Publications

Abstract Fluorescent carbon dots (CDs) and its nitrogen doped (N-CDs) nanoparticles have been synthesized from lactose as precursor using a bottom-up hydrothermal methodology. The synthesized nanoparticles have been characterized by elemental analysis, FUR, Raman, TEM, DLS, XPS, and steady-state and life-time fluorescence. The synthesized carbon nanoparticles, CDs and N-CDs, have a size at about 7.7 +/- 2.4 and 50 +/- 15 nm, respectively, and quantum yields of 8% (CDs) and 11% (N-CDs). These techniques demonstrated the effectiveness of the synthesis procedure and the functionalization of the CDs surface with amine and amide groups in the presence of NH3 in aqueous media. The effect of excitation wavelength and pH on the luminescent properties was studied. Under the optimal conditions, the nitrogen doped nanoparticles can be used as pyridine sensor in aqueous media because they show an enhancement of its fluorescence with a good linear relationship. The analytical method is simple, reproducible and very sensitive for pyridine determination.

Abstract Highly luminescent nanoparticles based in Silicon quantum dots, coated by hydroxyl PAMAM dendrimer (PAMAM-OH) of 5th generation, were obtained by one step process by hydrothermal treatment of 3-Aminopropyl)triethoxysilane (APTES) in aqueous solution. Previous to the optimization of the synthesis procedure, different dendritic molecules of 5th generation were tested to obtain the most intense fluorescence signal. The influence of different parameters such ratio APTES/PAMAM-OH, pH and ionic strength on the fluorescence intensity was studied. The fluorescence spectra showed maximum excitation and emission wavelengths at 370 and 446 nm, respectively. The obtained silicon nanoparticles (SiQDs@PAMAM-OH) were characterized by TEM, DLS and XPS, and were found to detect selectively Cr (VI) in aqueous solutions at 2.7 mu M level of detection, sensitivity of 0.2 mu M with a RSD of 0.16% (n=10). To study the feasibility of the proposed system for Cr(VI) detection, it was tested in real electrochemical solution bath and a tanning effluent obtained from electrochemical industry and with two certified waters, demonstrating promising outcomes as nano-sensor.

Abstract This work presents the synthesis, volatility study and electrospray ionization mass spectrometry with energy-variable collision induced dissociation of the isolated [(cation)(2)(anion)](+) of a novel series of 2-alkyl-1-ethyl pyridinium based ionic liquids, [(CN-2C2Py)-C-2-C-1][NTf2]. Compared to the imidazolium based ionic liquids, the new ionic liquid series presents a higher thermal stability and lower volatility. The [(cation)(2)(anion)](+) collision induced dissociation energies of both [(CN-2C2Py)-C-2-C-1][NTf2] and [CNPy][NTf2] pyridinium series show an identical trend with a pronounced decrease of the relative cation-anion interaction energy towards an almost constant value for N = 6. It was found that the lower volatility of [(CN-2C2Py)-C-2-C-1][NTf2] with a shorter alkyl chain length is due to its higher enthalpy of vaporization. Starting from [(C3C2Py)-C-2-C-1][NTf2], the lower volatility is governed by the combination of slightly lower entropies and higher enthalpies of vaporization, an indication of a higher structural disorder of the pyridinium based ionic liquids than the imidazolium based ionic liquids. Dissociation energies and volatility trends support the cohesive energy interpretation model based on the overlapping of the electrostatic and van der Waals functional interaction potentials.

Abstract Six N-substituted-phenyl 4-oxo-4H-chromene-3-carboxamides, namely N-(2-nitrophenyl)-4-oxo-4H-chromene-3-carboxamide, C16H10N2O5 (2b), N-(3-methoxyphenyl)-4-oxo-4H-chromene-3-carboxamide, C17H13NO4, (3a), N-(3-bromophenyl)-4-oxo-4H-chromene-3-carboxamide, C16H10BrNO3, (3b), N-(4-methoxyphenyl)-4-oxo-4H-chromene-3-carboxamide, C17H13NO4, (4a), N-(4-methylphenyl)- 4-oxo-4H-chromene-3-carboxamide, C17H13NO3, (4d), and N-(4-hydroxyphenyl)-4-oxo-4H-chromene-3-carboxamide, C16H11NO4, (4e), have been structurally characterized. All compounds exhibit an anti conformation with respect to the C-N rotamer of the amide and a trans-related conformation with the carbonyl groups of the chromone ring of the amide. These structures present an intramolecular hydrogen-bonded network comprising an N-H center dot center dot center dot O hydrogen bond between the amide N atom and the O atom of the carbonyl group of the pyrone ring, forming an S(6) ring, and a weak Car-H center dot center dot center dot O hydrogen bond in which the carbonyl group of the amide acts as acceptor for the H atom of an ortho-C atom of the exocyclic phenyl ring, which results in another S(6) ring. The N-H center dot center dot center dot O intramolecular hydrogen bond constrains the carboxamide moiety such that it is virtually coplanar with the chromone ring.

Abstract Globally it is estimated that between 7.9 and 15.1 % of agricultural harvests are destroyed by pests, being wheat, rice, maize, potato, soybean and cotton, the most affected crops. With the exponential growth of worldwide population, an optimization in the crops protection against pests is urgently required, and because of that a 15- to 20- fold increasing in the chemical pesticides use has been observed. However, no significant effects on pest control have been observed. Despite of pesticides harmful properties against pests, they can indirectly improve the nutritional value of food. Nevertheless, the increased knowledge on their benefits and risks posed additional safety issues, namely those related to their low water solubility (bioavailability) and easy photodegradation. Several pesticides are easily decomposed by light and in that way a large amount of pesticide is needed to be applied in the crops in order to be effective. Some estimates point to the fact that less than 1 % of applied pesticides effectively reach the target. Furthermore, in some cases the metabolites originated by photodegradation of pesticides display a higher toxicity level. These facts associated with their capacity to act as carcinogenic, mutagenic and teratogenic agents to mankind, have led to a growing concern among scientific community to find a solution aimed to reduce or minimize the mentioned drawbacks and increase pesticide efficiency against pests. To increase the solubility and photostability as well as to facilitate the handling of pesticides, microencapsulation in nanostructures, namely cyclodextrins (CDs), has been proposed as a putative solution. CDs are cyclic oligosaccharides composed by D-glucose units connected by α-1,4-glycosidic linkages. The CDs structural characteristics, hydrophobic interior cavity and hydrophilic shell, and its ability to alter the physical, chemical, and biological properties of guest molecules has been regarded as a solution to improve pesticide formulations and to attain environmental sustainability. In this chapter, we will give special attention to the main pesticide groups and their inherent health and environmental issues. General features of CDs and the progress done so far in the field of microencapsulation of pesticides in CDs, will also be reported.

Abstract As mitochondria have an important role as ATP supplier, cellular ROS producer and apoptosis regulator, these organelles are a promising target for pharmacological intervention in the treatment and management of several diseases. Consequently, research on mitochondria-targeted drugs, which exclude other intracellular structures or extracellular processes, is becoming a hot topic. One approach to address the specific targeting is to conjugate bioactive molecules to a lipophilic cation such as the triphenylphosphonium (TPP+). In this chapter, the development of a new antioxidant based on the dietary cinnamic acid-caffeic acid-is described as well as the demonstration of its mitochondriotropic activity. © Springer Science+Business Media New York 2015. All right reserved.

Abstract The in vivo NO sensing is of outstanding relevance for the comprehension of the diverse physiological and pathological process in which this species is involved. Nevertheless, in vivo NO sensing is a complex challenge due to its own physicochemical properties, antioxidant mechanisms and possible interferences. Some electrochemical and optical sensors have already been developed for in vivo NO sensing. Most of the electrochemical sensors are amperometric and most of the optical sensors are based on fluorescence. New materials are being developed for new NO electrochemical or optical sensors. Due to their intrinsic properties, the nanomaterials are one of the most promising emergent materials. This chapter review the most promising nanomaterials for the development of electrochemically or optical sensors for in vivo NO sensing. © 2015 Nova Science Publishers, Inc.

Abstract This work presents and highlights the differentiation of the physicochemical properties of the [C(1)Him][NTf2], [C(2)Him][NTf2], [(1)C(1)(2)C(1)Him][NTf2], and [(1)C(4)(2)C(1)(3)C(1)im][NTf2] that is related with the strong bulk interaction potential, which highlights the differentiation on the physicochemical arising from the presence of the acidic group (NH) as well as the methylation in position 2, C(2), of the imidazolium ring. Densities, viscosities, refractive indices, and surface tensions in a wide range of temperatures, as well as isobaric heat capacities at 298.15 K, for this IL series are presented and discussed. It was found that the volumetric properties are barely affected by the geometric and structural isomerization, following a quite regular trend. A linear correlation between the glass transition temperature, T-g, and the alkyl chain size was found; however, ILs with the acidic NH group present a significant higher Tg than the [(1)C(N-1)(3)C(1)im][NTf2] and [(1)C(N)(3)C(N)im][NTf2] series. It was found that the most viscous ILs, ([(1)C(1)Him][NTf2], [(1)C(2)Him][NTf2], and [(1)C(1)(2)C(1)Him][NTf2]) have an acidic NH group in the imidazolium ring in agreement with the observed increase of energy barrier of flow. The methylation in position 2, C(2), as well as the NH acidic group in the imidazolium ring contribute to a significant variation in the cationanion interactions and their dynamics, which is reflected in their charge distribution and polarizability leading to a significant differentiation of the refractive indices, surface tension, and heat capacities. The observed differentiation of the physicochemical properties of the [(1)C(1)Him][NTf2], [(1)C(2)Him][NTf2], [(1)C(1)(2)C(1)Him][NTf2], and [(1)C(4)(2)C(1)(3)C(1)im][NTf2] are an indication of the stronger bulk interaction potential, which highlights the effect that arises from the presence of the acidic group (NH) as well as the methylation in position 2 of the imidazolium ring.

Abstract Isobaric vapor-liquid equilibria of 1-butyl-3-methylimidazolium thiocyanate ([C(4)C(1)im][SCN]), 1-butyl-3-methylimidazolium dicyanamide ([C(4)C(1)im][N(CN)(2)]), 1-butyl-3-methylimidazolium tricyanomethanide ([C(4)C(1)im] [C-(CN)(3)]), and 1-ethyl-3-methylimidazolium tetracyanoborate ([C(2)C(1)im][B(CN)(4)]), with water and ethanol were measured over the whole concentration range at 0.1, 0.07, and 0.05 MPa. Activity coefficients were estimated from the boiling temperatures of the binary systems, and the data were used to evaluate the ability of COSMO-RS for describing these molecular systems. Aiming at further understanding the molecular interactions on these systems, molecular dynamics (MD) simulations were performed. On the basis of the interpretation of the radial and spatial distribution functions along with coordination numbers obtained through MD simulations, the effect of the increase of CN-groups in the IL anion in its capability to establish hydrogen bonds with water and ethanol was evaluated. The results obtained suggest that, for both water and ethanol systems, the anion [N(CN)(2)](-) presents the higher ability to establish favorable interactions due to its charge, and that the ability of the anions to interact with the solvent, decreases with further increasing of the number of cyano groups in the anion. The ordering of the partial charges in the nitrogen atoms from the CN-groups in the anions agrees with the ordering obtained for VLE and activity coefficient data.

Abstract Colloidal carriers based on silica (Si) matrices are an innovative approach within the context of therapeutic drug delivery systems. These carriers are emerging as a great promise for diagnosis and treatment of a wide range of injuries, particularly in cancer and infectious diseases. In addition, bioencapsulation for biosensing and cell therapy in silica sol-gel allows the survival of enzymes and cells for a long period of time. Owing to their porosity, large surface area, and high capability of functionalization, silica nanoparticles (SiNP) have been considered as an attractive option for several bioanalysis applications, such as selective bioseparation, imaging, and drug and gene delivery. However, although great advances are achieved in the biomedical fields, some toxicity effects can be associated with the use of SiNP. This article aims to present a comprehensive review of recent technological advances for silica matrices in biomedical applications, as well as the potential impact of silica-based materials on human health and environment. © 2014 International Union of Biochemistry and Molecular Biology, Inc.