Platinum-paper micromotors: An urchin-like nanohybrid catalyst for green monopropellant bubble-thrusters

Platinum nanourchins supported on microfibrilated cellulose films (MFC) were fabricated and evaluated as hydrogen peroxide catalysts for small-scale, autonomous underwater vehicle (AUV) propulsion systems. The catalytic substrate was synthesized through the reduction of chloroplatinic acid to create a thick film of Pt coral-like microstructures coated with Pt urchin-like nanowires that are arrayed in three dimensions on a two-dimensional MFC film. This organic/inorganic nanohybrid displays high catalytic ability (reduced activation energy of 50-63% over conventional materials and 13-19% for similar Pt nanoparticle-based structures) during hydrogen peroxide (H2O2) decomposition as well as sufficient propulsive thrust (\u3e0.5 N) from reagent grade H2O2 (30% w/w) fuel within a small underwater reaction vessel. The results demonstrate that these layered nanohybrid sheets are robust and catalytically effective for green, H2O2-based micro-AUV propulsion where the storage and handling of highly explosive, toxic fuels are prohibitive due to size-requirements, cost limitations, and close person-to-machine contact

Prospective, multicenter study of P4HB (Phasix™) mesh for hernia repair in cohort at risk for complications: 3-Year follow-up

Background: This study represents a prospective, multicenter, open-label study to assess the safety, performance, and outcomes of poly-4-hydroxybutyrate (P4HB, Phasix™) mesh for primary ventral, primary incisional, or multiply-recurrent hernia in subjects at risk for complications. This study reports 3-year clinical outcomes. Materials and methods: P4HB mesh was implanted in 121 patients via retrorectus or onlay technique. Physical exam and/or quality of life surveys were completed at 1, 3, 6,12, 18, 24, and 36 months, with 5-year (60-month) follow-up ongoing. Results: A total of n = 121 patients were implanted with P4HB mesh (n = 75 (62%) female) with a mean age of 54.7 ± 12.0 years and mean BMI of 32.2 ± 4.5 kg/m2 (±standard deviation). Comorbidities included: obesity (78.5%), active smokers (23.1%), COPD (28.1%), diabetes mellitus (33.1%), immunosuppression (8.3%), coronary artery disease (21.5%), chronic corticosteroid use (5.0%), hypo-albuminemia (2.5%), advanced age (5.0%), and renal insufficiency (0.8%). Hernias were repaired via retrorectus (n = 45, 37.2% with myofascial release (MR) or n = 43, 35.5% without MR), onlay (n = 8, 6.6% with MR or n = 24, 19.8% without MR), or not reported (n = 1, 0.8%). 82 patients (67.8%) completed 36-month follow-up. 17 patients (17.9% ± 0.4%) experienced hernia recurrence at 3 years, with n = 9 in the retrorectus group and n = 8 in the onlay group. SSI (n = 11) occurred in 9.3% ± 0.03% of patients. Conclusions: Long-term outcomes following ventral hernia repair with P4HB mesh demonstrate low recurrence rates at 3-year (36-month) postoperative time frame with no patients developing late mesh complications or requiring mesh removal. 5-year (60-month) follow-up is ongoing

Electrochemical experimental data for the reduction of TNT^a.

<p>1st E_pc = the first cathodic peak potential, 2nd E_pc = the second cathodic peak potential, 1^st I_pc = the first cathodic peak current.</p>a<p>Measured in air saturated water buffered at pH 8 with 100 mM potassium phosphate.</p>b<p>Limit of detection calculated at S/N = 3.</p><p>Electrochemical experimental data for the reduction of TNT^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115966#nt103" target="_blank">a</a>}.</p

Square Wave Voltammetry of TNT at Gold Electrodes Modified with Self-Assembled Monolayers Containing Aromatic Structures

<div><p>Square wave voltammetry for the reduction of 2,4,6-trinitrotoluene (TNT) was measured in 100 mM potassium phosphate buffer (pH 8) at gold electrodes modified with self-assembled monolayers (SAMs) containing either an alkane thiol or aromatic ring thiol structures. At 15 Hz, the electrochemical sensitivity (µA/ppm) was similar for all SAMs tested. However, at 60 Hz, the SAMs containing aromatic structures had a greater sensitivity than the alkane thiol SAM. In fact, the alkane thiol SAM had a decrease in sensitivity at the higher frequency. When comparing the electrochemical response between simulations and experimental data, a general trend was observed in which most of the SAMs had similar heterogeneous rate constants within experimental error for the reduction of TNT. This most likely describes a rate limiting step for the reduction of TNT. However, in the case of the alkane SAM at higher frequency, the decrease in sensitivity suggests that the rate limiting step in this case may be electron tunneling through the SAM. Our results show that SAMs containing aromatic rings increased the sensitivity for the reduction of TNT when higher frequencies were employed and at the same time suppressed the electrochemical reduction of dissolved oxygen.</p></div

Electrochemical simulation output^a.

<p><i>E</i> = formal redox potential, <i>k</i> = the standard heterogeneous rate constant.</p>a<p>Each peak was modeled as a 2 electron transfer step. Other parameters are listed in the text.</p><p>Electrochemical simulation output^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115966#nt106" target="_blank">a</a>}.</p

Experimental details.

<p><b>A.</b> Chemical structures for biphenyl-4-thiol (Biphenyl), 4-(phenylethynyl)benzenethiol (OPE) and undecane-1-thiol (C11) used to from SAMs on gold electrodes. <b>B.</b> The electrochemical setup.</p

Characteristics of SAMs on gold^a.

a<p>average of three electrodes.</p><p>Characteristics of SAMs on gold^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115966#nt101" target="_blank">a</a>}.</p

Characteristics of electrochemical detection of TNT.

<p><b>A.</b> Background subtracted peak current vs. [TNT] measured at the first reduction of TNT from the corresponding square wave voltammograms (average of two electrodes). <b>B</b> Slope (µA/ppm) of the calibration curves vs. SAM type and Hz. Black = 15 Hz, Red = 60 Hz.</p

Square wave voltammetry of several TNT concentrations in air-saturated 100 mM potassium phosphate, buffed at pH 8.

<p><b>A.</b> The response of TNT at a C11 modified gold electrode measured at 15 Hz. <b>B.</b> The response of TNT at a C11 modified gold electrode measured at 60 Hz including a comparison to a bare gold electrode. <b>C</b> & <b>D.</b> The response of TNT at a OPE modified gold electrode measured at 15 Hz and at 60 Hz, respectively. <b>E</b> & <b>F.</b> The response of TNT at a Biphenyl modified gold electrode measured at 15 Hz and at 60 Hz, respectively.</p

Platinum-paper micromotors: An urchin-like nanohybrid catalyst for green monopropellant bubble-thrusters

Platinum nanourchins supported on microfibrilated cellulose films (MFC) were fabricated and evaluated as hydrogen peroxide catalysts for small-scale, autonomous underwater vehicle (AUV) propulsion systems. The catalytic substrate was synthesized through the reduction of chloroplatinic acid to create a thick film of Pt coral-like microstructures coated with Pt urchin-like nanowires that are arrayed in three dimensions on a two-dimensional MFC film. This organic/inorganic nanohybrid displays high catalytic ability (reduced activation energy of 50-63% over conventional materials and 13-19% for similar Pt nanoparticle-based structures) during hydrogen peroxide (H2O2) decomposition as well as sufficient propulsive thrust (>0.5 N) from reagent grade H2O2 (30% w/w) fuel within a small underwater reaction vessel. The results demonstrate that these layered nanohybrid sheets are robust and catalytically effective for green, H2O2-based micro-AUV propulsion where the storage and handling of highly explosive, toxic fuels are prohibitive due to size-requirements, cost limitations, and close person-to-machine contact.This article is from ACS Applied Materials and Interfaces 6 (2014): 17837, doi: 10.1021/am504525e. Posted with permission.</p