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Laboratory studies of the radiation chemistry occurring in astrophysical ices have demonstrated the dependence of this chemistry on a number of experimental parameters. One experimental parameter which has received significantly less attention is that of the phase of the solid ice under investigation. In this present study, we have performed systematic 2 keV electron irradiations of the amorphous and crystalline phases of pure CH3OH and N2O astrophysical ice analogues. Radiation-induced decay of these ices and the concomitant formation of products were monitored in situ using FT-IR spectroscopy. A direct comparison between the irradiated amorphous and crystalline CH3OH ices revealed a more rapid decay of the former compared to the latter. Interestingly, a significantly lesser difference was observed when comparing the decay rates of the amorphous and crystalline N2O ices. These observations have been rationalised in terms of the strength and extent of the intermolecular forces present in each ice. The strong and extensive hydrogen-bonding network that exists in crystalline CH3OH (but not in the amorphous phase) is suggested to significantly stabilise this phase against radiation-induced decay. Conversely, although alignment of the dipole moment of N2O is anticipated to be more extensive in the crystalline structure, its weak attractive potential does not significantly stabilise the crystalline phase against radiation-induced decay, hence explaining the smaller difference in decay rates between the amorphous and crystalline phases of N2O compared to those of CH3OH. Our results are relevant to the astrochemistry of interstellar ices and icy Solar System objects, which may experience phase changes due to thermally-induced crystallisation or space radiation-induced amorphisation. [ABSTRACT FROM AUTHOR]

We describe the implementation of a simple three-electrode surface-induced dissociation (SID) cell on a cyclic ion mobility spectrometer (cIMS) and demonstrate the utility of multipass mobility separations for resolving multiple conformations of protein complexes generated during collision-induced and surface-induced unfolding (CIU & SIU) experiments. In addition to CIU and SIU, SID of protein complexes is readily accomplished within the native instrument software and with no additional external power supplies by entering a single SID collision energy, a simplification in user experience compared to prior implementations. A set of cyclic homomeric protein complexes and a heterohexamer with known CID and SID behavior were analyzed to investigate mass and mobility resolution improvements, the latter of which improved by 20–50% (median: 33%) compared to a linear travelling wave device. Multiple passes of intact complexes, or their SID fragments, increased the mobility resolution by an average of 15% per pass, with the racetrack effect being observed after ∼3 or 4 passes, depending on the drift time spread of the analytes. Even with modest improvements to apparent mobility resolving power, multipass experiments were particularly useful for separating conformations produced from CIU and SIU experiments. We illustrate several examples where either (1) multipass experiments revealed multiple overlapping conformations previously unobserved or obscured due to limited mobility resolution, or (2) CIU or SIU conformations that appeared 'native' in a single pass experiment were actually slightly compacted or expanded, with the change only being measurable through multipass experiments. The work conducted here, the first utilization of multipass cyclic ion mobility for CIU, SIU, and SID of protein assemblies and a demonstration of a wholly integrated SIU/SID workflow, paves the way for widespread adoption of SID technology for native mass spectrometry and also improves our understanding of gas-phase protein complex CIU and SIU conformationomes. [ABSTRACT FROM AUTHOR]

The formation of methyl formate (CH3OCHO) upon electron irradiation of mixed ices of carbon monoxide (CO) and methanol (CH3OH) has been monitored by post-irradiation thermal desorption spectrometry (TDS). The energy dependence of the product yields obtained with electron energies between 3 and 18 eV was studied. These energies are characteristic of secondary electrons that are released in vast numbers under the effect of ionizing radiation. Our results reveal that the reactions leading to methyl formate are initiated by a number of different electron–molecule interactions that produce CH3O˙ radicals. Dissociative electron attachment (DEA) to CH3OH around 5.5 eV and neutral dissociation (ND) above 7 eV release CH3O˙ radicals that can add to CO to initiate a reaction sequence leading to formation of methyl formate. Around 10 eV, DEA to CO yields an oxygen radical anion that reacts with CH3OH to also produce CH3O˙ radicals. Alternatively, CH3OH can also release H˙ radicals upon both DEA and ND. These can also add to CO to form HCO˙ radicals as an intermediate to formaldehyde (H2CO), which was also investigated to unravel the reaction mechanisms leading to formation of methyl formate. The recombination of HCO˙ and CH3O˙ as minority radical species is considered as an alternative but less probable pathway to the formation of methyl formate. To the best of our knowledge, this is the first study showing considerable contributions of DEA to the formation of methyl formate in CH3OH containing ices. Thus, our study has important implications for current astrochemical models. [ABSTRACT FROM AUTHOR]

H-addition reactions on the icy interstellar grains may play an important role in the formation of complex organic molecules. In the present work we propose a comparative study of H2CO + H, CH3CH2CHO + H and CH3OCHO + H solid state reactions at 10 K under interstellar conditions in order to characterize the main reaction pathways involved in the hydrogenation of a CHO functional group. We show that the most probable mechanism for the formation of alcohols under non-energetic conditions through the saturation of the CHO group corresponds to the attachment of the H atom to the CH group with noticeable variations of the energy barriers for each studied reaction. These energy barriers have been calculated to be 8.3, 14.6 and 32.7 kJ mol−1 for H2CO + H, CH3CH2CHO + H and CH3OCHO + H, respectively. The coupling of the experimental and theoretical analysis proves that while the simplest aldehyde, formaldehyde, is easily reduced to methanol, methylformate and propanal behave differently under H-bombardments but they cannot be a source of alcohol formation through H-addition reactions. Consequently, for the formation of alcohols larger than CH3OH, other chemical pathways should be taken into account, probably energetic processing such as the photolysis of interstellar ice analogues containing C-, H- and O-bearing compounds or the coupling of the H-addition reaction and photon-irradiation on species with a CHO functional group. [ABSTRACT FROM AUTHOR]

Currently, the strategy of combining photodynamic therapy (PDT) and chemotherapy for enhancing cancer therapeutic efficiency has aroused extensive interest. Nonetheless, weaknesses such as low local concentration, uncontrollable release of the drug, a non-suitable treatment light source, and a low response to the tumor site of PDT lead to the combined treatment effect not being ideal. Herein, we proposed simple and intelligent ROS-responsive zinc phthalocyanine sensitized TiO2 nanoparticles which conjugated with chlorambucil (CBL) (mTiO2–BCBL@ZnPC NPs) in an attempt to solve these issues. Not only were the nanoparticles triggered in near infrared radiation (NIR) for PDT with various reactive oxygen species (ROS) being generated, but the nanoparticles also realized the controllable release of CBL by H2O2, a major kind of ROS, through cleavage of the phenylboronic ester between CBL and the nanoparticle. Impressively, the controllable release of CBL under NIR irradiation showed an on–off characteristic and time dependency. In addition, the well-defined mTiO2–BCBL@ZnPC NPs with a 30 nm average diameter showed good stability and biocompatibility. The in vitro cytotoxicity studies demonstrated that the mTiO2–BCBL@ZnPC NPs were more cytotoxic under NIR irradiation than the mTiO2@ZnPC NPs and CBL, while the mTiO2–BCBL@ZnPC NPs were less cytotoxic under dark conditions. The above results implied that photo-controlled drug release is a promising choice for cancer therapy due to its high selectivity, good safety and low side-effects, and would be expected to be used in chemo-photodynamic combined therapy for improving the therapeutic efficiency. [ABSTRACT FROM AUTHOR]

In this combined experimental–theoretical work we focus on the physical and chemical changes induced by soft X-rays on sulfur dioxide (SO2) ice at a very low temperature, in an attempt to clarify and quantify its survival and chemical changes in some astrophysical environments. SO2 is an important constituent of some Jupiter moons and has also been observed in ices around protostars. The measurements were performed at the Brazilian Synchrotron Light Source (LNLS/CNPEM), in Campinas, Brazil. The SO2 ice sample (12 K) was exposed to a broadband beam of mainly soft X-rays (6–2000 eV) and in situ analyses were performed by IR spectroscopy. The X-ray photodesorption yield (upper limit) was around 0.25 molecules per photon. The values determined for the effective destruction (SO2) and formation (SO3) cross sections were 2.5 × 10−18 cm2 and 2.1 × 10−18 cm2, respectively. The chemical equilibrium (88% of SO2 and 12% of SO3) was reached after the fluence of 1.6 × 1018 photons cm−2. The SO3 formation channels were studied at the second-order Møller–Plesset perturbation theory (MP2) level, which showed the three most favorable reaction routes (ΔH ＜ −79 kcal mol−1) in simulated SO2 ice: (i) SO + O2→ SO3, (ii) SO2 + O → SO3, and (iii) SO2 + O+→ SO3+ + e−→ SO3. The amorphous solid environment effect decreases the reactivity of intermediate species towards SO3 formation, and ionic species are even more affected. The experimentally determined effective cross sections and theoretical reaction channels identified in this work allow us to better understand the chemical evolution of certain sulfur-rich astrophysical environments. [ABSTRACT FROM AUTHOR]

The effect of X-ray irradiation on methanol molecules (CH3OH, CD3OH, and 13CH3OH) isolated in solid noble gas matrices (Ne, Ar, Kr, and Xe) was studied by FTIR spectroscopy at 6 K. CH2OHṖ, H2CO, HCOṖ and CO were found to be the main degradation products. Somewhat unexpectedly, the production of CO is quite prominent, even at low doses, and it strongly predominates in low-polarizable matrices (especially, in neon). This result is explained by inefficient quenching of excess energy in the H2CO molecules initially generated from methanol. Relatively small amounts of CH4, CH3Ṗ and CO2 were also observed directly after irradiation. The latter species presumably originates from methanol dimers or methanol–water complexes. The mechanisms of radiolysis and annealing-induced reactions are discussed and possible implications for the astrochemically relevant ices are considered. [ABSTRACT FROM AUTHOR]

An iron(ii)phthalocyanine (Fepc) modified mesoporous titania (Fepc–TiO2) nanocatalyst with a specific surface area of 215 m2 g−1 has been synthesized by a hydrothermal method. Fepc–TiO2 degrades one of the highly toxic chemical warfare agents, sulfur mustard (SM), photocatalytically under sunlight with an exposure time of as low as 70 min. Furthermore, the mesoporous Fepc–TiO2 also captured 2.1 mmol g−1 of CO2 at 273 K and 1 atm. [ABSTRACT FROM AUTHOR]

The radiation induced chemical processing of methanol and methanol–carbon monoxide ices at 5.5 K exposed to ionizing radiation in the form of energetic electrons and subsequent temperature programmed desorption is reported in this study. The endogenous formation of complex organic molecules was monitored online and in situ via infrared spectroscopy in the solid state and post irradiation with temperature programmed desorption (TPD) using highly sensitive reflectron time-of-flight (ReTOF) mass spectrometry coupled with single photoionization at 10.49 eV. Infrared spectroscopic analysis of the processed ice systems resulted in the identification of simple molecules including the hydroxymethyl radical (CH2OH), formyl radical (HCO), methane (CH4), formaldehyde (H2CO), carbon dioxide (CO2), ethylene glycol (HOCH2CH2OH), glycolaldehyde (HOCH2CHO), methyl formate (HCOOCH3), and ketene (H2CCO). In addition, ReTOF mass spectrometry of subliming molecules following temperature programmed desorption definitely identified several closed shell C/H/O bearing organics including ketene (H2CCO), acetaldehyde (CH3COH), ethanol (C2H5OH), dimethyl ether (CH3OCH3), glyoxal (HCOCOH), glycolaldehyde (HOCH2CHO), ethene-1,2-diol (HOCHCHOH), ethylene glycol (HOCH2CH2OH), methoxy methanol (CH3OCH2OH) and glycerol (CH2OHCHOHCH2OH) in the processed ice systems. Additionally, an abundant amount of molecules yet to be specifically identified were observed sublimating from the irradiated ices including isomers with the formula C3H(x=4,6,8)O, C4H(x=8,10)O, C3H(x=4,6,8)O2, C4H(x=6,8)O2, C3H(x=4,6)O3, C4H8O3, C4H(x=4,6,8)O4, C5H(x=6,8)O4 and C5H(x=6,8)O5. The last group of molecules containing four to five oxygen atoms observed sublimating from the processed ice samples include an astrobiologically important class of sugars relevant to RNA, phospholipids and energy storage. Experiments are currently being designed to elucidate their chemical structure. In addition, several reaction pathways were identified in the irradiated ices of mixed isotopes based upon the results of both in situ FTIR analysis and TPD ReTOF gas phase analysis. In general, the results of this study provide crucial information on the formation of a variety of classes of organics including alcohols, ketones, aldehydes, esters, ethers, and sugars within the bulk ices upon exposure to ionizing radiation that are relevant to the molecular clouds within the interstellar medium. [ABSTRACT FROM AUTHOR]

In recent times, significant achievements in the use of zinc oxide (ZnO) nanoparticles (NPs) as delivery vehicles of cancer drugs have been made. The present study is an attempt to explore the key photoinduced dynamics in ZnO NPs upon complexation with a model cancer drug protoporphyrin IX (PP). The nanohybrid has been characterized by FTIR, Raman scattering and UV-Vis absorption spectroscopy. Picosecond-resolved Förster resonance energy transfer (FRET) from the defect mediated emission of ZnO NPs to PP has been used to study the formation of the nanohybrid at the molecular level. Picosecond-resolved fluorescence studies of PP-ZnO nanohybrids reveal efficient electron migration from photoexcited PP to ZnO, even-tually enhancing the ROS activity. The dichlorofluorescin (DCFH) oxidation and no oxidation of luminol in PP/PP-ZnO nanohybrids upon green light illumination unravel that the nature of ROS is essentially singlet oxygen rather than superoxide anions. Surface mediated photocatalysis of methylene blue (MB) in an aqueous solution of the nanohybrid has also been investigated. Direct evidence of the role of electron transfer as a key player in enhanced ROS generation from the nanohybrid is also clear from the photo-current measurement studies. We have also used the nanohybrid in a model photodynamic therapy application in a light sensitized bacteriological culture experiment. [ABSTRACT FROM AUTHOR]

We present conclusive evidence on the formation of glycolaldehyde (HOCH2CHO) synthesized within astrophysically relevant ices of methanol (CH3OH) and methanol–carbon monoxide (CH3OH–CO) upon exposure to ionizing radiation at 5.5 K. The radiation induced chemical processes of the ices were monitored on line and in situ via infrared spectroscopy which was complimented by temperature programmed desorption studies post irradiation, utilizing highly sensitive reflectron time-of-flight mass spectrometry coupled with single photon fragment free photoionization (ReTOF-PI) at 10.49 eV. Specifically, glycolaldehyde was observed via the ν14 band and further enhanced with the associated frequency shifts of the carbonyl stretching mode observed in irradiated isotopologue ice mixtures. Furthermore, experiments conducted with mixed isotopic ices of methanol–carbon monoxide (13CH3OH–CO, CH318OH–CO, CD3OD–13CO and CH3OH–C18O) provide solid evidence of at least three competing reaction pathways involved in the formation of glycolaldehyde via non-equilibrium chemistry, which were identified as follows: (i) radical–radical recombination of HCO and CH2OH formed via decomposition of methanol – the “two methanol pathway”; (ii) via the reaction of one methanol unit (CH2OH from the decomposition of CH3OH) with one carbon monoxide unit (HCO from the hydrogenation of CO) – the “one methanol, one carbon monoxide pathway”; and (iii) formation via hydrogenation of carbon monoxide resulting in radicals of HCO and CH2OH – the “two carbon monoxide pathway”. In addition, temperature programmed desorption studies revealed an increase in the amount of glycolaldehyde formed, suggesting further thermal chemistry of trapped radicals within the ice matrix. Sublimation of glycolaldehyde during the warm up was also monitored via ReTOF-PI and validated via the mutual agreement of the associated isotopic frequency shifts within the infrared band positions and the identical sublimation profiles obtained from the ReTOF spectra and infrared spectroscopy of the corresponding isotopes. In addition, an isomer of glycolaldehyde (ethene-1,2-diol) was tentatively assigned. Confirmation of the identified pathways based on infrared spectroscopy was also obtained from the observed ion signals corresponding to isotopomers of glycolaldehyde. These coupled techniques provide clear, concise evidence of the formation of a complex and astrobiologically important organic, glycolaldehyde, relevant to the icy mantles observed in the interstellar medium. [ABSTRACT FROM AUTHOR]