Uncapped Nanoparticles Research Articles

Beauveria bassiana biogenic nanoparticles for the control of Noctuidae pests.

Biogenic metallic and oxide metal nanoparticles have potential as alternatives for several current problems in agriculture, such as the control of caterpillars which cause huge losses in the production of important crops. In the present study, capped and uncapped silver, iron oxide and titanium dioxide nanoparticles were synthesized from the filtrate of Beauveria bassiana and evaluated in regard to physico-chemical characteristics, capping composition, cytotoxicity, genotoxicity and biological activity on Helicoverpa armigera and Spodoptera frugiperda caterpillars. A difference in the physico-chemical parameters of the capped and uncapped nanoparticles was observed, with larger aggregation and lower stability of the uncapped. In regard to the study of the capping, the presence of functional groups of biomolecules as well as the activity of B. bassiana hydrolytic enzymes were observed. Cytotoxic effects on the tested cell lines were not observed and DNA damage levels increased with more intense effects of the uncapped nanoparticles. In regard to the biological activity against Noctuidae pests, the uncapped and capped iron oxide, and uncapped titanium dioxide nanoparticles occasioned higher mortality (76%, 60% and 51%, respectively) but no differences in LC50 were recorded. Moreover, sublethal effects were reported on Helicoverpa armigera whereas Spodoptera frugiperda showed low susceptibility to the nanoparticles. The results demonstrate that biogenic metallic and oxide metal nanoparticles might show promising effects for the control of caterpillars which cause damage on important agricultural crops. Further investigations are necessary to understand the mechanisms of action and optimize the biological activity of these new nanomaterials. © 2023 Society of Chemical Industry.

“Green”-synthesized zinc oxide nanoparticles and plant extracts: A comparison between synthesis processes and antihyperglycemic activity

Zinc oxide nanoparticles (ZnONPs) have shown antidiabetic activity in multiple studies and can be produced by different plant-mediated (“green”) methods. This study aimed to compare ZnONPs prepared via different “green” approaches (heating at high temperatures (400 °C) vs. low temperature (70 °C)). The low temperature method involved addition of suspending agents (Tween 80 or gum arabic) and pH variations followed by lyophilization. The study evaluated the hypoglycemic potential of ZnONPs with the best properties (quantity of capped agents and stability) compared to the plant extract per se. The ZnONP synthesis involved a mixture of zinc nitrate hexahydrate as the zinc precursor and a plant extract with high antioxidant activity as the capping agent supplier. The results of the studies showed that the procedure using high-temperature heating resulted in almost uncapped nanoparticles with phytocompounds (0.01 % of phenolic compounds) and nanoparticle sizes larger than 300 nm. The low-temperature method produced ZnONPs with high retention of capping agents (92.90 % of phenolic compounds) and a size of approximately 200 nm. The use of Tween 80 with pH adjustment between 9 and 10 resulted in more stable nanoparticles than with gum arabic. These nanoparticles prepared with Tween 80, exhibited a pronounced in vivo antihyperglycemic activity at a much lower dose (10 mg ZnO/kg capped by 0.31 mg phenolic compounds per kg) than the extracts alone (400 mg extract/kg) following an oral glucose tolerance test. These results demonstrated that green-synthesized ZnONPs with a high retention rate of phytochemicals can induce antihyperglycemic effects at a low dose.

Impact of surfactant (EDTA) on the properties of zinc sulphide nanoparticles and their antibacterial activity

In the present study solvothermal route is chosen to synthesize uncapped and EDTA capped zinc sulphide (ZnS) nanoparticles. X-ray diffraction studies confirmed the zinc-blende crystal structure with crystallite size lying between 6 and 16 nm. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) show the prominent decrease in agglomeration of capped nanoparticles than that of uncapped nanoparticles while the elemental analysis confirmed the presence of Zinc and Sulphur. The optical band gap increased with decrease in particle size as calculated by UV-visible absorption spectroscopy. The photoluminescence spectroscopy (PL) shows that the blue-visible emission peaks are shifted to higher wavelength region for uncapped nanoparticles than that of EDTA capped nanoparticles. The presence of different organic and inorganic functional groups and encapsulation of EDTA in the prepared samples are confirmed by Fourier Transform Infrared Spectroscopy (FTIR). The synthesized nanoparticles are found to be good antibacterial agents of Escherichia coli and Staphylococcus aureus. The objective of the present work is to show that the EDTA capped nanoparticles are found more resistant towards the bacterial strains than that of uncapped nanoparticles which is the novelty of our work and the activity increases with increase in the concentration of nanoparticles. Thus, they may be used for biological and medicinal purposes such as an antiseptic, photo corrosion, antioxidant, antifungal etc.

Development of a predictive model for determination of urea in milk using silver nanoparticles and UV–Vis spectroscopy

Determination of urea in milk is inevitable in the dairy industry for the quality control processes. A simple and cost-effective method was developed to determine the concentration of urea in milk by silver nanoparticles (uncapped and citrate capped) and ultraviolet–visible (UV–Vis) spectroscopy. The developed nanoparticles were characterized by UV–Vis, scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy and a colour change was noted from yellow to blue upon nanoparticles interaction with urea. A predictive model was developed using the spectral data from the analyzed samples. The developed model was able to measure urea concentration (between 6 mg/dL to 90 mg/dL) in milk with the coefficient of determination (R2) more than0.90 and was validated through para-dimethylaminobenzaldehyde (DMAB) method suggested by the Food Safety and Standards Authority of India (FSSAI). The average accuracy and sample percent relative standard deviation (% RSD) obtained through the developed method + model ranged from 62.67 to 121.85% and 0.11–1.21%. The regression model for uncapped nanoparticles was found to be best-fitted (having R2 = 0.92, average accuracy 103.75 ± 8.69%), with higher closeness to the values obtained for urea by FSSAI-DMAB method. This proposed study proves to be useful for the qualitative and quantitative determination of urea in milk by small businesses in the dairy industry.

Influence of the capping of biogenic silver nanoparticles on their toxicity and mechanism of action towards Sclerotinia sclerotiorum

BackgroundBiogenic nanoparticles possess a capping of biomolecules derived from the organism employed in the synthesis, which contributes to their stability and biological activity. These nanoparticles have been highlighted for the control of phytopathogens, so there is a need to understand their composition, mechanisms of action, and toxicity. This study aimed to investigate the importance of the capping and compare the effects of capped and uncapped biogenic silver nanoparticles synthesized using the filtrate of Trichoderma harzianum against the phytopathogenic fungus Sclerotinia sclerotiorum. Capping removal, investigation of the composition of the capping and physico-chemical characterization of the capped and uncapped nanoparticles were performed. The effects of the nanoparticles on S. sclerotiorum were evaluated in vitro. Cytotoxicity and genotoxicity of the nanoparticles on different cell lines and its effects on nontarget microorganisms were also investigated.ResultsThe capped and uncapped nanoparticles showed spherical morphology, with greater diameter of the uncapped ones. Functional groups of biomolecules, protein bands and the hydrolytic enzymes NAGase, β-1,3-glucanase, chitinase and acid protease from T. harzianum were detected in the capping. The capped nanoparticles showed great inhibitory potential against S. sclerotiorum, while the uncapped nanoparticles were ineffective. There was no difference in cytotoxicity comparing capped and uncapped nanoparticles, however higher genotoxicity of the uncapped nanoparticles was observed towards the cell lines. Regarding the effects on nontarget microorganisms, in the minimal inhibitory concentration assay only the capped nanoparticles inhibited microorganisms of agricultural importance, while in the molecular analysis of the soil microbiota there were major changes in the soils exposed to the uncapped nanoparticles.ConclusionsThe results suggest that the capping played an important role in controlling nanoparticle size and contributed to the biological activity of the nanoparticles against S. sclerotiorum. This study opens perspectives for investigations concerning the application of these nanoparticles for the control of phytopathogens.

Interaction of borohydride stabilized silver nanoparticles with sulfur-containing organophosphates.

Understanding the interactions between nanoparticles and organophosphates is the key to developing cost-effective colorimetric pesticide detection. We have studied the interaction between three different organophosphates containing the P Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> S group and borohydride stabilized silver nanoparticles. Three different organophosphates, namely phorate, chlorpyrifos, and malathion, have been used. The colorimetric changes are corroborated with UV-visible absorption studies along with the change in particle size and zeta potential. This effect persists in the presence of NaCl solution also. The chlorpyrifos and malathion do not show significant interactions with uncapped nanoparticles over time, while phorate undergoes degradation due to the scission of the S–CH2 linkage. A reaction mechanism, wherein a silver and sulfur (Ag→S) complex is formed, which is in agreement with Raman spectroscopic studies is proposed. The orientations of phorate near Ag nanoparticles are discussed from the adsorption energy calculation using density functional theory.

Induction heating response of iron oxide nanoparticles in varyingly viscous mediums with prediction of brownian heating contribution

ABSTRACT This study examines the effects of nanoparticle concentration, magnetic field frequency, and carrier fluid viscosity on the induction heating response of nanofluids exposed to an alternating magnetic field. Uncapped iron-oxide nanoparticles with a mean diameter 14.42 nm were sonically dispersed into mixtures of deionized water and ethylene glycol (WEG) as well as highly viscous oil blends. The resulting nanofluids were exposed to an alternating magnetic field with a strength of 72.6 kA/m at frequencies of 217, 303, and 397 kHz with the heating response characterized calorimetrically through the specific absorption rate (SAR). Concentration and frequency effects mirror those found in literature with SAR reduction and enhancement, respectively. Additionally, SAR output is characterized across a wide range of viscosities showing a consistent decrease in heating output as viscosity increases through the WEG regime, however, the SAR was found to be relatively consistent across the oil blends. The effects of particle aggregation were measured through dynamic light scattering denoting particle clustering as a function of viscosity. Viscosity trends with SAR are accounted for by the viscous inhibition of particles reducing their Brownian heating, as well as clustering effects potentially inhibiting heat production in the low viscosity range where aggregation is pronounced. Lastly, a model predicting the Brownian contribution to heating as a function of frequency, concentration, and viscosity is proposed. This study provides a broad view of the effects on heating output for suspensions of commercially available iron oxide nanoparticles for several concentrations and field frequencies across an expansive range of viscosity.

Thermal Properties of Lipid Bilayers Determined Using Upconversion Nanothermometry

AbstractLuminescent nanomaterials have shown promise for thermal sensing in bio‐applications, yet little is known of the role of organic coatings such as supported lipid bilayers on the thermal conductivity between the nanomaterial and its environment. Additionally, since the supported lipid bilayer mimics the cell membrane, its thermal properties are fundamentally important to understand the spatial variations of temperature and heat transfer across membranes. Herein, a new approach is described that enables direct measurement of these thermal properties using a LiYF4:Er3+/Yb3+ upconverting nanoparticle encapsulated within a conformal supported lipid bilayer and dispersed in water as a temperature probe yielding the temperature gradient across the bilayer. The thermal conductivity of the lipid bilayer is measured as a function of the temperature, being 0.20 ± 0.02 W m−1 K−1 at 300 K. For the uncapped nanoparticles dispersed in water, the temperature dependence of the thermal conductivity is also measured in the 300–314 K range as [0.63–0.69] ± 0.11 W m−1 K−1. Using a lumped elements model, the directional heat transfer is calculated at each of the system interfaces, namely, nanoparticle–bilayer and bilayer–nanofluid, opening a new avenue to understand the membrane biophysical properties as well as the thermal properties of organic and polymer coatings.

Antibacterial activity of water soluble dye capped zinc oxide nanoparticles synthesised from waste Zn–C battery

Antibacterial activity of functionalized ZnO nanoparticles synthesized from waste Zn–C battery by microwave method was investigated, water soluble 1-(carboxymethyl)-4-[(E)-2-(3-methoxy-4-methylphenyl)ethenyl] pyridin-1-ium photosensitizer was used as capping agent to control the size of nanoparticle. The characterization of the samples was done with the help of UV–visible spectroscopy, FTIR, SEM–EDS and XRD. The nanoparticles have hexagonal wurtzite structure with a mean diameter of 19.7 nm for 3% dye capped nanoparticle and 30.6 nm for uncapped nanoparticle and are composed by a mixture of small crystallites and disordered ZnO particles. Capped ZnO nanoparticles showed high antibacterial (tested on E. coli and B. subtilis) activities compared to that of uncapped nanoparticles under the same experimental conditions. This novel water soluble dye capped ZnO nanoparticles emerged as excellent antibacterial agent, the results show minimum inhibitory concentration of 0.39 and 1.56 for B. subtilis and E. coli and highest zone of inhibition was at concentration of 5 mg/ml. The bioactivity showed dye capped nanoparticle to be new class of antibacterial agent.

Design and synthesis of imine linked ZnO nanoparticles functionalized with Al(III), candidate for application in light emitting diodes

Zinc oxide nanoparticles 1.ZnO decorated with dipodal organic receptor 1 bearing imine linkage were synthesized using wet chemical precipitation technique. The imine linked receptor 1 used as capping agent was synthesized using condensation reaction. 1.ZnO nanoparticles were characterized through FTIR, SEM, TEM, DLS and fluorescence spectroscopy. The emission spectra of surface modified ZnO nanoparticles authenticated the passivation of surface defects and dangling bonds which otherwise are available on the surface of uncapped ZnO nanoparticles. 1.ZnO nanoparticles demonstrated blue emission at 461 nm. The binding affinity of 1.ZnO nanoparticles was also checked in presence of metal ions through changes observed in the emission spectra. An enhancement up to threefold in the fluorescence intensity was achieved from 1.ZnO nanoparticles upon coordination with Al3+ metal ion. The results demonstrated that our design strategy resulted in pure and narrow emission with FWHM 70 nm. This effective way of achieving the selectivity factor and enhanced quantum yield can be utilized in electronic device like light emitting diodes.

Structural and optical characterization of hexagonal nanocrystalline bismuth-bismuth oxide core-shell structures synthesized at low temperature

We report the synthesis and optical properties of bismuth- bismuth oxide core-shell nanoparticles. In this work, the PEG capped and bare Bi-Bi2O3 core-shell nanoparticles are prepared by controlled oxidation of bismuth nitrate with citric acid at a temperature of 300 °C. Xrd analysis reveals the presence of a tetragonal β phase bismuth oxide for uncapped nanoparticles and a cubic δ-phase for PEG capped nanoparticles. TEM analysis shows the prepared nanoparticles are core-shell with hexagonal structure. The optical absorption studies reveal that a band gap of 4.05 eV for uncapped nanoparticles and 4.17 eV for capped nanoparticles. Fluorescence emission of these nanoparticles was observed and a dominant peak is observed around 426 nm and a feeble emission is around 457 nm.These emissions are found to be originated from surface state emission. An enhancement of fluorescence emission for uncapped nanoparticles compared to capped nanoparticles, which is found out to be from more number of oxygen defect states in the uncapped β-phase nanoparticles.

Abiotic stress of ZnO‐PEG, ZnO‐PVP, CuO‐PEG and CuO‐PVP nanoparticles enhance growth, sweetener compounds and antioxidant activities in shoots of Stevia rebaudiana Bertoni

Nanoparticles are known to play remarkable role as abiotic stress elicitors in plants. This study reports the comparative analysis of effects produced by capped [zinc oxide (ZnO)-polyethylene glycol (PEG), ZnO-polyvinyl pyrrolidone (PVP), copper oxide (CuO)-PEG, CuO-PVP] and uncapped (ZnO and CuO) nanoparticles on the medicinal plant, Stevia rebaudiana raised in vitro for the production of commercially important sweetener compounds. In context of shoot organogenesis, ZnO-PEG, ZnO-PVP, CuO-PEG, CuO-PVP were employed to the growth medium that resulted in increased growth parameters, and larger content of steviol glycosides as compared to the shoots raised in medium containing ZnO and CuO, revealed by high-performance liquid chromatography. In the meanwhile, non-enzymatic antioxidant activities including total phenolic content, total flavonoid content, total antioxidant capacity, total reducing power and 2,2-diphenyl-1-picryl hydrazyl-free radical scavenging activity were calculated and showed comparatively greater amounts in shoots grown in medium containing capped ZnO or CuO nanoparticles. Furthermore, the ZnO and its derivatives revealed to be more reactive at 1 mg/l of concentration. Whereas, the CuO and its derivatives produced greater response on Stevia at 10 mg/l concentration of nanoparticles. This study paves the way for more such studies encompassing capped and uncapped nanoparticles and their ultimate effect on in-vitro grown plant tissues for the production of active metabolites on industrial scale.

Hydrothermal growth of highly monodispersed TiO2 nanoparticles: Functional properties and dye-sensitized solar cell performance

Monodispersed anatase TiO2 nanoparticles were synthesized by hydrothermal method using citric acid as a capping agent. The effect of citric acid and the growth time on the formation of TiO2, functional properties and dye-sensitized solar cell performances were investigated. X-ray diffraction pattern (XRD) and Raman spectroscopy results revealed that the TiO2 nanoparticles possess the anatase phase. Transmission electron microscopy (TEM) measurement revealed the formation of spherical nanoparticles with monodispersity in size and morphology. An average size of 14nm was obtained for the growth period of 15h. The maximum efficiency (η) of dye-sensitized solar cell was achieved for TiO2 nanoparticles grown for 15h as 7.66% which was higher than that of commercial P25 TiO2 (5.23%) and uncapped nanoparticles (3.68%).

Understanding the Solvent Molecules Induced Spontaneous Growth of Uncapped Tellurium Nanoparticles.

Understanding the thermodynamic behavior and growth kinetics of colloidal nanoparticles (NPs) is essential to synthesize materials with desirable structures and properties. In this paper, we present specific uncapped Te colloidal NPs obtained through laser ablation of Te in various protic or aprotic solvents. At ambient temperature and pressure, the uncapped Te NPs spontaneously exhibited analogous evolution and growth of “nanoparticle-nanochain-agglomerate-microsphere” in different solvents. The distinctive growth kinetics of the formation of nanochains strongly depended on the polarity and dielectric constant of solvent molecules. The growth rate of agglomerates and microspheres was closely related to the zeta potential of the colloidal solution of Te nanochains and the average size of Te agglomerates. Furthermore, the resulting uncapped Te NPs and Te nanochains displayed a prominent size-dependent and structure-inherited chemical reductive ability. These findings provide insights into the growth of active uncapped nanoparticles in various dispersion media. This study also provides an alternative route in designing novel nanostructures of alloys, telluride, and functional composites using Te as a unique reactive precursor.

Effect of capping agents: Structural, optical and biological properties of ZnO nanoparticles

Different biological activities of capped and uncapped ZnO nanoparticles were investigated, and the effects of potential capping agents on these biological activities were studied. ZnO nanoparticles were synthesized and capped by polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) using a simple chemical method of co-precipitation. Characterization by X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR) and UV–vis spectroscopy confirmed the crystallinity, size, functional group, and band gap of synthesized nanoparticles. Reduction in size occurred from 34nm to 26nm due to surfactant. Results of all biological activities indicated significantly higher values in capped as compared to uncapped nanoparticles. Antibacterial activity against Staphylococcus aureus (ATCC 6538), Bacillus subtilis (ATCC 6633), Escherichia coli (ATCC15224), and Acetobacter was obtained. This activity was more prominent against Gram-positive bacteria, and ZnO-PVP nanoparticles elucidated highest antibacterial activity (zone of inhibition 17mm) against Gram-positive, Bacillus subtilis species. Antioxidant activities including total flavonoid content, total phenolic content, total antioxidant capacity, total reducing power and %age inhibition of DPPH, and antidiabetic activity against α-amylase enzyme found to be exhibited highest by ZnO-PEG nanoparticles.

Solvothermal growth of diethylamine capped TiO2 nanoparticles and functional properties

Size controlled anatase titanium dioxide (TiO2) nanoparticles with high surface area were prepared using diethylamine (DEA) as a passivating agent by simple hydrothermal growth. X-ray diffraction pattern revealed the formation of anatase crystal phase of TiO2. There is no phase transformation for capped and uncapped TiO2 nanoparticles. Ligand passivation on TiO2 nanoparticles were confirmed by Fourier transform infra red studies. Significant UV–visible absorption is shown by absorption analysis. Uncapped and DEA capped TiO2 nanoparticles were synthesized and compared. Monodispersed cubic like morphology of DEA capped TiO2 nanoparticles with an average size of 13 nm is observed by transmission electron microscope (TEM) analysis. TEM analysis confirms that agglomerations were restricted by adding DEA as a capping agent. DEA capped TiO2 nanoparticles showed surface area of 65 m2/g and it is higher than uncapped TiO2 nanoparticles as confirmed by Brunauer–Emmett–Teller method. Prepared materials can be used as photoanodes in dye-sensitized solar cell application.

Confined gold nanoparticles enhance the detection of small molecules in label-free impedance aptasensors.

A controlled architecture of nanoelectrodes, of a similar size to small molecule-binding aptamers, is synthesized inside nanoporous alumina. Gold nanoparticles with a controlled size (about 2 nm) are electrogenerated in the alumina cavities, showing a fast electron transfer process toward ferrocyanide. These uncapped nanoparticles are easily modified with a thiol-containing aptamer for label-free detection of adenosine monophosphate by electrochemical impedance spectroscopy. Our results show that the use of a limited electrical conducting surface inside an insulating environment can be very sensitive to conformational changes, introducing a new approach to the detection of small molecules, exemplified here by the direct and selective detection of adenosine monophosphate at the nanomolar scale.

Spin Depolarization of Muonium in Mesoporous Silica

We report muon spin rotation/relaxation measurements of muonium in mesoporous silica (SBA-15) with a high specific surface area of 600 m2/g. Up to 70 percent of the incoming muons form muonium and escape efficiently into the open pores at all temperatures between 3 and 300K. We present evidence that the interaction with the silica surfaces involves both spin exchange and a transition to a diamagnetic state, possibly due to dangling bonds on the surface. At very low temperatures, below 20K, the interaction between muonium and the silica surfaces is suppressed due to a He film coating the surfaces. These results indicate that it should be possible to use muonium to probe the surfaces of uncapped nanoparticles supported in silica.

Structure and optical properties of capped and uncapped CdS nanoparticles prepared in aqueous medium

We have prepared the hexagonal structure of CdS nanoparticles in an aqueous solution with different sizes and varied surface compositions by using fixed molar ratio of the starting precursors in the presence of capping molecules. In addition, we have prepared uncapped CdS nanoparticles by cadmium chloride and thiourea at low temperature. We showed that the environmental conditions and the type of the aqueous medium are the effective parameters for the exchange of the nanoparticle size. The prepared nanoparticles have sizes in the range from 25 to 100 A. We have compared the experimentally determined size of CdS nanoparticles with that determined by theoretical calculations. The comparison showed that the size determined by Scherrer’s equation is fitted well with the empirical tight binding calculations, and that the effective mass approximation yields size values is in good agreement with the size estimated by high resolution transmission electron microscopy. Photoluminescence spectroscopy revealed that the nanoparticles with stoichiometries composition S/Cd ~ 1 have a high intensity band edge emission in the blue region for the capped nanoparticles and green emission for the uncapped nanoparticles.

Surface modification of Y2O3:Er,Yb upconversion nanoparticles prepared by laser ablation in water

Y2O3:Er,Yb upconversion nanoparticles were prepared by laser ablation in liquid and capped with poly(ethylene glycol) (PEG). A Nd:YAG green laser with nanosecond pulse duration was used. Capping was carried out by a two-step process. The first step is surface modification using a silane coupling agent, (3-aminopropyl)triethoxysilane (APTES), to aminate the surface of nanoparticles. The second step was the conjugation of PEG chains to the surface by amido binding reaction between the surface amino groups and activated esters connected to PEG. The prepared upconversion nanoparticles were highly crystalline polycrystals, the particle size of which was approximately 20 nm. Dopants in phosphor nanoparticles were not removed by laser irradiation. The spectra of PEG-capped nanoparticles were almost the same as those of uncapped nanoparticles. The capped nanoparticles would be useful for biomedical applications.