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The engineering of advanced materials capable of mimicking the cellular micro-environment while providing cells with physicochemical cues is central for cell culture applications. In this regard, paper meets key requirements in terms of biocompatibility, hydrophilicity, porosity, mechanical strength, ease of physicochemical modifications, cost, and ease of large-scale production, to be used as a scaffold material for biomedical applications. Most notably, paper has demonstrated the potential to become an attractive alternative to conventional biomaterials for creating two-dimensional (2D) and three-dimensional (3D) biomimetic cell culture models that mimic the features of in vivo tissue environments for improving our understanding of cell behavior (e.g. growth, cell migration, proliferation, differentiation and tumor metastasis) in their natural state. On the other hand, integration of plasmonic nanomaterials (e.g. gold nanoparticles) within the fibrous structure of paper opens the possibility to generate multifunctional scaffolds equipped with biosensing tools for monitoring different cell cues through physicochemical signals. Among different plasmonic based detection techniques, surface-enhanced Raman scattering (SERS) spectroscopy emerged as a highly specific and sensitive optical tool for its extraordinary sensitivity and the ability for multidimensional and accurate molecular identification. Thus, paper-based plasmonic substrates in combination with SERS optical detection represent a powerful future platform for monitoring cell cues during cell culture processes. To this end, in this review, we will describe the different methods for fabricating hybrid paper-plasmonic nanoparticle substrates and their use in combination with SERS spectroscopy for biosensing and, more specifically, in cell culture applications., Graphical abstract Image 1

With the rapid development of the electronics industry, electronic products based on silicon and glass substrates electronic products will gradually be unable to meet the rising demand. Flexibility, environmental protection, and low costs are important for the development of electronic products. In this study, an efficient and low-cost method for preparing silver electrode structures by direct writing on paper has been demonstrated. Based on this method, a flexible paper-based sensor was prepared. The liquid printing ink used mainly comprises a precursor liquid without pre-prepared nanomaterials. The precursor liquid is transparent with good fluidity. Simple direct writing technology was used to write on the paper substrate using the precursor ink. When the direct-writing paper substrate was subsequently heated, silver nanostructures precipitated from the precursor liquid ink onto the paper substrate. The effect of different temperatures on the formation of the silver nanostructures and the influence of different direct writing processes on the structures were studied. Finally, a paper-based flexible sensor was prepared for finger-bending signal detection. The method is simple to operate and low in cost and can be used for the preparation of environment-friendly paper-based devices.

Silver nanoparticles (AgNPs) are in situ synthesized for the first time on microfibrillated silk (MFS) exfoliated from domesticated Philosamia cynthia ricini (eri) and Bombyx mori (mulberry) silkworm silk fibers. The process is rapid (hours time), does not rely on harmful chemicals, and produces robust and flexible AgNPs coated MFS (MFS-AgNPs) protein papers with excellent handling properties. None of these can be achieved by approaches used in the past to fabricate AgNPs silk systems. MFS bonds the AgNPs strongly, providing good support and stabilization for the NPs, leading to strong wash fastness. The mechanical properties of the MFS-AgNPs papers largely do not change compared to the MFS papers without nanoparticles, except for some higher concentration of AgNPs in the case of mulberry silk. The improved tensile properties of eri silk papers with or without AgNPs compared to mulberry silk papers can be attributed to the higher degree of fibrillation achieved in eri silk and its inherent higher ductility. MFS-AgNPs from eri silk also exhibit strong antibacterial activity. This study provides the basis for the development of smart protein papers based on silk fiber and functional nanomaterials.

Remediation of engineered-nanomaterials is an up-coming major environmental concern. This study demonstrates adsorptive-remediation of cobalt oxide nanoparticles (CoO NPs) from the water. The α-cellulose-fibers were extracted from waste-paper biomass (WP-αCFs) and magnetized with Fe3O4 NPs (M-WP-αCFs). The XRD, FT-IR, and TGA were performed for detailed characterization of the newly developed bioadsorbent. The M-WP-αCFs was then applied for adsorptive remediation of CoO NPs. The adsorptive kinetics of CoO NPs adsorption onto the M-WP-αCFs reveals the pseudo-second-order model. The various adsorption isotherm studies revealed Langmuir is a best-fit isotherm. A prominently high adsorption capacity qm (1567 mg/g) corroborated extraordinary adsorptive potential of M-WP-αCFs. Furthermore, CoO NPs were adsorbed onto M-WP-αCFs were analyzed by the XPS, VSM, and TEM. Therefore, this study gave rise WP biomass extracted and rapidly-separable nano-biocomposite of ‘M-WP-αCFs’ with a high-capacity for CoO NPs remediation and can be further applied in remediation of several other engineered-nanomaterials.

The recent boom of nanomaterials printing in the fields of biomedical engineering, bioanalysis and flexible electronics has greatly stimulated researchers' interest in printing technologies. However, specifically formulated nanomaterial inks have limited the types of printable nanomaterials. Here, a unique non-powered capillary force-driven stamped (CFDS) approach, combining a 3D-printed stamper with a paper substrate, is developed for directly printing patterned nanomaterials aqueous solution. The CFDS approach has two processes, including the loading process in which the capillary force of the stamper channel is stronger than gravity, and the deposition process, in which the synergistic action of the capillary force of the paper fibre tubes and gravity is approximately 20 times the capillary force of the stamper channel. Four additive-free nanomaterial aqueous solutions, including nanowires, nanosheets, nanostars and nanogels, are used to print patterns, and show slight diffusion and desired uniformity with a diffusion rate and roundness of 1.12 and 0.78, respectively, demonstrating the feasibility of this approach. Four kinds of nanogel with different fluorescence labels are simultaneously printed to challenge the approach and demonstrate its flexibility and scalability. The resolution of the approach is 0.3 mm. Without any post-processing, the stamped paper substrates directly serve as paper-based surface enhanced Raman scattering substrates with an enhancement factor of 4 × 106 and as electrodes with a resistance of 0.74 Ω, demonstrating their multi-functionality. Due to its general, flexible and scalable applicability, this simple, low-cost and non-powered approach could be widely applied to the personalized printing of nanomaterials on paper substrates.

Patterned paper has characteristics that lead to miniaturized assays that run by capillary action with small volumes of fluids. These methods suggest a path for the development of simple, inexpensive, and portable diagnostic assays that can be useful in remote settings, where simple immunoassays are becoming increasingly important for detecting disease and monitoring health. Incorporation of nanomaterials plays a major role in sensing probe immobilization and detection sensitivity of paper-based devices. Nanomaterial properties, such as increased surface area, have aided with signal amplification and lower detection limits. This review focuses on application of nanomaterials as signal amplification elements on origami paper-based electro-analytical devices for immune biomarkers detection with a brief introduction about various fabrication techniques and designs, biological and detection methods. In this review, we comprehensively summarize the selected latest research articles from 2013 to May 2015 on application of nanomaterials in various types of origami paper based electrochemical and photoelectrochemical immunosensors. The review breaks into two parts. The first part devotes to the development and applications of nanomaterials in electrochemical immunesensing. The second part provides an overview of recent origami paper based photoelectrochemical immunosensors.

In this paper, we present high-performance and versatile inkjet-printed paper photo-actuators based on two-dimensional (2D) nanomaterials. As a rapid fabrication method, inkjet printing of 2D materials is used to promptly fabricate photo-actuators in a bi-layer paper/polymer structure. Water-based and biocompatible inks based on graphene and molybdenum disulfide are developed based on liquid phase exfoliation and differential centrifugation technique. It is shown that incorporation of 2D materials with inkjet printing techniques and liquid phase exfoliation can lead to rapid fabrication of photo-actuators with huge opto-mechanical energy release and versatility with a broad range of applications due to specific design and methods presented in this paper.

As two-dimensional layered nanomaterials, the tungsten disulfide (WS2) nanosheets can be used as building blocks of paper-like electrodes for high-performance FSs. However, poor conductivity and mechanical property of WS2 nanosheets (NSs) paper greatly hinders their capacitance and/or rate performance. To solve these problems, we fabricated the WS2-multiwalled carbon nanotubes (MWCNTs)/polyaniline (PANI) composite papers based on liquid exfoliation and electrochemical deposition for high-performance flexible supercapacitors. The WS2-MWCNTs/PANI with conductive PANI chains linked WS2 NSs and MWCNTs takes the advantages of high-electronic double-layer capacitance originated from the internal surface areas of MWCNTs and effective pseudocapacitance generated by exfoliated WS2 NSs and PANI. Electrochemical studies showed that the gravimetric-specific capacitance of WS2-MWCNTs/PANI can reach ~760.1 F/g at a current density of 1 A/g. A symmetric flexible solid-state supercapacitor was also assembled and studied. The WS2-MWCNTs/PANI-assembled FS device also has an excellent area specific capacitance of 1158.7 mF/cm2 at a current density of 0.5 mA/cm2 together with a high-capacity retention of ~82.5% after 2000 cycles.

We proposed a new type of low-cost and environmentally friendly photoconductive sensor, based on GaSe/graphite nanocomposite fully dry drawn on paper. The proposed fully-drawn nanocomposite sensors successfully utilize the unique combination of structural and electrical properties of a layered semiconductor and graphite. In spite of the relatively pure photosensitivity of the proposed photodetectors, we believe that this work is the first step for the further development and enhancement of extremely simple and low-cost paper-based dry drawn layered semiconductor/graphite nanocomposite sensors.

Researchers have combined carbon nanotubes and nanoporous cellulose to make lithium-ion batteries and supercapacitors that are both lighter and more flexible than existing devices.

Cellulose nanomaterials with high yield and desired properties were sustainably produced using a facile recyclable acid treatment (oxalic acid) with mineral acid catalysis at ambient pressure. The resultant nanocellulose was uniform in dimensions (diameter and length distributions) and highly dispersible in the aqueous phase. The nanocellulose with yield up to 33.9%, a zeta potential of -53.9 mV, and 100% volume stability (24 h) was achieved via oxalic acid treatment in conjunction with sulfuric acid addition. The coating of such nanocellulose on paper created a uniform and dense layer on the surface, which lowered Gurley air permeability (i.e., prolonging the time required for air flow from 3.9 to 681.9 s per 100 mL). Moreover, the coated paper showed a complete grease barrier after 48 h and presented easy-cleaning behavior. The approach developed in this work offers an adoptable guidance to design green and sustainable easy-cleaning surfaces. In turn, this approach will provide potential applications of nanocellulose for green based packaging and environmental protection.

Two Australian native wooden sources (Acacia Mangium and Eucalyptus Globulus) derived pulps were explored as raw feed stocks to prepare the valuable nanomaterial of cellulose nanocrystals (CNC). After bleaching and acid hydrolysis, cellulose nanocrystals were successfully produced with high yields of approximately 60% for both kraft pulps. According to the characterization of SEM and AFM, the as prepared CNC had a rod like structure with the length and diameter in the range of 200~1000 nm and 10~100 nm, respectively based on the initial wooden source. XRD confirmed the crystalline structure of the resulting CNC. Further characterisation by TGA showed that the chemical treatment of the wood pulp had impact upon the thermal stability, evidenced by a lower onset temperature of the thermal decomposition of CNC.

Extensive production of nanomaterials of various properties needs to be coupled with rapid toxicity testing in order to provide information about their potential risks to the environment and human health. Miniaturization of toxicity tests may accelerate economical testing of nanomaterials, but is not a common practice. We describe a case study to miniaturize a commonly used toxicity test with plant duckweed Lemna minor. 6-well, 12-well and 24-well culture plates were used to assess their potential use for the duckweed toxicity test with potassium chloride as reference material. The results were compared to the standard test design using 100 mL glass beakers. The comparison showed that the best agreement was with the 6-well vessels. This set-up was further used for toxicity testing of zinc oxide nanoparticles (ZnO NP) and zinc chloride. Zinc was not adsorbed onto either glass or plastic walls of the miniaturized system. We assume that in both vessels a fast agglomeration and settling of ZnO NP took place. Linear regression and statistical testing indicated a good correlation between the toxicity results obtained in the standard test and miniaturized 6-well vessels. The miniaturization of the test system for assessing the biological effect of nanomaterials on Lemna minor could become an appropriate alternative to the traditionally used high volume vessels.

Scheelite-type Ca1−xMnxMoO4 (x = 0.0, 0.01, 0.05, 0.10 and 0.15) nanomaterials were successfully synthesized via a combustion route. Dielectric studies showed a weak n-type electrical conductivity characteristic for insulators and low relative permittivity (er

Fume hoods are one of the most common types of equipment applied to reduce the potential of particle exposure in laboratory environments. A number of previous studies have shown particle release during work with nanomaterials under fume hoods. Here, we assessed laboratory workers’ inhalation exposure during synthesis and handling of CuO, TiO2 and ZnO in a fume hood. In addition, we tested the capacity of a fume hood to prevent particle release to laboratory air during simulated spillage of different powders (silica fume, zirconia TZ-3Y and TiO2). Airborne particle concentrations were measured in near field, far field, and in the breathing zone of the worker. Handling CuO nanoparticles increased the concentration of small particles (

Green graphene materials prepared by photoreduction of graphite oxide were first time blended with aqueous-based silk fibroin proteins to improve the mechanical and thermal properties of silk biomaterials, and their nanocomposite interaction mechanism was illustrated. Powder X-ray diffraction (XRD) analysis confirmed the complete exfoliation of graphite oxide to graphene in presence of focused pulses of solar radiation. By varying the concentration of graphene (0.1 wt% to 10 wt%), a series of free standing graphene-silk films were prepared and were systematically characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nanoindentation measurements. The homogeneity of graphene in silk as well as the thermal stability of the composite films was demonstrated by thermal gravimetric analysis (TGA) and temperature-modulated differential scanning calorimetry (TMDSC). Surprisingly, silk composite film containing only 0.5 wt% of graphene gives the highest Young's modulus of 1.65 GPa (about 5.8 times higher than the pure silk's modulus), indicating a nano-composite to micro-composite transition of silk-graphene structure occurred around this mixing ratio. This finding provided an easy approach to improve the elastic modulus and other physical properties of silk materials by adding a tiny amount of graphene sheets. Fibroblast cells studies also proved that these graphene-silk materials can significantly improve cell adhesion, growth and proliferation. This protein nanocomposite study provided a useful model to understand how to manipulate the hydrophobic-hydrophobic and polar-polar interactions between high-surface-area inorganic nanomaterials and amphiphilic protein materials, which has many emerging applications in the material science and engineering, such as bio-device fabrication, drug storage and release, and tissue regeneration.

Transition metals, such as iron (Fe)- or cobalt (Co)-based nanomaterials, are promising electrocatalysts for oxygen reduction reactions (ORR) in fuel cells due to their high theoretical activity and low cost. However, a major challenge to using these metals in place of precious metal catalysts for ORR is their low efficiency and poor stability, thus new concepts and strategies should be needed to address this issue. Here, we report a hybrid aciniform nanostructures of Fe nanofragments embedded in thin nitrogen (N)-doped graphene (Fe@N-G) layers via a heat treatment of graphene oxide-wrapped iron oxide (Fe2O3) microparticles with melamine. The heat treatment leads to transformation of Fe2O3 microparticles to nanosized zero-valent Fe fragments and formation of core-shell structures of Fe nanofragments and N-doped graphene layers. Thin N-doped graphene layers massively promote electron transfer from the encapsulated metals to the graphene surface, which efficiently optimizes the electronic structure of the graphene surface and thereby triggers ORR activity at the graphene surface. With the synergistic effect arising from the N-doped graphene and Fe nanoparticles with porous aciniform nanostructures, the Fe@N-G hybrid catalyst exhibits high catalytic activity, which was evidenced by high E1/2 of 0.82 V, onset potential of 0.93 V, and limiting current density of 4.8 mA cm−2 indicating 4-electron ORR, and even exceeds the catalytic stability of the commercial Pt catalyst.

The volume-specific surface area (VSSA) of a particulate material is one of two apparently very different metrics recommended by the European Commission for a definition of “nanomaterial” for regulatory purposes: specifically, the VSSA metric may classify nanomaterials and non-nanomaterials differently than the median size in number metrics, depending on the chemical composition, size, polydispersity, shape, porosity, and aggregation of the particles in the powder. Here we evaluate the extent of agreement between classification by electron microscopy (EM) and classification by VSSA on a large set of diverse particulate substances that represent all the anticipated challenges except mixtures of different substances. EM and VSSA are determined in multiple labs to assess also the level of reproducibility. Based on the results obtained on highly characterized benchmark materials from the NanoDefine EU FP7 project, we derive a tiered screening strategy for the purpose of implementing the definition of nanomaterials. We finally apply the screening strategy to further industrial materials, which were classified correctly and left only borderline cases for EM. On platelet-shaped nanomaterials, VSSA is essential to prevent false-negative classification by EM. On porous materials, approaches involving extended adsorption isotherms prevent false positive classification by VSSA. We find no false negatives by VSSA, neither in Tier 1 nor in Tier 2, despite real-world industrial polydispersity and diverse composition, shape, and coatings. The VSSA screening strategy is recommended for inclusion in a technical guidance for the implementation of the definition. Graphical abstractWe evaluate the extent of agreement between classification by electron microscopy (EM) and classification by Volume-Specific Surface Area (VSSA) on a large set of diverse particulate substances. These represent the challenges anticipated for identification of nanomaterials by the European Commission recommendation for a definition of nanomaterials for regulatory purposes. Electronic supplementary material The online version of this article (doi:10.1007/s11051-017-3741-x) contains supplementary material, which is available to authorized users.

Graphene is a two dimensional (2D) planar and hexagonal array of carbon atoms and has been studied extensively as advanced nanomaterials for important technological applications. This review summarizes the recent developments in chemistry, materials and energy applications of graphene, doped graphene and their composites with nanoparticles (NPs). It first highlights the new chemistry used to synthesize high quality graphene. It then outlines the methodologies developed to dope graphene with heteroatoms to modify and control graphene properties. It further describes the general approaches to graphene–NP composites via either direct NP growth onto graphene or self-assembly of the pre-formed NPs on graphene surface. These graphene–NP composites provide some ideal systems for studying synergistic effects between graphene and NPs on catalysis. The review focuses on applications of graphene–NP composites in increasing electrochemical energy storage density and in catalyzing chemical reactions with much desired electrochemical efficiencies.

Characterisation of engineered nanomaterials (NMs) is of outmost importance for the assessment of the potential risks arising from their extensive use. NMs display indeed a large variety of physico-chemical properties that drastically affect their interaction with biological systems. Among them, hydrophobicity is an important property that is nevertheless only slightly covered by the current physico-chemical characterisation techniques. In this work, we developed a method for the direct characterisation of NM hydrophobicity. The determination of the nanomaterial hydrophobic character is carried out by the direct measurement of the affinity of the NMs for different collectors. Each collector is an engineered surface designed in order to present specific surface charge and hydrophobicity degrees. Being thus characterised by a combination of surface energy components, the collectors enable the NM immobilisation with surface coverage in relation to their hydrophobicity. The experimental results are explained by using the extended DLVO theory, which takes into account the hydrophobic forces acting between NMs and collectors. Graphical abstractDetermination of hydrophobicity character of nanomaterials by measuring their affinity to engineered surfaces. Electronic supplementary material The online version of this article (doi:10.1007/s11051-017-3804-z) contains supplementary material, which is available to authorized users.

Herein, we report three different analytical applications of multi–layers of oxidised graphene nanoribbons (GNOs). In the first section of this paper, the most significant results concern the effect of GNOs on the proliferation of NIH3T3 murine fibroblasts. Results show that GNOs represent the most biocompatible nanomaterials (compared with other ones, such as carbon black, single–wall carbon nanotubes pristine and treated carbon nanotubes) to use as nano–carrier in nanomedicine. In fact, GNO has been successfully used 'in vitro', for the transfection of the viral genome, particularly that relating to the hepatitis A virus (HAV - that normally is not able to replicate in some cell lines), in mammalian cells (BGM–Buffalo Green Monkey). The cell imaging is performed using the auto–fluorescence property of GNO (without additional steps of chemical conjugation with fluorescent probes), one of many extraordinary optical features exhibited by this new nanomaterial. In the second section, GNOs have been functionalised with ionic liquids (ILs) in order to obtain nanocomposite materials with enhanced physical–chemical properties. Latter are very useful for the restoration of modern tracing papers, obtained by refining forced (suffering from typical problems due to poor preservation of cultural heritage, such as gaps, tears and flaps). The results show that the tear is to be newly 'consolidated' and GO/ILs create bridges that make solidify the flaps. The optical microscope images show encouraging results because they do not appreciate significant variations in the optical properties of the substrate, after the treatment. In the third section, ionic liquids are used to disperse GNO to obtain stable and homogeneous nano–emulsions, to cast directly on the Screen–Printed Electrode (SPE) surfaces. New chemical sensors for the selective electrochemical detection of (a) neurotransmitters and (b) NADH (for the assembly of dehydrogenase biosensors) have also been assembled.

The rapid production and accurate deposition of graphene composites are first integrated into one process, due to the strong interaction between the polymer bond with sodium dodecyl sulfonate (SDS) and graphene. It is demonstrated that tension-shear exfoliation in high viscosity fluid may get a higher graphene production rate than in N-methyl-pyrrolidone. In addition, the micro-scale patterns of graphene nanomaterials produced by this method show high electrical conductivity and superior sensitivity to pressure due to their porous structure.

Currently established and projected regulatory frameworks require the classification of materials (whether nano or non-nano) as specified by respective definitions, most of which are based on the size of the constituent particles. This brings up the question if currently available techniques for particle size determination are capable of reliably classifying materials that potentially fall under these definitions. In this study, a wide variety of characterisation techniques, including counting, fractionating, and spectroscopic techniques, has been applied to the same set of materials under harmonised conditions. The selected materials comprised well-defined quality control materials (spherical, monodisperse) as well as industrial materials of complex shapes and considerable polydispersity. As a result, each technique could be evaluated with respect to the determination of the number-weighted median size. Recommendations on the most appropriate and efficient use of techniques for different types of material are given. Graphical Abstract Electronic supplementary material The online version of this article (doi:10.1007/s11051-016-3461-7) contains supplementary material, which is available to authorized users.

In this contribution, the advantages and limitations of two computational techniques that can be used for the investigation of nanoparticles activity and toxicity: classic nano-QSAR (Quantitative Structure–Activity Relationships employed for nanomaterials) and 3D nano-QSAR (three-dimensional Quantitative Structure–Activity Relationships, such us Comparative Molecular Field Analysis, CoMFA/Comparative Molecular Similarity Indices Analysis, CoMSIA analysis employed for nanomaterials) have been briefly summarized. Both approaches were compared according to the selected criteria, including: efficiency, type of experimental data, class of nanomaterials, time required for calculations and computational cost, difficulties in the interpretation. Taking into account the advantages and limitations of each method, we provide the recommendations for nano-QSAR modellers and QSAR model users to be able to determine a proper and efficient methodology to investigate biological activity of nanoparticles in order to describe the underlying interactions in the most reliable and useful manner. Electronic supplementary material The online version of this article (doi:10.1007/s11051-016-3564-1) contains supplementary material, which is available to authorized users.

Highly water dispersible rhodium–graphene nanocomposite have been successfully synthesized by the simple reduction of Rh3+ salt on poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO/PPO/PEO) triblock copolymer or pluronic-stabilized graphene oxide (GO) nanosheets with borohydride. Rhodium nanoparticles, having average size of 1–3 nm, are homogeneously distributed through out the graphene sheets. Some porous structures of graphene sheets have also been observed after the reduction of pluronic-stabilized GO in the presence of metal ions. The material is very effective for hydrogenation of arenes, especially for benzene as the substrate material at the room temperature and 5 atm pressure of hydrogen.

5 páginas, 4 figuras, 1 tabla.-- et al., Nanostructured biological materials inspire the creation of materials with tunable mechanical properties. Strong cellulose nanofibrils derived from bacteria or wood, can form ductile or tough networks, that are suitable as functional materials. Here, we show that freeze-dried bacterial cellulose nanofibril aerogels can be used as templates for making lightweight porous magnetic aerogels, which can be compacted into a stiff magnetic nanopaper. The 20–70-nm-thick cellulose nanofibrils act as templates for the non-agglomerated growth of ferromagnetic cobalt ferrite nanoparticles (diameter, 40–120 nm). Unlike solvent-swollen gels and ferrogels our magnetic aerogel is dry, lightweight, porous (98%), flexible, and can be actuated by a small household magnet. Moreover, it can absorb water and release it upon compression. Owing to their flexibility, high porosity and surface area, these aerogels are expected to be useful in microfluidics devices and as electronic actuators., This work was supported by the Stiftelsen för Strategisk Forskning Center BIOMIME at KTH (Royal Institute of Technology), the Swedish Research Council, the Swedish Foundation for Strategic Research, the Wallenberg Wood Science Center, the Knut and Alice Wallenberg Foundation (Mikro/Nanovetenskap), the Swedish Defence Research Agency, the Spanish Ministerio de Ciencia e Innovación (MAT2007-66309-C02 and CSD2006-00012 Consolider-Ingenio 2010), the Catalan Direcció General de Recerca (2009-DGR-1292) and the Academy of Finland.

Inherent nanomaterial characteristics, composition, surface chemistry, and primary particle size, are known to impact particle stability, uptake, and toxicity. Nanocomposites challenge our ability to predict nanoparticle reactivity in biological systems if they are composed of materials with contrasting relative toxicities. We hypothesized that toxicity would be dominated by the nanoparticle surface (shell vs core), and that modulating the surface ligands would have a direct impact on uptake. We exposed developing zebrafish (Danio rerio) to a series of ~70 nm amine-terminated silver nanoparticles with silica shells (AgSi NPs) to investigate the relative influence of surface amination, composition, and size on toxicity. Like-sized aminated AgSi and Si NPs were more toxic than paired hydroxyl-terminated nanoparticles; however, both AgSi NPs were more toxic than the Si NPs, indicating a significant contribution of the silver core to the toxicity. Incremental increases in surface amination did not linearly increase uptake and toxicity, but did have a marked impact on dispersion stability. Mass-based exposure metrics initially supported the hypothesis that smaller nanoparticles (20 nm) would be more toxic than larger particles (70 nm). However, surface area-based metrics revealed that toxicity was independent of size. Our studies suggest that nanoparticle surfaces play a critical role in the uptake and toxicity of AgSi NPs, while the impact of size may be a function of the exposure metric used. Overall, uptake and toxicity can be dramatically altered by small changes in surface functionalization or exposure media. Only after understanding the magnitude of these changes, can we begin to understand the biologically available dose following nanoparticle exposure. Electronic supplementary material The online version of this article (doi:10.1007/s11051-014-2761-z) contains supplementary material, which is available to authorized users.

A tremendous work is being done to apply graphene to create novel advanced nanomaterials. The minimized number of few-layer graphene, the absence of different dispersants in the films produced from dispersions of graphene, the concentration of these dispersions are often a key to realizing the goal of achieving high functional performance. Here we show an efficient preparation of graphene by ultrasound disintegration in an organic solvent of the nanostructured graphite obtained by solvent-free mechanochemical delamination in the absence of chemically active compounds. The predominant part of single-sheet graphene nanoparticles in the obtained dispersions is experimentally confirmed. The proposed approach essentially improves the known liquid exfoliation method based on ultrasound disintegration of the bulk graphite, because the proposed preliminary mechanochemical treatment of the initial bulk graphite could provide more than 75 % yield of the single-sheet graphene nanoparticles in the dispersant-free high concentration dispersions (in different organic solvents, including ethanol).

A simple co-precipitation reaction between Ln3+ cations (Ln = lanthanide) and phosphate ions in the presence of polyethylene glycol (PEG), including post-treatment under hydrothermal conditions, leads to the formation of Tb3+-doped LaPO4 crystalline nanorods. The nanoparticles obtained can be successfully coated with amorphous and porous silica, forming core/shell-type nanorods. Both products reveal intensive green luminescence under UV lamp irradiation. The surface of the core/shell-type product can also be modified with –NH2 groups via silylation procedure, using 3-aminopropyltriethoxysilane as a modifier. Powder X-ray diffraction, transmission electron microscopy, and scanning electron microscopy confirm the desired structure and needle-like shape of the products synthesized. Fourier transform infrared spectroscopy and specific surface area measurements by Brunauer–Emmett–Teller method reveal a successful surface modification with amine groups of the core/shell-type nanoparticles prepared. The nanomaterials synthesized exhibit green luminescence characteristic of Tb3+ ions, as solid powders and aqueous colloids, examined by spectrofluorometry. The in vitro cytotoxicity studies reveal different degree toxicity of the products. LaPO4:Tb3+@SiO2@NH2 exhibits the smallest toxicity against B16F0 mouse melanoma cancer cells and human skin microvascular endothelial cell lines, in contrast to the most toxic LaPO4:Tb3+@SiO2. Graphical Abstract

Graphene-based hybrid nanomaterials have recently been investigated and proposed as a promising platform for electronic, optoelectronic, and electrochemical devices because of their high-surface area, remarkable chemical stability, and electrical conductivity. In this study, we demonstrated a facile method for the preparation of graphene/Ni(OH)2 hybrid nanomaterials. First, polymer-functionalized graphene oxide (PGO) was prepared by Cu(I)-catalyzed click coupling of alkyne-functionalized graphene oxide with azide-terminated poly(vinylpyrrolidone). Subsequently, Ni(OH)2 nanoparticles were deposited onto graphene nanosheets using PGO as a template. Upon reduction with NaBH4, graphene/Ni(OH)2 hybrid nanostructures were constructed. The as-prepared graphene/Ni(OH)2 hybrid nanosheets were directly immobilized onto the surface of glassy carbon electrode for glucose determination. The as-fabricated nonenzymatic glucose sensor exhibited a wider linearity range from 0.3 to 750 μM with a detection limit of 30 nM (S/N = 3).

A bifunctional hybrid nanomaterial, which can show magnetic and luminescent properties, was obtained. A magnetic phase was synthesized as a core/shell type composite. Nanocrystalline magnetite, Fe(3)O(4) was used as the core and was encapsulated in a silica shell. The luminescent phase was GdPO(4) doped with Eu(3+) ions, as the emitter. The investigated materials were synthesized using a coprecipitation method. Encapsulated Fe(3)O(4) was "trapped" in a nano-scaffold composed of GdPO(4) crystalline nanoneedles. When an external magnetic field was applied, this hybrid composite was attracted in one direction. Also, the luminescent phase can move simultaneously with magnetite due to a "trapping" effect. The structure and morphology of the obtained nanocomposites were examined with the use of transmission electron microscopy and X-ray powder diffraction. Spectroscopic properties of the Eu(3+)-doped nanomaterials were studied by measuring their excitation and emission spectra as well as their luminescence decay times. GRAPHICAL ABSTRACT

Controlled patterning and formation of nanostructures on surfaces based on self-assembly is a promising area in the field of "bottom-up" nanomaterial engineering. We report formation of net-like structures of gold nanoparticles (Au NPs) in a matrix of liquid crystalline amphiphile 4'-n-octyl-4-cyanobiphenyl at the air-water interface. After initial compression to at least 18 mN m(-1), decompression of a Langmuir film of a mixture containing both components results in formation of net-like structures. The average size of a unit cell of the net is easily adjustable by changing the surface pressure during the decompression of the film. The net-like patterns of different, desired average unit cell areas were transferred onto solid substrates (Langmuir-Blodgett method) and investigated with scanning electron microscopy and X-ray reflectivity (XRR). Uniform coverage over large areas was proved. XRR data revealed lifting of the Au NPs from the surface during the formation of the film. A molecular mechanism of formation of the net-like structures is discussed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11051-012-0826-4) contains supplementary material, which is available to authorized users.

1 s -1 ), high carrier density (10 13 cm -2 ), high thermal conductivity, room temperature Hall effect, ambipolar field-effect characteristics, high signal-to-noise ratio (due to low intrinsic noises), and extremely high mechanical strength (200 times greater than steel, tensile modulus of 1 TPa). The large surface area of graphene enhances the surface loading of desired biomolecules, either through passive adsorption, or by covalent crosslinking to the reactive groups of biomolecules. On the other hand, the excellent conductivity and small band gap of graphene are beneficial for the conduction of electrons between the biomolecules and the electrode surface. Graphene has about two-fold higher effective surface area and greater cost-effectiveness than carbon nanotubes. Additionally, it has greater homogenous surface that is responsible for highly uniform and efficient functionalization. Graphene has been synthesized by several methods that include exfoliation of graphite, electric arc discharge, epitaxial growth on electrically insulating surfaces, opening of carbon nanotubes, growth from metal-carbon melts, pyrolysis of sodium ethoxide, sonication of graphite, reduction of carbon dioxide, Chemical Vapor Deposition (CVD), and reduction of graphene oxide. The mechanical exfoliation is unable to produce large graphene sheets and also has low throughput. However, CVD can produce large areas of single layer graphene for mass production. The chemical or thermal reduction of graphene oxide is another mass production method that is most commonly employed due to its higher cost-effectiveness. It has also been reported that graphene synthesized by chemical redox reaction possess many structural defects that are highly beneficial for electrochemical applications. A wide range of chemical modification and biomolecular binding strategies [3], have been developed for the induction of specific functional groups (such as carboxyl, hydroxyl, sulfonate, acid chloride and amine) on graphene and for binding the chemically-modified graphene to the biomolecules, respectively. Similarly, several methods have also been developed for preparing graphene-nanocomposites by conjugating graphene to nanomaterials, and/or polymers.

Graphene is a novel two-dimensional nanomaterial that holds great potential in electronic and sensor applications. By etching the edges to form nanoribbons or introducing defects on the basal plane, it has been demonstrated that the physical and chemical properties of graphene can be drastically altered. However, the lithographic or chemical techniques required to reliably produce such nanoribbons remain challenging. Here, we report the fabrication of nanosensors based on holey reduced graphene oxide (hRGO), which can be visualized as interconnected graphene nanoribbons. In our method, enzymatic oxidation generated holes within the basal plane of graphene oxide, and after reduction with hydrazine, hRGO was formed. When decorated with Pt nanoparticles, hRGO exhibited a large and selective electronic response toward hydrogen gas. By combining experimental results and theoretical modeling, we propose that the increased edge-to-plane ratio, oxygen moieties, and Pt nanoparticle decoration were responsible for the observed gas sensing with hRGO nanostructures.

13 pages, 5 figures; International audience; Excellent electronic properties notwithstanding, the use of graphene in field- effect transistors is not practical at room temperature without modification of its intrinsically semi-metallic nature to introduce a band gap. Quantum confinement effects can create a band gap in graphene nanoribbons, but existing nanoribbon fabrication methods are slow and often produce disordered edges that compromise electronic properties. Here we demonstrate the self- organized growth of graphene nanoribbons on a templated silicon carbide substrate prepared using scalable photolithography and microelectronics processing. Direct nanoribbon growth avoids damaging post-processing. Raman spectroscopy, high-resolution transmission electron microscopy, and electrostatic force microscopy confirm that nanoribbons as narrow as 40 nm can be grown at specifed positions on the substrate. Our prototype graphene devices exhibit quantum confinement at low temperature (4 K), and an on-off ratio of 10 and carrier mobilities up to 2,700 cm2/(V . s) at room temperature. We demonstrate the scalability of this approach by fabricating 10,000 top-gated graphene tran-sistors on a 0.24 cm2 SiC chip, which is the largest density of graphene devices reported to date.

The adhesion energies for atomically thin graphene membranes on silicon dioxide substrates have now been measured.

Directed self-assembly of nano or microsized materials as building blocks is a very exciting research topic to construct large-scale but still uniform 2D or 3D architectures. Graphene shows great potential as an advanced building block for fabricating varied graphene-based functional films or architectures together with other metal, metal oxide and semiconductor nanomaterials. In our work, we demonstrated an approach to fabrication of flexible, transparent conductive thin films via layer-by-layer (LbL) assembly of oppositely charged reduced graphene oxides (RGOs). The graphene thin films showed remarkable optical–electronic properties. Inspired by this, we further fabricated transparent conductive hybrid thin film via LbL assembly of oppositely charged RGO nanosheets and Pt nanoparticles. The graphene– Pt hybrid thin film showed transient optical property as well as appropriate conductive and wetting properties. Moreover, we demonstrated graphene wrapped- MnO2 (GW- MnO2 ) nanocomposites by self-assembly of honeycomb MnO2 nanospheres and graphene sheets via an electrostatic co-precipitation method. The hybrid materials had a good electrochemical performance.

Gold nanoparticles are one of the most used nanomaterials. They are usually synthesized by the reduction of gold(III) chloride. However, the presence of halide ions in the reaction mixture is not always welcome. In some cases, these ions have detrimental influence on the morphology and structure of resulting nanoparticles. Here, we present a simple and halogen-free procedure to prepare gold nanoparticles by reduction of gold(III) oxide in neat oleylamine. The method provides the particles with an average size below 10 nm and dispersity of tens of percent. The process of nanoparticle formation was monitored using UV–Vis spectroscopy. The structure and chemical composition of the nanoparticles was determined by SEM, XPS and EDX. We also proposed the mechanism of reduction of gold(III) oxide based on MS, IR and NMR data. Importantly, the synthetic protocol is general and applicable for the preparation of other coinage metal nanoparticles from the corresponding metal oxides. For instance, we demonstrated that the absence of halogen enables efficient alloying of metals when preparing gold–silver bimetallic nanoparticles. Electronic supplementary material The online version of this article (doi:10.1007/s11051-016-3576-x) contains supplementary material, which is available to authorized users.

Radiolabelling of industrially manufactured nanoparticles is useful for nanoparticle dosimetry in biodistribution or cellular uptake studies for hazard and risk assessment. Ideally for such purposes, any chemical processing post production should be avoided as it may change the physico-chemical characteristics of the industrially manufactured species. In many cases, proton irradiation of nanoparticles allows radiolabelling by transmutation of a tiny fraction of their constituent atoms into radionuclides. However, not all types of nanoparticles offer nuclear reactions leading to radionuclides with adequate radiotracer properties. We describe here a process whereby in such cases nanoparticles can be labelled with 7Be, which exhibits a physical half-life of 53.29 days and emits γ-rays of 478 keV energy, and is suitable for most radiotracer studies. 7Be is produced via the proton-induced nuclear reaction 7Li(p,n)7Be in a fine-grained lithium compound with which the nanoparticles are mixed. The high recoil energy of 7Be atoms gives them a range that allows the 7Be-recoils to be transferred from the lithium compound into the nanoparticles by recoil implantation. The nanoparticles can be recovered from the mixture by dissolving the lithium compound and subsequent filtration or centrifugation. The method has been applied to radiolabel industrially manufactured SiO2 nanoparticles. The process can be controlled in such a way that no alterations of the 7Be-labelled nanoparticles are detectable by dynamic light scattering, X-ray diffraction and electron microscopy. Moreover, cyclotrons with maximum proton energies of 17–18 MeV that are available in most medical research centres could be used for this purpose.

Granulometry is the regulatory category where the differences between traditional materials and nanomaterials culminate. Reported herein is a careful validation of methods for the quantification of dispersability and size distribution in relevant media, and for the classification according to the EC nanodefinition recommendation. Suspension-based techniques can assess the nanodefinition only if the material in question is reasonably well dispersed. Using dispersed material of several chemical compositions (organic, metal, metal-oxide) as test cases we benchmark analytical ultracentrifugation (AUC), dynamic light scattering (DLS), hydrodynamic chromatography, nanoparticle tracking analysis (NTA) against the known content of bimodal suspensions in the commercially relevant range between 20 nm and a few microns. The results validate fractionating techniques, especially AUC, which successfully identifies any dispersed nanoparticle content from 14 to 99.9 nb% with less than 5 nb% deviation. In contrast, our screening casts severe doubt over the reliability of ensemble (scattering) techniques and highlights the potential of NTA to develop into a counting upgrade of DLS. The unique asset of centrifuges with interference, X-ray or absorption detectors—to quantify the dispersed solid content for each size interval from proteins over individualized nanoparticles up to agglomerates, while accounting for their loose packing—addresses also the adsorption/depletion of proteins and (de-)agglomeration of nanomaterials under cell culture conditions as tested for toxicological endpoints.

Here, we present our work on preparing a novel nanomaterial composed of inorganic binding peptides and magnetic nanoparticles for inorganic mining. Two previously selected and well-characterized gold-binding peptides from cell surface display, AuBP1 and AuBP2, were exploited. This nanomaterial (AuBP-MNP) was designed to fulfill the following two significant functions: the surface conjugated gold-binding peptide will recognize and selectively bind to gold, while the magnetic nano-sized core will respond and migrate according to the applied external magnetic field. This will allow the smart nanomaterial to mine an individual material (gold) from a pool of mixture, without excessive solvent extraction, filtration, and concentration steps. The working efficiency of AuBP-MNP was determined by showing a dramatic reduction of gold nanoparticle colloid concentration, monitored by spectroscopy. The binding kinetics of AuBP-MNP onto the gold surface was determined using surface plasmon resonance (SPR) spectroscopy, which exhibits around 100 times higher binding kinetics than peptides alone. The binding capacity of AuBP-MNP was demonstrated by a bench-top mining test with gold microparticles. Graphical abstract Electronic supplementary material The online version of this article (doi:10.1007/s11051-017-3752-7) contains supplementary material, which is available to authorized users.

The commercial applications of silicon nanomaterials as anode in lithium-ion batteries must solve two important problems, namely low expansion and long-term cycle stability. The former is related to nano-silicon structure, while the latter depends on silicon/carbon composite structure and preparation process. In order to suppress volume expansion appeared during lithiation, this paper selects a kind of silicon nanoparticles (SiNPs) with a high degree of amorphization (81.9%), and designs a stable silicon/carbon composite material structure. Inside this structure, graphite nanoflakes (GNFs) with high specific surface are used as the skeleton, which can provide enough surface area for SiNPs to adhere and avoid the local accumulation of SiNPs. Outside this structure is uniformly coated with a layer of amorphous carbon. Raman and x-ray diffraction results show that after the high-temperature carbonization, the nano-silicon in the composite material still maintains a high degree of amorphization (67.1%) and the average crystallite size of Si has only increased from 3.7 to 9.5 nm. The initial Coulombic efficiency and reversible specific capacity of the composite material are 86.7% and 1374.8 mAh g-1, respectively. After mixing with commercial graphite, the initial Coulombic efficiency and reversible specific capacity are 93.7% and 426.4 mAh g-1, respectively. LiNi0.8Co0.1Mn0.1O2(NCM811) is used as the cathode to produce a soft-pack battery. After 900 cycles at room temperature, the capacity remains 86.2%. The silicon/carbon anode material reported in this paper is of great potential for commercialization.

The paper deals with the fabrication, modeling and experimental characterization of a monitorable and renewable graphene-based pollution filter. The main goal is that of demonstrating a method able to monitor in real time the status of such a filter during its operating phases: pollutant adsorption, saturation, and regeneration. The filter is realized by a disk of pressed graphene nanoplatelets. This is a low-cost type of graphene which has recently drawn a great interest due to its potential use in large scale industrial production. Here the nanomaterial is obtained through the exfoliation method assisted by microwave irradiation, by exploiting the thermal expansion of commercial intercalated graphite, according to a low-cost and ecologically friendly procedure. The filter is here used to adsorb acetonitrile, a toxic water-soluble organic compound that is present in some industrial solvents and paints. The monitoring method is based on the interpretation of the time variation of the electrical impedance measured during the filter operating. Two are the main results of the paper. From one side, the graphene filter is shown to be effective in adsorbing the above pollutant, with the additional feature to be fully renewable: all the pollutant is removed from the filter without the need of costly physical or chemical processes. From the other side, the monitoring of the time-evolution of the electrical impedance allows an efficient detection of the different phases of the filter life cycle: clean, polluted, saturated and regenerated. This feature is of potential interest since it enables the predictive maintenance of such filters.

In bioelectrocatalysis, nanomaterials are typically used as a conductive bridge for the gap between the site of oxidation/reduction (i.e., enzymatic biocatalyst) and the current collector (electrode). In this paper, carbon nanomaterial supports have been employed in conjunction with heme-c containing pyrroloquinoline quinone-dependent alcohol dehydrogenase (PQQ-ADH) and aldehyde dehydrogenase (PQQ-AldDH) oxidoreductase enzymes as oxidation catalysts to produce stable high surface area catalyst supports for the bioelectrocatalysis of ethanol in biofuel cells. The structure of PQQ-ADH and PQQ-AldDH allow for direct electron transfer (DET) between the enzymes and carbon nanomaterial support without the use of additional charge carrying chemical mediators. In this paper, the employment of nanomaterials are used to produce stable, high surface area catalyst supports which aid in enzyme adsorption and direct electron transfer. Fundamental DET studies were performed on both PQQ-ADH and PQQ-AldDH in order to understand the processes occurring at the electrode surface. Data shows a direct correlation between concentration of substrate and peak potential and peak current. Incorporating nanotubes into this technology has allowed an increase in the current density of ethanol/air biofuel cells by up to 14.5 fold and increased the power density by up to 18.0 fold.

The utilization of biomaterials such as proteins or peptides has recently been focused on as an attractive way to construct nanomaterials by “bottom-up” strategy. We focus on α-synuclein as a novel scaffold material for functional nanomaterial fabrication. This protein constructs an amyloid-like nanostructure by self-assembly under mild conditions. In this paper, we demonstrate nanomaterial fabrication by utilizing two peptide fragments of the non-amyloid-β component of Alzheimer’s disease amyloid region, which is the key region for α-synuclein fibrillation. One of these peptide fragments contains the sequence corresponding to residues 66–82 of wild-type α-synuclein, while the other contains the same region from the Val70Thr/Val71Thr mutant, whose character is drastically different. In this paper, we confirmed that these two peptides individually formed different rod-like structures. Moreover, these peptides modify the fibril nanostructure of full-length α-synuclein, and these effects depend on the peptide sequences. Therefore, we propose the combination of amyloid-forming protein, and its partial peptide fragments with some mutations have a potential for novel nanomaterial fabrication.

This paper reviews the recent research and development of novel visible-light induced photocatalysts with nanostructures. In recent years, Ag3PO4-based and BiVO4-based nanomaterials have drawn wide attention due to their narrow band gap and excellent photocatalytic performance. The development of the new material covers the synthesis condition, unique morphology, further modification which focused on the Ag3PO4 and BiVO4, respectively. Meanwhile, titanium dioxide has already become one of the classical photocatalyst. However, the band gap of TiO2 (3.2 eV) limits its efficient utilization of solar energy, two categories novel modification methods of TiO2 are proposed to make them active under visible light illumination. Using polymers and dye to modify TiO2 is a wonderful approach to achieve excellent electronic and optical properties mainly in aspect of photocatalytic application. Therefore, the paper summarizes novel nanosized photocatalysts with visible-light response including Ag3PO4-based, BiVO4-based and TiO2-based materials, and suggests the further research prospect for the visible-light induced photocatalysts.

Nanotechnology has the ability to produce novel nano-sized materials with excellent physical and chemical properties to act against phytopathogenic diseases, essential for revolution of agriculture and food industry. The development of facile, reliable and eco-friendly processes for the synthesis of biologically active nanomaterials is an important aspect of nanotechnology. In the present paper, we attempted to compare sonochemical and co-precipitation method for the synthesis of metal sulfide nanoparticles (MS-NPs) for their structural and antifungal properties against various phytopathogenic fungi of rice. The preparation of nanospheres (NSs) and nano rods (NRs) of CuS, FeS and MnS was monitored by UV-Visible spectroscopy complemented by transmission electron microscope (TEM), scanning electron microscope (SEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and Zeta potential analyser. Sonochemical method resulted in formation of spherical shaped nanoparticles of size (7–120 nm), smaller than those of nanorods (50–200 nm) prepared by co-precipitation produced. It was observed that the metal sulfide nanospheres exhibited a better antifungal potential against D. oryzae, C. lunata and S. oryzae as compared to rod shaped metal sulfide nanoparticles. Smaller size and large surface area of spherical shaped particles opens up an important perspective of the prepared MS-NPs.

Compared with bulk material-based sensors, functional sensors fabricated with nanomaterials have many advantages, such as high sensitivity, multifunctional integration, low power-dissipation, and low cost. Black phosphorus (BP) is a two-dimensional (2D) crystal material, which has a higher molecular adsorption energy, tunable direct band gap, high carrier mobility, ambipolar characteristics, and high current on/off ratio. In this paper, BP bulk was ground into powder, and then the powder was dispersed in dimethylformamide (DMF) to obtain two-dimensional BP nanosheets solution. Afterwards, the black phosphorus nanosheets and H2PtCl6 solution were mixed to obtain the Pt functionalized BP nanocomposite by one-step reduction method. Pt nanoparticles were dispersed on the surface of BP nanosheets with highly uniform size. The Pt functionalized BP nanocomposite exhibited a high response of 2.19 to 10 ppm NOx in a short period of 1.93 s at room temperature. The detection limit was as low as 30 ppb. The Pt functionalized BP nanocomposite will be useful for precise detection of NOx.