Use Of Surface Modification Research Articles

Thermally conductive, mechanically robust alumina-incorporated polyurethane films prepared by ultraviolet light curing

Abstract The development of heat dissipating composite materials for electronic systems can be expedited using alumina particles as modifiable polymer-matrix fillers. However, these composites are difficult to synthesize given the tradeoffs between thermal conductivity, insulating characteristics, and conduciveness to processing. To that end, the present study is focused on synthesizing environmentally friendly polyurethane films that could be cured by ultraviolet light within minutes, without requiring high-temperature heat treatment. Through the optimization of alumina modification, hybridization of thermally conductive fillers, filler content, and stirring time on the thermal conductivity of the polyurethane composites, this study improves the process for sustainability, low-cost, and convenient preparation. The experimental results confirmed that the use of surface modification and hybrid fillers is effective for enhancing the thermal conductivity, with the value of the polyurethane integrated with 50 wt% Al2O3 and 5 wt% Al2O3–poly (catechol/polyamine) being 76.40 wt% higher than that of pure PU (0.44 W/mK). Additionally, the use of hybrid fillers resulted in superior mechanical and thermal properties (such as tensile strain, tensile strength, thermal expansion coefficient, and temperature resistance) compared with those of pure PU and films incorporated with only a single filler.

Femtosecond laser induced porous surface on polymethyl methacrylate for filmwise condensation to improve solar still productivity

The decline in freshwater availability has spurred research into employing solar desalination technology. Recent research has concentrated on investigating the use of surface modification to improve the productivity of solar still for desalination. This paper presents the use of femtosecond laser texturing to induce a porous surface on the polymethyl methacrylate (PMMA) cover of a solar still for producing filmwise condensation. Vertical lines 2.5 mm wide were fabricated on the PMMA surface using ultrafast laser texturing, and experiments were conducted using the modified cover on a solar still at a constant basin water temperature. Results show that the static water contact angle measured on the cleaned laser textured surface is hydrophobic. However, the formation of the porous structure leads to a change in wetting state from Cassie-Baxter to Wenzel upon exposure to water vapour. This change in wetting state enables the formation of filmwise condensation under the continuous presence of water vapours. The solar still productivity improves by 15.4 % and 23.1 % using both cleaned and uncleaned laser textured surfaces respectively. The modified surface is stable upon repeated exposure to water vapour, thus proving to be an excellent surface modification method for enhancing PMMA covered solar still performance.

A Surface Modification Strategy Towards Reversible Na-ion Intercalation on Graphitic Carbon Using Fluorinated Few-Layer Graphene

Na-ion batteries (NIBs) are proposed as a promising candidate for beyond Li-ion chemistries, however, a key challenge associated with NIBs is the inability to achieve intercalation in graphite anodes. This phenomenon has been investigated and is believed to arise due to the thermodynamic instability of Na-intercalated graphite. We have recently demonstrated theoretical calculations showing it is possible to achieve thermodynamically stable Na-intercalated graphene structures with a fluorine surface modifier. Here, we present experimental evidence that Na+ intercalation is indeed possible in fluorinated few-layer graphene (F-FLG) structures using cyclic voltammetry (CV), ion-sensitive scanning electrochemical microscopy (SECM) and in situ Raman spectroscopy. SECM and Raman spectroscopy confirmed Na+ intercalation in F-FLG, while CV measurements allowed us to quantify Na-intercalated F-FLG stoichiometries around NaC14–18. These stoichiometries are higher than the previously reported values of NaC186 in graphite. Our experiments revealed that reversible Na+ ion intercalation also requires a pre-formed Li-based SEI in addition to the surface fluorination, thereby highlighting the critical role of SEI in controlling ion-transfer kinetics in alkali-ion batteries. In summary, our findings highlight the use of surface modification and careful study of electrode-electrolyte interfaces and interphases as an enabling strategy for NIBs.

Study of cytotoxic activity of Ti\u201313Nb\u201313Zr medical alloy with different surface finishing techniques

The characterization of materials surface is essential, as the initial in vivo response is highly dependent on surface properties. Surface topography is a key aspect that influences the response of cells to products resulting from interaction with the surface of a titanium alloy, including parameters such as adhesion, spread, migration, proliferation, and differentiation of cells. Various surface modifications are used to improve the interface properties between MC3T3 and NHDF cells and the Ti–13Nb–13Zr-based surface. Among the techniques discussed in this paper, scanning electron microscopy, laser confocal scanning microscopy, and computed tomography are adequate to investigate materials topography at different scale levels. Chemical characterization of the outer layers of Ti–13Nb–13Zr samples was performed with X-ray photoelectron spectrometry. Studies have shown that the surfaces resulting from the treatment enabling the formation of titanium oxide and zirconium oxide show the lowest cytotoxicity. Implants made from the new generation of titanium alloy, not containing toxic elements, with the use of surface modification could be an essential innovation in implantology.

Liposomes –A Overview

Liposomes are sphere-shaped vesicles made up of one or more bilayers of phospholipids. The ability of delayed vesicles to transport medications, vaccines, diagnostic specialists, and other bioactive operators has accelerated development in the liposomal drug delivery system. The liposomal delivery system's pharmacyelements and pharmacokinetics properties have been altered, resulting in a higher therapeutic index and lower overall toxicity. There are many factors to consider, including size, size distribution, surface electrical potential, lamella count, and encapsulation efficacy. The use of surface modification in the development of liposomes with various mechanisms, kinetic properties, and biodistribution was discovered to be beneficial. Drug delivery, drug targeting, controlled release, and improved solubility have all been studied extensively with liposomes.

Alumina and tricalcium phosphate added CoCr alloy for load-bearing implants.

Cobalt-chromium (CoCr) alloys are used in load-bearing implants due to their excellent wear resistance. However, poor tissue-material interactions can originate due to the release of wear and corrosion-induced Co and Cr ions, motivating the use of surface modification to reduce such phenomena. Premixed feedstock powders of CoCrMo + 2 wt.% tricalcium phosphate (TCP, CoCrTCP) and CoCrMo + 2 wt.% tricalcium phosphate + 4 wt.% Al2O3 (CoCrTCP+Al) were used to surface coat CoCr alloy via Laser Engineered Net Shaping (LENS™) with the objective of increasing CoCr alloy's wear resistance. Electron micrographs of the microstructure revealed the dissociation of intergranular globular carbide phases and reprecipitation into a finer network-like microstructure with homogeneous distribution of Co and Cr. X-ray diffraction (XRD) spectra revealed texturing or preferential crystallographic orientation amongst the LENS™ processed materials, with the TCP added CoCr displaying some ε-phase stabilization. Tribological testing resulted in an 82.3% and 71.6% decrease in wear rate and wear coefficient, respectively, for CoCrTCP when compared to commercially available CoCr alloy. Additionally, in situ tribofilm development was observed for the fabricated samples via an increase in contact resistance. The current study resulted in not only a decrease in wear volume but also a decrease in the overall degradation of the coated CoCr alloy.

Non-enthalpic enhancement of spatial distribution and orientation of CNTs and GNRs in polymer nanofibers

Multi-wall carbon nanotubes (CNTs) and their unzipped counterparts graphene nanoribbons (GNRs) are promising materials for energy storage applications, due to their unique architecture and properties. However, spatial distribution and orientation in polymer matrices plays a crucial role in determining the charge and mass transfer effectiveness of the nanocomposite. Here, we report a controlled enhancement of dispersion and spatial alignment of CNTs and GNRs via gas-assisted electrospinning (GAES). This methodology obviates the use of surface modifications to ensure effective enthalpic interactions between a substrate and filler, and offers a “single-step” procedure for electrode fabrication. We conducted a rigorous TEM image analysis of as-spun PVA nanofibers and observed an average of 60 and 90% improvement in dispersion area due to the application of high but controlled air flow for CNTs and GNRs, respectively. Alignment results demonstrate that stiff CNTs respond uniformly to the external deformation applied by GAES, while more flexible GNRs have a limited response.

Surface Activation and Pretreatments for Biocompatible Metals and Alloys Used in Biomedical Applications.

To improve the biocompatibility of medical implants, a chemical composition of bone-like material (e.g., hydroxyapatite) can be deposited on the surface of various substrates. When hydroxyapatite is deposited on surfaces of orthopedic implants, several parameters must be addressed including the need of rapid bone ingrowth, high mechanical stability, corrosion resistance, biocompatibility, and osseointegration induction. However, the deposition process can fail due to poor adhesion of the hydroxyapatite coating to the metallic substrate. Increasing adhesion by enhancing chemical bonding and minimizing biocoating degradation can be achieved through surface activation and pretreatment techniques. Surface activation can increase the adhesion of the biocoating to implants, providing protection in the biological environment and restricting the leaching of metal ions in vivo. This review covers the main surface activation and pretreatment techniques for substrates such as titanium and its alloys, stainless steel, magnesium alloys, and CoCrMo alloys. Alkaline, acidic, and anodizing techniques and their effects on bioapatite deposition are discussed for each of the substrates. Other chemical treatment and combination techniques are covered when used for certain materials. For titanium, the surface pretreatments improve the thickness of the TiO2 passive layer, improving adhesion and bonding of the hydroxyapatite coating. To reduce corrosion and wear rates on the surface of stainless steel, different surface modifications enhance the bonding between the bioapatite coatings and the substrate. The use of surface modifications also improves the morphology of hydroxyapatite coatings on magnesium surfaces and limits the concentration of magnesium ions released into the body. Surface treatment of CoCrMo alloys also decreased the concentration of harmful ions released in vivo. The literature covered in this review is for pretreated surfaces which then undergo deposition of hydroxyapatite using electrodeposition or other wet deposition techniques and mainly limited to the years 2000-2019.

Synthesis and characterization of thiophene-based push-pull chromophores for tuning the electrical and optical properties of surfaces with controlled SAM formation

Due to their efficient light absorption properties and their electronic dipole, “push-pull” chromophores with thiophene-based spacer between donor and acceptor groups are very promising for potential use in optoelectronics, photovoltaics, non-linear optics, or electronics. Such applications could benefit from chromophore deposition on a surface in an ordered way with oriented dipoles. For this purpose, self-assembled monolayers (SAMs) constitute an interesting approach. In this work we present a multi-step synthesis of a series of push-pull structures based on 2,2′-bithiophene or dithieno[3,2-b:2′,3′-d]thiophene frameworks born on an alkyl chain terminated with an anchoring group for further use in surface modification. Obtained molecules and SAMs were analyzed by cyclic voltammetry, spectroscopy and scanning probe microscopy. We show that varying the acceptor moiety allows to tune the absorption band in a wide spectral range, and that a longer chain length improves the organization of the dipole-oriented chromophore SAM.

EDTA-Cu (II) chelating magnetic nanoparticles as a support for laccase immobilization

Developments in nanotechnology have led to the discovery of new materials, namely, magnetic nanoparticles (MNPs), that present easy surface functionalization and high surface-to-volume ratios. These properties allow a high mass transfer rate and easy removal from a reaction matrix. Simple separation under an external magnetic field makes them a promising immobilization support for enzymes. In this work, new MNPs were prepared by functionalization with EDTA-TMS and characterized by TEM, FTIR and BET analytical techniques, among others. These MNPs were applied as support for laccase immobilization to create a promising biocatalyst. Despite the known chelating nature of EDTA-TMS, its use for surface modification of MNPs for laccase immobilization is a rather unexplored strategy and is reported here for the first time. At pH 3.5, the immobilization process showed approximately 97% of enzymatic activity recovery. The Michaelis-Menten kinetic properties of immobilized laccase showed a lower Vmax and a similar KM compared to free laccase. Regarding operational stability, the immobilized enzyme presented approximately 73% of its initial activity after five sequential reactive cycles. The immobilized enzyme was successfully applied to the biocatalysis of Indigo Carmine dye degradation. These MNPs with immobilized laccase showed important advantages compared to other materials for application in industrial biochemical processes, biocatalysis and biosensors.

Removal of thorium from water using modified magnetite nanoparticles capped with rosin amidoxime

The present study describes synthesis and characterization of diacrylamidoxime triaethylenetetralevopimaramide (DPAO) and its use in surface modification of Fe3O4 magnetic nanoparticles to obtain DPAO-based magnetic nanoparticles (DPAO-MNPs). The prepared composite was characterized by FTIR, 1HNMR, XRD, DLS, TEM, SEM and EDX. Vibrating sample magnetometer is used to determine the magnetic properties of DPAO-MNPs. Results of analyses indicate that the surface of Fe3O4 was successfully capped with DPAO. The adsorption features of the prepared composite towards thorium ions were investigated in a batch system. Kinetic study of Th(IV) adsorption on DPAO-MNPs indicate the adsorption equilibrium achieved within 150 min and is pH dependent. The adsorption results were described mathematically using Langmuir and Freundlich sorption models. The composite showed a maximum Th(IV) loading capacity of 666 mg/g at 25 °C and pH 4. The thermodynamic results indicated that the adsorption process was thermodynamically favorable, spontaneous and endothermic nature. The obtained results suggest that DPAO-MNPs composite may be considered as a potential fast, effective and simple adsorbent for sorption thorium(IV) from water.

아라미드섬유의 표면개질에 의한 시멘트 복합재료의 강도특성 및 내충격성능의 향상효과

아라미드섬유의 표면개질에 의한 시멘트 복합재료의 강도특성 및 내충격성능의 향상효과

POLYDADMAC Treatment on Cotton for Improving Printing with Reactive Dye

Eco-friendly chemical processing of textile is now necessary for recent trends. Surface modification with p o- lyelectrolytes on cotton might bring to a new approach. Reactive printing of cotton requires salt, and also hygr oscopic agent in large quantity, which increase pollution load. To overcome from this problem, polydiallyldimethylammonium chloride (POLYDADMAC) is use for surface modification of cotton, which increase colour value of reactive dye in printing. Printing is carried out with four different methods. The colour strength and fastness pro perties of printed sam- ple were assessed and reported in this paper.

Upconversion nanoparticles: from hydrophobic to hydrophilic surfaces.

CONSPECTUS: Photon upconversion nanoparticles (UCNPs) have emerged as a promising new class of nanomaterials due to their ability to convert near-IR light into visible luminescence. Unfortunately, most efficient methods for preparing UCNPs yield hydrophobic materials, but water-dispersibility is needed in the major fields of applications of UCNPs, that is, in bioimaging, labeling, and bioassays. Numerous methods therefore have been reported in the past years to convert the hydrophobic surface of UCNPs to a more hydrophilic one so to render them dispersible in aqueous systems. We present a classification respective for these strategies and assess the main methods. These include (A) chemical modification of the hydrophobic (typically oleate) ligand on the surface, (B) addition of an extra layer, (C) addition of a thin shell on top of the UCNP, and (D) complete replacement of the original ligand by another one. Chemical modification (A) involves oxidation of the oleate or oleylamine and leads to particles with terminal oxygen functions. This method is less often used because solutions of the resulting UCNPs in water have limited colloidal stability, protocols are time-consuming and often give low yields, and only a limited number of functional groups can be introduced. Methods B and C involve coating of UCNPs with amphiphiles or with shells made from silica oxide, titanium oxide, or metallic gold or silver. These methods are quite versatile in terms of further modifications, for example, by further cross-linking or by applying thiol-gold chemistry. Growing an extra shell is, however, often accompanied by a higher polydispersity. Method D can be divided into subgroups based on either (i) the direct (single-step) replacement of the native ligand by a new ligand or (ii) two-step protocols using nitrosyltetrafluoroborate (NOBF4) or strong acids as reagents to produce ligand-free UCNPs prior to the attachment of a new ligand. These methods are simple and versatile, and the distance between the new ligand and the luminescent particle can be well controlled. However, the particles often have limited stability in buffer systems. The methods described also are of wider interest because they are likely to be applicable to other kinds of nanomaterials. We additionally address the need for (a) a better control of particle size and homogeneity during synthesis, (b) more reproducible methods for surface loading and modification, (c) synthetic methods giving higher yields of UCNPs, (d) materials displaying higher quantum yields in water solution without the need for tedious surface modifications, (e) improved methods for workup (including the suppression of aggregation), (f) new methods for surface characterization, and (g) more affordable reagents for use in surface modification. It is noted that most synthetic research in the area is of the trial-and-error kind, presumably due to the lack of understanding of the mechanisms causing current limitations. Finally, all particles are discussed in terms of their biocompatibility (as far as data are available), which is quintessential in terms of imaging, the largest field of application.

Nanocomposites based on Polypropylene and Copper Nanoparticles: Preparation, Surface Activation by Plasma and Antibacterial Activity

This work reports the preparation of polypropylene nanocomposites with copper nanopar­ticles (PP/nCu) by melt blending, as well as their surface treatment by argon plasma in order to increase the antibacterial activity of compounds obtained. The nanocomposite surface analysis, corroborated by means of Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), demonstrates that argon plasma treatment modifies the surface of the compound, increasing the exposure of nanoparticles and, therefore, roughness of the mate­rial. Argon plasma favors polymeric chain scission at the surface, removing polymer chains and forming active sites, which in contact with the environment incorporates oxygen and nitrogen species, increasing the material´s polarity, as demonstrated by X-ray photoelec­tron spectroscopy (XPS) analysis and contact angle measurements. The exposure of surface nanoparticles and polarity shifts of eroded nanocomposites produced a significant increase in antimicrobial activity against pathogenic bacteria Staphylococcus aureus and Pseudomo­nas aeruginosa. Plasma treatment use for surface modification of nanocomposites is an ef­fective tool to obtain antimicrobial nanomaterials with a high value-added.

Determination of artificial sweeteners by capillary electrophoresis with contactless conductivity detection optimized by hydrodynamic pumping

The common sweeteners aspartame, cyclamate, saccharin and acesulfame K were determined by capillary electrophoresis with contactless conductivity detection. In order to obtain the best compromise between separation efficiency and analysis time hydrodynamic pumping was imposed during the electrophoresis run employing a sequential injection manifold based on a syringe pump. Band broadening was avoided by using capillaries of a narrow 10μm internal diameter. The analyses were carried out in an aqueous running buffer consisting of 150mM 2-(cyclohexylamino)ethanesulfonic acid and 400mM tris(hydroxymethyl)aminomethane at pH 9.1 in order to render all analytes in the fully deprotonated anionic form. The use of surface modification to eliminate or reverse the electroosmotic flow was not necessary due to the superimposed bulk flow. The use of hydrodynamic pumping allowed easy optimization, either for fast separations (80s) or low detection limits (6.5μmolL−1, 5.0μmolL−1, 4.0μmolL−1 and 3.8μmolL−1 for aspartame, cyclamate, saccharin and acesulfame K respectively, at a separation time of 190s). The conditions for fast separations not only led to higher limits of detection but also to a narrower dynamic range. However, the settings can be changed readily between separations if needed. The four compounds were determined successfully in food samples.

Recent Developments in Electronic, Functional, and Biological Thin Films

The use of surface modification by humans dates back several millennia. As noted by Myers, the art of Cro-Magnon man in 15,000 B.C. can be considered to be a decorative coating. Oddy noted that applying gold to surfaces has been performed for at least 5000 years. Processing of thin films for applications other than gilding began in earnest in the nineteenth century. At the beginning of the nineteenth century, Luigi Brugnatelli used electroplating to deposit gold; by the middle of that century, deposition of a variety of metals had been demonstrated. Sir Robert Grove described a process that he termed ‘‘cathodic disintegration’’ in 1852; Sir John Thompson later renamed this process ‘‘sputtering.’’ As noted by Mattox, Michael Faraday described sputtering within a glow discharge tube for deposition of films in the mid-nineteenth century. At the turn of the last century, Thomas Edison used sputtering to deposit gold coatings on master wax cylinders, which were subsequently used to produce ‘‘Gold Moulded Records.’’ The origin of chemical vapor deposition has been traced to early studies by von Guericke and Henry. It was used for development of light bulb materials in the 1880s and for purification of refractory metals in the 1940s. Over the past half century, rapid developments in thin film technology were associated with increases in complexity and reductions in size of electronic and optical devices. For example, Smith and Turner used evaporation by a ruby laser to create films of a variety of materials, including As2S3, Ge, MoO3, PbTe, Sb2S3, Se, Te, and ZnTe. Currently, pulsed laser deposition is commonly used for deposition of a variety of thin films, including multicomponent systems and biologically relevant materials, at low temperatures. At the beginning of the twenty-first century, significant thin film research activities involve the development of thin films for medical and energy applications. In this issue, Gupta et al. considered the protein adsorption and wettability of composite materials containing ultrahigh molecular weight polyethylene, hydroxyapatite, alumina, and carbon nanotubes; these materials have potential use in joint replacement prostheses. Palkowski et al. created a three-layered stainless steel/polypropylene copolymer/stainless steel sandwich sheet material with biomimetic properties. Skoog et al. deposited ultrananocrystalline diamond films on microporous silicon nitride membranes using microwave plasma chemical vapor deposition and evaluated the growth of human epidermal keratinocytes on these materials. Shet et al. prepared zinc oxide thin films using radio frequency sputtering in the presence of a gas ambient containing argon and nitrogen. They demonstrated that aligned nanoscale structures with enhanced photoelectrochemical response were prepared under an appropriate gas ambient. It is hoped that this special issue helps to generate discussions in industry, academia, and government regarding use of thin film technology for electronic, functional, and biological applications.

Viscosity measurements of antibody solutions by photon correlation spectroscopy: an indirect approach – limitations and applicability for high-concentration liquid protein solutions

Photon correlation spectroscopy (PCS) is compared with classic rheological measurements using the cone-and-plate technique for the determination of the viscosity of protein solutions. The potential advantages using PCS are small sample volume and fast determination of zero-shear viscosity. The present study assesses potentials and limitations of the applicability of this method for the determination of viscosity of antibody solutions in protein science development. The principle of the assay is based on the determination of the apparent hydrodynamic radius of commercial available latex beads of known size added to protein solutions. Using the Stokes–Einstein equation, the hydrodynamic radius can be converted to viscosity. Several latex particle sizes and concentrations were evaluated and the assay optimized. The PCS assay for viscosity determination was tested using water/glycerol-mixtures, where the viscosity was measured with rheometer using the cone-and-plate method and also compared with published data. Different protein solutions of bovine serum albumin, lysozyme and monoclonal antibodies were then used and the PCS results were compared with viscosity data obtained by the cone-and-plate method. It could be shown that the PCS assay has limitations for the determination of the viscosity of protein solutions, especially monoclonal antibodies. The main reason is due to protein–latex bead interactions leading to the formation of larger aggregates. The use of surface modification of the latex beads can in principle prevent this interaction.

The contribution of the capillary endothelium to blood clearance and tissue deposition of anionic quantum dots in vivo

The increasing interest in biomedical applications of semiconductor quantum dots (QDs) is closely linked to the use of surface modifications to target specific sites of the body. The immense surface area of vascular endothelium is a possible interaction platform with systemically administered QDs. Therefore, the aim of this study was to investigate the microvascular distribution of neutral, cationic, and anionic QDs in vivo. QDs with carboxyl-, amine- and polyethylene glycol surface coatings were injected into the blood circulation of mice. In vivo microscopy of the cremaster muscle, two-photon microscopy of skeletal and heart muscle, as well as quantitative fluorescence measurements of blood, excreta, and tissue samples were performed. Transmission electron microscopy was used to detect QDs at the cellular level. The in vitro association of QDs with cultured endothelial cells was investigated by flow cytometry and confocal microscopy. Anionic QDs exhibited a very low residence time in the blood stream, preferably accumulated in organs with a prominent mononuclear phagocytic component, but were also found in other tissues with low phagocytic properties where they were predominantly associated with capillary endothelium. This deposition behavior was identified as a new, phagocyte-independent principle contributing to the rapid clearance of anionic QDs from the circulation.

The Biological Mechanisms and Physicochemical Characteristics Responsible for Driving Fullerene Toxicity

This review provides a comprehensive critical review of the available literature purporting to assess the toxicity of carbon fullerenes. This is required as prior to the widespread utilization and production of fullerenes, it is necessary to consider the implications of exposure for human health. Traditionally, fullerenes are formed from 60 carbon atoms, arranged in a spherical cage-like structure. However, manipulation of surface chemistry and molecular makeup has created a diverse population of fullerenes, which exhibit drastically different behaviors. The cellular processes that underlie observed fullerene toxicity will be discussed and include oxidative, genotoxic, and cytotoxic responses. The antioxidant/cytoprotective properties of fullerenes (and the attributes responsible for driving these phenomena) have been considered and encourage their utilization within the treatment of oxidant-mediated disease. A number of studies have focused on improving the water solubility of fullerenes in order to enable their exploitation within biological systems. Manipulating fullerene water solubility has included the use of surface modifications, solvents, extended stirring, and mechanical processes. However, the ability of these processes to also impact on fullerene toxicity requires assessment, especially when considering the use of solvents, which particularly appear to enhance fullerene toxicity. A number of the discussed investigations were not conducted to reveal if fullerene behavior was due to their nanoparticle dimensions but instead addressed the biocompatibility and toxicity of fullerenes. The hazards to human health, associated with fullerene exposure, are uncertain at this time, and further investigations are required to decipher such effects before an effective risk assessment can be conducted.