Chemistry

The complete oxidation of isobutane has been studied using the oxidation catalysts-MnO 2 ,-Fe 2 O 3 , Co 3 O 4 and NiO, prior to and following addition of 5 wt% Au nanoparticles. The activity order is Co 3 O 4 >-MnO 2 >-Fe 2 O 3 , with the position of NiO dependent on the Ni 3+ content which changes with temperature. Preformed n-hexanethiolate-stabilized gold nanoparticles, following adsorption and thermolysis in air, introduce a small amount of sulfur as adsorbed sulfate. The sulfate appears to block the reoxidation step in the Mars-van Krevelen mechanism. This can have a significant effect on catalytic activity, as observed for-MnO 2. TEM/STEM studies indicate that gold nanoparticles of 2–4 nm in diameter form, which depends on the identity of the metal oxide and its specific surface area. Gold nanoparticle size effects have been studied on NiO, and show that the apparent activation energy and temperature of initial reaction depend on nanoparticle size. Comparisons of the multicomponent Au/MO x /-Al 2 O 3 (M:Al = 1:10) catalysts, where M = Mn, Fe, Co, Ni, have also been studied, and all are more active catalysts than Au/-Al 2 O 3 , but less active than the unsupported catalysts. Gold 4f 7/2 XPS studies on Au/MO x and Au/MO x /-Al 2 O 3 have shown that the only common species present is Au(0), suggesting that higher oxidation states of Au are not important in oxidation catalysis.

n-Alkanethiolate-stabilized gold (n-C n SAu) nanoparticles (n = 6, 12, 16) have been studied as the source of gold nanoparticles supported on the metal oxides NiO, TiO 2 (anatase and rutile), CeO 2 , and-Al 2 O 3 following adsorption from n-hexane and thermolysis in air at 340 • C. Adsorption times increase with an increase in length of the carbon chain and vary with the metal oxide, particularly with specific surface area. Evidence of oxidation of some of the thiolate sulfur to give sulfoxide-and sulfone-type species has been established. TG/DTA studies and FT-IR (attenuated total reflectance) spectroscopy show that the adsorbed n-C n SAu nanoparticles thermally decompose at about 210–340 • C depending on the metal oxide, with some decomposition products, particularly those containing sulfur, adsorbing onto the metal oxide surface. Following thermolysis at 340 • C, XPS and the FT-IR studies, combined with laser-ablation mass spectrometry, show that all organic material decomposition products are generally lost, and that the residual sulfur exists as sulfate at about 0.2 wt% or lower. TEM/STEM studies have shown that the n-C n SAu nanoparticles, originally about 2 nm in diameter, produce gold nanoparticles with a range of 2–4 nm in size on the oxide surface following thermolysis at 340 • C. The final average size of the gold nanoparticles depends on the metal oxide. For NiO, HRSTEM images shows little evidence of preferred orientation following immediate adsorption of n-C 6 SAu nanoparticles, indicating weak interaction with the oxide surface, while a preferred orientation occurs on thermolysis at 340 • C, indicating a much stronger interaction. The total oxidation of a representative alkane, isobutane, over TiO 2 (both anatase and rutile) and NiO, together with the addition of 5 wt% Au nanoparticles has been studied. Anatase and rutile are initially inactive but addition of the gold nanoparticles generates active oxidation catalysts, with anatase slightly more active than rutile. For NiO and 5 wt% Au/NiO reaction begins at 205–215 • C and complete oxidation occurs by 430–440 • C. The presence of the gold nanoparticles reduces the apparent activation energy from 89 to 51 kJ/mol. All active catalysts show formation of CO as well as CO 2 at about 20% conversion of isobutane, but at 100% oxidation the main product is almost exclusively CO 2 (>99.0%). The presence of the sulfate from the decomposition of the n-C n S − ligands has minimal apparent poisoning effect on the oxidation of isobutane for anatase, rutile, or NiO.

The complete oxidation of isobutane has been studied over CeO 2 and Au/CeO 2 , as well as the composite catalysts MO x /CeO 2 and Au/MO x /CeO 2 , where M = Mn, Fe, Co and Ni, using a range of CeO 2 surface areas. The catalytic ability of CeO 2 depended on the specific surface area, and the addition of gold always increased activity. Similarly, addition of MO x to CeO 2 (M:Ce = 1:10) increased catalytic activity, and there was a synergic interaction between the MO x and CeO 2 phases. For Au/MO x /CeO 2 catalysts the presence of gold nanoparticles did not affect the initial reaction temperature or that for 100% conversion, or the apparent activation energy compared to MO x /CeO 2 catalysts. The rate determining step in these reactions is suggested to be C H bond activation. This was supported by TG/DTA studies under 10% H 2 in N 2 that showed there was no correlation between the catalysis results and the temperature of initial mass loss of lattice oxygen. Gold nanoparticles (5 wt%) were introduced by adsorption and subsequent thermolysis of preformed n-hexanethiolate-stabilized gold nanoparticles. STEM and XRD studies showed that the average size of the gold nanoparticles depended on the surface area. Introduction of gold nanoparticles by this method introduces a small amount of sulfur as adsorbed sulfate, but this did not have any major poisoning effect on isobutane oxidation. Gold 4f 7/2 XPS studies on Au/MO x /CeO 2 showed that the only common gold species was Au(0), suggesting that higher oxidation states were not important in the oxidation , while Ce 3d 5/2 studies established the presence of Ce(III) in addition to Ce(IV), indicating their involvement in the Mars-van Krevelen mechanism, including possible participation in reoxidation of reduced MOx .

Robert Burns for his support, motivation and enthusiasm through this course of the project. His guidance and patience helped me during the research and in the writing of this thesis. I am grateful to have had the opportunity to work and learn from him a lot. I would like to extend my thanks to my co-supervisor Dr. Warwick Belcher for his support and assistance. My sincere thanks go to Dr. Glenn Bryant for help in recording the X-ray photoelectron spectra, Mr. David Phelan for help in recording the scanning electron microscopy and transmission electron microscopy images, and Ms. Jennifer Zobec for help in recording the X-ray powder diffraction data. I would also like to thank A/Prof. Scott Donne for performing the surface area measurements I would like also to acknowledge the technical and academic staff members in the Faculty for their kind assistance and warm support. Most importantly, my deepest gratitude goes to my mum and dad and my sisters and brothers. Thank you so much. You have been a constant source of love, encouragement and support. For them I will be forever grateful. Last, but not least, I would like to thank the Ministry of Higher Education in Saudi Arabia and the Cultural Mission of Royal Embassy of Saudi Arabia in Canberra for their funding, support and encouragement.

The complete oxidation of isobutane has been studied over CeO 2 and Au/CeO 2 , as well as the composite catalysts MO x /CeO 2 and Au/MO x /CeO 2 , where M = Mn, Fe, Co and Ni, using a range of CeO 2 surface areas. The catalytic ability of CeO 2 depended on the specific surface area, and the addition of gold always increased activity. Similarly, addition of MO x to CeO 2 (M:Ce = 1:10) increased catalytic activity, and there was a synergic interaction between the MO x and CeO 2 phases. For Au/MO x /CeO 2 catalysts the presence of gold nanoparticles did not affect the initial reaction temperature or that for 100% conversion, or the apparent activation energy compared to MO x /CeO 2 catalysts. The rate determining step in these reactions is suggested to be C H bond activation. This was supported by TG/DTA studies under 10% H 2 in N 2 that showed there was no correlation between the catalysis results and the temperature of initial mass loss of lattice oxygen. Gold nanoparticles (5 wt%) were introduced by adsorption and subsequent thermolysis of preformed n-hexanethiolate-stabilized gold nanoparticles. STEM and XRD studies showed that the average size of the gold nanoparticles depended on the surface area. Introduction of gold nanoparticles by this method introduces a small amount of sulfur as adsorbed sulfate, but this did not have any major poisoning effect on isobutane oxidation. Gold 4f 7/2 XPS studies on Au/MO x /CeO 2 showed that the only common gold species was Au(0), suggesting that higher oxidation states were not important in the oxidation, while Ce 3d 5/2 studies established the presence of Ce(III) in addition to Ce(IV), indicating their involvement in the Mars-van Krevelen mechanism, including possible participation in reoxidation of reduced MO x .

Biofilm formation in the resin-composite interface is a major challenge for resin-based dental composites. Using doped z nanoparticles (NPs) to enhance the antibacterial properties of resin composites can be an effective approach to prevent this. The present study focused on the effectiveness of Selenium-doped ZnO (Se/ZnO) NPs as an antibacterial nanofiller in resin composites and their impact on their mechanical properties. Pristine and Se/ZnO NPs were synthesized by the mechanochemical method and confirmed through UV-Vis Spectroscopy, FTIR (Fourier Transform Infrared) analysis, X-ray Diffraction (XRD) crystallography, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Zeta analysis. The resin composites were then modified by varying concentrations of pristine and Se/ZnO NPs. A single species (S. mutans and E. faecalis) and a saliva microcosm model were utilized for antibacterial analysis. Hemolytic assay and compressive strength tests were also performed...

Background: Nickel stannate nanocomposites could be useful for removing organic and toxic water pollutants, such as methyl orange (MO). Aim: The synthesis of a nickel oxide–tin oxide nanocomposite (NiO-SnO2 NC) via a facile and economically viable approach using a leaf extract from Ficus elastica for the photocatalytic degradation of MO. Methods: The phase composition, crystallinity, and purity were examined by X-ray diffraction (XRD). The particles’ morphology was studied using scanning electron microscopy (SEM). The elemental analysis and colored mapping were carried out via energy dispersive X-ray (EDX). The functional groups were identified by Fourier transform infrared spectroscopy (FTIR). UV–visible diffuse reflectance spectroscopy (UV–vis DRS) was used to study the optical properties such as the absorption edges and energy band gap, an important feature of semiconductors to determine photocatalytic applications. The photocatalytic activity of the NiO-SnO2 NC was evaluated by ...

Introduction: In this paper, MgO@AgO/Ag2O nanoparticles were greenly synthesized, the current idea is to replace the harmful chemical technique with an ecofriendly synthesis of metal oxide nanoparticles (NPs) utilizing biogenic sources.Methods: The current investigation was conducted to create silver oxide NPs decorated by MgO NPs (namely, MgO@AgO/Ag2O nanocom-posite) using the leaves extract of Purslane (Portulaca Oleracea) as the reducing and capping agent. The nanopowder was investigated by means of X-ray diffraction, scanning electron mi-croscope, BET surface area, Fourier transform infrared, and UV-vis spectrophotom-eter studies. XRD studies reveal the monophasic nature of these highly crystalline silver nano-particles. SEM studies the shape and morphology of the synthesis AgO/Ag2O and MgO@AgO/Ag2O NPs. The presence of magnesium and oxygen was further confirmed by EDS profile.Results and discussion: The surface area was found to be 9.1787 m2/g and 7.7166 m2/g, respectively. FTI...

Renewable energy can be harnessed from wastewater, whether from municipalities or industries, but this potential is often ignored. The world generates over 900 km3 of wastewater annually, which is typically treated through energy-consuming processes, despite its potential for energy production. Environmental pollution is a most important and serious issue for all and their adulterations to the aquatic system are very toxic in very low concentrations. Photocatalysis is a prominent approach to eliminating risky elements from the environment. The present study developed Zinc oxide (ZnO), Copper-doped Zinc oxide (CuZnO), and Cobalt-doped Zinc oxide (CoZnO) nanostructures (NSs) by facile hydrothermal route. The crystalline and structural stability of the synthesized nanostructures were evident from XRD and FESEM analysis. Metal, and oxygen bond and their interaction on the surfaces and their valency were explored from XPS spectra. Optical orientations and electron movements were revealed...

The nanostructures synthesized using the green chemistry method have recently attracted the attention of scientists due to their significance in many scientific domains. This work provides an overview of the biosynthesis of zinc oxide (ZnO) nanosheets (NSs) using Phyllanthus emblica plant (PEP) extract. X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) were used to analyze the synthesized ZnO-NSs. Evaluation of the antibacterial activity of biosynthesized ZnO-NSs was performed. ZnO-NSs exhibit effective antibacterial activity against Gram-positive (S. pyogenes and S. aureus) and Gram-negative (S. typhi and E. coli) bacterial strains. S. typhi is the most sensitive microbe towards ZnO-NSs and formed a 21 mm zone of inhibition (ZOI). ZnO-NSs are also tested as a photocatalyst in the degradation of methyl orange (MO) and rhodamine B (RB). The degradation rate of MO was 90%, and RB was 96% ...

Antibacterial restorative materials against caries-causing bacteria are highly preferred among high-risk patients, such as the elderly, and patients with metabolic diseases such as diabetes. This study aimed to enhance the antibacterial potential of resin composite with Magnesium-doped Zinc oxide (Mg-doped ZnO) nanoparticles (NPs) and to look for their effectiveness in the alloxan-induced diabetic model. Hexagonal Mg-doped ZnO NPs (22.3 nm diameter) were synthesized by co-precipitation method and characterized through ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. The Mg-doped ZnO NPs (1, 2.5 and 5% w/w) were then evaluated for antibacterial activity using a closed system in vitro biofilm model. Significant enhancement in the antibacterial properties was observed in composites with 1% Mg-doped ZnO compared to composites with bare ZnO reinforc...

The complete oxidation of isobutane has been studied over CeO 2 and Au/CeO 2 , as well as the composite catalysts MO x /CeO 2 and Au/MO x /CeO 2 , where M = Mn, Fe, Co and Ni, using a range of CeO 2 surface areas. The catalytic ability of CeO 2 depended on the specific surface area, and the addition of gold always increased activity. Similarly, addition of MO x to CeO 2 (M:Ce = 1:10) increased catalytic activity, and there was a synergic interaction between the MO x and CeO 2 phases. For Au/MO x /CeO 2 catalysts the presence of gold nanoparticles did not affect the initial reaction temperature or that for 100% conversion, or the apparent activation energy compared to MO x /CeO 2 catalysts. The rate determining step in these reactions is suggested to be C H bond activation. This was supported by TG/DTA studies under 10% H 2 in N 2 that showed there was no correlation between the catalysis results and the temperature of initial mass loss of lattice oxygen. Gold nanoparticles (5 wt%) were introduced by adsorption and subsequent thermolysis of preformed n-hexanethiolate-stabilized gold nanoparticles. STEM and XRD studies showed that the average size of the gold nanoparticles depended on the surface area. Introduction of gold nanoparticles by this method introduces a small amount of sulfur as adsorbed sulfate, but this did not have any major poisoning effect on isobutane oxidation. Gold 4f 7/2 XPS studies on Au/MO x /CeO 2 showed that the only common gold species was Au(0), suggesting that higher oxidation states were not important in the oxidation, while Ce 3d 5/2 studies established the presence of Ce(III) in addition to Ce(IV), indicating their involvement in the Mars-van Krevelen mechanism, including possible participation in reoxidation of reduced MO x .

MCM-41 (#41 Mobil Composition of Matter) is a favorable material for heterogeneous reactions because of its unique porous structure. However, the catalytic activity of MCM-41 for the oxidative dehydrogenation (ODH) of isobutane to isobutene is known to be quite low. In the present study, a metal-doping method was employed to improve this catalytic activity. Doping of Cr, Co, Ni, or Mo into MCM-41 resulted in a great improvement in the catalytic activity. Since chromium-doped MCM-41 (Cr-MCM-41) showed the greatest catalytic activity among these catalysts, its redox property was further analyzed via XPS, XAFS and H 2-TPR techniques. The XPS spectrum of Cr-MCM-41 suggested that it has Cr 3 and Cr 6 species on its surface. Also, a pre-edge peak due to Cr 6 species was con rmed in the XANES spectrum of Cr-MCM-41. In H 2-TPR measurement, Cr-MCM-41 was more reducible than crystalline Cr 2 O 3 , which showed low catalytic activity for the ODH of isobutane. The reducible Cr 6 species on Cr-MCM-41 contributed to an improvement in the catalytic activity of MCM-41.

Flephedrone (4-fluoromethcathinone, 4-FMC) was analysed using 1 H, 13 C, 15 N HMBC, and 19 F observe spectroscopy, gas chromatography-flame ionisation detection (GC-FID), and electrospray ionisationmass spectrometry (ESI-MS). Analysis of four 4-FMC samples (from a Bristol nightclub in 2013) showed that they all contained benzocaine as the cutting agent present in different amounts from 5 to 12%. Using these methods, we successfully differentiated between flephedrone regioisomers and mephedrone in an analytical method validated for flephedrone as a substituted cathinone. The data show that these now illegal cathinone-derived stimulants (highs) are now being cut; users cannot be certain of the purity of the drug they are taking. Furthermore, there are risks from the pharmaceutically active cutting agents themselves.

3,4-Methylenedioxymethylamphetamine (MDMA;'ecstasy') produces prosocial subjective effects that may extend to affiliative feelings towards the self. Behavioural techniques can produce similar self-directed affiliation. For example, compassionate imagery (CI) and ecstasy reduce self-criticism and increase self-compassion to a similar extent, with the effects of CI enhanced in the presence of ecstasy. Here, we examine self-compassion and self-criticism in recreational users who consumed chemically verified MDMA in a within-subjects crossover study. In a naturalistic setting, polydrug-using participants performed a self-focused CI exercise on two occasions separated by ≥6 days: once having consumed self-sourced MDMA and once not. Effects on state self-criticism, self-compassion and emotional empathy were assessed before and after MDMA use (or over an extended baseline period on the occasion that MDMA was not consumed) and reassessed after CI. In participants (n = 20; 8 women) whose ecstasy contained MDMA and no other drug, CI and MDMA appeared to separately increase emotional empathy (to critical facial expressions) and self-compassion. The effects of CI and MDMA on self-compassion also appeared to be additive. Establishing the observed effects in controlled studies will be critical for determining the combined utility of these approaches in fostering adaptive selfattitudes in a therapeutic context.