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In recent years, much effort has been invested into developing multifunctional drug delivery systems to overcome the drawbacks of conventional carriers. Magnetic nanoparticles are not generally used as carriers but can be functionalised with several different biomolecules and their size can be tailored to present a hyperthermia response, allowing for the design of multifunctional systems which can be active in therapies. In this work, we have designed a drug carrier nanosystem based on Fe3O4 nanoparticles with large heating power and 4-amino-2-pentylselenoquinazoline as an attached drug that exhibits oxidative properties and high selectivity against a variety of cancer malignant cells. For this propose, two samples composed of homogeneous Fe3O4 nanoparticles (NPs) with different sizes, shapes, and magnetic properties have been synthesised and characterised. The surface modification of the prepared Fe3O4 nanoparticles has been developed using copolymers composed of poly(ethylene-alt-maleic anhydride), dodecylamine, polyethylene glycol and the drug 4-amino-2-pentylselenoquinazoline. The obtained nanosystems were properly characterised. Their in vitro efficacy in colon cancer cells and as magnetic hyperthermia inductors was analysed, thereby leaving the door open for their potential application as multimodal agents.

Lithium metal batteries (LMBs) are one of the most promising energy storage technologies that would overcome the limitations of current Li-ion batteries, based on their low density (0.534 g cm−3), low reduction potential (−3.04 V vs Standard Hydrogen Electrode) as well as their high theoretical capacities (3860 mAh g−1 and 2061 mAh cm−3). The overall cell mass and volume would be reduced while both gravimetric and volumetric energy densities would be greatly improved. Their electrochemical performance, however, is hampered by the low efficiency at high current densities and continuous degradation, which are related, among other factors, to the properties of the lithium metal anode (LMA). Hence, the production and processing of LMAs is crucial to obtain the desired properties that would enable LMBs. Here, the conventional method used for the production of LMAs, which is the combination of extraction, electrowinning, extrusion, and rolling processes, is reviewed. Then, the advances in the different alternative methods that can be used to produce and improve the properties of LMAs are described, which are divided into vapor phase, liquid phase, and electrodeposition. Within this last method, the anode-less concept, for which different approaches to the development of advanced current collectors are illustrated, is included. I.R.L. acknowledges the support of the Ministerio de Ciencia, Innovación y Universidades (No. PID2019-107468RB-C21) and Gobierno Vasco/Eusko Jaurlaritza (No. IT1546-22). This project has received funding from the Basque Government within the ELKARTEK 2021 call (project CICe2021) under the application number KK-2021/00064.

An alternative anodeto metallic sodium based on the high capacity of Sn4P3 alloy is investigated for the first time in Na–O2 batteries. This alloy is synthesised by an easy and scalable method based on ball milling which is further optimized in order to obtain the most suitable morphology while avoiding agglomeration of the material. First, the stability of Sn4P3/C composite within the battery environment is analysed and compared to that of metallic Na. Second, the electrochemical study reveals the formation of sodium superoxide on both the metallic anode and Sn4P3 alloy for the first time, which evidences the existence of O2/O2− crossover processes. Complementary impedance studies, at various voltages and as a function of cycle number, demonstrate a higher stability of the solid electrolyte interphase (SEI) throughout cycling in addition to presenting lower reactivity and greater stability than the metallic Na system. Regarding the cycling performance, although it is lower than that of metallic Na, it surpasses that exhibited by other alternative anodes under similar conditions. This work therefore demonstrates the viability of a new family of anodes, paving the way for the development of more stable and safer Na–O2 batteries. Moreover, the importance of oxygen crossover is highlighted which is a common problem regardless of the anode used.

The main objective of the preparation of the Fe

Due to the increase in global energy demand and the unsustainability of burning fossil fuels, the search for optimized energy systems has become a priority in recent years. In 1990, lithium batteries revolutionized the energy market; however, the unceasing increase in demand and the limited lithium supplies induce the need for alternative energy storage systems. Li–O2 batteries are promising to make a difference in applications such as those related to electromobility. In the last few years the interest in metal–air batteries has increased exponentially; however, several challenges must be overcome to improve their efficiency. For this system to be viable, it is necessary to solve key problems such as the high polarization of the charge reaction. To overcome this limitation, facilitate the oxidation of the Li2O2 discharge product, and increase the efficiency of these batteries, the use of redox mediators has been widely investigated. In the present work, the mediators reported in the Li–O2 literature are classified into four groups according to their charge state in both their reduced and oxidized forms and their performance is discussed. Finally, a summary of the redox mediators used in analogous Na–O2 batteries is presented. This work provides a clear view about the use of redox mediators as a powerful strategy for the commercialization of these metal–O2 batteries, discussing the advantages and disadvantages of this type of homogenous catalyst, and suggesting future directions.

International audience; Based on the combined corrected chemical analysis, the single-crystal X-ray structural results, and the revised Mössbauer spectral analysis, the best formulation of Li1.4(1)[Fe4.4(1)IIFe0.6(1)III(HPO3)6]·1.47(3) H2O, 1b, has been obtained; also, from a revised Mössbauer spectral analysis, a revised formulation of K0.95(5)[Fe3.95(5)IIFe1.05(5)III(HPO3)6]·0.5 H2O, 2m, has been obtained. The revised analysis of the room-temperature Mössbauer spectral parameters for both compounds is consistent with their crystallographic structures and the different nature and occupancies of the Li+ and K+ crystallographic sites. From a detailed analysis of the impedance spectroscopy measurements of Li1.43[Fe4.43IIFe0.57III(HPO3)6]·1.5 H2O, 1, between 123 and 189 °C, two processes involving the electric charge response to the ac electric field have been identified. An activation energy for the charge transfer in 1 of 0.91(2) eV or 7340(160) cm–1 has been obtained; the charge transfer may involve a correlated hopping of the Li+ ion and an electron between the iron(II) and iron(III) ions.

A novel imidazolium halometallate molten salt with formula (trimim)[FeCl

The depletion of fossil fuels, the rapid evolution of the global economy, and high living standards require the development of new energy‐storage systems that can meet the needs of the world's population. Metal–oxygen batteries (M=Li, Na) arise, therefore, as promising alternatives to widely used lithium‐ion batteries, due to their high theoretical energy density, which approaches that of gasoline. Although significant progress has been made in recent years, there are still several challenges to overcome to reach the final commercialization of this technology. One of the most limiting and challenging factors is the development of bifunctional cathodes towards oxygen reduction and evolution reactions. In this sense, graphene, which is very promising and tunable, has been widely explored by the research community as a key material for this technology. Herein, a wide literature overview is presented and analyzed with the aim of guiding future research in this field., Future is flat: Graphene is a very versatile and promising air cathode in M–O2 (M=Li, Na) batteries due to its high electronic conductivity, large specific surface area, high mechanical strength, low density, and intrinsic catalytic activity towards oxygen reduction and reactions.

A novel imidazolium halometallate molten salt with formula (trimim)[FeCl4] (trimim: 1,2,3-trimethylimidazolium) was synthetized and studied with structural and physico-chemical characterization. Variable-temperature synchrotron X-ray powder diffraction (SXPD) from 100 to 400 K revealed two structural transitions at 200 and 300 K. Three different crystal structures were determined combining single crystal X-ray diffraction (SCXD), neutron powder diffraction (NPD), and SXPD. From 100 to 200 K, the compound exhibits a monoclinic crystal structure with space group P21/c. At 200 K, the former crystal system and space group are retained, but a disorder in the organic cations is introduced. Above 300 K, the structure transits to the orthorhombic space group Pbcn, retaining the crystallinity up to 400 K. The study of the thermal expansion process in this temperature range showed anisotropically evolving cell parameters with an axial negative thermal expansion. Such an induction occurs immediately after the crystal phase transition due to the translational and reorientational dynamic displacements of the imidazolium cation within the crystal building. Electrochemical impedance spectroscopy (EIS) demonstrated that this motion implies a high and stable solid-state ionic conduction (range from 4 10 6 S cm 1 at room temperature to 5.5 10 5 S cm 1 at 400 K). In addition, magnetization and heat capacity measurements proved the presence of a three-dimensional antiferromagnetic ordering below 3 K. The magnetic structure, determined by neutron powder diffraction, corresponds to ferromagnetic chains along the a-axis, which are antiferromagnetically coupled to the nearest neighboring chains through an intricate network of superexchange pathways, in agreement with the magnetometry measurements Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 financed by SODERCAN_FEDER), Universidad del Pa´ıs Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239- C2-(1,2)-P).

Sodium-oxygen (Na-O2) batteries have been considered as promising alternatives to lithium-oxygen batteries for high energy density applications. Herein, we report the utilisation of Li+ and K+ salts to the Na+ based electrolyte in order to tailor the oxygen reduction reaction (ORR) route in Na-O2 cells. Li+ salt addition promotes a surface confined ORR due to the incapability to stabilize superoxide radical intermediate product in the electrolyte leading to a poor electrochemical performance. The discharge capacities achieved using K+ salt additive are also lower than those obtained without it due to the incapability of KO2 to precipitate on the oxygen electrode, turning the initial solution-phase ORR to a surface-confined ORR after supersaturation. In this work we show that stabilization of the intermediate products and an efficient precipitation of the final products at the oxygen electrode are key factors governing the electrochemical performance in Na O2 batteries.

Sodium-oxygen batteries are becoming of increasing interest in the research community as they are able to overcome some of the difficulties associated with lithium-oxygen batteries. The interpretation of the processes governing the discharge and charge of these batteries, however, has been under debate since their early development. In this work we combine different electrochemical methods to build up a model of the discharge product formation and decomposition. We initially analyze the formation and decomposition of the discharge products by means of electrochemical impedance spectroscopy. After that, and for the first time, oxygen electrode processes in Na-O2 cells are analyzed by means of electrochemical quartz crystal microbalance experiments. Based on the combination of these two techniques it is possible to evidence the stabilization of the discharge products in the electrolyte prior to their precipitation. The deposition of passivating products that cannot be stripped off during charge is also demonstrated. Cyclic voltammetry experiments at different potential limits further confirm these passivation reactions. In conclusion, this work provides an accurate picture of the mechanism of the Na-O2 cell reactions by combining different electrochemical techniques.

A new route to enhance the performance of Na-O2 cells is demonstrated. Redox mediators (such as ethyl viologen) are shown to facilitate the discharge reaction, producing an increased capacity (due to suppressed electrode passivation), higher discharge potential (due to faster kinetics) and stable cycling.

The depletion of fossil fuels, the rapid evolution of the global economy and high life standards require the development of new energy storage systems that can meet the needs of world´s population. Metal‐oxygen batteries (M = Li, Na) arise, therefore, as promising alternatives to wide‐extended lithium‐ion batteries, due to their high theoretical energy density which approaches that of gasoline. Although significant progress has been made in the last years, there are still several challenges to overcome in order to reach the final commercialization of this technology. One of the most limiting and challenging factors is the development of bifunctional cathodes towards oxygen reduction and evolution reactions. In this sense, graphene‐ very promising and tunable ‐ has been widely explored by the research community as a key material for this technology. Herein, a wide literature overview is presented and analyzed with the aim of guiding future research in this field.

espanolThe use of nanotechnology has become a key tool for the development of an endless number of applications. The food sector is not an exception since the bene-fits of nanotechnology are expected to allow us to enjoy healthier, more resilient and long-lasting foods. In this work, we present the main advances related to the introduc-tion of nanotechnology in the food sector, focusing on three areas: nano-enriched foods, novel designs for food packaging and nanosensors. Finally, the controversy sur-rounding nanofood is analyzed, since although nanotechnology can contribute with lots of benefits, its use still causes fear and insecurity among the population. euskaraNanoteknologiaren erabilpena funtsezko erreminta bilakatu da apli-kazio askoren garapenean, eta elikagaien sektorea ez da alde batera geratu. Modu ho-rretan, nanoelikagaien garapenak osasuntsuagoak, erresistenteagoak eta iraupen luzea-goa duten elikagaiz gozatzea ahalbidetuko duela uste da. Lan honetan, nanoteknologia elikadura sektorean ezartzeak eragindako aurrerapen nagusiak aurkezten dira eta, be-reziki, honako hiru arlo hauetan jarri da arreta: nano-aberastutako elikagaiak, elikagai biltegiratzeko diseinu berriak eta nanosentsoreak. Amaitzeko, elikadura industrian na-noteknologiaren erabilpenak eragindako eztabaida aztertuko da; abantaila asko ekar di-tzakeen arren, egun gizartearengan beldurra eta kezkak eragiten baititu.

Rechargeable metal-oxygen batteries are receiving significant interest as a possible alternative to current state of the art lithium ion batteries due to their potential to provide higher gravimetric energies, giving significantly lighter or longer-lasting batteries. Recent advances suggest that the Na-O2 battery, in many ways analogous to Li-O2 yet based on the reversible formation of sodium superoxide (NaO2), has many advantages such as a low charge overpotential (∼100 mV) resulting in improved efficiency. In this Perspective, we discuss the current state of knowledge in Na-O2 battery technology, with an emphasis on the latest experimental studies, as well as theoretical models. We offer special focus on the principle outstanding challenges and issues and address the advantages/disadvantages of the technology when compared with Li-O2 batteries as well as other state-of-the-art battery technologies. We finish by detailing the direction required to make Na-O2 batteries both commercially and technologically viable.

The presence of singlet oxygen in metal-O2 batteries is one of the major factors responsible for the degradation of the electrolyte. The formation of singlet oxygen, 1O2, at Na O2 cathodes in sodium trifluoromethane sulfonate (NaOTf)-diglyme electrolyte has been detected in-operando by fluorescence quenching of 9,10-dimethylanthracene, DMA, a specific chemical monitor of singlet oxygen. Furthermore, ammonium Bronsted acid protonates superoxide and the further disproportionation of HO2 results in a catalytic EC' mechanism that recycles oxygen, a fraction of which has been found to be 1O2. Unlike, ammonium trifluoromethane sulfonate (NH4OTf), in tetrabutylammonium trifluoromethane sulfonate (TBAOTf), which lacks acidic protons, superoxide is stabilized by the large cation and no 1O2 could be detected. The addition of sodium azide to the electrolyte, an efficient specific physical quencher of singlet oxygen, results in negligible detection of this harmful oxygen reduction intermediate and proves the nature of 1O2.

Correction for ‘Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4]’ by Palmerina González-Izquierdo et al., RSC Adv., 2020, 10, 11200–11209. DOI: 10.1039/D0RA00245C.

With the aim of studying the influence of synthesis parameters in structural and magnetic properties of cobalt-doped magnetite nanoparticles, Fe3-xCoxO4 (0 < x < 0.15) samples were synthetized by thermal decomposition method at different reaction times (30-120 min). The Co ferrite nanoparticles are monodisperse with diameters between 6 and 11 nm and morphologies depending on reaction times, varying from spheric, cuboctahedral, to cubic. Chemical analysis and X-ray diffraction were used to confirm the composition, high crystallinity, and pure-phase structure. The investigation of the magnetic properties, both magnetization and electronic magnetic resonance, has led the conditions to improve the magnetic response of doped nanoparticles. Magnetization values of 86 emu center dot g(-1) at room temperature (R.T.) have been obtained for the sample with the highest Co content and the highest reflux time. Magnetic characterization also displays a dependence of the magnetic anisotropy constant with the varying cobalt content. This work was supported by institutional funding from the Ministry of Economy and Competitiveness and Basque Government under Projects MAT2016-78266-P, FEDER, and GIC-IT-570-13. Technical and human support provided by SGIker (UPV/EHU) is also gratefully acknowledged. A grant from the University of the Basque Country (UPV/EHU) to I. G. is acknowledged. We are grateful to I. Orue for helpful discussion on magnetic properties.

Inorganic nanoparticles are frequently engineered with an organic surface coating to improve their physicochemical properties, and it is well known that their colloidal properties may change upon internalization by cells. While the stability of such nanoparticles is typically assayed in simple in vitro tests, their stability in a mammalian organism remains unknown. Here, we show that firmly grafted polymer shells around gold nanoparticles may degrade when injected into rats. We synthesized monodisperse radioactively labelled gold nanoparticles ((198)Au) and engineered an (111)In-labelled polymer shell around them. Upon intravenous injection into rats, quantitative biodistribution analyses performed independently for (198)Au and (111)In showed partial removal of the polymer shell in vivo. While (198)Au accumulates mostly in the liver, part of the (111)In shows a non-particulate biodistribution similar to intravenous injection of chelated (111)In. Further in vitro studies suggest that degradation of the polymer shell is caused by proteolytic enzymes in the liver. Our results show that even nanoparticles with high colloidal stability can change their physicochemical properties in vivo.

The performance of Li-O2 batteries is typically evaluated by specific capacity and cyclability in order to facilitate quantitative comparison in literature. The accuracy of such comparison is limited, however, due to the wide range of factors which control the reported specific capacities. These comparisons are not always fair as some factors, which can highly influence the obtained specific capacities, are often neglected. A rigorous and systematic study has been conducted in order to identify the isolated effect of diverse parameters on the performance of these promising batteries. The analysis of cells with different carbon contents reveals that the discharge reactions do not necessarily take place throughout the electrode mass, but instead occur preferentially in closest proximity to the oxygen gas-electrolyte interface. The effective activity of the cathode material is therefore reduced as distance from this interface increases. This work demonstrates that the lack of standardized measurement protocols hinders the rapid development of this technology due to the difficulties inherent in the direct comparison of cells with wide-ranging measurement conditions. In addition, it has been demonstrated that both the employed carbon loading and current rate critically affect cycling lifetime. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0191502jes] All rights reserved.

International audience; The microstructure and chemical composition of the discharge products generated in sodium-oxygen batteries are analyzed by transmission X-ray microscopy (TXM) revealing a complex architecture. Unexpectedly, sodium peroxide is detected in the cubic-shaped discharge deposits associated with the often reported sodium superoxide. Analyses on the product distribution show a surface layer rich in decomposition products in contact with an O-deficient region enclosing the bulk of these cubes. In addition, we show that oxygen evolution reaction (OER) occurs by a process that involves oxidation and re-dissolution of the bulk fraction, leading to a contraction of the discharge particles and a composition similar to that found in the intermediate phase of the deposits observed at the end of discharge. All these solid compounds are eventually removed at the end of recharge, but formation of these structures evidence possible irreversible pathways that need to be considered for the cycle life improvement.

The stabilization of the intermediates formed during oxygen reduction reaction and their efficient solubilization and diffusion is a crucial issue that needs to be improved in non-aqueous lithium oxygen batteries. By adding 0.1 M K+ (as KOTf salt) to the electrolyte we have observed remarkable improvements in the rate capability of the discharge process. The K+ cation facilitates a more homogeneous discharge product deposition in the porous cathode. Instead, as evidenced by synchrotron measurements, we find that K+ does not influence the cell chemistry, suggesting that it rather assists the superoxide solvation, thus enhancing the solution-based growth of the discharge products. In addition, if iodide (I-) is added as redox mediator we find an extended cycle life when K+ instead of Li+ is used as cation. This finding remarks the benefits of stabilizing the oxygen reduction products in the electrolyte leading to a solution-based mechanism., This work has been partially financed by the Spanish Ministry of Economy, Industry and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV- 2015-0496), through projects MAT2013-41128-R, MAT2016-78266-P, MAT2015-68394-R, by the “Fondo Europeo de Desarrollo Regional” (FEDER), by the Eusko Jaurlaritza/Gobierno Vasco (through project IT-570-13), and by the Generalitat de Catalunya (grant 2014 SGR 1505). I. Landa-Medrano thanks the Universidad del País Vasco (UPV/EHU) for his predoctoral fellowship. M. Olivares-Marín acknowledges CSIC for a JAE-DOC research contract co-funded by the European Social Fund. J. Janek acknowledges financial support by BMBF (Federal Ministry of Education and Research) within the project BENCHBATT. The xray microscopy experiments were performed at MISTRAL beamline at ALBA Synchrotron with the collaboration of ALBA staff.

Gaining insight into the reaction mechanisms underway during charge and discharge in Li–air batteries is essential to allow the target development of improved power and performance devices. This work reports the in situ monitoring of Li–air cells by electrochemical impedance spectroscopy and, for the first time, the development of an electrochemical model allowing the identification and attribution of the processes involved. The voltage at which each reaction product forms has been identified, including Li 2 O 2 or Li 2 CO 3 during discharge, together with the delithiation of the outer part of Li 2 O 2 and oxidation reactions and electrolyte decomposition. The developed model can be used as a valuable tool for the optimisation of composition and structure of the air electrode through the investigation of the resistance associated with each process.

Sodium-oxygen batteries currently stimulate extensive research due to their high theoretical energy density and improved operational stability when compared to lithium-oxygen batteries. Cell stability, however, needs to be demonstrated also under resting conditions before future implementation of these batteries. In this work we analyze the effect of resting periods on the stability of the sodium superoxide (NaO2) discharge product. The instability of NaO2 in the cell environment is demonstrated leading to the evolution of oxygen during the resting period and the decrease of the cell efficiency. In addition, migration of the superoxide anion (O2(-)) in the electrolyte is observed and demonstrated to be an important factor affecting Coulombic efficiency.

Perovskite-type oxides with the general formula ABO3 have been widely studied and are utilized in a large range of applications due to their tremendous versatility. In particular, the high stability of the perovskite structure compared to other crystal arrangements and its ability, given the correct selection of A and B cations, to maintain a large oxygen vacancy concentration makes it a good candidate as electrode in solid oxide fuel cell (SOFC) applications. Utilizing this novel structure allows the engineering of advanced, effective electrolytes for such devices. This review details the development of current state-of-the-art perovskite-type oxides for solid oxide fuel cell (SOFC) applications.

Exposure to arsenic (As), even at trace level, is believed to be a risk for human health and ecological systems. Thus, how to effectively and deeply remove arsenic from water systems is a very important but still challenging task for environmental researchers. A great variety of water treatment methodologies such as precipitation, oxidation, membrane processes, surface complexation or selective adsorption have been studied for significant reduction or remove arsenic from contaminated effluents. The use of nanomaterials as adsorbent materials for environmental remediation has a great potential due to their physical and chemical properties. This work aims to provide greater depth of understand of the successful integration of nanoadsorbents in water treatment technologies and give new insights into future research directions for the implementation of the nanotechnologies in a near future.; Artsenikoarekiko esposizioak, nahiz eta kontzentrazio txikietan izan, osasunerako eta sistema ekologikoetarako oso kaltegarria da. Hori dela eta, artsenikoa modu eraginkorrean erauziko duen metodo berria aurkitzea ingurumen ikertzaile askorentzako erronka bihurtu da. Gaur egun, disoluzioan dagoen artsenikoa erauzteko metodo asko daude: prezipitazioa, oxidazioa, mintz bidezko bereizketa prozesuak, gainazaleko konplexazioa edo adsortzio selektiboa. Adsorbatzaile nanometrikoak dituzten propietate kimiko eta fisikoek ingurumen erremediaziorako materialik egokienak bihurtze dituzte. Lan honek artsenikoz kutsatutako uren tratamenduan erabiltzen diren nanoadsorbatzilei buruzko ezagutza handiagoa eskaintzea du helburu, nanoteknologia barneratzen duen ikerkuntzaren etorkizunaren inguruko ikuspegi berria emanez.

Nanomaterials offer opportunities to construct novel compounds for many different fields. Applications include devices for energy, including solar cells, batteries, and fuel cells, and for health, including contrast agents and mediators for photodynamic therapy and hyperthermia. Despite these promising applications, any new class of materials also bears a potential risk for human health and the environment. The advantages and innovations of these materials must be thoroughly compared against risks to evaluate each new nanomaterial. Although nanomaterials are often used intentionally, they can also be released unintentionally either inside the human body, through wearing of a prosthesis or the inhalation of fumes, or into the environment, through mechanical wear or chemical powder waste. This possibility adds to the importance of understanding potential risks from these materials. Because of fundamental differences in nanomaterials, sound risk assessment currently requires that researchers perform toxicology studies on each new nanomaterial. However, if toxicity could be correlated to the basic physicochemical properties of nanomaterials, those relationships could allow researchers to predict potential risks and design nanomaterials with minimum toxicity. In this Account we describe the physicochemical properties of nanoparticles (NPs) and how they can be determined and discuss their general importance for cytotoxicity. For simplicity, we focus primarily on in vitro toxicology that examines the interaction of living cells with engineered colloidal NPs with an inorganic core. Serious risk assessment of NPs will require additional in vivo studies. Basic physicochemical properties of nanoparticulate materials include colloidal stability, purity, inertness, size, shape, charge, and their ability to adsorb environmental compounds such as proteins. Unfortunately, the correlation of these properties with toxicity is not straightforward. First, for NPs released either unintentionally or intentionally, it can be difficult to pinpoint these properties in the materials. Therefore, researchers typically use NP models with better defined properties, which don't include the full complexity of most industrially relevant materials. In addition, many of these properties are strongly mutually connected. Therefore, it can be difficult to vary individual properties in NP models while keeping the others constant.