Surface Modification Of Zinc Oxide Nanoparticles Research Articles

Eco-friendly synthesis and surface modification of ZnO nanoparticles using Pueraria montana root extract: enhanced photocatalytic performance with trisodium pyrophosphate

ABSTRACT The synthesis of zinc oxide (ZnO) nanoparticles using Pueraria montana (kudzu) plant extracts highlights advancements in green nanotechnology. This study explores the use of Pueraria montana roots, rich in phytochemicals such as phenols, terpenoids and flavonoids, which serve as natural reducing and stabilizing agents for nanoparticle synthesis. The eco-friendly production and surface modification of ZnO nanoparticles were achieved using these plant extracts, enhancing their photocatalytic performance with trisodium pyrophosphate (TSPP).Characterization techniques, including XRD, TEM, and FE-SEM, confirmed the nanoparticles’ crystalline structure, with a BET surface area of 14.01 m²/g and a type II adsorption isotherm. The synthesized nanoparticles exhibited exceptional dye degradation capabilities, achieving 99.9% removal of malachite green (MG) and 97.78% for aniline blue (AB). Kinetic analysis revealed a steady-state rate constant (k) of 2 × 10⁻⁴ min⁻¹ for MG where as the response rate constant(k) for the photocatalytic degradation of AB using modified ZnO nanostructures was 3.0 × 10−3 min−1 allowing near-total dye removal within 600 minutes for MG and 350 min for AB . Adsorption studies were well described by Langmuir and Freundlich isotherms, indicating maximum adsorption capacities of 59.7 mg/g for MG and 61.2 mg/g for AB. Surface modification with TSPP improved charge carrier separation and enhanced the generation of reactive oxygen species under UV exposure, further increasing dye degradation efficiency.Statistical analysis indicated high reproducibility, with close mean adsorption values of 99.125 for MG and 97.3125 for AB, supported by small standard deviations. The findings affirm the potential of using Pueraria montana in synthesizing efficient photocatalysts, providing a sustainable and cost-effective approach for water treatment applications. Overall, this research underscores the effectiveness of plant-based materials in advancing eco-friendly nanotechnology solutions.

Biodegradable PLA-ZnO nanocomposite biomaterials with antibacterial properties, tissue engineering viability, and enhanced biocompatibility

Polylactic acid (PLA) is a well-known biomaterial on account of its biocompatibility and biodegradability. Zinc oxide (ZnO) nanofillers may endow PLA with advantageous antibacterial and tissue regenerative properties, but may also compromise the biocompatibility of PLA. Several strategies have been developed to improve the biomedical practicality of such composites. The importance of surface properties on amplifying the therapeutic properties and safety of a material enables two potential strategies: (i) surface modification of ZnO nanoparticles, and (ii) surface engineering of the PLA/ZnO composites. Moreover, the controllable biodegradation of PLA allows a third possible strategy: (iii) biodegradation-controlled release of ZnO. The first part of this review introduces the controllable degradation of PLA and the mechanisms of therapeutic properties and cytotoxicity of ZnO. Following this, the paper highlights current research trends regarding the biomedical application of PLA-based ZnO nanocomposites. The final section of this review discusses the potential use of ZnO in tuning the degradation rate of PLA, and the possibility of manipulating the surface properties of ZnO nanoparticles and PLA/ZnO composites in order to optimize the therapeutic properties and safe usage of PLA/ZnO composites in the biomedical field.

Fabrication of gum acacia protected zinc oxide nanoparticles for UV assisted photocatalysis of methyl green textile dye

In this communication, zinc oxide (ZnO) nanoparticles using zinc acetate as precursor, potassium hydroxide as reducing agent and natural polysaccharide (gum acacia) as capping agent is prepared to photocatalytically degrade methyl green textile dye. Surface modification of ZnO nanoparticles with gum acacia leads to change in morphology coupled with reduction in size from 31 to 16 nm. Gum acacia capped ZnO nanoparticles as photocatalyst shows greater efficiency (95%) of degrading methyl green than the bare ZnO nanoparticles (90%). Therefore, gum acacia capped zinc oxide nanoparticles could be used to treat various dye effluents from textile industries.

Surface modification of zinc oxide nanoparticles by vinyltriethoxy silane (VTES)

Zinc oxide (ZnO) nanoparticles are hydrophilic in nature and difficult to disperse in polymer matrix due to agglomeration behavior. To disperse the zinc oxide nanoparticles in polymer matrix, it is necessary to modify their surface with hydrophobic groups such as silanes or surfactants. In this article, zinc oxide nanoparticles were modified with various concentration of vinyl triethoxysilane (VTES). To investigate the effect of different concentrations of VTES, on surface modification of zinc oxide nanoparticles, these were characterized using physical characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), Energy Dispersive X-rays Spectroscopy (EDX), X-ray diffraction (XRD) and contact angle. The results of FTIR, TGA, SEM, EDX and contact angle confirm the surface modification of zinc oxide nanoparticles by VTES. The XRD results show that the crystalline behavior of ZnO nanoparticles was not changed after surface modification by VTES. The crystallite size of surface modified ZnO nanoparticles was calculated using Debye-Scherrer equation and it was found approx 20 nm. In FTIR results, some new peaks at 1409, 1014 and 970 cm−1 were observed as compare to unmodified zinc oxide nanoparticles. In contact angle analysis, it was observed that the surface modified zinc oxide nanoparticles have very high contact angle (greater than150°) in comparison with hydrophilic behavior of unmodified zinc oxide nanoparticles. SEM analysis also showed the improved dispersity of ZnO nanoparticles. Based on characterization results, it was observed that the 15 wt% VTES concentration is suitable to carry out surface modification of ZnO nanoparticles.

Impact of co-mixing technique and surface modification of ZnO nanoparticles using stearic acid on their dispersion into HDPE to produce HDPE/ZnO nanocomposites

In this article, the effectiveness of the co-mixing processing technique and surface modification of zinc oxide (ZnO) filler on the characteristics of the developed high-density polyethylene (HDPE)/ZnO was investigated. ZnO was treated and co-mixed with stearic acid (SA) at a ratio of 50/50 wt% using kitchen coffee grinder and the mixture was then added to the HDPE matrix in a Brabender plastograph with various ZnO contents of 0.5, 1 and 2 wt%. The morphology of the nanocomposites was characterized using scanning electron microscopy (SEM). The micrographs showed well and uniform dispersion of both treated and untreated ZnO nanofiller; however, the treated ZnO particles showed better dispersion. The nanocomposite containing 1 wt% ZnO nanoparticles was found to have the optimal properties. The results of the SEM were supported by the atomic force microscopic technique. The uniform dispersion of ZnO was further investigated through X-ray diffraction spectra. The minor peaks of ZnO in the HDPE/treated and untreated ZnO nanocomposites are considered as an evidence for the presence of uniform and well-dispersed ZnO. The electrical conductivity of the nanocomposite samples is higher than that of neat HDPE due to the semiconducting nature of ZnO and increases with ZnO content. The results of this work proved that dispersibility can be achieved through the addition of SA and conductivity of the nanocomposite depends on the ZnO content. Moreover, co-mixing technique and the surface modification of the nanofillers are very effective in producing the HDPE/ZnO nanocomposites that have many potential industrial applications such as food packaging, drug and pharmaceutical bottles.

Surface Modified Zinc Oxide Nanoparticles as Smart UV Sensors

The present paper examines the synthesis of ZnO nanoparticles and their surface modification via the microwave assisted sonochemical method along with its successful application in designing a smart UV sensor. The structure of the prepared samples was investigated using XRD, XPS and its respective crystallinity studies. The photoluminescence spectroscopy identified an increase in the green emission intensity due to surface modification which is attributed to the density of oxygen vacancies. The variation in the dielectric constant and dielectric loss values with surface modification is clearly substantiated. As a case study, it was observed a smart UV sensor fabricated using this surface modified ZnO response and decay time that are 14 s and 16 s, respectively. Also, the possibility of surface modification in tuning the sensing responses has been investigated in detail.

Core-Shell Nanostructured Mixed Ligand Directed ZnO Nanoparticles with Excellent Structural, Optical and Electronic Properties for Application in Light Emitting Devices

In the present study, three salicylaldehyde based surface directing agents (L1, L2, L3) were synthesized from the same amine, but different aldehydes using condensation reaction for their employment as capping layer. Surface decorated zinc oxide (ZnO) nanoparticles (N1, N2 and N3) were then synthesized by wet chemical precipitation. The optical studies of mixed ligand directed ZnO nanoparticles were carried out using ultraviolet-visible (UV-Vis) absorption spectroscopy and photoluminescence techniques. The capping with ligand resulted in the successful amendment of surface of ZnO nanoparticles as it reduced the surface defects and controlled the defect-related emissions. The photoluminescence studies of surface modified ZnO nanoparticles N1, N2 and N3 were further carried out to check their binding ability. N2 and N3 exhibited selective behavior towards Al(III) and Cu(II) respectively with change in the fluorescence emission profile; however, no such change was noticed for other metal ions. An increased fluorescence intensity together with narrow spectrum is observed in N2 with the addition of Al(III) ion. The surface modified ZnO nanoparticles demonstrated semiconducting behavior when incorporated in Light emitting diode (LED) structure with steady-state current densities of up to 1.9 A/cm2.

Exploiting in vitro potential and characterization of surface modified Zinc oxide nanoparticles of Isodon rugosus extract: Their clinical potential towards HepG2 cell line and human pathogenic bacteria.

Little is known about biogenically synthesized Zinc oxide nanoparticles (ZnONPs) from Isodon rugosus. Synthesis of metal oxide NPs from essential oil producing medicinal plants results in less harmful side effects to the human population as compared to chemically synthesized NPs. In this article, we report biogenic synthesis of ZnONPs from in vitro derived plantlets and thidiazuron (TDZ) induced callus culture of Isodon rugosus. Synthesized NPs were characterized using UV-spectra, XRD, FTIR, SEM and EDX. Furthermore, the NPs were evaluated for their potential cytotoxic (against HepG2 cell line) and antimicrobial (against drug resistant Staphylococcus epidermidis, Bacillus subtilis, Klebsiella pneumoniae and Pseudomonas aeruginosa) activities. Pure crystalline ZnONPs with hexagonal and triangular shapes were obtained as a result of callus extract (CE) and whole plant extract (WPE), respectively. ZnONPs showed potent cytotoxic and antimicrobial potential. The antimicrobial and cytotoxic activities of ZnONPs were found to be shape and surface bound phytochemicals dependent. CE mediated hexagonal ZnONPs showed superior anti-cancer and antimicrobial activities as compared to WPE mediated triangular shaped ZnONPs. It is concluded that biogenic ZnONPs have incredible potential as theranostic agents and can be adopted as useful drug delivery system in next generation treatment strategies.

Physicochemical characteristics and toxicity of surface-modified zinc oxide nanoparticles to freshwater and marine microalgae

Because of wide applications of surface-modified zinc oxide nanoparticles (ZnO-NPs) in commercial sunscreens and their easiness of being released into water, concerns have been raised over their potential effects on aquatic organisms. This study compared physicochemical properties of silane-coated and uncoated ZnO-NPs to elucidate their toxic potencies toward three freshwater and three marine microalgae. Surfaces of ZnO-NPs (20 nm) were modified by coating with 3-aminopropyltrimethoxysilane (A-ZnO-NPs) that provides the particles with a more hydrophilic surface, or dodecyltrichlorosilane (D-ZnO-NPs) that turns the particles to hydrophobic. Uncoated ZnO-NPs formed larger aggregates and released more Zn2+ than did either of the two coated ZnO-NPs. The three nanoparticles formed larger aggregates but released less Zn2+ at pH 8 than at pH 7. Although sensitivities varied among algal species, A-ZnO-NPs and uncoated ZnO-NPs were more potent at inhibiting growth of algal cells than were D-ZnO-NPs after 96-h exposure to ZnO, uncoated ZnO-NPs, each of the coated ZnO-NPs or ZnSO4 at 10 concentrations ranging from 0.1 to 100 mg/L. The marine diatom Thalassiosira pseudonana exposed to ZnO-NPs, A-ZnO-NPs or D-ZnO-NPs resulted in differential expressions of genes, suggesting that each of the coatings resulted in ZnO-NPs acting through different mechanisms of toxic action.

Surface modification of SiO2 coated ZnO nanoparticles for multifunctional cotton fabrics

A simple chemical synthetic route was designed to prepare zinc oxide nanoparticles (ZnO-NPs) by using sodium alginate as anti-agglomeration agent in the presence of sodium hydroxide as alkali. Next, surface modification of ZnO-NPs with SiO2 nanoparticles was achieved as per to sol-gel process. Further enhancing of the multifunctional properties of SiO2@ZnO-NPs was conducted successfully thanks to (aminopropyl)triethoxysilan (APTES) and vinyltriethoxysilan (VTES) which, in turns, increase the affinity of the SiO2@ZnO-NPs nanocomposite towards glycosidic chains of cotton fabrics. Thorough characterizations of synthesized ZnO-NPs, SiO2@ZnO-NPs, SiO2@ZnO-NPs/APTES and SiO2@ZnO-NPs/VTES were conducted by the making use of well advanced techniques such as FT-IR, XRD, TEM, DLS and SEM-EDX. The data obtained clarified the formation of an interfacial chemical bond between ZnO and SiO2 as affirmed by FT-IR and XRD analysis. In addition, the results revealed by TEM, zeta sizer and SEM-EDX techniques, declared that the amorphous layers of SiO2, APTES or VTES evenly coated the surface of ZnO-NPs. For these nanocomposites, the work was extended to render cotton fabrics multifunctional properties such as antibacterial and UV protection with high durability even after 20 washing cycles using pad dry cure method. Taking the advantages of the silane compounds terminated by active groups such as OH, NH2, etc., open the door for further functionalization of the cotton fabrics’ surfaces by durable multifunctional agents applied in various applications.

Preparation, structural characterization, and gas separation properties of functionalized zinc oxide particle filled poly(ether-amide) nanocomposite films

In this study, a new diacid monomer containing amide, imide, and sulfone functional groups was successfully used to synthesize a new poly(ether-amide) for membrane-based gas separation applications. The synthesized poly(ether-amide) was soluble in organic solvents, has high thermal stability (up to 460℃ under nitrogen atmosphere, for 10% weight loss), and high glass transition temperature (Tg = 274℃). This poly(ether-amide) was combined with different amounts of surface-modified zinc oxide nanoparticles to provide organic–inorganic nanocomposites. The optically transparent and flexible membranes of these hybrid nanocomposites were prepared. The obtained materials were characterized by Fourier transform-infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, X-ray powder diffraction, field emission-scanning electron microscopy, and transmission electron microscopy techniques. Transmission electron microscopy of the nanocomposite film with 15 wt% zinc oxide confirms that the nanoparticles are well dispersed in the polymer matrix. Thermal gravimetric analysis data indicated that the hybrid materials had better thermal behavior with increasing surface-modified zinc oxide nanoparticles nanoparticle content. The poly(ether-amide)/surface-modified zinc oxide nanoparticles nanocomposite film mechanical properties improved with increasing surface-modified zinc oxide nanoparticles content. The permeability and selectivity of the poly(ether-amide)/zinc oxide membranes as a function of the surface-modified zinc oxide nanoparticles weight percentage were studied, and the results indicated that the CO2 and CH4 permeability increased with increasing zinc oxide content. In general, the membranes prepared from these polymers showed very good permeability and permselectivity for a pair of gases.

Surface functionalized zinc oxide (ZnO) nanoparticle filled organic–inorganic hybrid materials with enhanced thermo-mechanical properties

Abstract The aim of this work is to use surface modified ZnO nanoparticles in combination with hyperbranched reactive polymer network to prepare moisture cure eco-friendly hybrid coatings and study their structure property relationship. The surface of the ZnO nanoparticles has been modified with silane coupling agent to get organo functional modified ZnO nanoparticles and were used for coatings formulation. The structure–properties of HBPUU (hyperbranched polyurethane urea)-modified nano ZnO hybrid materials were compared with HBPUU–nano-ZnO hybrid coatings. The viscoelastic, thermal and surface morphology of these coatings were characterized by Dynamic Mechanical and Thermal Analyzer (DMTA), Thermogravimetric Analyzer (TGA), Atomic Force Microscope (AFM), High Resolution Transmission Electron Microscopy (HR-TEM) and Contact Angle Instrument. TGA and DMTA data suggest higher thermal stability and glass transition temperature ( T g ) for the coatings prepared using modified nano ZnO (5%) as compared to nano ZnO (5%) hybrids. The contact angle data suggest better hydrophobic character of the hybrid coatings prepared using modified ZnO. The AFM result suggests that the surface roughness value of modified nano ZnO hybrid coatings is less when compared to their corresponding nano ZnO based hybrid coatings.

Zinc oxide nanoparticles with surface modified by degradation of capping polymers in situ during microwave synthesis

Surface modified zinc oxide nanoparticles with variable lipophilicity were prepared by the help of microwave-assisted solvothermal synthesis from mechano-chemically prepared precursor. Sodium carbonate and zinc acetate dihydrate were used as starting materials, diethylene glycol was used as a solvent, poly(ethylene glycol) and polyvinyl alcohol were used as surface capping agents. The zinc oxide was obtained during the first three minutes of reaction and its surface was further modified with prolonged time of the reaction due to degradation of polymers used as capping and stabilising agents. Scanning Electron Microscopy was employed for powder morphology evaluation. Inorganic phase structure development was characterized by means of X-ray diffraction. Nanostructured composite materials with crystallite size below 10nm were obtained with specific surface area varying from 35 to 86m2g−1 according to Brunauer–Emmett–Teller analysis. The progress of degradation of adsorbed polymer moieties was manifested by the powder colour change. Optical properties as well as the structure of materials were further analysed by Diffuse Reflectance Ultraviolet–visible Spectroscopy and Diffuse Reflectance Infrared Fourier Transform Spectroscopy and correlated with Thermogravimetric observations and Lipophilicity degree analysis.

Lack of genotoxic potential of ZnO nanoparticles in in vitro and in vivo tests

The industrial application of nanotechnology, particularly using zinc oxide (ZnO), has grown rapidly, including products such as cosmetics, food, rubber, paints, and plastics. However, despite increasing population exposure to ZnO, its potential genotoxicity remains controversial. The biological effects of nanoparticles depend on their physicochemical properties. Preparations with well-defined physico-chemical properties and standardized test methods are required for assessing the genotoxicity of nanoparticles. In this study, we have evaluated the genotoxicity of four kinds of ZnO nanoparticles: 20nm and 70nm size, positively or negatively charged. Four different genotoxicity tests (bacterial mutagenicity assay, in vitro chromosomal aberration test, in vivo comet assay, and in vivo micronucleus test, were conducted, following Organization for Economic Cooperation and Development (OECD) test guidelines with good laboratory practice (GLP) procedures. No statistically significant differences from the solvent controls were observed. These results suggest that surface-modified ZnO nanoparticles do not induce genotoxicity in in vitro or in vivo test systems.

Preparation of new polymer nanocomposites based on chiral poly(amide-imide)/surface-modified ZnO nanoparticles containing 4,4′-methylene bis(3-chloro-2,6-diethylaniline) linkages via ultrasonication-assisted process

In the present investigation, a novel chiral poly(amide-imide) (PAI) was synthesized via direct polycondensation reaction of chiral diacid monomer with 4,4′-methylene bis(3-chloro-2,6-diethylaniline) in molten tetrabutylammonium bromide as a green solvent. Then PAI-based bionanocomposites (BNC)s have been successfully prepared via ultrasonic irradiation method using zinc oxide (ZnO) nanoparticles functionalized by γ-aminopropyltriethoxysilane as a coupling agent to decrease aggregation of nanoparticles in polymer matrix. The physicochemical and morphology properties of the neat PAI and BNCs were studied using 1H-NMR, FT-IR spectroscopy, specific rotation, elemental analysis, X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). FT-IR and TEM depicted that the ZnO nanoparticles function as a physical cross-linking agent with PAI through hydrogen bonding between the OH on the ZnO nanoparticles and the C=O of the amide and imide groups. Also, TEM and FE-SEM images revealed that ZnO nanoparticles were dispersed in PAI matrix with particle size between 15 and 25 nm. Thermogravimetric analysis data showed an improvement of thermal stability of new BNCs in comparison with the pure PAI.

Study on constructional design and structural analysis of poly(amide-imide)/ZnO nanocomposites containing pyromellitoyl-bis-l-isoleucine moieties

Hybrid nanocomposites (NCs) produced by the dispersion of zinc oxide (ZnO) nanoparticles (NPs) in thermoplastic poly(amide-imide)s (PAIs) are designed and synthesized using ultrasonic-assisted technology. ZnO NPs were functionalized with 3-aminopropyltriethoxysilane (KH550) coupling agent to increase the hydrophobic nature of NPs. Reaction of diamine containing N-(4-hydroxyphenyl) benzamide and a diacid chloride comprising pyromellitoyl-bis-l-isoleucine segments at low temperature provided the polymeric matrix with well-designed groups. Surface treatments of ZnO NPs gave a better dispersion and enhancing possible interactions of NPs with functional units of polymer matrix. The surface-modified ZnO NPs were dispersed uniformly in the PAIs matrix using ultrasonic irradiation. The obtained NCs were characterized by Fourier-transform infrared spectroscopy, x-ray powder diffraction, atomic force microscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetry analysis. The FE-SEM and TEM pictures confirmed the globular-like structures for NCs.

Simultaneous synthesis of biodiesel and zinc oxide nanoparticles using supercritical methanol

Biodiesel and zinc oxide nanoparticles were synthesized simultaneously using supercritical methanol. Zinc nitrate was used as the source of zinc for the formation of the zinc oxide nanoparticles, which acted as a catalyst during the transesterification of rapeseed oil. In addition, the in situ formed zinc oxide nanoparticles led to a reduction in the reaction temperature and time. The fatty acid methyl ester (FAME) yields in the various biodiesels synthesized were determined using gas chromatography (GC). The zinc oxide nanoparticles formed were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The results of these analyses confirmed the formation of surface-modified zinc oxide nanoparticles of sizes smaller than those obtained using conventional techniques. This newly developed method provides an economical advantage since it results in the lowering of the operational temperature and the production of zinc oxide as an additional byproduct.

Synthesis, characterization and study of photocatalytic activity of surface modified ZnO nanoparticles by PEG capping

Nanoparticles of bare and PEG (Polyethylene glycol) capped zinc oxide (ZnO) were synthesized by precipitation method. The photocatalytic activity of bare and modified ZnO nanoparticles was studied by monitoring the degradation of Rhodamine B (RhB). The results show that PEG capped ZnO nanoparticles has reduced photocatalytic activity than the bare ZnO nanoparticles. The reduction in the chemical oxygen demand (COD) and total organic carbon (TOC) results also revealed the reduced photocatalytic activity of PEG capped ZnO. The UV-shielding property was evaluated by measuring the transmittance which shows that both bare and PEG capped ZnO nanoparticles possess good UV-shielding ability.

New surface-modified zinc oxide nanoparticles with aminotriethylene oxide chains linked by 1,2,3-triazole ring: Preparation, and visible light-emitting and noncytotoxic properties

Novel surface-modified, visible light-emitting and noncytotoxic ZnO nanoparticles (NPs) (ZPAZ) having aminotriethylene oxide chains linked by 1,4- and/or 1,5-disubstituted 1,2,3-triazole rings were prepared from ZnO NPs (ZPA) with ethynyl groups on the surfaces and an azide derivative of triethylene oxide chain linking terminal amino group (ATA) via 1,3-dipolar azide/alkyne click reaction by heating without Cu(I) catalyst. FTIR spectroscopy, elemental analysis, XRD analysis and TEM observation suggested that the resulting ZPA and ZPAZ NPs have the particle sizes below 10nm in diameters, triethylene oxide chains linking the terminal amino groups and wurtzite crystal structure. UV–vis absorption spectrum of the ZPAZ NPs in methanol showed maximum absorption band at 346.5nm, supporting the TEM observation. PL spectra depicted that the ZPA and ZPAZ NPs display broad light green and lightly greenish yellow visible light emitting bands in methanol. Zeta potentials measured in distilled water suggested that the ZPAZ NPs have a low tendency to aggregate and possess better stability than the ZPA NPs. Cytotoxicity assay revealed that the ZPAZ NPs, having water-dispersion properties, are noncytotoxic at low concentrations and almost all RAW264.7 cells are alive after 24h of treatment.

The interaction of carbon monoxide with clean and surface-modified zinc oxide nanoparticles: A UHV-FTIRS study

The interaction of CO with differently modified polycrystalline ZnO has been studied by FTIR spectroscopy under ultrahigh vacuum conditions (UHV-FTIRS). After exposing the clean, adsorbate-free ZnO nanoparticles to CO at 110 K we observe an intense vibrational band at 2187 cm −1 which is assigned to a majority of CO species bound to the Zn 2+ sites on the mixed-terminated ZnO( 1 0 1 ¯ 0 ) surface. After the exposure of CO 2-pretreated ZnO nanoparticles to CO at 110 K, a new CO band is observed at 2215 cm −1, which originates from CO species adsorbed on the “free” Zn sites embedded within the (2 × 1) tridentate carbonate structure on the ZnO( 1 0 1 ¯ 0 ) surface. UHV-FTIRS data recorded at different sample temperatures demonstrate that the binding energy of CO on polycrystalline ZnO is substantially increased in the presence of pre-adsorbed CO 2. The presence of hydroxyl species on the ZnO powder particles does not lead to substantial changes of the CO vibrational bands detected at 110 K under UHV conditions.