In Situ Nanomechanical Measurements of Interfacial Strength in Membrane-Embedded Chemically Functionalized Si Microwires for Flexible Solar Cells

Arrays of vertically aligned Si microwires embedded in polydimethylsiloxane (PDMS) have emerged as a promising candidate for use in solar energy conversion devices. Such structures are lightweight and concurrently demonstrate competitive efficiency and mechanical flexibility. To ensure reliable functioning under bending and flexing, strong interfacial adhesion between the nanowire and the matrix is needed. In situ uniaxial tensile tests of individual, chemically functionalized, Si microwires embedded in a compliant PDMS matrix reveal that chemical functionality on Si microwire surfaces is directly correlated with interfacial adhesion strength. Chemical functionalization can therefore serve as an effective methodology for accessing a wide range of interfacial adhesion between the rigid constituents and the soft polymer matrix; the adhesion can be quantified by measuring the mechanical strength of such systems

Synthesis and Characterization of Mixed Methyl/Allyl Monolayers on Si(111)

The formation of mixed methyl/allyl monolayers has been accomplished through a two-step halogenation/alkylation reaction on Si(111) surfaces. The total coverage of alkylated Si, the surface recombination velocities, and the degree of surface oxidation as a function of time have been investigated using X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and microwave conductivity measurements. The total coverage of alkyl groups, the rate of oxidation, and the surface recombination velocities of Si(111) terminated by mixed monolayers were found to be close to those observed for CH_3−Si(111) surfaces. Hence, the mixed-monolayer surfaces retained the beneficial properties of CH_3−Si(111) surfaces while allowing for convenient secondary surface functionalization

Heck Coupling of Olefins to Mixed Methyl/Thienyl Monolayers on Si(111) Surfaces

The Heck reaction has been used to couple olefins to a Si(111) surface that was functionalized with a mixed monolayer comprised of methyl and thienyl groups. The coupling method maintained a conjugated linkage between the surface and the olefinic surface functionality, to allow for facile charge transfer from the silicon surface. While a Si(111) surface terminated only with thienyl groups displayed a surface recombination velocity, S, of 670 ± 190 cm s^(–1), the mixed CH_3/SC_4H_3–Si(111) surfaces with a coverage of θ_(SC_4H_3) = 0.15 ± 0.02 displayed a substantially lower value of S = 27 ± 9 cm s^(–1). Accordingly, CH_3/SC_4H_3–Si(111) surfaces were brominated with N-bromosuccinimide, to produce mixed CH_3/SC_4H_2Br–Si(111) surfaces with coverages of θ_(Br–Si) < 0.05. The resulting aryl halide surfaces were activated using [Pd(PPh_3)_4] as a catalyst. After activation, Pd(II) was selectively coordinated by oxidative addition to the surface-bound aryl halide. The olefinic substrates 4-fluorostyrene, vinylferrocene, and protoporphyrin IX dimethyl ester were then coupled (in dimethylformamide at 100 °C) to the Pd-containing functionalized Si surfaces. The porphyrin-modified surface was then metalated with Co, Cu, or Zn. The vinylferrocene-modified Si(111) surface showed a linear dependence of the peak current on scan rate in cyclic voltammetry, indicating that facile electron transfer had been maintained and providing evidence of a robust linkage between the Si surface and the tethered ferrocene. The final Heck-coupled surface exhibited S = 70 cm s^(–1), indicating that high-quality surfaces could be produced by this multistep synthetic approach for tethering small molecules to silicon photoelectrodes

Techno–ecological synergies of solar energy for global sustainability

The strategic engineering of solar energy technologies—from individual rooftop modules to large solar energy power plants—can confer significant synergistic outcomes across industrial and ecological boundaries. Here, we propose techno–ecological synergy (TES), a framework for engineering mutually beneficial relationships between technological and ecological systems, as an approach to augment the sustainability of solar energy across a diverse suite of recipient environments, including land, food, water, and built-up systems. We provide a conceptual model and framework to describe 16 TESs of solar energy and characterize 20 potential techno–ecological synergistic outcomes of their use. For each solar energy TES, we also introduce metrics and illustrative assessments to demonstrate techno–ecological potential across multiple dimensions. The numerous applications of TES to solar energy technologies are unique among energy systems and represent a powerful frontier in sustainable engineering to minimize unintended consequences on nature associated with a rapid energy transition

Developmental alterations in noxious-evoked EEG activity recorded from rat primary somatosensory cortex

Primary somatosensory cortex (S1) contains a nociceptive map that localizes potential tissue damage on the body and encodes stimulus intensity. An objective and specific biomarker of pain however is currently lacking and is urgently required for use in non-verbal clinical populations as well as in the validation of pre-clinical pain models. Here we describe studies to see if the responses of the S1 in juvenile rats are different to those in the adult. We recorded electroencephalogram (EEG) responses from S1 of lightly-anesthetized Sprague–Dawley rats at either postnatal day 21 or postnatal day 40 during the presentation of noxious (55 °C) or innocuous (30 °C) thermal stimuli applied to the plantar surface of the left hindpaw. The total EEG power across the recording period was the same in both ages after stimulation but the frequency distribution was significantly affected by age. Noxious heat evoked a significant increase in theta band (4–8 Hz) activity in adults only (P < 0.0001 compared to baseline; P < 0.0001 compared to juveniles). There were no significant differences in EEG responses to innocuous thermal stimuli. These data show that there are significant alterations in the processing of nociceptive inputs within the maturing cortex and that cortical theta activity is involved only in the adult cortical response to noxious stimulation

Low pH enhances the action of maximin H5 against Staphylococcus aureus and helps mediate lysylated phosphatidylglycerol induced resistance

Maximin H5 (MH5) is an amphibian antimicrobial peptide specifically targeting Staphylococcus aureus. At pH 6, the peptide showed an increased ability to penetrate (∆П = 6.2 mN m-1) and lyse (lysis = 48 %) S. aureus membrane mimics, which incorporated physiological levels of lysylated phosphatidylglycerol (Lys-PG, 60 %) as compared to pH 7 (∆П = 5.6 mN m-1 and lysis = 40 % at pH 7) where levels of Lys-PG are lower (40 %). The peptide therefore appears to have optimal function at pH levels known to be optimal for the organism’s growth. MH5 killed S. aureus (minimum inhibitory concentration = 90 µM) via membranolytic mechanisms that involved the stabilization of α-helical structure (circa 45-50 %) and which showed similarities to the ‘Carpet’ mechanism based on its ability to increase the rigidity (Cs-1 = 109.94 mN m-1) and thermodynamic stability (∆Gmix = -3.0) of physiologically relevant S. aureus membrane mimics at pH 6. Based on theoretical analysis this mechanism may involve the use of a tilted peptide structure and efficacy was noted to vary inversely with the Lys-PG content of S. aureus membrane mimics for each pH studied (R2 circa 0.97), which led to the suggestion that under biologically relevant conditions, low pH helps mediate Lys-PG induced resistance in S. aureus to MH5 antibacterial action. The peptide showed a lack of haemolytic activity (< 2 % haemolysis) and merits further investigation as a potential template for development as an anti-staphylococcal agent in medically and biotechnically relevant areas

Age influences the effects of nicotine and monoamine oxidase inhibition on mood-related behaviors in rats

Epidemiological studies have demonstrated a comorbidity of smoking with depression and anxiety, particularly during adolescence. However, few animal studies have considered possible synergistic interactions between nicotine and other tobacco smoke constituents, such as monoamine oxidase (MAO) inhibitors, in the regulation of mood. The aim of the study was to test the hypothesis that nicotine combined with the irreversible MAO inhibitor, tranylcypromine, will differentially affect depression- and anxiety-related behaviors in adolescent and adult rats. Nicotine (0, 0.05, 0.2&nbsp;mg/kg, s.c.) and tranylcypromine (3&nbsp;mg/kg, i.p.) were tested separately, or together, on male rats aged postnatal days 30 and 68, in three mood-related behavioral tests: forced swim test (FST), elevated plus maze (EPM), and open field. Nicotine (0.2&nbsp;mg/kg) in adults significantly decreased floating time in the FST and increased time spent in the open arm of the EPM, with no change in locomotor activity. Tranylcypromine pretreatment combined with nicotine (0.2&nbsp;mg/kg) significantly increased locomotor activity and time spent in the center of the open field. Whereas nicotine alone had no significant effect on adolescents, it significantly increased locomotor activity and decreased floating time in the FST when combined with tranylcypromine pretreatment. There is an age-dependent effect of nicotine, alone and in combination with MAO inhibition, on mood-related behaviors. Whereas nicotine alone induces mood improvement in adults, it has no effect on adolescents. Nicotine combined with tranylcypromine has unique, age-dependent effects. Thus, experimental studies of smoking should consider both age and other tobacco constituents, such as MAO inhibitors, as critical factors