Luminescence properties of the ternary terbium complexes with (ortho and para) aminobenzoic acids and 1,10-phenanthroline incorporated in silica matrix by a sol-gel method

Ternary complexes of terbium with ortho (and pam) aminobenzoic acid and 1,10-phenanthroline were introduced into silica gel by the sol-gel method. The luminescence behavior of the solid-state samples was studied during the sol-gel aging process by means of emission. excitation spectra, lifetimes and quantum efficiencies.

Organic acids and protein compounds causing the photoluminescence properties of natural rubber membranes and the quenching phenomena from Au nanoparticle incorporation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Studies on the thermal decomposition behaviour, kinetics and electrical conductivity of the non-isothermal decomposition of pyridine mono carboxylic acids and some of their transition metal complexes

The thesis is divided into four chapters. They are: introduction, experimental, results and discussion about the free ligands and results and discussion about the complexes. The First Chapter, the introductory chapter, is a general introduction to the study of solid state reactions. The Second Chapter is devoted to the materials and experimental methods that have been used for carrying out tile experiments. TIle Third Chapter is concerned with the characterisations of free ligands (Picolinic acid, nicotinic acid, and isonicotinic acid) by using elemental analysis, IR spectra, X-ray diffraction, and mass spectra. Additionally, the thermal behaviour of free ligands in air has been studied by means of thermogravimetry (TG), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) measurements. The behaviour of thermal decomposition of the three free ligands was not identical Finally, a computer program has been used for kinetic evaluation of non-isothermal differential scanning calorimetry data according to a composite and single heating rate methods in comparison with the methods due to Ozawa and Kissinger methods. The most probable reaction mechanism for the free ligands was the Avrami-Erofeev equation (A) that described the solid-state nucleation-growth mechanism. The activation parameters of the decomposition reaction for free ligands were calculated and the results of different methods of data analysis were compared and discussed. The Fourth Chapter, the final chapter, deals with the preparation of cobalt, nickel, and copper with mono-pyridine carboxylic acids in aqueous solution. The prepared complexes have been characterised by analyses, IR spectra, X-ray diffraction, magnetic moments, and electronic spectra. The stoichiometry of these compounds was ML2x(H20), (where M = metal ion, L = organic ligand and x = water molecule). The environments of cobalt, nickel, and copper nicotinates and the environments of cobalt and nickel picolinates were octahedral, whereas the environment of copper picolinate [Cu(PA)2] was tetragonal. However, the environments of cobalt, nickel, and copper isonicotinates were polymeric octahedral structures. The morphological changes that occurred throughout the decomposition were followed by SEM observation. TG, DTG, and DSC measurements have studied the thermal behaviour of the prepared complexes in air. During the degradation processes of the hydrated complexes, the crystallisation water molecules were lost in one or two steps. This was also followed by loss of organic ligands and the metal oxides remained. Comparison between the DTG temperatures of the first and second steps of the dehydration suggested that the water of crystallisation was more strongly bonded with anion in Ni(II) complexes than in the complexes of Co(II) and Cu(II). The intermediate products of decomposition were not identified. The most probable reaction mechanism for the prepared complexes was also Avrami-Erofeev equation (A) characteristic of solid-state nucleation-growth mechanism. The tempemture dependence of conductivity using direct current was determined for cobalt, nickel, Cl.nd copper isonicotinates. An activation energy (ΔΕ), the activation energy (ΔΕ ) were calculated.The ternperature and frequency dependence of conductivity, the frequency dependence of dielectric constant, and the dielectric loss for nickel isonicotinate were determined by using altemating current. The value of s paralneter and the value of'density of state [N(Ef)] were calculated. Keyword Thermal decomposition, kinetic, electrical conduclion, pyridine rnono~ carboxylic acid, cOlnplex, transition metal compJex.

Progress in the development of mesoporous solid acid and base catalysts for converting carbohydrates into platform chemicals

This chapter provides a general overview of recent studies on catalytic conversion of fructose, glucose, and cellulose to platform chemicals over porous solid acid and base catalysts, including zeolites, ion-exchange resins, heteropoly acids, as well as structured carbon, silica, and metal oxide materials. Attention is focused on the dehydration of glucose and fructose to HMF, isomerization of glucose to fructose, hydrolysis of cellulose to sugar, and glycosidation of cellulose to alkyl glucosides. The correlation of porous structure, surface properties, and the strength or types of acid or base with the catalyst activity in these reactions is discussed in detail in this chapter.

Microwave-assisted extraction of phenolic acids and flavonoids and production of antioxidant ingredients from tomato: a nutraceutical-oriented optimization study

The production of natural extracts requires suitable processing conditions to maximize the preservation of the bioactive ingredients. Herein, a microwave-assisted extraction (MAE) process was optimized, by means of response surface methodology (RSM), to maximize the recovery of phenolic acids and flavonoids and obtain antioxidant ingredients from tomato. A 5-level full factorial Box-Behnken design was successfully implemented for MAE optimization, in which the processing time (t), temperature (T), ethanol concentration (Et) and solid/liquid ratio (S/L) were relevant independent variables. The proposed model was validated based on the high values of the adjusted coefficient of determination and on the non-significant differences between experimental and predicted values. The global optimum processing conditions (t=20 min; T=180 ºC; Et=0 %; and S/L=45 g/L) provided tomato extracts with high potential as nutraceuticals or as active ingredients in the design of functional foods. Additionally, the round tomato variety was highlighted as a source of added-value phenolic acids and flavonoids.

Hydrogen bonding in the anhydrous 1:1 proton-transfer compounds of isonipecotamide with nitro-substituted benzoic acids: the salts of the three isomeric mononitrobenzoic acids and of 3,5-dinitrobenzoic acid

The structures of the anhydrous 1:1 proton-transfer compounds of isonipecotamide (piperidine-4-carboxamide) with the three isomeric mononitro-substituted benzoic acids and 3,5-dinitrobenzoic acid, namely 4-carbamoylpiperidinium 2-nitrobenzoate (I), 4-carbamoylpiperidinium 3-nitrobenzoate (II), 4-carbamoylpiperidinium 4-nitrobenzoate (III), (C6H13N2O+ C7H4NO4-) and 4-carbamoylpiperidinium 3,5-dinitrobenzoate (IV) (C6H13N2O+ C7H5N2O6-)respectively, have been determined at 200 K. All salts form hydrogen-bonded structures: three-dimensional in (I), two-dimensional in (II) and (III) and one-dimensional in (IV). Featured in the hydrogen bonding of three of these [(I), (II) and (IV)] is the cyclic head-to-head amide--amide homodimer motif [graph set R2/2~(8)] through a duplex N---H...O association, the dimer then giving structure extension via either piperidinium or amide H-donors and carboxylate-O and in some examples [(II) and (IV)], nitro-O atom acceptors. In (I), the centrosymmetric amide-amide homodimers are expanded laterally through N-H...O hydrogen bonds via cyclic R2/4(8) interactions forming ribbons which extend along the c cell direction. These ribbons incorporate the 2-nitrobenzoate cations through centrosymmetric cyclic piperidine N-H...O(carboxyl) associations [graph set R4/4(12)], giving inter-connected sheets in the three-dimensional structure. In (II) in which no amide-amide homodimer is present, duplex piperidinium N-H...O(amide) hydrogen-bonding homomolecular associations [graph set R2/2(14)] give centrosymmetric head-to-tail dimers. Structure extension occurs through hydrogen-bonding associations between both the amide H-donors and carboxyl and nitro O-acceptors as well as a three-centre piperidinium N-H...O,O'(carboxyl) cyclic R2/1(4) association giving the two-dimensional network structure. In (III), the centrosymmetric amide-amide dimers are linked through the two carboxyl O-atom acceptors of the anions via bridging piperidinium and amide N-H...O,O'...H-N(amide) hydrogen bonds giving the two-dimensional sheet structure which features centrosymmetric cyclic R4/4(12) associations. In (IV), the amide-amide dimer is also centrosymmetric with the dimers linked to the anions through amide N-H...O(nitro) interactions. The piperidinium groups extend the structure into one-dimensional ribbons via N-H...O(carboxyl) hydrogen bonds. The structures reported here further demonstrate the utility of the isonipecotamide cation in molecular assembly and highlight the efficacy of the cyclic R2/2(8) amide-amide hydrogen-bonding homodimer motif in this process and provide an additional homodimer motif type in the head-to-tail R2/2(14) association.

A spectroscopic comparison of YBCO superconductors synthesised by solid-state and co-precipitation methods

Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) have been used to compare samples of YBa2Cu3O7 (YBCO) synthesised by the solid-state method and a novel co-precipitation technique. XRD results indicate that YBCO prepared by these two methods are phase pure, however the Raman and SEM results show marked differences between these samples.

The individual and interactive relationship between long chain omega-3 polyunsaturated fatty acids and physical activity as predictors of cognition in cognitively impaired and non-impaired older adults

Alterations in cognitive function are characteristic of the aging process in humans and other animals. However, the nature of these age related changes in cognition is complex and is likely to be influenced by interactions between genetic predispositions and environmental factors resulting in dynamic fluctuations within and between individuals. These inter and intra-individual fluctuations are evident in both so-called normal cognitive aging and at the onset of cognitive pathology. Mild Cognitive Impairment (MCI), thought to be a prodromal phase of dementia, represents perhaps the final opportunity to mitigate cognitive declines that may lead to terminal conditions such as dementia. The prognosis for people with MCI is mixed with the evidence suggesting that many will remain stable within 10-years of diagnosis, many will improve, and many will transition to dementia. If the characteristics of people who do not progress to dementia from MCI can be identified and replicated in others it may be possible to reduce or delay dementia onset, thus reducing a growing personal and public health burden. Furthermore, if MCI onset can be prevented or delayed, the burden of cognitive decline in aging populations worldwide may be reduced. A cognitive domain that is sensitive to the effects of advancing age, and declines in which have been shown to presage the onset of dementia in MCI patients, is executive function. Moreover, environmental factors such as diet and physical activity have been shown to affect performance on tests of executive function. For example, improvements in executive function have been demonstrated as a result of increased aerobic and anaerobic physical activity and, although the evidence is not as strong, findings from dietary interventions suggest certain nutrients may preserve or improve executive functions in old age. These encouraging findings have been demonstrated in older adults with MCI and their non-impaired peers. However, there are some gaps in the literature that need to be addressed. For example, little is known about the effect on cognition of an interaction between diet and physical activity. Both are important contributors to health and wellbeing, and a growing body of evidence attests to their importance in mental and cognitive health in aging individuals. Yet physical activity and diet are rarely considered together in the context of cognitive function. There is also little known about potential underlying biological mechanisms that might explain the physical activity/diet/cognition relationship. The first aim of this program of research was to examine the individual and interactive role of physical activity and diet, specifically long chain polyunsaturated fatty acid consumption(LCn3) as predictors of MCI status. The second aim is to examine executive function in MCI in the context of the individual and interactive effects of physical activity and LCn3.. A third aim was to explore the role of immune and endocrine system biomarkers as possible mediators in the relationship between LCn3, physical activity and cognition. Study 1a was a cross-sectional analysis of MCI status as a function of erythrocyte proportions of an interaction between physical activity and LCn3. The marine based LCn3s eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have both received support in the literature as having cognitive benefits, although comparisons of the relative benefits of EPA or DHA, particularly in relation to the aetiology of MCI, are rare. Furthermore, a limited amount of research has examined the cognitive benefits of physical activity in terms of MCI onset. No studies have examined the potential interactive benefits of physical activity and either EPA or DHA. Eighty-four male and female adults aged 65 to 87 years, 50 with MCI and 34 without, participated in Study 1a. A logistic binary regression was conducted with MCI status as a dependent variable, and the individual and interactive relationships between physical activity and either EPA or DHA as predictors. Physical activity was measured using a questionnaire and specific physical activity categories were weighted according to the metabolic equivalents (METs) of each activity to create a physical activity intensity index (PAI). A significant relationship was identified between MCI outcome and the interaction between the PAI and EPA; participants with a higher PAI and higher erythrocyte proportions of EPA were more likely to be classified as non-MCI than their less active peers with less EPA. Study 1b was a randomised control trial using the participants from Study 1a who were identified with MCI. Given the importance of executive function as a determinant of progression to more severe forms of cognitive impairment and dementia, Study 1b aimed to examine the individual and interactive effect of physical activity and supplementation with either EPA or DHA on executive function in a sample of older adults with MCI. Fifty male and female participants were randomly allocated to supplementation groups to receive 6-months of supplementation with EPA, or DHA, or linoleic acid (LA), a long chain polyunsaturated omega-6 fatty acid not known for its cognitive enhancing properties. Physical activity was measured using the PAI from Study 1a at baseline and follow-up. Executive function was measured using five tests thought to measure different executive function domains. Erythrocyte proportions of EPA and DHA were higher at follow-up; however, PAI was not significantly different. There was also a significant improvement in three of the five executive function tests at follow-up. However, regression analyses revealed that none of the variance in executive function at follow-up was predicted by EPA, DHA, PAI, the EPA by PAI interaction, or the DHA by PAI interaction. The absence of an effect may be due to a small sample resulting in limited power to find an effect, the lack of change in physical activity over time in terms of volume and/or intensity, or a combination of both reduced power and no change in physical activity. Study 2a was a cross-sectional study using cognitively unimpaired older adults to examine the individual and interactive effects of LCn3 and PAI on executive function. Several possible explanations for the absence of an effect were identified. From this consideration of alternative explanations it was hypothesised that post-onset interventions with LCn3 either alone or in interation with self-reported physical activity may not be beneficial in MCI. Thus executive function responses to the individual and interactive effects of physical activity and LCn3 were examined in a sample of older male and female adults without cognitive impairment (n = 50). A further aim of study 2a was to operationalise executive function using principal components analysis (PCA) of several executive function tests. This approach was used firstly as a data reduction technique to overcome the task impurity problem, and secondly to examine the executive function structure of the sample for evidence of de-differentiation. Two executive function components were identified as a result of the PCA (EF 1 and EF 2). However, EPA, DHA, the PAI, or the EPA by PAI or DHA by PAI interactions did not account for any variance in the executive function components in subsequent hierarchical multiple regressions. Study 2b was an exploratory correlational study designed to explore the possibility that immune and endocrine system biomarkers may act as mediators of the relationship between LCn3, PAI, the interaction between LCn3 and PAI, and executive functions. Insulin-like growth factor-1 (IGF-1), an endocrine system growth hormone, and interleukin-6 (IL-6) an immune system cytokine involved in the acute inflammatory response, have both been shown to affect cognition including executive functions. Moreover, IGF-1 and IL-6 have been shown to be antithetical in so far as chronically increased IL-6 has been associated with reduced IGF-1 levels, a relationship that has been linked to age related morbidity. Further, physical activity and LCn3 have been shown to modulate levels of both IGF-1 and IL-6. Thus, it is possible that the cognitive enhancing effects of LCn3, physical activity or their interaction are mediated by changes in the balance between IL-6 and IGF-1. Partial and non-parametric correlations were conducted in a subsample of participants from Study 2a (n = 13) to explore these relationships. Correlations of interest did not reach significance; however, the coefficients were quite large for several relationships suggesting studies with larger samples may be warranted. In summary, the current program of research found some evidence supporting an interaction between EPA, not DHA, and higher energy expenditure via physical activity in differentiating between older adults with and without MCI. However, a RCT examining executive function in older adults with MCI found no support for increasing EPA or DHA while maintaining current levels of energy expenditure. Furthermore, a cross-sectional study examining executive function in older adults without MCI found no support for better executive function performance as a function of increased EPA or DHA consumption, greater energy expenditure via physical activity or an interaction between physical activity and either EPA or DHA. Finally, an examination of endocrine and immune system biomarkers revealed promising relationships in terms of executive function in non-MCI older adults particularly with respect to LCn3 and physical activity. Taken together, these findings demonstrate a potential benefit of increasing physical activity and LCn3 consumption, particularly EPA, in mitigating the risk of developing MCI. In contrast, no support was found for a benefit to executive function as a result of increased physical activity, LCn3 consumption or an interaction between physical activity and LCn3, in participants with and without MCI. These results are discussed with reference to previous findings in the literature including possible limitations and opportunities for future research.

Mass spectrometric study of the dissociation of Group XI metal complexes with fatty acids and glycerolipids : Ag2H+ and Cu2H+ ion formation in the presence of a double bond

Results of mass spectrometric studies are reported for the collisional dissociation of Group XI (Cu, Ag, Au) metal ion complexes with fatty acids (palmitic, oleic, linoleic and a-linolenic) and glycerolipids. Remarkably, the formation of M2H+ ions (M = Cu, Ag) is observed as a dissociation product of the ion complexes containing more than one metal cation and only if the lipid in the complex contains a double bond. Ag2H+ is formed as the main dissociation channel for all three of the fatty acids containing double bonds that were investigated while Cu2H+ is formed with one of the fatty acids and, although abundant, is not the dominant dissociation channel. Also. Cu(I) and Ag(I) ion complexes were observed with glycerolipids (including triacylglycerols and glycerophospholipids) containing either saturated or unsaturated fatty acid substituents. Interestingly. Ag2H+ ion is formed in a major fragmentation channel with the lipids that are able to form the complex with two metal cations (triacylglycerols and glycerophosphoglycerols), while lipids containing a fixed positive charge (glycerophospocholines) complex only with a single metal cation. The formation of Ag2H+ ion is a significant dissociation channel from the complex ion Ag-2(L-H)(+) where L = Glycerophospholipid (GP) (18:1/18:1). Cu(I) also forms complexes of two metal cations with glycerophospholipids but these do not produce Cu2H+ upon dissociation. Rather organic fragments, not containing Cu(I), are formed, perhaps due to different interactions of these metal cations with lipids resulting from the much smaller ionic radius of Cu(I) compared to Ag(I) (C).

Advances in solid-catalytic and non-catalytic technologies for biodiesel production

The insecure supply of fossil fuel coerces the scientific society to keep a vision to boost investments in the renewable energy sector. Among the many renewable fuels currently available around the world, biodiesel offers an immediate impact in our energy. In fact, a huge interest in related research indicates a promising future for the biodiesel technology. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is environmentally benign needs no water washing and product separation is much easier. The number of well-defined catalyst complexes that are able to catalyze transesterification reactions efficiently has been significantly expanded in recent years. The activity of catalysts, specifically in application to solid acid/base catalyst in transesterification reaction depends on their structure, strength of basicity/acidity, surface area as well as the stability of catalyst. There are various process intensification technologies based on the use of alternate energy sources such as ultrasound and microwave. The latest advances in research and development related to biodiesel production is represented by non-catalytic supercritical method and focussed exclusively on these processes as forthcoming transesterification processes. The latest developments in this field featuring highly active catalyst complexes are outlined in this review. The knowledge of more extensive research on advances in biofuels will allow a deeper insight into the mechanism of these technologies toward meeting the critical energy challenges in future.

X-ray studies on crystalline complexes involving amino acids and peptides. XXXIII. Crystal structures of L- and DL-arginine complexed with oxalic acid and a comparative study of amino acid oxalic acid complexes

The DL- and L-arginine complexes of oxalic acid are made up of zwitterionic positively charged amino acid molecules and semi-oxalate ions. The dissimilar molecules aggregate into separate alternating layers in the former. The basic unit in the arginine layer is a centrosymmetric dimer, while the semi-oxalate ions form hydrogen-bonded strings in their layer. In the L-arginine complex each semi-oxalate ion is surrounded by arginine molecules and the complex can be described as an inclusion compound. The oxalic acid complexes of basic amino acids exhibit a variety of ionization states and stoichiometry. They illustrate the effect of aggregation and chirality on ionization state and stoichiometry, and that of molecular properties on aggregation. The semi-oxalate/oxalate ions tend to be planar, but large departures from planarity are possible. The amino acid aggregation in the different oxalic acid complexes do not resemble one another significantly, but the aggregation of a particular amino acid in its oxalic acid complex tends to have similarities with its aggregation in other structures. Also, semi-oxalate ions aggregate into similar strings in four of the six oxalic acid complexes. Thus, the intrinsic aggregation propensities of individual molecules tend to be retained in the complexes.

A technique for steady-state polarisation of stationary solid electrodes and its applications

A new technique has been devised to achieve a steady-state polarisation of a stationary electrode with a helical shaft rotating coaxial to it. A simplified theory for the convective hydrodynamics prevalent under these conditions has been formulated. Experimental data are presented to verify the steady-state character of the current-potential curves and the predicted dependence of the limiting current on the rotation speed of the rotor, the bulk concentration of the depolariser and the viscosity of the solution. Promising features of the multiple-segment electrodes concentric to a central disc electrode are pointed out.

X-ray Studies on Crystalline Complexes Involving Amino Acids and Peptides. XIII. Effect of Chirality on Molecular Aggregation: The Crystal Structures of L-Arginine D-Aspartate and L-Arginine D-Glutamate Trihydrate

The crystal structures of (1) L-arginine D-asparate, C6HIsN40~.C4H6NO4 [triclinic, P1, a=5.239(1), b=9.544(1), c=14.064(2)A, a=85"58(1), /3=88.73 (1), ~/=84.35 (1) °, Z=2] and (2) L-arginine D-glutamate trihydrate, C6H15N40~-.CsHsNO4.3H20 [monoclinic, P2~, a=9.968(2), b=4.652(1), c=19.930 (2) A, fl = 101.20 (1) °, Z = 2] have been determined using direct methods. They have been refined to R =0.042 and 0.048 for 2829 and 2035 unique reflections respectively [I>2cr(I)]. The conformations of the two arginine molecules in the aspartate complex are different from those observed so far in the crystal structures of arginine, its salts and complexes. In both complexes, the molecules are organized into double layers stacked along the longest axis. The core of each double layer consists of two parallel sheets made up of main-chain atoms, each involving both types of molecules. The hydrogen bonds within each sheet and those that interconnect the two sheets give rise to EL-, DD- and DE-type head-to-tail sequences. Adjacent double layers in (1) are held together by side-chain-side-chain interactions whereas those in (2) are interconnected through an extensive network of water molecules which interact with sidechain guanidyl and carboxylate groups. The aggregation pattern observed in the two LD complexes is fundamentally different from that found in the corresponding EL complexes.