4-Chloroisocoumarins as Chlamydial Protease Inhibitors and Anti-Chlamydial Agents.

4-Chloroisocoumarin compounds have broad inhibitory properties against serine proteases. Here, we show that selected 3-alkoxy-4-chloroisocoumarins preferentially inhibit the activity of the conserved serine protease High-temperature requirement A of Chlamydia trachomatis. The synthesis of a new series of isocoumarin-based scaffolds has been developed, and their anti-chlamydial properties were investigated. The structure of the alkoxy substituent was found to influence the potency of the compounds against High-temperature requirement A, and modifications to the C-7 position of the 3-alkoxy-4-chloroisocoumarin structure attenuate anti-chlamydial properties.

Organic impurity profiling of 3,4-methylenedioxyamphetamine (MDA) synthesised from helional.

The organic impurity profile of 3,4-methylenedioxyamphetamine (MDA) synthesised from helional via the "twodogs" method was examined to identify route-specific and condition-specific impurities. The synthesis used a condensation reaction, followed by a Beckmann rearrangement, then Hofmann rearrangement, and then conversion to a hydrochloride salt. Two chlorinating agents were investigated for the Hofmann rearrangement reaction, trichloroisocyanuric acid (TCCA) and sodium hypochlorite. Three route-specific impurities were identified in MDA using TCCA, and two of these impurities were condition-specific such that the impurities that formed were dependent on the alcohol used as solvent. Three additional impurities were identified as non-route-specific as they have previously been identified in MDA synthesised from 3,4-methylenedioxycinnamic acid or piperonal. These non-route-specific impurities were also identified in MDA synthesised using sodium hypochlorite. No impurities were detected in MDA hydrochloride. This study identified route- and condition-specific organic impurities in MDA synthesised via the "twodogs" synthetic route using helional as starting material. The results in this study provide further understanding into the illicit synthesis of MDA and highlight the expanding nature of precursors used for illicit drug manufacture. It provides valuable information to decision makers to enact legislative measures and restrict precursors of concern.

The fate of organic species upon sintering of thiol-stabilised gold nanoparticles under different atmospheric conditions.

Understanding and controlling the sintering behavior of gold nanoparticles is important for applications such as printed electronics, catalysis and sensing that utilise these materials. Here we examine the processes by which thiol-protected gold nanoparticles thermally sinter under a variety of atmospheres. We find that upon sintering, the surface-bound thiyl ligands exclusively form the corresponding disulfide species when released from the gold surface. Experiments conducted using air, hydrogen, nitrogen, or argon atmospheres revealed no significant differences between the temperatures of the sintering event nor on the composition of released organic species. When conducted under high vacuum, the sintering event occurred at lower temperatures compared to ambient pressures in cases where the resulting disulfide had relatively high volatility (dibutyl disulfide). Hexadecylthiol-stabilized particles exhibited no significant differences in the temperatures of the sintering event under ambient pressures compared to high vacuum conditions. We attribute this to the relatively low volatility of the resultant dihexadecyl disulfide product.

A long-life lithium-oxygen battery via a molecular quenching/mediating mechanism.

The advancement of lithium-oxygen (Li-O2) batteries has been hindered by challenges including low discharge capacity, poor energy efficiency, severe parasitic reactions, etc. We report an Li-O2 battery operated via a new quenching/mediating mechanism that relies on the direct chemical reactions between a versatile molecule and superoxide radical/Li2O2. The battery exhibits a 46-fold increase in discharge capacity, a low charge overpotential of 0.7 V, and an ultralong cycle life >1400 cycles. Featuring redox-active 2,2,6,6-tetramethyl-1-piperidinyloxy moieties bridged by a quenching-active perylene diimide backbone, the tailor-designed molecule acts as a redox mediator to catalyze discharge/charge reactions and serves as a reusable superoxide quencher to chemically react with superoxide species generated during battery operation. The all-in-one molecule can simultaneously tackle issues of parasitic reactions associated with superoxide radicals, singlet oxygen, high overpotentials, and lithium corrosion. The molecular design of multifunctional additives combining various capabilities opens a new avenue for developing high-performance Li-O2 batteries.

A versatile functionalized ionic liquid to boost the solution-mediated performances of lithium-oxygen batteries.

Due to the high theoretical specific energy, the lithium-oxygen battery has been heralded as a promising energy storage system for applications such as electric vehicles. However, its large over-potentials during discharge-charge cycling lead to the formation of side-products, and short cycle life. Herein, we report an ionic liquid bearing the redox active 2,2,6,6-tetramethyl-1-piperidinyloxy moiety, which serves multiple functions as redox mediator, oxygen shuttle, lithium anode protector, as well as electrolyte solvent. The additive contributes a 33-fold increase of the discharge capacity in comparison to a pure ether-based electrolyte and lowers the over-potential to an exceptionally low value of 0.9 V. Meanwhile, its molecule facilitates smooth lithium plating/stripping, and promotes the formation of a stable solid electrolyte interface to suppress side-reactions. Moreover, the proportion of ionic liquid in the electrolyte influences the reaction mechanism, and a high proportion leads to the formation of amorphous lithium peroxide and a long cycling life (> 200 cycles). In particular, it enables an outstanding electrochemical performance when operated in air.

From Lead(II) Dithiocarbamate Precursors to a Fast Response PbS Positive Temperature Coefficient Thermistor.

PbS submicron crystals were formed by thermolysis of two different lead dithiocarbamate complexes. These precursors were readily synthesized and fully characterized, and in situ synchrotron powder diffraction experiments were performed to characterize their decomposition. The structure and purity of resultant PbS was examined using scanning electron and transmission electron microscopies, powder X-ray diffraction, and infrared spectroscopy. Submicron crystalline PbS was used to create a new PbS thermistor with excellent sensitivity and an ultrarapid thermal response time.

Photomechanical photochromism in a cetyltrimethylammonium isopolytungstate.

The photochromic properties of a hybrid compound comprised of the surfactant cation cetyltrimethylammonium [(C16H33)N(CH3)3]+ (CTA+) and the isopolytungstate anion [H2W12O40]6- is investigated. The compound, which has the nominal formula (CTA)7[H2W12O40]Cl·2H2O, changes from white to blue when exposed to UV radiation. The sample returns to the bleached state if stored in the dark-ambient. Application of XPS indicates that the coloring species are WV and WIV. The CTA+ component is found by XPS and FTIR to undergo progressive and irreversible oxidation during this cycle. Examination of FTIR suggests that the changes occur at multiple sites across the amphiphile. Surprisingly, the photochromic cycle is correlated with changes in the X-ray diffraction pattern, indicating partially reversible changes in the ordering of the Keggin ions and their spacing. In particular, application of the UV radiation causes the progressive accumulation of strain in the [001] direction. This is due to permanent oxidative changes in the CTA+ accumulating from cycle to cycle, resulting in an increase in interlamellar-distance due to less interdigitation of the chains. This provides a controllable photomechanical response.

Synthesis and organic impurity profiling of 4-methoxymethamphetamine hydrochloride and its precursors.

4-Methoxymethamphetamine (PMMA) was synthesised from star anise and from 4-methoxytoluene and the organic impurity profiles examined. These two starting materials are unrestricted chemicals in many jurisdictions and contain the requisite functional groups and are thus well suited for clandestine manufacturers. trans-Anethole was extracted from star anise and oxidised to 4-methoxyphenyl-2-propanone (PMP2P). 4-Methoxytoluene was oxidised to anisaldehyde, converted to 4-methoxyphenyl-2-nitropropene, and then reduced to PMP2P. The PMP2P obtained by both methods was then converted to PMMA via the Leuckart reaction. 4-Methoxymethamphetamine hydrochloride (PMMA·HCl) was synthesised from PMMA using hydrogen chloride gas. Both of the examined synthetic methods were found to be feasible routes into PMMA·HCl. The products of each step were analysed by gas chromatography-mass spectrometry (GC-MS) and proton nuclear magnetic resonance spectroscopy (1H NMR). Impurities were examined in an attempt to identify route specific compounds, which may provide valuable information about the synthetic pathway and precursors.

Organic impurity profiling of methylone and intermediate compounds synthesized from catechol.

This work examined the synthesis and organic impurity profile of methylone prepared from catechol. The primary aim of this work was to determine whether the synthetic pathway used to prepare 3,4-methylenedioxypropiophenone could be ascertained through analysis of the synthesized methylone. The secondary aim was the structural elucidation and origin determination of the organic impurities detected in methylone and the intermediate compounds. The organic impurities present in the reaction products were identified using GC-MS and NMR spectroscopy. Six organic impurities were detected in 1,3-benzodioxole and identified as the 1,3-benzodioxole dimer, 1,3-benzodioxole trimer, [1,3] dioxolo[4,5-b]oxanthrene, 4,4'-, 4,5'-, and 5,5'-methylenebis-1,3-benzodioxole. Six organic impurities were detected in 3,4-methylenedioxypropiophenone and identified as (2-hydroxyphenyl) propanoate, [2-(chloromethoxy) phenyl] propanoate, (2-propanoyloxyphenyl)propanoate, 5-[1-(1,3-benzodioxol-5-yl)prop-1-enyl]-1,3-benzodioxole, (5E)- and (5Z)-7-(1,3-benzodioxol-5-yl)-5-ethylidene-6-methyl-cyclopenta[f][1,3]benzodioxole). Exploratory synthetic experiments were also conducted to unambiguously identify the organic impurities detected in 3,4-methylenedioxypropiophenone. Two organic impurities were detected in 5-bromo-3,4-methylenedioxypropiophenone and identified as [2-(chloromethoxy)phenyl] propanoate and 3,4-methylenedioxypropiophenone. Five organic impurities were detected in methylone and identified as 3,4-methylenedioxypropiophenone, 1-(1,3-benzodioxol-5-yl)-N-methyl-propan-1-imine, 1-(1,3-benzodioxol-5-yl)-2-methylimino-propan-1-one, 1-(1,3-benzodioxol-5-yl)-N1,N2-dimethyl-propane-1,2-diimine and butylated hydroxytoluene. The origin of these organic impurities was also ascertained, providing valuable insight into the chemical profiles of methylone and the intermediate compounds. However, neither the catechol precursor nor the 1,3-benzodioxole intermediate could be identified based on the organic impurities detected in the synthesized methylone using standard techniques. This demonstrated that the organic impurity profiling of methylone had limitations in the determination of precursor chemical and synthetic pathways used. Copyright © 2017 John Wiley & Sons, Ltd.

Remarkable thermal stability of gold nanoparticles functionalised with ruthenium phthalocyanine complexes.

A gold nanoparticle (AuNP) ruthenium phthalocyanine (RuPc) nanocomposite has been synthesised that exhibits high thermal stability. Electrical resistance measurements revealed that the nanocomposite is stable up to ∼320 °C. Examination of the nanocomposite and the RuPc stabiliser complex using thermogravimetric analysis and differential scanning calorimetry show that the remarkable thermal stability is due to the RuPc molecules, which provide an effective barrier to sintering of the AuNPs.

Versatile method for template-free synthesis of single crystalline metal and metal alloy nanowires.

Metal and metal alloy nanowires have applications ranging from spintronics to drug delivery, but high quality, high density single crystalline materials have been surprisingly difficult to fabricate. Here we report a versatile, template-free, self-assembly method for fabrication of single crystalline metal and metal alloy nanowires (Co, Ni, NiCo, CoFe, and NiFe) by reduction of metal nitride precursors formed in situ by reaction of metal salts with a nitrogen source. Thiol reduction of the metal nitrides to the metallic phase at 550-600 °C results in nanowire growth. In this process, sulfur acts as a uniaxial structure-directing agent, passivating the surface of the growing nanowires and preventing radial growth. The versatility of the method is demonstrated by achieving nanowire growth from gas-phase, solution-phase or a combination of gas- and solution-phase precursors. The fabrication method is suited to large-area CVD on a wide range of solid substrates.

Organic impurity profiling of 3,4-methylenedioxymethamphetamine (MDMA) synthesised from catechol.

This work examines the organic impurity profile of 3,4-methylenedioxymethamphetamine (MDMA) that has been synthesised from catechol (1,2-dihydroxybenzene), a common chemical reagent available in industrial quantities. The synthesis of MDMA from catechol proceeded via the common MDMA precursor safrole. Methylenation of catechol yielded 1,3-benzodioxole, which was brominated and then reacted with magnesium allyl bromide to form safrole. Eight organic impurities were identified in the synthetic safrole. Safrole was then converted to 3,4-methylenedioxyphenyl-2-propanone (MDP2P) using two synthetic methods: Wacker oxidation (Route 1) and an isomerisation/peracid oxidation/acid dehydration method (Route 2). MDMA was then synthesised by reductive amination of MDP2P. Thirteen organic impurities were identified in MDMA synthesised via Route 1 and eleven organic impurities were identified in MDMA synthesised via Route 2. Overall, organic impurities in MDMA prepared from catechol indicated that synthetic safrole was used in the synthesis. The impurities also indicated which of the two synthetic routes was utilised.

Charging of gold/metal oxide/gold nanocapacitors in a scanning electron microscope.

Triangular parallel-plate nanocapacitors were fabricated by a combination of microsphere lithography and physical vapor deposition. The devices were comprised of a 20 nm layer of dielectric material sandwiched between two 20 nm layers of gold. Dielectric materials with a range of relative permittivities were investigated. Charging of the capacitors was probed in a scanning electron microscope (SEM) by monitoring the change in brightness of the images of the devices as a function of time. The time constants, RC, associated with the charging of the capacitors, were extracted from the SEM grayscale data. The resulting average RC values were 248 ± 27 s for SiO2, 70 ± 8 s for Al2O3, 113 ± 80 s for ZnO and 125 ± 13 s for HfO2. These values are consistent with the anticipated RC values based on the resistivities and permittivities of the materials used in the devices and importantly, were measured without the need to attach any wires or leads.

Zinc hydroxide sulphate and its transformation to crystalline zinc oxide.

The thermal transformation of zinc hydroxide sulphate hydrate to zinc oxide has been examined using synchrotron X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and surface area measurements. By collecting X-ray diffraction data in situ, we found that the dehydration of zinc hydroxide sulphate pentahydrate proceeded in discrete steps to form anhydrous zinc hydroxide sulphate. This compound then decomposed to a mixture of zinc oxide and a compound tentatively identified as Zn3(OH)2(SO4)2 at ~235 °C. At ~360 °C, the final dehydroxylation occurred with the formation of zinc oxy-sulphate, Zn3O(SO4)2, which then decomposed to ZnO at about ~800 °C. Interruption of the dehydration process can be used to synthesize the intermediate compounds.

Synthesis and impurity profiling of MDMA prepared from commonly available starting materials.

This work examines the synthesis of 3,4-methylenedioxy-N-methylamphetamine (MDMA) from common starting materials that may be utilised by clandestine laboratory operators. Piperonal was prepared from two common starting materials, piperine (from pepper) and vanillin (a common flavouring). Piperine was converted to piperonal by ozonolysis and oxidative cleavage with potassium permanganate and tetrahydrofuran. Vanillin was converted to piperonal by demethylation with pyridine and aluminium chloride followed by methylenation with dichloromethane. The resulting piperonal samples were converted via a commonly encountered route to MDMA. The impurities that indicate a particular route were identified and the feasibility of each method was also assessed.

Formation of gold nanorods by a stochastic "popcorn" mechanism.

Gold nanorods have significant technological potential and are of broad interest to the nanotechnology community. The discovery of the seeded, wet-chemical synthetic process to produce them may be regarded as a landmark in the control of metal nanoparticle shape. However, the mechanism by which the initial spherical gold seeds acquire anisotropy is a critical, yet poorly understood, factor. Here we examine the very early stages of rod growth using a combination of techniques including cryogenic transmission electron microscopy, optical spectroscopy, and computational modeling. Reconciliation of the available experimental observations can only be achieved by invoking a stochastic, "popcorn"-like mechanism of growth, in which individual seeds lie quiescent for some time before suddenly and rapidly growing into rods. This is quite different from the steady, concurrent growth of nanorods that has been previously generally assumed. Furthermore we propose that the shape is controlled by the ratio of surface energy of rod sides to rod ends, with values of this quantity in the range of 0.3-0.8 indicated for typical growth solutions.

Methods for the enhancement of fingermarks in blood.

Fingermarks formed in or by blood often require specific development techniques. This review examines techniques and materials that may be used to enhance and record fingermarks deposited in blood or fingermarks generated by blood-contaminated papillary ridges. A large number of techniques are presented here and are discussed from a chemical as well as practical perspective. It is concluded that an optimized sequence of techniques targeting both latent (non-bloody) and bloody fingermarks must be applied to detect and enhance the maximum number of marks, and therefore optimize the information content from exhibits that may bear marks in blood.

Enhancement of latent fingermarks on non-porous surfaces using anti-L-amino acid antibodies conjugated to gold nanoparticles.

Enantioselective anti-L-amino acid antibodies conjugated to gold nanoparticles are shown to facilitate the detection of latent fingermarks by interacting with amino acids present in friction ridge secretions. This antibody-based system is particularly effective for the enhancement of aged and dried fingermarks on non-porous surfaces, an area unexploited by current techniques.

Exploiting zinc oxide re-emission to fabricate periodic arrays.

The synthesis of hexagonal ring-shaped structures of zinc oxide using nanosphere lithography and metal/metal oxide sputtering is demonstrated. This synthesis exploits the surface re-emission of zinc oxide to deposit material in regions lying out of the line-of-sight of the sputtering source. These rings can nucleate the hydrothermal growth of zinc oxide crystals. Control over the growth could be exercised by varying growth solution concentration or temperature or by applying an external potential.