Controlled Positioning of Nanoparticles on Graphene by Non-Invasive AFM lithography

Atomic force microscopy is shown to be an excellent lithographic technique to directly deposit nanoparticles on graphene by capillary transport without any previous functionalization of neither the nanoparticles nor the graphene surface while preserving its integrity and conductivity properties. Moreover this technique allows for (sub)micrometric control on the positioning thanks to a new three-step protocol that has been designed with this aim. With this methodology the exact target coordinates are registered by scanning the tip over the predetermined area previous to its coating with the ink and deposition. As a proof-of-concept, this strategy has successfully allowed the controlled deposition of few nanoparticles on 1 μm2 preselected sites of a graphene surface with high accuracy

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Exploring the Limitations of the Use of Competing Reducers to Control the Morphology and Composition of Pt and PtCo Nanocrystals

10 páginas, 9 figuras, 2 tablas.We have explored size- and shape-controlled synthesis of platinum nanocrystals (Pt NCs) by systematically comparing the differential reducing performance of two competing reducing agents in a one-pot synthesis: hexadecanediol, a weak reducer, and metallic cobalt or superhydride, stronger reducers of Pt. In addition to its role as a metal reducer, Co also functions as a shape-directing agent and is incorporated into the Pt NCs, forming a PtCo alloy structure. By maintaining a constant HDD concentration and systematically increasing the Co content, the shape of the resulting NCs was found to alter from polypods, when no Co was present, to cuboctahedrons and cubes when trace amounts of Co were added, and back to polypods when Co dominated the reduction process. On the other hand, when the concentration of HDD was systematically increased (with Co kept constant), evolution from polypod morphology to prismatic/spherical/cubic NCs, followed by irregular shapes was observed. Both experimental results indicate the importance of the competitive role between the reducing agents, their concentration limits for achieving a controlled morphology, and the presence of Co as a shape-directing agent to alter the NC shape. This allows the exploration of a wide range of NC morphologies without significant modification of the synthesis recipe.This work is supported by the Spanish MICINN. S.L. acknowledges the support of the Beatriu de Pinós fellowship from the Catalan Government. M.V. acknowledges the support from project: MAT2006-13572- C02-02.Peer reviewe

Pt nanocrystal evolution in the presence of Au(III)-salts at room temperature: spontaneous formation of AuPt heterodimers

6 páginas, 5 figuras.-- El pdf del artículo es el manuscrito de autor.Room temperature synthesis of AuPt heterodimers is reported using a simple protocol. The role of oleylamine and Pt NCs in the reduction and nucleation of Au has been investigated. There are two unique aspects in this synthesis. Firstly, the synthesis was conducted at room temperature, which enabled the heterodimer growth to progress at a slower rate and thus allowed monitoring of the Au nucleation process. Secondly, these conditions allowed epitaxial growth with no crystal modification at the Au–Pt interphase. The presence of Pt NC seeds markedly accelerated the reaction, serving both as nucleation platforms and as an initial catalytic reducer of the Au ions in solution. The growth of Au on Pt NCs was monitored at different times by UV-vis, HRTEM and XRD.This work was supported by the Spanish MICINN. S.L. thanks the Catalan Gov. for a B.P. grant, and M.V. for the support from project: MAT2006-13572-C02-02.Peer reviewe

Synthesis of Platinum Cubes, Polypods, Cuboctahedrons, and Raspberries Assisted by Cobalt Nanocrystals

10 páginas, 10 figuras, 1 tabla, 1 esquema.The introduction of metallic traces into the synthesis of platinum nanocrystals (Pt NCs) has been investigated as a surfactant-independent means of controlling shape. Various nanocrystal morphologies have been produced without modification of the reaction conditions, composition, and concentration other than the presence of cobalt traces (<5%). In the presence of metallic cobalt (a strong reducer for Pt cations) cubic Pt NCs are obtained, while cobalt ions or gold NCs have no effect on the synthesis, and as a result, polypods are obtained. Intermediate shapes such as cemented cubes or cuboctahedron NCs are also obtained under similar conditions. Thus, various NC shapes can be obtained with subtle changes, which illustrates the high susceptibility and mutability of the NC shape to modification of the reaction kinetics during the early reduction process. Our studies help progress toward a general mechanism for nanocrystal shape control.The work is supported by the Spanish MICIN. S.L. acknowledges the support from a Beatriu de Pinós fellowship from the Catalan Government.Peer reviewe

Biocompatible polydopamine-like particles for the removal of heavy metals at extremely low concentrations

A family of catechol-based submicron particles, with sizes between 200 and 300 nm, was tested for the removal of Cd(II), Pb(II) and Cr(VI) in water. The highest adsorption capacity was obtained with catechol-based particles in the case of Pb(II), followed by Cd(II). However, the catechol particles failed to adsorb Cr(VI). Our results indicate an up to four-fold increase of the adsorption capacity of these particles compared to that of activated carbon under the same experimental conditions. To check the biocompatible character of the submicron particles, their stability was evaluated in a phosphate buffer solution (PBS) and in a cell culture medium. The results confirmed that the presence of proteins in the medium favors their stability. A bioluminescent Vibrio fischeri test and a cytotoxicity assay on the HepG2 cell line were used to determine that the catechol particles did not exhibit any substantial toxicity. The results show that these catechol-based particles can be used as an efficient biocompatible adsorbent to remove heavy metals at extremely low concentrations.A. R. Contreras Rodríguez thanks the financial support through the scholarship provided by the Consejo Nacional de Ciencia y Tecnologia (CONACYT, Mexico). D. Komilis is recipient of a scholarship from the TECNIOSPRING program (ACCIO, Generalitat de Catalunya). We also acknowledge financial support from MINECO (Project CTQ2010-15380/BQU) and MAT2012-38318-C03-02 from the Spanish Government and by FEDER funds. ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295). Authors also thank CM1101 and MP1106 Cost Actions.Peer Reviewe

Biocompatible polydopamine-like particles for the removal of heavy metals at extremely low concentrations

A family of catechol-based submicron particles, with sizes between 200 and 300 nm, was tested for the removal of Cd(II), Pb(II) and Cr(VI) in water. The highest adsorption capacity was obtained with catecholbased particles in the case of Pb(II), followed by Cd(II). However, the catechol particles failed to adsorb Cr(VI). Our results indicate an up to four-fold increase of the adsorption capacity of these particles compared to that of activated carbon under the same experimental conditions. To check the biocompatible character of the submicron particles, their stability was evaluated in a phosphate buffer solution (PBS) and in a cell culture medium. The results confirmed that the presence of proteins in the medium favors their stability. A bioluminescent Vibrio fischeri test and a cytotoxicity assay on the HepG2 cell line were used to determine that the catechol particles did not exhibit any substantial toxicity. The results show that these catechol-based particles can be used as an efficient biocompatible adsorbent to remove heavy metals at extremely low concentrations