Photo-induced enhanced Raman spectroscopy as a probe for photocatalytic surfaces.

Photo-induced enhanced Raman spectroscopy (PIERS) has emerged as a highly sensitive surface-enhanced Raman spectroscopy (SERS) technique for the detection of ultra-low concentrations of organic molecules. The PIERS mechanism has been largely attributed to UV-induced formation of surface oxygen vacancies (Vo) in semiconductor materials, although alternative interpretations have been suggested. Very recently, PIERS has been proposed as a surface probe for photocatalytic materials, following Vo formation and healing kinetics. This work establishes comparison between PIERS and Vo-induced SERS approaches in defected noble-metal-free titanium dioxide (TiO2-x) films to further confirm the role of Vo in PIERS. Upon application of three post-treatment methods (namely UV-induction, vacuum annealing and argon etching), correlation of Vo kinetics and distribution could be established. A proposed mechanism and further discussion on PIERS as a probe to explore photocatalytic materials are also presented. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.

The Infant KIdney Dialysis and Utrafiltration (I-KID) Study: A Stepped-Wedge Cluster-Randomized Study in Infants, Comparing Peritoneal Dialysis, Continuous Venovenous Hemofiltration, and Newcastle Infant Dialysis Ultrafiltration System, a Novel Infant Hemodialysis Device.

OBJECTIVES: Renal replacement therapy (RRT) options are limited for small babies because of lack of available technology. We investigated the precision of ultrafiltration, biochemical clearances, clinical efficacy, outcomes, and safety profile for a novel non-Conformité Européenne-marked hemodialysis device for babies under 8 kg, the Newcastle Infant Dialysis Ultrafiltration System (NIDUS), compared with the current options of peritoneal dialysis (PD) or continuous venovenous hemofiltration (CVVH). DESIGN: Nonblinded cluster-randomized cross-sectional stepped-wedge design with four periods, three sequences, and two clusters per sequence. SETTING: Clusters were six U.K. PICUs. PATIENTS: Babies less than 8 kg requiring RRT for fluid overload or biochemical disturbance. INTERVENTIONS: In controls, RRT was delivered by PD or CVVH, and in interventions, NIDUS was used. The primary outcome was precision of ultrafiltration compared with prescription; secondary outcomes included biochemical clearances. MEASUREMENTS AND MAIN RESULTS: At closure, 97 participants were recruited from the six PICUs (62 control and 35 intervention). The primary outcome, obtained from 62 control and 21 intervention patients, showed that ultrafiltration with NIDUS was closer to that prescribed than with control: sd controls, 18.75, intervention, 2.95 (mL/hr); adjusted ratio, 0.13; 95% CI, 0.03-0.71; p = 0.018. Creatinine clearance was smallest and least variable for PD (mean, sd ) = (0.08, 0.03) mL/min/kg, larger for NIDUS (0.46, 0.30), and largest for CVVH (1.20, 0.72). Adverse events were reported in all groups. In this critically ill population with multiple organ failure, mortality was lowest for PD and highest for CVVH, with NIDUS in between. CONCLUSIONS: NIDUS delivers accurate, controllable fluid removal and adequate clearances, indicating that it has important potential alongside other modalities for infant RRT.

Dynamics of Photo-Induced Surface Oxygen Vacancies in Metal-Oxide Semiconductors Studied Under Ambient Conditions.

Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical technique commonly used in the detection of traces of organic molecules. The mechanism of SERS is of a dual nature, with Raman scattering enhancements due to a combination of electromagnetic (EM) and chemical contributions. In conventional SERS, the EM component is largely responsible for the enhancement, with the chemical contribution playing a less significant role. An alternative technique, called photo-induced enhanced Raman spectroscopy (PIERS) has been recently developed, using a photo-activated semiconductor substrate to give additional chemical enhancement of Raman bands over traditional SERS. This enhancement is assigned to surface oxygen vacancies (V o) formed upon pre-irradiation of the substrate. In this work, the exceptional chemical contribution in PIERS allows for the evaluation of atomic V o dynamics in metal oxide surfaces. This technique is applied to study the formation and healing rates of surface-active V o in archetypical metal-oxide semiconductors, namely, TiO2, WO3, and ZnO. Contrary to conventional analytical tools, PIERS provides intuitive and valuable information about surface stability of atomic defects at ambient pressure and under operando conditions, which has important implications in a wide range of applications including catalysis and energy storage materials.

Monitoring plasmonic hot-carrier chemical reactions at the single particle level.

Plasmon excitation in metal nanoparticles triggers the generation of highly energetic charge carriers that, when properly manipulated and exploited, can mediate chemical reactions. Single-particle techniques are key to unearthing the underlying mechanisms of hot-carrier generation, transport and injection, as well as to disentangling the role of the temperature increase and the enhanced near-field at the nanoparticle-molecule interface. Gaining nanoscopic insight into these processes and their interplay could aid in the rational design of plasmonic photocatalysts. Here, we present three different approaches to monitor hot-carrier reactivity at the single-particle level. We use a combination of dark-field microscopy and photoelectrochemistry to track a hot-hole driven reaction on a single Au nanoparticle. We image hot-electron reactivity with sub-particle spatial resolution using nanoscopy techniques. Finally, we push the limits by looking for a hot-electron induced chemical reaction that generates a fluorescent product, which should enable imaging plasmonic photocatalysis at the single-particle and single-molecule levels.

Understanding and Reducing Photothermal Forces for the Fabrication of Au Nanoparticle Dimers by Optical Printing.

Optical printing holds great potential to enable the use of the vast variety of colloidal nanoparticles (NPs) in nano- and microdevices and circuits. By means of optical forces, it enables the direct assembly of NPs, one by one, onto specific positions of solid surfaces with great flexibility of pattern design and no need of previous surface patterning. However, for unclear causes it was not possible to print identical NPs closer to each other than 300 nm. Here, we show that the repulsion restricting the optical printing of close by NPs arises from light absorption by the printed NPs and subsequent local heating. By optimizing heat dissipation, it is possible to reduce the minimum separation between NPs. Using a reduced graphene oxide layer on a sapphire substrate, we demonstrate for the first time the optical printing of Au-Au NP dimers. Modeling the experiments considering optical, thermophoretic, and thermo-osmotic forces we obtain a detailed understanding and a clear pathway for the optical printing fabrication of complex nano structures and circuits based on connected colloidal NPs.

Haemodynamic changes with paracetamol in critically-ill children.

PURPOSE: Paracetamol has been associated with a reduction in blood pressure, especially in febrile, critically-ill adults. We hypothesised that blood pressure would fall following administration of paracetamol in critically-ill children and this effect would be greater during fever and among children with a high body surface area to weight ratio. METHODS: A 12-month prospective observational study of children (0-16years) admitted to paediatric intensive care, who underwent pulse contour analysis and received paracetamol concurrently. RESULTS: Mean arterial blood pressure decreased significantly by 4.7% from baseline (95% CI 1.75-8.07%) in 31 children following 148 doses of paracetamol. The nadir was 2-hour post-dose. The effect was pronounced in children with fever at baseline (6.4%, 95% CI 2.8-10%), although this was not statistically significant. There was no simple relationship between this effect and body surface area to weight ratio. The association between a change in blood pressure and changes in heart rate or measured stroke volume was poor; therefore it was likely that a change in the systemic vascular resistance contributes most to this effect. CONCLUSION: There is a significant but modest reduction in blood pressure post-paracetamol in critically-ill children. This is likely related to a change in systemic vascular resistance.

Attitudes towards fever amongst UK paediatric intensive care staff.

The role played by fever in the outcome of critical illness in children is unclear. This survey of medical and nursing staff in 35 paediatric intensive care units and transport teams in the United Kingdom and Ireland established attitudes towards the management of children with fever. Four hundred sixty-two medical and nursing staff responded to a web-based survey request. Respondents answered eight questions regarding thresholds for temperature control in usual clinical practice, indications for paracetamol use, and readiness to participate in a clinical trial of permissive temperature control. The median reported threshold for treating fever in clinical practice was 38 °C (IQR 38-38.5 °C). Paracetamol was reported to be used as an analgesic and antipyretic but also for non-specific comfort indications. There was a widespread support for a clinical trial of a permissive versus a conservative approach to fever in paediatric intensive care units. Within a trial, 58% of the respondents considered a temperature of 39 °C acceptable without treatment. CONCLUSIONS: Staff on paediatric intensive care units in the United Kingdom and Ireland tends to treat temperatures within the febrile range. There was a willingness to conduct a randomized controlled trial of treatment of fever. What is known: • The effect of fever on the outcome in paediatric critical illness is unknown. • Paediatricians have traditionally been reluctant to allow fever in sick children. What is new: • Paediatric intensive care staff report a tendency towards treating fever, with a median reported treatment threshold of 38 °C. • There is widespread support amongst PICU staff in the UK for a randomized controlled trial of temperature in critically ill children. • Within a trial setting, PICU staff attitudes to fever are more permissive than in clinical practice.

Risks and benefits of transfusion for children with severe anemia in Africa.

Severe anemia contributes significantly to child mortality in sub-Saharan Africa. Blood transfusion is used in emergencies but carries risks. In BMC Medicine, Olupot-Olupot and colleagues report the findings of a phase II trial in children with severe anemia in Eastern Uganda. They provide important early safety and efficacy data supporting large volume whole blood transfusion (30 ml/kg) compared with the World Health Organization recommendation of 20 ml/kg. Large volume transfusions result in more rapid and frequent correction of severe anemia; they can be expected to reduce the risk of transfusions, and help manage the scarce resource of donor blood. However, severe anemia arises from varying combinations of acute, sub-acute and chronic etiologies. The Fluid Expansion As Supportive Therapy study reminds us that the risks and benefits of even simple interventions are complex, and that rapid normalization of physiology may not always be the best strategy. There is no substitute for high quality evidence and to this end we strongly support Olupot-Oluput and colleagues' call for a definitive trial of large volume transfusions in severe anemia. Please see related research article http://www.biomedcentral.com/1741-7015/12/67/abstract.

Water contamination in urban south India: household storage practices and their implications for water safety and enteric infections.

Water contamination, at source and during household storage, is a major cause of enterically transmitted infections in developing countries. This study assessed contamination of the municipal water in a south Indian town, which obtains its water intermittently from a surface lake and by pumping subsurface water from a dry river bed, and monitored microbial contamination during household storage. All samples of the 'treated' municipal water were contaminated when freshly pumped, and on household storage, 25/37 (67%) showed increased contamination during storage periods from 1 to 9 days. Household storage in brass, but not in containers of other materials significantly decreased contamination of water (p = 0.04). This was confirmed in the laboratory by testing water seeded with 10(3) to 10(5) Escherichia coli per 100 ml stored in containers of different materials (p < 0.01). Despite the requirements for provision of safe drinking water in municipal areas, in practice the water supplied in Vellore is contaminated and current household storage practices increase the level of contamination in at least two-thirds of households. The implementation of locally appropriate point-of-use disinfection and safe household storage practices in developing countries is an urgent need to ensure a safe, reliable year-round supply in areas where clean water is not available.