Metal Oxide ZnO Research Articles

Investigation of the microstructural, surface, and optical properties of WO3-doped ZnO thin films

The paper investigates the microstructural characteristics, surface features, and optical properties of WO3-doped ZnO thin film. The deposited samples exhibit polycrystalline characteristics, with reflections corresponding to bimetal oxides and metals. Specifically, ZnO shows (101) and (200) reflections, while (400) reflections are observed in the WO3 phase of the deposited sample. The crystallite sizes of the ZnO metal oxide phase in the film are 85 nm and 55 nm, while the crystallite size of the Zn nanoparticles is found to be 47 nm. The atomic concentrations of W and Zn are 53.4 % and 46.6 % for films deposited on uncoated glass, and 41.2 % and 58.8 %, for films deposited onto ITO-coated glass, respectively. An optical band gap value of 3.40 eV was obtained for both films. It was found that certain properties remain relatively unchanged despite variations in the substrate.

Dual Eu3+ and Er3+ doping in ZnO nanoporous 2D frameworks for tuning photocatalytic activity, linear and non-linear optical response

Recent days, the greater attention of research materials are focusing on the porous nano frame structure due to their distinctive properties and high photocatalytic activity. The porous defective materials revealed a significant role in numerous research fields like sensors, catalysts, energy production, magnetic memory storage, bio medical etc. In our work, pure ZnO and 4f shell shielded rare earth metals doped ZnO metal oxide nanomaterials attributed in the photocatalytic dye degradation, non-linear optical and magnetic properties. We were synthesized pure ZnO and ZnO0.1–2xEuxErxHMT0.1–2x (2x = 0.025,0.05,0.075, 0.010 wt%) nanoparticles using a straightforward hydrothermal route. The hexagonal wurtzite structure of ZnO and Eu:Er-doped ZnO (Eu:Er@ZnO) exhibited by PXRD, and the optical bandgap (Eg) range from 3.14 eV to 3.18 eV was determined by Tauc relation (αhγ)2 = 0. The porous nanoplate morphology of as-synthesized materials revealed by HR-SEM and HR-TEM techniques. All synthesized materials exposed weak ferromagnetic property nature by VSM studies. Among all the synthesized materials, the 0.0025 wt% Eu:Er@ZnO nanoparticles exhibited porous nanoplate structures capable of catalyzing the breakdown of reactive black 5 (RB5) dye, achieving a photocatalytic activity of 93.2 % after 65 min of UV light exposure. The dopant concentration significantly influenced this photocatalytic activity, with lower concentrations showing enhanced performance, particularly in acidic conditions. Moreover, all synthesized porous nano-plate materials followed pseudo-first-order kinetics. Additionally, the Z-scan technique was employed to assess the nonlinear optical properties of the synthesized materials using Q-switched nanosecond Nd laser pulses at 532 nm wavelength. The open-aperture Z-scan revealed reverse saturable absorption (RSA) in all samples. The Eu:Er@ZnO porous nano-plates exhibited promising nonlinear absorption characteristics, with a higher nonlinear absorption coefficient ranging from 5.21 to 7.84 × 10−11 m/W and a lower optical limiting threshold between 0.87 and 0.95 × 1012 W/m2.

Efficient elimination of organic contaminants via a non-radical pathway involving activation of sulfite by synergistic adsorption-catalysis bifunctional chitosan-modified MOF derivative

Usually, Metal-based sulfite activation systems follow a radical generation pathway but are rare in non-radical pathways. Singlet oxygen (1O2) generation-targeted catalyst was synthesized by introducing non-redox metal oxides ZnO into chitosan-modified cobalt-zinc bimetallic oxides (CZ1.0C) via template method. Compared with Co3O4, the catalyst CZ1.0C coupled to the sulfite system (CZ1.0C/SO32-) maintained good adaptability in a common water background and a wide pH range (7–11). In addition, the CZ1.0C/SO32- system showed high efficiency in the degradation of Congo red (kobs = 0.190 min−1) and 100 % sulfite utilization. EPR, probe experiments, and DFT calculations proved the dominant role of 1O2, with a concentration three orders of magnitude higher than that of radicals. The controlled generation of non-radicals was achieved owing to the doping of ZnO and the conversion of lattice oxygen and oxygen vacancies. The catalytic oxidation intermediate HSO5- has also been demonstrated in the system, which achieves non-radical pathway oxidation through electron-mediated interactions. This article aims to develop a new “waste control by waste” strategy, which combines high selective adsorption and catalysis to achieve sulfur resource recovery and water pollutants elimination.

Hyaluronic acid mediated ZnO-NPs: In relation to electrical and photocatalytic activity for dye degradation

Various processes have been implemented to purify water; however, photocatalysis is comprehensively utilized in wastewater treatment and plays a significant role in water remediation. A photocatalyst is a nanostructured metal oxide ZnO nanoparticles, which boosts the reaction rate by its existence. ZnO nanoparticles show great performance in the absorption of various organic pollutants from wastewater. The objective of this research was to enhance the photocatalytic degradation performance of HA-added ZnO NPs using methylene blue as a model wastewater. Adjusting the main physical properties and photocatalytic efficiency of ZnO-NPs was performed using hyaluronic acid (HA), a natural bioactive stabilizer. The characterization of the fabricated ZnO-NPs samples with and without HA involved the utilization of FE-SEM, AFM, XRD, FTIR, PL, and I-V. As demonstrated by the FE-SEM analysis, ZnO formed rod-like structures, 3.0 % HA:ZnO exhibited cauliflower-like structures, and 5.0 % HA:ZnO displayed honeycomb-like structures. The X-ray diffraction (XRD) analysis demonstrated that the HA:ZnO nanoparticles exhibited hexagonal wurtzite structures. The average crystallite sizes of the ZnO, 3.0 % HA:ZnO, and 5.0 % HA:ZnO NPs were determined to be 25.20, 27.30, and 20.20 nm, respectively, using the XRD patterns. The surface area was 4.439, 2.987, and 5.204 m²/g of bare ZnO, 3.0 % HA:ZnO, and 5.0 % HA:ZnO-NPs were 4.439, 2.987, and 5.204 m2/g, respectively. It is very likely that there are two different decay and/or capture mechanisms in the emission spectra because the TRPL decay profile behaves in a double-exponential way. The fast decay time constant (τ1) was 212 ps for bare ZnO and 3.0 % HA:ZnO NPs and 231 ps for 5.0 % HA:ZnO NPs. The slow decay time constant (τ2) has a similar pattern, with values of 3.716, 2.836, and 2.984 ns. The specific contact resistance values of the ZnO NPs increased from 0.113 to 45.624 ( × 105 Ω cm2) as a function of the HA concentration, as evidenced by the results of the electrical studies. The outcomes of this research present comprehensive information on noble-modified ZnO-NP materials containing HA for direct applications in electronic materials and photocatalytic degradation of organic waste in water.

RF sputtered metal oxide layers as ARCs to improve photovoltaic performance of commercial monocrystalline solar cell

The rf-sputtered ZnO, MgO and Al2O3 transition metal oxide nano layers were developed as efficient antireflection coatings (ARCs) on commercial monocrystalline silicon (m-Si) photovoltaic cells. Wavelength dependence reflectance measurements show minimal reflectance (i.e., ∼1.3–2.0%) between 350 and 800 nm wavelength regions affirming antireflection behavior of oxide layers. The phase formation studies of these oxide layers display the crystalline phase however the presence of non-crystalline phase is noted in Al2O3 diffractogram pattern. Cross section microstructure characterization carried out using scanning electron microscopy (SEM) to know the ARC layer thickness illustrates MgO, ZnO and Al2O3 layers with coating thickness around 85 nm, 87 nm and 77 nm respectively. Also, the thickness of antireflection coatings computed using wavelength dependent refractive index measurement is consistent with cross section microstructure images. Photon to energy conversion (PEC) of ARC coated device under 1 sun condition display 1.99%, 1.07% and 0.39% improvement in efficiencies compared with commercial m-Si-solar cell endorsing suitability of selected transition metal oxides as efficient ARC materials. The external quantum efficiency (EQE) measurements show notable improvement in efficiency for MgO, ZnO and Al2O3 coated devices reaffirming their usability as efficient ARC materials on commercial m-Si-solar cells.

Influence of metal oxides on circumcorannulene for the design of new push-pull corannulene models: applications in nano-electronics, optoelectronics and non-linear optics

ABSTRACT The search for new high-performance push-pull materials for use in nonlinear optics (NLO) and optics is currently a popular area of research. In this study, the effects of metal oxides -(MO) n = 1,2 (monomer: MO=TiO2, CuO, Al2O3, and ZnO; and dimer: MO = Ti2O4, Cu2O2, Al4O6, and Zn2O2) on the electronic, absorption, optoelectronic and NLO characteristics of circumcorannulene (CO) in the gas phase and in acetonitrile have been investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at the B3LYP and CAM-B3LYP/6-311+G(d,p)/LANL2DZ levels of theory. Research has shown that adding metal oxides to CO leads to the formation of new push-pull CO derivatives. These derivatives include T1, U1, A1, Z1, T2, U2, A2, and Z2 formed from TiO2, CuO, Al2O3, ZnO, Ti2O4, Cu2O2, Al4O6, and Zn2O2 metal oxides, respectively. They exhibit excellent stability, low |HOMO-LUMO| gap energy, high NLO, and photocurrent responses compared to CO in gaseous media and polar solvents. However, it is interesting to note that the use of the copper oxide monomer configuration on corannulene family compounds is effective in improving their NLO response, while increasing the alumina chain proves necessary to improve their photocurrent response in the visible region.

Efficient adsorption‐photocatalysis activity of ternary ZnO‐Sm2O3‐MgO co‐modified biochar for dye removal

To boost the adsorption‐photocatalytic performances of biochar in wastewater treatment, biochar was modified with ternary metal oxides ZnO, Sm2O3, and MgO (ZnSm/Mg‐biochar) via the one‐step pyrolysis method. The optimal 2b‐ZnSm/Mg‐biochar with a Zn/Sm molar ratio of 1:1 exhibited the better removal activity of RhB in comparison with biochar, 2‐Mg/biochar, and b‐ZnSm/biochar. The removal efficiency and adsorption capacity of 2b‐ZnSm/Mg‐biochar was 99.46% and 979.22 mg g−1 for RhB solution of 410 mg g−1, respectively. The adsorption kinetics and isotherms of ZnSm/Mg‐biochar composites were as described by second‐order and Langmuir models, respectively. The abundant vacant sites at the junction interface of ZnO, Sm2O3, MgO, and biochar were favorable for the adsorption and photon capturing, achieving the efficient photo‐conversion of RhB under the stimulated solar‐light irradiation.

Metal oxide nanocrystals embedded polypyrrole nanohybrid: Exploring role of interface in photocatalytic hydrogen generation

Photocatalytic water splitting is considered as a sustainable way to produce hydrogen in the water−based energy cycle. Inorganic semiconductors, specifically metal oxides are extensively used as efficient photocatalysts, however, intrinsically poor charge-transfer and wide band gap with lower negative conduction band potential than the hydrogen evolution potential affect the water-splitting efficiency. In view of superior charge-transfer, and tunable energy levels, polymer-based nanohybrids (NHs) have been fabricated using polypyrrole (PPy) nanofibers with a series of transition metal oxides (MO) nanoparticles, namely TiO2, ZnO, CeO2, Fe2O3, NiO, and SnO2. A series of photoanodes have been tested for photoelectrochemical water splitting to elucidate the effect of interfacial charge transfer at the interfaces of NHs. The high photocurrent response of 44 μA cm−2 at 0.9 V vs. Ag/AgCl has been achieved for Fe2O3/PPy. While, ZnO/PPy NHs demonstrated a superior photocatalytic H2 generation rate of ∼162 mmol/g/h, which is ∼27 times higher than pure PPy. Based on energy level calculation, the charge transfer mechanism occurs through p−n junction in TiO2/PPy and SnO2/PPy NHs while the other NHs structures follow a Z−Scheme of charge transfer pathway. This finding opens an avenue for designing highly efficient polymer-metal oxide heterojunctions for water splitting and solar fuel applications.

Exceptional tribo-catalytic degradation of concentrated methyl orange and methylene blue solutions by DXN-RT30 TiO2 nanoparticles

As tribo-catalysis gains increasing attention to harness mechanical energy for environmental remediation, it is time to explore its application to those organic pollutants that have been challenging to degrade. In this study, four commercial metal oxide nanoparticles, BaTiO3, ZnO, P25 TiO2, and DXN-RT30 TiO2 nanoparticles, were stimulated through magnetic stirring to degrade 20 mg/L methyl orange (MO) and 30 mg/L methylene blue (MB) solutions. While all the other nanoparticles showed rather poor performance, DXN-RT30 TiO2 nanoparticles performed exceptionally well: With Teflon magnetic disks rotating at 400 rpm, 98.2% of MO and 100% of MB were degraded within 330 and 420 min, respectively. DXN-RT30 TiO2 nanoparticles demonstrated a unique absorption for MB molecules, yielding significantly different outcomes in active species trapping experiments between degradation of MO and MB solutions by DXN-RT30 TiO2. Complemented by electron paramagnetic resonance analysis, our findings suggest that for DXN-RT30 TiO2 nanoparticles under magnetic stirring, MO molecules are degraded by h+, ·OH, and e− in solution, while MB molecules are absorbed and degraded via h+ and e− on the surface of DXN-RT30 TiO2 nanoparticles. This study identifies DXN-RT30 TiO2 nanoparticles as a cost-effective, high-performance, and environmentally friendly tribo-catalyst for environmental remediation, stimulating further exploration for more excellent tribo-catalysts.

The Comparison of Titanium Dioxide and Zinc Oxide Used in Sunscreen Based on Their Enhanced Absorption

Nanomaterials have become increasingly popular in the cosmetic industry, especially in sunscreen production. These tiny particles can improve the performance of sunscreen products by enhancing their capacity to reflect and absorb ultraviolet (UV) radiation. This paper introduces two typical metal oxide nanoparticles (NPs), TiO2 NPs and ZnO NPs, in sunscreen and cosmetic products. Because of their propensity to absorb and deflect harmful UV radiation, they are frequently utilised. However, there is rising worry regarding the safe use of nanoparticles in these products especially the potential negative impact on human health. Moreover, the environmental risks associated with them, particularly in terms of their enhanced absorption properties also make their use an ongoing debate. In fact, studies have suggested that while they can result in more effective sun protection, they may also lead to unintended consequences. This paper also compares their sun protection effects, environmental impacts and health risks. It is crucial for customers to weigh the benefits and risks of nanomaterials in cosmetics and for both manufacturers and governments to adopt appropriate and detailed measures to ensure their safe and responsible use.

A theoretical analysis of performance enhancement of SPR sensor based on ZnO and BaTiO3 for NH3 detection

Surface plasmon resonance (SPR) sensors have attracted enormous attention due to their applications in various fields. A novel SPR-based sensor with ZnO and BaTiO3 metal oxide layers is designed for NH3 gas detection. Gold and silver are used as plasmonic materials and corresponding results are compared. The prism and plasmonic materials effects on sensor response are investigated. Moreover, thicknesses of gold and silver and metal oxide layers are optimized to obtain suitable performance parameters. sensor response is analyzed in terms of minimum reflectance, sensitivity, detection accuracy and quality parameter. Applying ZnO and BaTiO3 layers lead to 37.88% and 26.03% enhancement of quality parameter and 37.91% and 26.07% improvement of detection accuracy, and more than 3.4 times improvement of detection resolution in gold and silver-based sensors, respectively. The recommended sensor structure provides appropriate performance parameters for 1 to 200 ppm of NH3 gas that can have potential applications in toxic gas sensing.

Chitosan-ZnO Composite for Removal of Methylene Blue

This study aims to determine the effectiveness and increase in absorption of the chitosan-ZnO composite in the process of removing methylene blue when using the photodegradation method with the help of a UV lamp. Chitosan was synthesized from shrimp shell waste composite with metal oxide ZnO. The results of the characterization using XRD obtained the diffraction peak for chitosan at an angle of 2θ, namely 19.85°; 29.43°; 34.76° and chitosan-ZnO composite at an angle of 20.18°; 28.93°; 33.57°. The SEM-EDX characterization shows that chitosan-ZnO has small, light-colored grains and more gaps and contains elements of chitosan and Zn. In the FTIR characterization, there was a decrease in intensity at a peak of around 3360 cm1 which was caused by the chitosan-ZnO composite producing OH groups which reacted with methylene blue dye. In testing the effect of contact time using a UV lamp, there was an increase in the percentage of degraded methylene blue compared to without using a UV lamp. The maximum contact time is obtained at 60 minutes. While testing the effect of methylene blue dye concentration, the maximum absorption concentration was 45 ppm at 60 minutes of contact time. The adsorption capacity of the composite against methylene blue dye without UV light was 18.91 mg/g while using a UV lamp it increased to 20.145 mg/g. Based on this research, the chitosan/ZnO composite can be used quite well as a methylene blue dye remover.

Studies on properties of green synthesised CuO/ZnO nano particle/nano rod composites in PVA matrix

In this research article, we have investigated the structural, microstructural, optical and electrical properties of CuO/ZnO nanoparticle/nanorod composites in PVA matrix using a facile two-step method via the sol-gel technique. In this report, we have synthesized four samples as: (i) pure PVA (ii) CuO/PVA (iii) ZnO/PVA and CuO/ZnO/PVA. The structural properties of all the samples have been understood by carrying out X-ray diffraction measurements, which confirm the crystalline properties of CuO, ZnO metal oxides in PVA matrix. The microstructural properties of all the samples have been analyzed by Field Emission Scanning Electron Microscopy (FESEM) and Elemental Compositions in the samples have been identified by Energy Dispersive X-ray analysis (EDAX). The optical properties of all the samples have been analyzed using UV–visible spectroscopy. The electrical properties, such as dielectric behavior, AC conductivity and impedance behavior of all the samples have been characterized by an LCR meter at room temperature.

Picosecond Pulsed Laser Deposition of Metals and Metal Oxides.

In this work, we present the fabrication of thin films/nanostructures of metals and metal oxides using picosecond laser ablation. Two sets of experiments were performed: the depositions were carried out in vacuum and in air at atmospheric pressure. The subjects of investigation were the noble metals Au and Pt and the metal oxides ZnO and TiO2. We studied and compared the phase composition, microstructure, morphology, and physicochemical state of the as-deposited samples' surfaces in vacuum and in air. It was found that picosecond laser ablation performed in vacuum led to the fabrication of thin films with embedded and differently sized nanoparticles. The implementation of the same process in air at atmospheric pressure resulted in the fabrication of porous nanostructures composed of nanoparticles. The ablation of pure Pt metal in air led to the production of nanoparticles with an oxide shell. In addition, more defects were formed on the metal oxide surface when the samples were deposited in vacuum. Furthermore, the laser ablation process of pure Au metal in a picosecond regime in vacuum and in air was theoretically investigated using molecular dynamics simulation.

Effect of sintering temperature on the structural, morphological and humidity sensing properties of ZnO nanostructure

ZnO metal oxide powder was prepared using co-precipitation method and the effect of sintering temperature was studied. Powder X-ray diffraction (PXRD) technique has been used to investigate the crystal structure and phase analysis. The wurtzite hexagonal crystal structure of the ZnO powder has been clearly seen in the PXRD pattern. Using the Scherer’s formula, the average crystallite size of ZnO powder was determined to be between 27 and 37 nm. The surface has grown spherical nanoparticles with size varying from ~100 nm to ~200 nm, as shown in the scanning electron microscopy (SEM) photograph.

Synthesis, structural, photoluminescence, ultraviolet blocking and antibacterial performances of Ba-doped ZnO nanostructures

In the current experimental work, pure ZnO and Ba-doped ZnO nanorods have been prepared by implementing a facile wet chemical technique. XRD study reveals the formation of the hexagonal wurtzite phase of pure ZnO and Ba-doped ZnO nanorods. Interestingly, Ba-doped ZnO nanorods show very good absorption in the UVA (93% at 351 nm), UVB (90% at 300 nm) and UVC (61% at 220 nm) regions. The obtained results of the UV–visible absorbance study validate in such a way that the Ba-doped ZnO nanorods could be a better bet to be utilized as a UV blocker for the next generation of UV shielding materials. The Photoluminescence spectrum of Ba-doped ZnO nanoparticles reveals widespread UV–Visible bands between 350 and 600 nm. Also, the zone of inhibition is found to be 15 nm for both bacterial strains S.aures and E.coli and implies excellent antibacterial activity. Interestingly, the outcome as observed in the zone of inhibition towards S. aureus and E. coli in the present study is found to be higher than many doped ZnO and Ba-doped metal oxide nanostructures. The observed experimental results via the aforementioned characterizations imply that the synthesized samples possess the potential ingredients required for the applications related to the field of health care.

Enhanced Performance of CsPbIBr2 Perovskite Solar Cell by Modified Zinc Oxide Nanorods Array with [6,6]-Phenyl C61 Butyric Acid.

Although Metal oxide ZnO is widely used as electron transport layers in all-inorganic PSCs due to high electron mobility, high transmittance, and simple preparation processing, the surface defects of ZnO suppress the quality of perovskite film and inhibit the solar cells' performance. In this work, [6,6]-Phenyl C61 butyric acid (PCBA) modified zinc oxide nanorods (ZnO NRs) is employed as electron transport layer in perovskite solar cells. The resulting perovskite film coated on the zinc oxide nanorods has better crystallinity and uniformity, facilitating charge carrier transportation, reducing recombination losses, and ultimately improving the cells' performance. The perovskite solar cell with the device configuration of ITO/ZnO nanorods/PCBA/CsPbIBr2 /Spiro-OMeTAD/Au delivers a high short circuit current density of 11.83 mA cm-2 and power conversion efficiency of 12.05 %.

Construction of ternary heterostructured Ag/Ag2O@ZnO@g-C3N4 nanocomposite as an widened visible light photocatalyst for the organic oxidation

Two dimension g-C3N4 was synthesized by thermal polymerization using mixture urea and melamine. The metal oxide Ag2O and ZnO were loaded to nanolayer of g-C3N4. The composites Ag/Ag2O@ZnO@g-C3N4 were constructed by Ag2O and ZnO which were defined for p-type and n-type semiconductor to form heterojunctions. The samples were characterized by X ray diffraction(XRD), transmission electron microscopy(TEM), X ray photoelectron spectroscopy (XPS) and UV/Vis diffuse reflectance spectroscopy (UV–vis DRS). The experiment results indicate that Ag2O and ZnO were uniformly loaded to nanolayer of g-C3N4 and heterojunction of Ag/Ag2O@ZnO@g-C3N4 was constructed. The photocatalytic activity of Ag/Ag2O@ZnO@g-C3N4 was characterized by degradation of methylene blue (MB) under the widened visible light-driven. The photodegradation efficiency of MB was 64.486%, 87.724%, 91.611%, 96.700% and 99.999% over g-C3N4, ZnO@g-C3N4, Ag/Ag2O@g-C3N4, Ag/Ag2O@ZnO@g-C3N4-1 and Ag/Ag2O@ZnO@g-C3N4-2, respectively. The results show that the photocatalytic activity of Ag/Ag2O@ZnO@g-C3N4 was enhanced based on the p-n structure which decreased the recombination rates of photoinduced electron hole between metal oxide and g-C3N4. Finally, photocatalytic mechanism of Ag/Ag2O@ZnO@g-C3N4 was discussed for ternary heterostructured catalysts.

ZnO metal oxide nanoparticle as biological tool

Abstract Inorganic metal oxide ZnO in the form of nano particles can change the way diseases are diagnosed and treated. ZnO Nps are selective in targeting cancer cells and due to its nano size can enter into cells and destroy it. Drugs, fluorescent agents (for imaging), targeting agents (to target diseased cells only) etc. be loaded on ZnO Nps to deliver drugs selectively in a controlled manner to specific site. ZnO Nps is non toxic as declared by medical community and hence can replace the inaccuracy and harmful side effects of conventional medicine in bulk form. In this review we have discussed about the preparation and characterization of ZnO Nps. Later part concentrated on applications in various fields including biomedical field.

Nanometer-Thick Carbon Coatings with Covalent Chemical Functionalization of Metal Oxide Nanoparticles for Environmental and Biological Applications

Metal oxide nanoparticles have many useful applications in environmental studies, as tracking agents in life sciences, and in nutrient delivery for nano-enhanced agriculture. A key challenge in controlling the behavior of metal oxide nanoparticles in aqueous media is that molecular ligands are unstable with respect to hydrolytic cleavage from the surfaces. This instability limits the practical application of metal oxide nanoparticles in aqueous media. We have developed a method for producing nanometer-thin carbon shells on the surface of Al2O3, Cr3+:Al2O3 (nanoruby), ZnO, and Fe3O4 (magnetite) metal oxides that provides a scaffold for subsequent covalent chemical functionalization. Fluorescence measurements using carbonized Cr3+:Al2O3 (nanoruby) confirm that these thin carbon coatings have relatively little impact on the optical properties, allowing bright emission with less than 50% decrease in fluorescence intensity compared to an identical nanoruby without carbon coating. We demonstrate the utility for functionalization by modifying C-coated Al2O3 with molecular ligands bearing positive and negative charges. This approach provides a pathway for functionalization of a broad range of metal oxide nanoparticles with molecular ligands that can confer specific molecular properties to the nanoparticle surfaces in aqueous media while taking advantage of the high strength and stability of C–C interfacial bonds between surface ligands and the carbon shell.