Average Size Of Nanoparticles Research Articles

Bioinspired green synthesis of copper, nickel, and hybrid nanoparticles using Myristica Fragrans seeds: Biomedical applications and beyond

Nanotechnology focuses on materials at the molecular and atomic levels, with sizes ranging from 0.1 to 100 nm. This study explores the synthesis and characterization of copper oxide (CuO), nickel oxide (NiO), and hybrid nanoparticles using an aqueous seed extract from Myristica fragrans. The nanomaterials underwent comprehensive characterization employing various techniques: UV analysis, FTIR spectroscopy, XRD, TGA, EDX and SEM. We explored their biological applications through antioxidant and antibacterial assays. UV analysis determined the optical absorption spectra values for CuO, NiO and hybrid nanoparticles. FTIR analysis confirmed functional groups in the plant extract responsible for capping and reducing the reaction medium. XRD and SEM analysis demonstrated the crystalline nature and morphology of the nanoparticles. CuO nanoparticles exhibited polyhedral morphology, while NiO nanoparticles were primarily spherical with some agglomeration. The CuO-NiO hybrid nanoparticles showed a wurtzite morphology with significant agglomeration and larger mean size than CuO and NiO nanoparticles. EDX indicated higher quantities of Cu and Ni. XRD spectra revealed the average particle sizes of nanoparticles. TGA indicated the thermal stability of the nanoparticles, with hybrid nanoparticles being the most stable. The nanoparticles exhibited excellent antioxidant activity, with hybrid nanoparticles showing the highest values in measuring total antioxidant capacity, total reducing power (TRP), ABTS assay, and DPPH-free radical scavenging assay at 400 μg/mg. Antibacterial assays against multidrug-resistant bacterial strains demonstrated that antibiotics-coated hybrid nanoparticles exhibited potent antibacterial properties against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. In conclusion, CuO, NiO, and CuO-NiO hybrid nanoparticles mediated by Myristica fragrans showcase promising characteristics for various applications, especially in biomedical and clinical settings. The nanoparticles eco-friendly synthesis and biocompatible nature make them attractive candidates for future research and development.

Fabrication of MnO2/g-C3N4 nanocomposite for methylene blue dye degradation under light illumination

The synthesis of manganese oxide/graphitic carbon nitride (MnO2/g-C3N4) heterostructure was carried out via hydrothermal method. The obtained material was analyzed using several analytical techniques, including X-ray diffraction, Transmission Electron Microscope, UV–vis spectrophotometer, photoluminescence, and Scanning electron microscope, to determine its morphological, elemental, structural, and optical properties. The average size of the MnO2 nanoparticles is 33.6 ± 1 nm, with a range of 1.0 to 60 nm in TEM analysis. The optical bandgap of MnO2, g-C3N4, and MnO2/g-C3N4 nanocomposites were determined to be 1.75 eV, 2.75 eV, and 2.33 eV, respectively. The results indicate that the MnO2/g-C3N4 hybrid catalyst exhibits a degrading efficiency of 93.6 % in 120 min and great stability after five cycles. The mechanism of separating electron-hole pairs (e−/h+) that are created by photons and delaying the recombining of free charges has been widely reported.

A Systematic Microfluidic Study of the Use of Diluted Silica Sols to Enhance Oil Displacement.

The paper presents the results of a systematic microfluidic study of the application of nanosuspensions for enhanced oil recovery. For the first time, approximately a dozen nanosuspensions prepared by the dilution of silica sols as displacement fluids were considered. The concentration of nanoparticles in the suspensions varied from 0.125 to 2 wt%, and their size ranged from 10 to 35 nm. Furthermore, the silica sols under consideration differed in their compositions of functional groups and pH. The effects of concentration, nanoparticle size, fluid flow rate, and the viscosity of the displaced oil were investigated using microfluidic technology. The microfluidic experiments demonstrated that the application of nanosuspensions for water flooding has significant potential. The efficiency of oil displacement by nanosuspensions was found to increase significantly (up to 30%) with the increasing concentration and decreasing average size of nanoparticles. The application of nanosuspensions for the enhancement of oil recovery is most appropriate for reservoirs with highly viscous oil.

Single-bubble sonoluminescence of itterbium(II or III) and thulium(II or III) chloride nanoparticles colloidal suspensions in dodecane

Colloidal suspensions of nanoparticles of di- and trivalent ytterbium and thulium chloride crystals in dodecane were prepared by ultrasonic dispersion. The average nanoparticle size in the suspensions was 20–35 nm. During single-bubble sonolysis with the bubble moving at the standing wave antinode, identical bands with a maximum at 550 nm appeared in the sonoluminescence spectra with spectral resolution Δλ = 15 nm for suspensions of both Yb(II) and Yb(III) salts. Bands with a maximum at 600 nm were found for suspensions of Tm(II) and Tm(III) salts. These sonoluminescence bands coincide with the photoluminescence bands of Yb(II) (550 nm) or Tm(II) (600 nm) salts, respectively. For suspensions of divalent lanthanide salts, these sonoluminescence bands appear when nanoparticles get into a moving bubble, because of collisional excitation of Yb(II) or Tm(II) in the bubble plasma, which periodically appears during acoustic oscillations: [Ln(II)]suspension → [Ln(II)]bubble → [Ln(II)]plasma → [Ln(II)*]plasma → Ln(II) + hνLn(II). The presence of analogous bands for suspensions of trivalent lanthanide salts is caused, in particular, by also their reduction in the plasma after they get into a bubble: [Ln(III)]suspension → [Ln(III)]bubble → [Ln(III)]plasma → [Ln(II), Ln(II)*]plasma → [Ln(II)*]plasma → Ln(II) + hνLn(II). The reduction of lanthanide ions in the bubble plasma is not limited to the reaction Ln(III) → Ln(II), Ln(II)*, but can proceed further giving singly charged lanthanide cations and lanthanide atoms: Ln(II) → Ln(I), Ln(I)* → Ln(0), Ln(0)*. The single-bubble sonoluminescence spectra with Δλ = 1.5 nm for a suspension of Yb(III) salt showed characteristic lines of Yb(I) and Yb(0). These characteristic lines and bands for ytterbium and thulium atoms and ions are suitable for sonoluminescent spectroscopic analysis, that is, identification and quantification of ions in solutions and suspensions and determination of electronic temperature in bubble plasma.

Copper - nickel electro-explosive powder feedstocks for extrusion-based additive manufacturing

The average sizes of copper and nickel nano- and microparticles formed at exploding wires in the range of inhomogeneous and homogeneous heating have been established. The average size of nanoparticles grows, and that of microparticles decreases when the value of energy input into wires reaching E ≈ 0,5Es (Es - sublimation energy). While E > 0.5Es the dependence of the average sizes of nano- and microparticles is weakly expressed. The viscosity of feedstocks increases as the proportion of nanoparticles in the powder increases and their size decreases. At equal dispersity and mass content of particles in the polymer, the feedstock viscosity has been found to depend on the adsorption behavior of metals. The analysis of temperature dependence of the feedstock viscosity based on copper and nickel powders has shown that the optimum values of E/Es for one-stage production of micro-nanoparticle powders by the exploding wires lie in the range of 0.4 … 0.7.

Olive leaf extract-assisted preparation of nanoferrite for adsorptive removal of cationic dye

In this work, magnetic Fe3O4 nanoparticles synthesized with olive leaf extract were used to investigate the adsorption of Basic violet 16 from aqueous solutions. The physicochemical characteristics of Fe3O4 nanoparticles were evaluated by DLS, zeta potential, XRD, FTIR SEM, EDX, N2 adsorption-desorption, TEM, and VSM analyses. Using DLS analysis, the average size of the Fe3O4 nanoparticles was found to be 231.2 nm. Zeta potential studies indicated that the synthesized nanoparticles were moderately stable, and zeta potential was calculated as −14.9 mV. According to TEM analysis, the synthesized nanoparticles ranged in size from 6.28 to 17.3 nm. The optimum parameters for the adsorption of basic violet 16 with Fe3O4 nanoparticles were determined as pH: 9.0, adsorbent dose: 0.8 g, contact time: 210 min, stirring speed: 250 rpm. Langmuir, Freundlich, Dubinin Radushkevich (D-R) and Temkin isotherm models were used to characterize the basic violet 16 sorption data onto Fe3O4 nanoparticles and it was seen that Basic violet 16 adsorption onto the Fe3O4 nanoparticles followed Langmuir isotherm model at all temperatures. The maximum adsorption capacity of Basic violet 16 with Fe3O4 nanoparticles was determined as 117.64 mg/g at 318 K. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to describe the adsorption kinetics at 298–318 K. The adsorption followed the pseudo-second-order kinetic model. Adsorption of Basic violet 16 onto Fe3O4 nanoparticles occurred spontaneously and endothermically. Characteristic peaks Fe3O4 nanoparticles were visible in the XRD analysis. The SBET surface area dropped from 110.42 m2/g to 91.27 m2/g after dye adsorption. Peaks in the FTIR analysis showed that Basic violet 16 had been successfully adsorbed on Fe3O4 nanoparticles.

Characterization of Copper nanoparticles obtained in AOT reverse micelles using flavonoids as a reducing agent

Purpose of the study. To characterize copper nanoparticles obtained in reverse micelles of sodium bis-(2-ethylhexyl)-sulfosuccinate (AOT) using flavonoids: quercetin and rutin in comparison with traditional reducing agents - sodium borohydride and hydrazine. Methods. Chemical synthesis of copper nanoparticles, spectrophotometry to determine the maximum of the plasmon absorption band of copper nanoparticles, electron transmission microscopy. Results. The reduction of copper ions using flavonoids – quercetin and rutin – confirmed the possibility of obtaining copper nanoparticles in the Cu+2/AOT/isooctane system (AOT is sodium bis-(2-ethylhexyl)-sulfosuccinate, an anionic surfactant that forms the micelle shell). During the formation of nanoparticles, “plasmonic” absorption bands were observed in the electronic spectra in the region of 400-440 nm. In the case of the traditional reducing agent, sodium borohydride, absorption is observed in the region of (439 ± 3) nm, which can also be attributed to the “plasmonic band” of copper nanoparticles, but its intensity is very low, which indicates the formation of a small amount of copper nanoparticles. Using transmission electron microscopy. The average size of copper nanoparticles was determined: 7.1, 8.2 and 18.5 nm in the case of quercetin, rutin and hydrazine, respectively. From the histograms constructed from the results of electron transmission microscopy, it follows that the use of flavonoids as reducing agents makes it possible to reduce the average size of copper nanoparticles and narrow their size distribution. Conclusion. Copper nanoparticles obtained in a reverse micellar solution of AOT in iso-octane using the flavonoids quercetin and rutin as a reducing agent have an average size of 7-8 nm and a narrower size distribution compared to reduction with hydrazine.

Enhancing Radiator Cooling with CuO Nanofluid Microchannels

The study explores in employing copper oxide (CuO) nanofluid as a cooling medium in the vehicle radiators. To simulate the heat transfer process, the microchannel is constructed using elec-tron discharge machining (EDM) and a computational fluid dynamics (CFD) modeling is em-ployed. UV-visible spectroscopy, scanning electron microscopy (SEM), and dynamic light scat-tering (DLS) are used to characterize the CuO nanofluid. CuO nanofluid surpasses water in the heat transfer capabilities, with a 40% improvement in thermal conductivity. The average size of CuO nanoparticles was determined via DLS to be 485.1 nm. The heat transfer coefficient of CuO nanofluid is 5366 W/m2K, which is 116% larger than that of water. The increased heat transfer capabilities of CuO nanofluid microchannel flow indicate to its potential as a viable replacement for conventional radiators in the automotive applications. Lower engine tempera-tures, increased fuel efficiency, and longer engine lifespan may result from improved cooling performance. Due of the small size of microchannels, more efficient and space-saving radiators for automobiles are conceivable. More research is needed to improve the microchannel design as well as to realize the practical benefits of CuO nanofluids in car cooling systems.

Contact electro catalysis driven degradation of malachite green dye by RGO/ZnO nanohybrid

This work demonstrates the potential of reduced graphene/zinc oxide (RGO/ZnO) nanohybrid for the degradation of malachite green dye (MG) via involving the mechanochemistry contact electro catalysis (CEC) approach through electronic transfer. Dielectric and piezoelectric RGO/ZnO nanohybrid in contact with aqueous medium offers electron transfer via direct catalytic reaction at solid-liquid interface which promotes CEC process than that of conventional photocatalysis. RGO/ZnO nanohybrid is prepared via ultrafast microwave irradiation method in 60 s using Mangifera indica leaves extract as a green reducing agent. The prepared RGO/ZnO nanohybrid is characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and UV–Visible (UV–Vis) spectroscopy. XRD analysis reveals the formation of pure ZnO with wurtzite hexagonal phase and signature reflection of the RGO. Raman, FTIR and UV–Vis spectroscopy results confirm the presence of bands corresponding to ZnO and RGO and hence the formation of RGO/ZnO nanohybrid without any impurity phase. Field emission-scanning electron microscopy (FE-SEM) reveals the growth of spherical shaped ZnO nanoparticles over the RGO matrix. The average particle size of ZnO nanoparticles is ⁓ 9.2 nm. Catalytic properties of RGO/ZnO nanohybrid is investigated by using 10 mg and 20 mg dosage in aqueous solution of MG. About 85.72 % degradation efficiency for MG in 60 min is achieved by using 20 mg RGO/ZnO nanohybrid via sonication through CEC process. Probably, contact electrolysis at ZnO-water interface induces electronic exchange and generation of free radicals to degrade the dye molecules. Reaction kinetics analysis reveals the suitability of the pseudo first-order kinetics for dye degradation and reusability of RGO/ZnO nanohybrid confirms its excellent stability up to three cycles with 60 % degradation ability. This research establishes RGO/ZnO nanohybrid as highly promising catalytic agents for wastewater treatment and hazard free CEC approach.

Phytomediated zinc oxide and sulfur nanoparticles for management of soft-rot causing pathogenic fungi in ginger

Diseases management has been the greatest challenge to agriculture leading to huge crop failure, represented in low-profit production. Phytopathogenic fungi are among pathogens causing a variety of agricultural diseases. Various nanoparticles (NPs) have previously been employed to combat phytopathogenic fungi. Post-harvest deterioration due to fungal invasion is the most imperative cause of loss of ginger (Zingiber officinale) production. In the present study, four fungal pathogens isolated from soft-rot infected ginger were identified as Pythium spp. (isolate I and II), one Fusarium sp. (isolate III) and one Aspergillus sp. (isolate IV). Moringa oleifera mediated zinc oxide (ZnONPs) and sulfur nanoparticles (SNPs) were characterized by UV–Visible spectrophotometry and showed absorption maxima at 356 nm and 295 nm. Average size of NPs under Nanoparticle Tracking Analyzer was 78 nm and 26 nm respectively, confirmed by FESEM. Stable NPs with zeta potential of −14.1 mV (Standard deviation = 4.51 mV) and −21.1 mV (Standard deviation = 9.56 mV) were synthesized. FTIR detected the presence of various functional groups in NPs. In vitro antifungal activity was assessed by Kirby-Bauer disc diffusion assay and MIC values compared to antibiotic ketoconazole and fungicide mancozeb. Time kill assay represented the minimum time required by selected NPs to inhibit the growth of test pathogenic fungi. ZnONPs and SNPs can be used for further antifungal studies in the field as novel nanofungicides. Extrapolated and uncontrolled use can lead to the inhibition of germination, reduction in photosynthesis rate, and disruption of the plant roots. Thorough small-scale experimentation is necessary before commercialization.

Ultrasensitive detection of Ag+ and Ce3+ ions using highly fluorescent carboxyl-functionalized carbon nitride nanoparticles

The fluorescence quenching of carboxyl-rich g-C3N4 nanoparticles was found to be selective to Ag+ and Ce3+ with a limit of detection as low as 30 pM for Ag+ ions. A solid-state thermal polycondensation reaction was used to produce g-C3N4 nanoparticles with distinct green fluorescence and high water solubility. Dynamic light scattering indicated an average nanoparticle size of 95 nm. The photoluminescence absorption and emission maxima were centered at 405 nm and 540 nm respectively which resulted in a large Stokes shift. Among different metal ion species, the carboxyl-rich g-C3N4 nanoparticles were selective to Ag+ and Ce3+ ions, as indicated by strong fluorescence quenching and a change in the fluorescence lifetime. The PL sensing of heavy metal ions followed modified Stern–Volmer kinetics, and CNNPs in the presence of Ag+/Ce3+ resulted in a higher value of K app (8.9 × 104 M−1) indicating a more efficient quenching process and stronger interaction between CNNP and mixed ions. Sensing was also demonstrated using commercial filter paper functionalized with g-C3N4 nanoparticles, enabling practical on-site applications.

Insights on the effect of process conditions on the optical properties of silver ion exchanged soda-lime silicate glass

The effects of ion exchange time and temperature on the optical properties and plasmonic response of silver ion exchanged soda-lime silicate glass were investigated using scanning electron microscopy (SEM) in energy dispersive spectrometry (EDS) configuration, m-lines spectroscopy, photoluminescence (PL) spectroscopy, and UV–visible absorption spectroscopy. SEM analyses in EDS mode provided profiles of silver oxide molar concentration. These profiles were directly correlated to the silver diffusion coefficient using an adjustment procedure. The effective indices of ion exchanged glasses measured by the standard prism coupling technique (m-lines) allowed access to refractive index distributions in ion exchange regions. These ion-exchanged glasses underwent evaluation to determine their potential suitability for use in multimode planar systems. The PL results acquired after ion exchange demonstrated that the creation of Ag0 atoms from Ag+ ions was responsible for the decline and quenching of PL intensity at ion exchange times and temperatures increase. Silver nanoparticles were generated in the samples subjected to ion exchange at 480 °C without the need for post-exchange treatments. The emergence of the surface plasmon resonance band around 427 nm in the optical absorption spectra confirmed the formation of Ag nanoparticles in annealed glasses. Estimates of the UV–visible absorption spectra indicated an average size of silver nanoparticles ranging from 1.8 to 2.4 nm.

Gamma-ray-elicited alterations in the structural, optical, and morphological attributes of spinel nickel cobaltite NiCo2O4

BackgroundIrradiation is thought to be the most effective approach to change the crystal structure and properties of solid materials. Higher energy gamma-irradiation may change the physical properties of semiconductor materials. Gamma irradiation is recognized as an effective method for altering the crystal structure and properties of solid materials. ObjectiveThe primary goal of this study was to assess how gamma irradiation affects different properties of spinel nickel cobaltite. Materials and methodsThe co-precipitation technique was operated to synthesize spinel nickel cobaltite. The synthesized spinel nickel cobaltite nanoparticles were subjected to gamma irradiation. The study employed gamma doses ranging from 40 KGy to 60 KGy. A gamma irradiator was used for this purpose. Changes induced in the structural, optical, and morphological properties of spinel nickel cobaltite had been investigated by XRD, UV–Vis spectroscopy, SEM, and FTIR. ResultsXRD revealed that the average crystalline size of nanoparticles was decreased with gamma irradiation. The band gap, Urbach energy, and extinction coefficient, real and imaginary components of dielectric constant using absorbance and transmittance spectra. The refractive index evaluated from the Moss relation increased from 2.31 to 2.46. The refractive index calculated from Van Vechan's relation increased from 2.60 to 2.78. Urbach energy values increased from 2.14 eV to 2.89 eV with an increased dosage of gamma. It was observed that all parameters were changed by gamma irradiation. SEM study showed that the grain size of particles was decreased with gamma doses. FTIR study verified the spinel-type structure of nickel cobaltite. ConclusionThe study aimed to shed light on the effects of gamma irradiation on spinel nickel cobaltite, with a focus on its structural, optical, and morphological properties. By using a combination of characterization techniques, the researchers can assess how gamma irradiation alters the material's properties and potentially tailor it for specific applications.

Synthesis of Silver Nanoparticles, Study of Structure, Properties and Applications in the Treatment of Wounds

Silver nanoparticles are used in many areas of medicine as part of antibacterial and wound-healing ointments and preparations. Research objectives: study the synthesis of silver nanoparticles, structure, properties and applications in the treatment of burn wounds. The synthesis of silver nanoparticles was performed by chemical precipitation. As synthesized silver nanoparticles have a cubic crystalline shape; the average size of nanoparticles is 18 nm. No skin-irritating effect of medicinal cosmetic gel containing silver nanoparticles was detected.

Environmental-related applications of ZnO nanopowders: Photocatalytic activity and photoluminescence response to ethanol

Zinc oxide (ZnO) and copper-doped zinc oxide (ZnO:Cu) nanopowders were synthesized via solvothermal methods using methanol and hexamethylenetetramine (HMTA). Undoped ZnO nanopowders underwent calcination in O2-rich and H2-rich atmospheres at 600 °C. Samples were studied by scanning electron microscopy, Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), and Raman, photoluminescence (PL) and UV–vis absorbance spectroscopies. The doping and calcinations led to a reduction of the optical bandgap of the nanopowders, while their structure remained hexagonal wurtzite with some changes in lattice parameters and average nanoparticle sizes. The Cu2+ doping led to a BET surface area and violet PL component increase. Samples were also examined for environmental related applications, namely as photocatalyzers for dye degradation and as ethanol optical sensors. For photocatalytic activity in methylene blue degradation under UV, H2-rich calcined powders excelled, with a rate constant of −0.076 min−1, surpassing −0.057 min−1 (ZnO:Cu), −0.056 min−1 (O2-rich calcination), and −0.041 min−1 (as-grown ZnO). We propose that this improvement can be attributed to the formation of ZnO/Zn interfaces stemming from the reduction of surface interstitial zinc by H2 during calcination, in addition to the observed reduction of the ZnO bandgap. The doped nanopowders PL also showed excellent response when exposed to ethanol vapor.

Exploring Enhanced Hydrolytic Dehydrogenation of Ammonia Borane with Porous Graphene-Supported Platinum Catalysts.

Graphene is a good support for immobilizing catalysts, due to its large theoretical specific surface area and high electric conductivity. Solid chemical converted graphene, in a form with multiple layers, decreases the practical specific surface area. Building pores in graphene can increase specific surface area and provide anchor sites for catalysts. In this study, we have prepared porous graphene (PG) via the process of equilibrium precipitation followed by carbothermal reduction of ZnO. During the equilibrium precipitation process, hydrolyzed N,N-dimethylformamide sluggishly generates hydroxyl groups which transform Zn2+ into amorphous ZnO nanodots anchored on reduced graphene oxide. After carbothermal reduction of zinc oxide, micropores are formed in PG. When the Zn2+ feeding amount is 0.12 mmol, the average size of the Pt nanoparticles on PG in the catalyst is 7.25 nm. The resulting Pt/PG exhibited the highest turnover frequency of 511.6 min-1 for ammonia borane hydrolysis, which is 2.43 times that for Pt on graphene without the addition of Zn2+. Therefore, PG treated via equilibrium precipitation and subsequent carbothermal reduction can serve as an effective support for the catalytic hydrolysis of ammonia borane.

On the Structural and Molecular Properties of PEO and PEO-PPG Functionalized Chitosan Nanoparticles for Drug Delivery.

Chitosan nanoparticles (CS-NPs) are currently under investigation for a wide range of applications in nanomedicine. We investigated the structural, morphological, and molecular properties of CS-NPs synthesized via ionic gelation and designed specifically for drug delivery. The CS-NPs were prepared at concentrations ranging from 0.25 to 1.0% w/v. The 1.0% w/v CS-NPs were also functionalized with polyethylene oxide (PEO) alone and with a diblock copolymer of PEO and polypropylene glycol (PPG). The average nanoparticle size determined from TEM imaging is in the 11.3 to 14.8 nm range. The XRD and TEM analyses reveal a semi-crystalline structure with a degree of crystallinity dependent upon the nature of CS-NP functionalization. Functionalizing with PEO had no effect, whereas functionalizing with PEO-PPG resulted in a significant increase in the crystallinity of the 1.0% w/v CS-NPs. Additionally, the CS/TPP concentration (CS:TPP fixed at a 1:1 ratio) did not impact the degree of crystallinity of the CS-NPs. FTIR analysis confirmed the incorporation of TPP with CS and an increase in hydrogen bonding in more crystalline CS-NPs.

Selectivity control between reverse water-gas shift and fischer-tropsch synthesis in carbon-supported iron-based catalysts for CO2 hydrogenation

CO2 hydrogenation to chemicals and fuels has the potential to alleviate CO2 emissions and displace fossil resources simultaneously via consecutive RWGS and FTS reactions, also known as CO2-FTS. As Fe-based catalysts are active and selective for both reactions, their bifunctionality requires a delicate balance between the RWGS and FTS. In this work, we investigated the thermodynamic constraints of RWGS and CO2-FTS, the influence of CO2 conversion on selectivity and the influence of Fe nanoparticle size within the range of 4.7 to 10.3 nm. An inert carbon support was selected to rule out metal-support interaction and promoting effects of the support. Catalytic performance was evaluated at 300 °C, 11 bar, H2/CO2/Ar = 3/1/1, 600 to 72000 mL·gcat-1·h-1. At a CO2 conversion level below RWGS equilibrium conversion of 23 %, RWGS was found to be the primary and dominant reaction. No primary Sabatier reaction was observed. At higher CO2 conversion till the CO2-FTS threshold of 42 %, the secondary FTS reaction became dominant. Notably, a non-linear relation between CO2 conversion and CO selectivity was discovered. Comparing two catalysts with identical 5 wt% Fe loading but different average Fe nanoparticle size (6.6 and 8.4 nm), the 8.4 nm Fe catalyst was at least two times more active than the 6.6 nm Fe catalyst. In situ Mössbauer spectroscopy suggested a positive correlation between particle size, carburization and selectivity towards long-chain hydrocarbons. For these potassium-promoted carbon-supported Fe-based catalysts, nanoparticles of at least 8 nm are required for the formation of Fe carbides and improved reactivity.

Cu-doped LaFe1-xCuxO3 perovskites nano-crystallites for enhanced VOCs detection

Highly sensitive, and versatile metal oxide semiconductors, including perovskites, are used in gas sensors for environmental, and safety applications. This study described the substitution of Cu for Fe in LaFe1-xCuxO3 nanostructured perovskites, denoted as Cx’s, using Pechini sol-gel method at 600 °C, to detect the volatile organic compounds (VOCs). Characterization techniques, including TGA/DTA, XRD, BET, FE-SEM/EDS, Raman, PL, XPS, UV-DRS, FTIR, TPD-O2 and ethanol chemisorption showed significant enhancements in physicochemical, and gas sensing properties of LaFeO3 perovskites, upon copper doping in its structure. The responses to ethanol improved, the average crystallite and nanoparticle sizes decreased, and the electrical conductivity increased as the perovskite copper content increased to x = 0.6. The crystallite size of 20.5 nm for LaFeO3 decreased to 12.7 nm for LaFe0.4Cu0.6O3. The SC0.6 thick film gas sensor showed high potential in the VOCs detection, with best responses of 17 for ethanol, 18 for acetone, and 16 for acetaldehyde when exposed to each of 300 ppm at 300 °C. At these conditions, the response and recovery times of highly stable SC0.6 sensor for ethanol gas were 4 and 11 min, respectively.

Comparing silver and gold nanoislands’ surface plasmon resonance for bisacodyl and its metabolite quantification in human plasma

Gold and silver nanoparticles have witnessed increased scientific interest due to their colourful colloidal solutions and exceptional applications. Comparing the localized surface plasmon resonance (LSPR) of gold and silver nanoparticles is crucial for understanding and optimizing their optical properties. This comparison informs the design of highly sensitive plasmonic sensors, aids in selecting the most suitable nanoparticles for applications like surface-enhanced infrared spectroscopy (SEIRA) and biomedical imaging, and guides the choice between gold and silver nanoparticles based on their catalytic and photothermal properties. Ultimately, the study of LSPR facilitates the tailored use of these nanoparticles in diverse scientific and technological applications. Two SEIRA methods combined with partial least squares regression (PLSR) chemometric tools were developed. This development is based on the synthesis of homogeneous, high-dense deposited metal nanoparticle islands over the surface of glass substrates to be used as lab-on-chip SEIRA sensors for the determination of bisacodyl (BIS) and its active metabolite in plasma. SEM micrographs revealed the formation of metallic islands of colloidal citrate-capped gold and silver nanoparticles of average sizes of 29.7 and 15 nm, respectively. BIS and its active metabolite were placed on the nanoparticles’ coated substrates to be directly measured, then PLSR chemometric modelling was used for the quantitative determinations. Plasmonic citrate-capped gold nanoparticle substrates showed better performance than those prepared using citrate-capped silver nanoparticles in terms of preparation time, enhancement factor, PLSR model prediction, and quantitative results. This study offers a way to determine BIS and its active metabolite in the concentration range 15–240 ng/mL in human plasma using inexpensive disposable glass-coated substrates that can be prepared in 1 h to get results in seconds with good recovery between 98.77 and 100.64%. The sensors provided fast, simple, selective, molecular-specific and inexpensive procedures to determine molecules in their pure form and biological fluid.