Search

A functional capacitive sensing device with five touch points was fabricated on the curved surfaces of polyvinyl chloride, polycarbonate and acrylonitrile butadiene styrene piping. The capacitive touch sensor points and conductive traces were printed with an Optomec™ Aerosol Jet printer using silver nanoparticle ink. We present a solution to a common problem with hybrid printed electronics of transitioning from the printed electronic components on a three-dimensional object to traditional rigid circuit board electronics. We highlight the need for CAD/CAM technology as an essential tool for printing on three-dimensional surfaces. The capacitive touch sensor library of an Arduino Uno Bard Rev 3 microcontroller enabled the detection of contact at the printed touch points. Corresponding LEDs attached to the surface of the pipe light up to indicate contact at the touch points. This hybrid printed electronic device presents a fully integrated and functioning electronic device printed on a three-dimensional surface and highlights the requirement of multidisciplinary knowledge for the field of hybrid printed electronics.

Vascular relaxation to nitroglycerin (glyceryl trinitrate; GTN) requires its bioactivation by mechanisms that remain controversial. We report here that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the release of nitrite from GTN. In assays containing dithiothreitol (DTT) and NAD+, the GTN reductase activity of purified GAPDH produces nitrite and 1,2-GDN as the major products. A vmax of 2.6 nmol min−1 mg−1 was measured for nitrite production by GAPDH from rabbit muscle and a GTN KM of 1.2 mM. Reductive denitration of GTN in the absence of DTT results in dose- and time-dependent inhibition of GAPDH dehydrogenase activity. Disulfiram, a thiol-modifying drug, inhibits both the dehydrogenase and GTN reductase activity of GAPDH, while DTT or tris(2-carboxyethyl)phosphine reverse the GTN-induced inhibition. Incubation of intact human erythrocytes or hemolysates with 2 mM GTN for 60 min results in 50% inhibition of GAPDH’s dehydrogenase activity, indicating that GTN is taken up by these cells and that the dehydrogenase is a target of GTN. Thus, erythrocyte GAPDH may contribute to GTN bioactivation.

Oxybenzone (OXB) is one of the most widely employed sunscreen ingredients, yet its allowed load is limited to a maximum of 6% reflecting the frequency with which adverse effects are reported. From a spectroscopic point of view, OXB has excellent absorption properties in both the UVB and UVA regions. We propose that zeolite encapsulation can lead to a sunscreen composite ingredient, that we describe as a supramolecular sunscreen, that will retain the excellent spectroscopic properties of OXB, while preventing contact between the skin and the active ingredient. OXB is very photostable, with the only photodegradative pathway observed being the monophotonic photoejection of electrons that leads to trace yields of phenoxyl radicals; this trace reaction is so minor that it cannot be detected from the recovery of unreacted OXB following UV exposure. Solution, as well as powder and in vitro studies of the supramolecular sunscreen, demonstrate that the protective properties of OXB are totally preserved when encapsulated in zeolite NaY.

Fluorescein (2-(6-hydroxy-3-oxo-(3H)-xanthen-9-yl)benzoic acid) has been prepared inside the pores of zeolite-Y via ship-in-a-bottle synthesis. Fluorescein, whose dimensions prevent it from entering through the ∼7 A windows of the faujasite zeolite used, was prepared by the acid-catalyzed reaction of resorcinol and phthalic anhydride. In this article we report initial spectroscopic data as well as an example of the usefulness of these fluorescence-labeled nanoparticles for imaging applications such as confocal fluorescence microscopy. Encapsulated fluorescein shows a remarkable increase in photostability.

Methyl triazone (4,4′,4″-[1,3,5-triazine-2,4,6-triyltriimino]tris-trimethyl benzoate) has been included in mesoporous MCM-41 (Mobil's composition of matter-41) silica, and its fluorescence emission has been compared in solution and in the solid state. Although inclusion does not affect significantly the absorption properties, a fluorescence emission shift and a behavior similar to the solid state has been observed by increasing the loading. It is believed that this observation reflects molecular aggregation inside the MCM-41 channels. The potential of formulations of this type for sunscreen applications is discussed.

Zeolites are nanoporous, crystalline aluminosilicate materials comprised of a series of strictly uniform channels and cavities repeating along the tri-directional structure of the lattice. Over the last 30 years, researchers have increasingly recognized the desirable properties of these materials as hosts for photochemical reactions. This review will endeavor to draw attention to the properties of zeolite materials that make them appealing substrates for hosting guest molecules during photochemical reactions. An overview of some classical examples in zeolite host-guest photochemistry will be presented along with a brief description of a new use for zeolite materials as protective encapsulators.

The phototoxic and photoallergic effects of the once popular UV sunscreen p-aminobanzoic acid are related, in part, to its ability to sensitize the formation of singlet oxygen as well as other reactive oxygen species. In this work we demonstrate that the sunscreen-photoinduced inactivation of a model protein, horseradish peroxidase, is reduced by approximately a factor of three when the sunscreen is encaspsulated in zeolite sodium Y. These results provide evidence that using the technology of zeolite encapsulation to prepare a supramolecular sunscreen that minimizes the skin contact of active ingredients may reduce the adverse effects of "naked" sunscreens on biological systems. These radiation-induced effects, unfortunately, frequently accompany the desirable UV-screening role of these products. These results provide an important benchmark for the use of zeolite encapsulation as a means of improving the safety of UV sunscreens for topical application.

Fluorescence sensors have been developed to monitor radical reactions, DNA damage, acid-catalyzed processes, detection of electron-deficient molecules, and zeolite applications. The examples presented emphasize applications in polymer and supramolecular systems.

Zeolite Y containing Ru(bpy)32+ and TP+ has been obtained by the stepwise ship-in-a-bottle synthesis of the two components. The identity of the two ions has been demonstrated by diffuse reflectance...

Prefluorescent probe dansyl-TEMPO was synthesized within NaY supercages by means of a base-catalyzed ship-in-a-bottle synthesis to yield the supramolecular assembly DT@NaY, providing the first example of base-catalyzed synthesis in the normally acidic zeolite cavities. This material was successfully employed in the solid state as a sensor to monitor intercavity diffusion of carbon-centered radicals produced by AIBN thermolysis and in a slurry to study the interpore diffusion of carbon-centered radicals produced in solution from a suitable precursor (3,3‘-diphenyl-3H,3‘H-[3,3‘]bibenzofuranyl-2,2‘-dione, 6). The dynamics of hydrogen atom transfer from a good donor, such as the synthetic lactone antioxidant 3-phenyl-2-coumaranone, to DT@NaY were also investigated in benzene slurry.

The photostability of the widely used UVB sunscreen agents 2′-ethylhexyl-2-cyano-3-phenylcinnamate (1), 2-hydroxy-4-methoxybenzophenone (2), octyl salicilate (3), and 2′-ethylhexyl-4-methoxycinnamate (4) has been investigated under UVA irradiation in the absence and presence of TiO2, an inorganic filter commonly employed in combination with organic filters in sunscreen preparations. In the absence of TiO2, 1–3 are photostable and 4 undergoes the expected E–Z isomerization; the presence of TiO2 caused mineralization of the organic filters and, surprisingly, the process is noticeably faster in the presence of surfactant than in sunscreen and water suspensions. The results indicate that in water suspension, mineralization is likely to occur on or near the TiO2 particle surface; when the organic sunscreens are segregated in the micelle core, reactive radicals, produced during TiO2-promoted degradation of the micellar system, may participate in sunscreen degradation. In addition, a pre-fluorescent probe for carbon-centered radical detection, 4-(3-hydroxy-2-methyl-4-quinolineoxy)-2,2,6,6,-tetramethylpiperidine-1-oxyl free radical or QT (5), was employed to demonstrate that carbon-centered radicals are evolved during micelle degradation and may participate in the mineralization of sunscreens.

Direct irradiation of fenvalerate (FV) in aqueous solution (4 x 10(-3) M) gives rise to 2,3-diarylisohexanitrile through the homolytic CO-CH(i-Pr) bond cleavage, followed by a rapid decarboxylation of the primary carbonyloxy radical, and radical recombination. The unusual exclusive formation of the cross combination product suggests that the persistent free radical effect is operative in this system and controls product formation. Spectroscopic evidence of the intermediacy of benzylic radicals decaying in microsecond time scale has been obtained by laser flash photolysis. These studies also reveal a remarkable attenuation of radical reactivity toward oxygen resulting from cyano substitution at the radical center. TPY photocatalyzed degradation of FV also leads to decarboxylation products accompanied by oxidative mineralization (38%). The TPY-photocatalyzed degradation can occur through two operating mechanisms involving the generation of OH(*) radicals and/or FV(*+) radical cations. Evidence for the latter intermediate has been obtained by laser flash photolysis in acetonitrile solution (detection of TP(*) radical) and by the quenching by FV of the emission from the TPY solid.

Samples of zeolite Y containing 2,4,6-triphenylpyrylium or tris(bipyridyl)ruthenium(II) have been prepared and their photophysical and photochemical properties compared to those of the same samples containing encapsulated nanoscopic TiO2 clusters as relays. The emission of encapsulated Ru(bpy)32+ and TP+ photolumophores undergoes static quenching in the presence of codoped TiO2 clusters. This is the expected behavior for systems, where photosensitizer and relay lack diffusional mobility. Time-resolved diffuse reflectance laser flash photolysis shows the transient generation of TP• pyranyl radical and Ru(bpy)33+, upon irradiation of TP+ and Ru(bpy)32+ in the presence of TiO2, respectively. This provides firm support for the occurrence of photoinduced electron transfer between excited TP+ as acceptor and TiO2 clusters as donors and from Ru(bpy)32+ to the conduction band of TiO2. Using the photoinactivation of horseradish peroxidase as a test reaction in aqueous medium, a synergism has been found with respec...

Photolysis of p-toluidides of methacrylic (1a) and cyclohex-2-enecarboxylic (1b) acids in nitrogen-saturated cyclopentane solution yields the corresponding 2-quinolones with over 90% chemoselectivity at almost complete conversion. In the presence of substoichiometric amounts (0.1 equivalents) of chiral inductor, low to moderate enantiomeric excesses (ee) are observed in the photo-product. Ephedrine gave the highest ee (37% ee for the photocyclization of 1a) in a series of 11 chiral inductors including alcohols, amines, aminoalcohols, α-amino and α-hydroxy acids. In the case of the irradiation of 1b in the presence of chiral inductors, both diastereo- and enantioselectivity were observed. A weakly absorbing transient species (λmax 400 nm) was detected following 308 nm laser excitation and was assigned to the zwitterionic enolate intermediate resulting immediately after the concerted electrocyclic ring closure. The lifetime of this intermediate is unaffected by oxygen but is quenched by trifluoroacetic acid (kq = 3.76 × 107 M−1 s−1) and ephedrine (kq = 1.19 × 107 M−1 s−1).

Dibenzotropylium ion (DT+) has been generated as an indefinitely persistent species within the channels of ZSM-5 in its H+-form. Diffuse reflectance laser flash photolysis has allowed detection of a transient (two bands: 300 nm, sharp and ∼440 nm broad) decaying in the μs time-scale that has been assigned to the corresponding triplet excited state. The tight fit of DT+ within the straight channels ( 5.2×5.7 A 2 ) of ZSM-5 and the presence of coadsorbed water explain why the DT+ triplet excited state is not quenched by oxygen but interacts with triethylamine, which is highly water-soluble. In the latter case, formation of a new transient compatible with DT (λmax=270 and 350 nm) through electron transfer from the amine to DT+ triplet is observed.

The photodecomposition of ketones by the Norrish Type I reaction, leading to the efficient release of reducing ketyl or alpha-amino alkyl radicals, provides a facile route for the synthesis of copper nanoparticles (CuNP) in both aqueous and organic solvents. The role of different counterions (especially halides) and surfactants has been used to 'tune' the morphology and size of the nanostructures formed. In aqueous solutions chloride ions catalyze the disproportionation that mediates the Cu(I) --Cu(0) --CuNP conversion. This article concentrates on spherical nanoparticles and offers some insights into the routes to other nanostructures.

Absorption and fluorescence spectroscopy studies reveal the formation of a weak complex between pyrene and C(6)F(6) even in very dilute systems. The complex affects the photophysics of pyrene and reveals a combination of static and dynamic-quenching phenomena in both polar and nonpolar solvents. The results are supported by computational studies that shed light on the structure of the complex and the interactions involved and suggest that ground and excited-state interactions are of comparable magnitude; the association is believed to be driven by quadrupolar interactions. Understanding these interactions in solution is important for applications that aim at controlling the regio- or stereoselectivity of organic reactions.

Oxytocin (OT; Cys-Tyr-Ile-Gln-Asn-Cys-Pro-leu-Gly), a posterior pituitary peptide hormone, is characterized by a Cys1-Cys6 disulfide bond in its stable, isolated state. This paper describes a simple, one-step method for the production of OT in its reduced, dithiol form (OT dithiol), free of reducing agent. The effects of temperature, pH, and metal-ion chelators on the autoxidation of OT dithiol were examined to establish if this form is likely to persist under biological conditions. It was found that OT dithiol has a half-life of 1.8h with respect to reformation of OT disulfide at 37 degrees C and pH 6.9 in the presence of the copper chelators, DTPA and neocuproine. S-Nitrosation of OT dithiol by acidified nitrite at pH 3.0 was examined by absorption spectroscopy and HPLC-UV-MS, which revealed that both singly and doubly S-nitrosated OT are formed. These results suggest novel chemical aspects to OT signaling, the biological implications of which are discussed here.

Inclusion of 2-(hydroxymethyl)anthraquinone in zeolite NaY leads to a solid, photoactivated, reusable oxygen sensor capable of reporting and memorizing oxygen contamination events by simple visual inspection.

Carbanions have been detected for the first time in zeolite cavities where their lifetime is more than ten times longer than in solution; included carbanions show Grignard-like behaviour.

A [2]-catenane consisting of a bipyridinium cyclophane and a dioxybenzene macrocyclic polyether has been encapsulated within the supercages of zeolite Y by ship-in-a-bottle synthesis; laser flash photolysis reveals that the charge-separated species decays in hundreds of microseconds in contrast to the few picoseconds previously reported for the same transient in acetonitrile.