The PLAL medium (water and methanol) significantly affected the optical properties. The antimicrobial activity was checked against set of bacterial strains and MnO2 NCs showed promising antibacterial activity in comparison with standard antibiotic rifampicin. The Pseudomonas aeruginosa, Escherichia coli and Salmonella typhi were substantially inhibited by MnO2 NCs. These results suggest that MnO2 NCs could possibly be prepared by PLAL technique and might have application as antibacterial agent. This study offers a new approach to utilize the waste battery cell powder for preparation of MnO2 NCs.

Characterization and magnetic properties of nickel and nickel-iron nanoparticle colloidal suspensions in imidazolium-based ionic liquids prepared by magnetron sputtering

Colloids of Ni and Ni-Fe nanoparticles in two imidazolium-based ionic liquids were prepared by magnetron sputtering of nickel and co-sputtering of nickel and iron, respectively, on the surface of the ionic liquids. The liquids consist of the same cation 1-butyl-3-methylimidazolium [BMIM] and two different anions: hexafluorophosphate [PF6] or bis(trifluoromethylsulfonyl)imide [Tf2N]. The nanoparticle preparation method was based on extremely low vapour pressures of the ionic liquids, which allowed them to be used in vacuum. Magnetic properties of the metal nanocolloids (NCs) and the pure ionic liquids were analysed in detail, including the effect of ageing over a period of more than 30 months. The NCs were studied by TEM microscopy, UV–Vis spectroscopy and SQUID magnetometry. They were stable in time. No sedimentation or agglomeration of nanoparticles was observed after more than 24 months. The ionic liquid ions play more than the role of a surfactant, e.g. magnetic data gave evidence of a strong interaction between the ionic liquids and metal nanoparticles.