Emerging Research in Science and Engineering Based on Advanced Experimental and Computational Strategies

Plasmonics is an emerging area concerning in the fields of optics, telecommunications, optoelectronics and photovoltaics. Plasmonic nanostructures in general possess the capability to effectively concentrate and trap the electromagnetic field into the active region of the device covering different spectral regions of the entire solar spectrum. This could be finely tuned by optimizing several parameters such as the type of material, its shape, size and the local dielectric medium surrounding the particles. Excitonics, on the other hand is another independent branch of study primarily involving with the manipulation in generation and recombination of electron-hole pairs in inorganic and organic semiconductors, dyes and polymers. There is a subtle, yet a strong complementarity that exists between Plasmonics and Excitonics which could be exploited to generate several hybrid functional materials and devices to potentially enhance/boost the performance and efficiency of the devices. In this book chapter, I will start by discussing with the background on Plasmonics and Excitonics and how we can combine materials from these individual fields to develop hybrid heterostructures and fabricate all next generation photovoltaic devices. Next, I will give a detailed survey on how these materials could be synthesized using several substrate and solution based wet-chemistry, solvothermal, continuous flow and hot-injection methods. Several surface, optical and electrical characterization techniques will be thoroughly discussed concerning the plasmonic and excitonic nanostructures. The latter half of the chapter will be followed by discussing the underlying design principles and the device physics involving the interfacial exciton generation, recombination and charge carrier extraction processes when these plasmonic and excitonic materials are incorporated/embedded in between other transport layers. Finally, in conclusion, I will briefly discuss certain future prospects and perspectives involving these materials that could potentially open up new opportunities in the fabrication strategies of several high performance hybrid photovoltaic devices.

In the present work, the influence of the short-range disorder on the photocatalytic activity of TiO₂ nanocrystals obtained by a rapid microwave solvothermal method was evaluated. The synthesis of TiO₂ was performed without synthesis additives and with two different capping agents, sodium dodecyl sulfate (SDS) or carboxymethyl cellulose (CMC). Higher short-range disorder was obtained when SDS was used, as indicated by photoluminescence (PL) and also in the Raman spectra. In the second step, TiO₂ samples were used as photocatalysts for the degradation of remazol golden-yellow dye (RNL). High efficiency was observed, with meaningful variations in the percentage efficiency depending on the short-range order of the photocatalyst. Our best results were comparable to those of commercial TiO₂ Degussa P25. Adsorption isotherms were also evaluated as a function of time, indicating that chemisorption appears to take place, with a high adsorption capacity of the RNL by the photocatalysts.

For the synthesis of magnetic molecularly imprinted polymers (MMIPs), quinoline was used as a template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent and toluene as porogenic solvent, adding magnetic character with nanoparticles of maghemite (γ-Fe₂O₃). The solvents for extraction of the template were cyclohexane (EC) or a mixture of methanol/acetic acid (9:1 v/v) (EM), obtaining the materials MMIP-EC and MMIP-EM nomenclatures corresponding to the respective extractions. The materials were characterized by thermogravimetric analysis (TGA), infrared with Fourier transform (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and specific area (BET). The adsorption capacity of the materials was evaluated through kinetic tests and adsorption isotherms at different temperatures. 288.15, 298.15, 308.15 and 318.15 K. The adsorption process was evaluated with thermodynamic parameters ∆_adsG°, ∆_adsH°, and ∆_adsS°. In order to shed some light on the interaction between monomer and template, theoretical calculations were carried out. Results indicate 3-hour balance time. For MMIP-EM, more efficient adsorption was shown with the temperature increase, with an adsorption capacity q_max in 318.15 K of 36.66 mg g⁻¹. Negative values of ∆_adsG° and positives of Δ_adsH° indicate spontaneous, favorable, endothermic and physical adsorption processes. The printing factor (IF) of quinoline over MMIP-EM was 1.086 indicating better adsorption effectiveness in the selective process.

Chitosan-based nanoparticles are interesting bioactive polymers for a variety of emergent applications, due to their excellent physicochemical properties. Diverse strategies have been widely used for preparation and processing of chitosan-related nanoparticles. Notable examples include emulsion, ionic gelation, reverse micellar and self-assembling methods. This chapter endeavors to summarize current progress in the understanding of their synthesis and pharmacological potential, from a computational and experimental perspective in order to afford new chemical insights in the materials design with new/tailored properties. This combined approach could contribute to the development of more efficient materials and stimulate creative innovation in this research field. Critical assessment of selected therapeutic usages of this polymer is also discussed in this chapter.

The green coconut business is responsible for the generation of large amounts of waste. Sustainable development requires the transformation of such waste into value-added biotechnological products. The aim of this study was to optimize, by photostimulation, the hydrolysis of the coconut biomass. The thermo-cellulolytic consortium was collected from a composting pile, subjected to nutritional stress and irradiated either by Laser (λ660 ηm) or LED (λ632 ± 2 ηm). Microbial quantification after irradiation showed a significant stimulatory biological response. Despite cultures irradiated by LED significantly differed from the Laser-irradiated ones (p < 0.0001) both were significantly different from the control (p < 0.0001). The microbial consortium irradiated either by Laser or LED light showed the increase of RNA production and consequently protein synthesis causing anticipation and increase of the RBBR catabolism. The generation of products by cellulose hydrolysis (TRS and glucose) was significantly higher in the photostimulated groups, being the most effective catabolism observed within the first 48-h in the LED group and, after 144-h, in the Laser group. Photostimulation, especially by LED, might be considered as a booster of the bioprocess at low cost.

We start with short review of inorganic nanotubes leading to gas sensors, which among others, can be important application of semiconductor oxides. We investigate the interaction of H₂, CH₄, NH₃ and H₂O gases at high internal and external coverage with the [(SnO₂)₁₈]₃ nanotube designed from the (110) plane of SnO₂ in the rutile structure. We have used the PM7 and DFT methods, and B3LYP as the functional with Huzinaga and LANL2DZ basis sets to determine adsorption energies, interatomic distances, LUMO, HOMO, energy gaps and hardness. DFT was used in order to investigate these systems formed by the high coverage of internal and external adsorbed gases on the nanotube. The adsorption energies, and inter/intra atomic distances indicate stronger interaction of the nanotube with the NH₃ and H₂O gases. Our calculated adsorption energies, interaction distances, energy gaps and sensitivity trends are in agreement with reported theoretical and experimental values. For these large systems (~1000 atoms), it is observed that the selected computational methods, despite their lower computational demand, can provide satisfactory physical/chemical insights. The intermolecular distances of the adsorbed gas suggest hydrogen bonding among the adsorbed gases of H₂O and NH₃ which helps to stabilize the interaction process.

The optical properties of nanocrystal (NC) colloidal quantum dots (QDs) largely depend on their size and shape. These properties can be easily tuned by temperature and the concentration of ligands during their synthesis to generate QD particles with different optical features. However, the enormous complexity of these QD systems limits the understanding of the critical impact of passivating ligands and surface defects on their optical properties. In the present study, we systematically investigated the effect of different strategies on the optical properties of alloyed CdSe/CdSe_xCdS_1−x/CdS core shell (CS) QDs capped with several ligands, including trioctylphosphine (TOP) and hexadecylamine (HDA). The CdSe covered with TOP ligands were produced using the hot injection method, whereas CdSe covered with HDA ligands were produced by the exchange reaction method from as-synthesized samples. The CdSe/CdSe_xCdS_1−x/CdS QDs samples were prepared from a simple chemical route that involved an increasing concentration of thioglycerol to grow the CdS shell on the top of the as-precipitated CdSe core with different ligands in a controlled manner. Two emission peaks (at approximately 595 and 635 nm) were observed for three different surface coverages beyond the exciton recombination. These emissions were mainly attributed to the surface localized state in all samples and the charge carrier transfer between the exciton and surface states. Our findings revealed an increase in the photoluminescence (PL) intensity with increasing temperature for the alloyed CdSe/CdSe_xCdS_1−x/CdS CS QDs. The findings also revealed a continuous red-shift in the optical absorption peak, as a function of ligand concentration. This suggests a strong electronic coupling between the surface localized states and delocalized excitonic alloyed CdSe/CdSe_xCdS_1−x/CdS CS QDs. However, such colloidal nanocrystals (NCs) need to be further investigated to gain an in-depth understanding of their nanoscale behavior as well as explore their huge potential for several emerging technological applications.

Nanotechnology is applied in many topics of health sections with great benefits for humans. The concern with bacterial resistance has abruptly increased and the number of infections caused by multidrug-resistant (MDR) bacteria today is very high. Extending this problem, there is a struggle in developing new efficient antimicrobials. As an alternative solution, different nanoparticles have been studied to be used as antimicrobials due their promising activity and potentialized biological properties. Several studies about antimicrobials and nanotechnology have showed that nanocrystals can act as antimicrobial against different microorganisms such as bacteria, fungi and protozoa, including MDR bacteria. Some nanocrystalline metals have been applied in materials for wound care such as gold and silver nanocrystals in biomedical applications. Cellulose nanocrystals have exhibited antimicrobial properties in different materials such as food-packaging against important foodborne pathogens. Another aspect is about experimental methods for evaluation of antimicrobial activity of nanoparticles, including nanocrystals. The analysis of this antimicrobial effect is associated with chemical and physical properties of nanomaterials that can be affected depending on synthesis and kind of compounds. The study of the antimicrobial properties of nanocrystals is important for prevention of human infections, and development of new alternatives and strategies to control of pathogens as well as bacterial resistance.

Insulin resistance is characterized by molecular defects in the insulin-signaling pathway. Such defects disrupt cellular homeostasis and impede normal biochemical response. The mechanistic obstruction of biomolecules in the pathway leads to a number of health consequences that are grouped into a cluster of illnesses widely known as “metabolic syndrome” which creates abnormal health states of chronic condition like heart disease, diabetes, cancer, and Alzheimer’s disease, a type of dementia also known as “diabetes type 3,” which all have a profound effect and greatly impact the overall health. The interplay of major pathways leading to glucose homeostasis and energy production is explored. Molecular docking is utilized to understand possible intermolecular forces between key molecules in the signaling pathways. Emphasis is placed on the major components of insulin signaling, especially on how individual protein molecules of the pathways are interacting with each other in the signaling cascade. The relationship between the respective diseases and the signaling cascades is explored. Molecular links in the insulin pathway will be explored in detail, in order to correlate major mechanisms that lead to insulin resistance and related pathological conditions.

Citrus canker, caused by the bacterium Xanthomonas citri subsp. citri (XAC) is one of the most important diseases in citrus, presenting a significant impact on the Brazilian economy. A promising target enzyme for such disease control is phosphomannose isomerase (PMI). Phosphomannose isomerase is an enzyme that catalyses the interconversion of fructose-6-phosphate (F6P) and mannose-6-phosphate (M6P) and allows the synthesis of GDP-mannose in eukaryotic organisms. In Xanthomonas sp., phosphomannose isomerase is related to the production of xanthan gum, which is a defense mechanism of bacteria to prevent dehydration in harmful environments. Due to the lack of a resolved protein structure, a PMI model was created using the protein homology modeling method and, after protein selection by a BLASTp algorithm and subsequent alignment using ClustalOmega, the model was built using the MODELLER Software. The model was analysed and validated using the WhatIf, ProCheck, Errat, Prove and Verify-3D softwares. The Xanthomonas PMI model proved reliable through the validation and evaluation tests.

In many cancers such as breast, colon and pancreatic carcinomas, the tumor-associated stroma constitutes the microenvironment necessary to provide their nutritional support and survival/growth factors. In these tissues, cancer-associated fibroblasts express the fibroblast activation protein α (FAP), a dipeptidyl peptidase involved in the proteolytic remodeling of the stromal extracellular matrix of the tumor. Accordingly, high levels of stromal FAP correlate with a rapid progression of colorectal cancers, for example, increasing the potential for the development of metastasis. The presence of FAP on the surface of the cells is associated with other enzymes (specially metalloproteinases) and their regulators in order to promote an extensive degradation of the extracellular matrix. FAP is the only peptidase able to type-I collagen as a substrate and it acts in association with matrix metalloproteinases to produce biologically active fragments of denatured collagen. Therefore, the resulting proteolytic degradation (remodeling) of the extracellular matrix allows the neoplastic cells to invade the surrounding tissues, to migrate to distant sites (metastasis) and the increase in the microvessel density (angiogenesis) to provide the proper nutrition of the tumor. Herein we reviewed the role of FAP in cancers and the main synthetic and computer-aided strategies for the development of FAP inhibitors. As an example of structure-based drug design, we also used docking simulations coupled to in silico analyses of pharmacokinetics and toxicity profiles to identify new potential FAP inhibitors. In this concern, we started from 60,000 structures and applied a shape-fitting sampling algorithm to select compounds that could potentially fit into the binding pocket of FAP. The top 2% compounds were rescored and had their binding affinity energies calculated. We studied the binding modes for the top-twelve compounds, estimating their drug-likeness and predicted some toxicity endpoints. All ligands displayed significant binding affinity energies, and none was potentially mutagenic or tumorigenic and only one was expected to be teratogenic. Nine of the twelve selected compounds displayed drug-likeness scores that would confer a proper lipophilicity balance for oral use. Although these compounds must be subjected to experimental validation concerning FAP inhibition, they seem promising due to the good predicted binding affinities, adequate pharmacokinetic profiles and general low toxicity.

The use of pancreatic lipase (LP) inhibitors to reduce the absorption of dietary fats has become one of the pharmacological approaches adopted for the treatment of obesity. Since natural products continue to play a significant role in drug discovery and development the search for natural compounds with PL inhibitory activity is an interesting approach to provide new lead compounds for drug discovery and to guide dietary trends in order to prevent or treat obesity. The consumption of Myrciaria genus plant species is also related to increased HDL cholesterol and improved triglycerides excretion in animal models. In addition, extracts of species from Myrciaria genus are related to in vitro inhibitory activity against PL. Hence it is important to identify which chemical markers from Myrciaria genus species are structurally related to PL inhibitory activity. Ligand-based pharmacophore modeling is one of the most applied approaches in medicinal chemistry in order to detect molecular features related to molecules that are able to modulate a particular biological target. Some Myrciaria genus chemical markers including polyphenols, glycosides and lactonic derivatives share molecular features found in classic PL inhibitors. Such phytomolecules from Myrciaria species are a starting point to develop novel therapeutic options for obesity with PL inhibitory activity.

In this study, ab initio density functional theory calculations were performed for different materials considering the existence of different chemical bonds in NaCl, TiO₂ in anatase and rutile phases, and Graphite. Our insight was investigate materials with very specific and stablished chemical bonds, such as, strongly ionic (NaCl); mixed ionic-covalent bonds (TiO₂) and strongly covalent (Graphite) simulating each material in the PBE (pure), PBE0 (hybrid), B3LYP (parametrized and hybrid) functionals with Grimme dispersion (D) to build a case of study for this approach. We evaluated structural, mechanical and electronic properties as regards the role of different exchange-correlation functional. From such properties, the chemical nature dependence regarding to different exchange-correlations functionals was revised proving that the precision of DFT calculations depends on the chemical bond character showing the hard work in describe the chemical bond from general exchange-correlation functional. This proposition is an initial discussion for other theoretical studies.

The zeolites are aluminosilicates with perfectly crystalline structure based on tetrahedral arrangements of silicon and aluminum. These materials present great potential for application in catalytic, adsorption and ion exchange processes. In addition, the zeolite crystallinity results in a highly stable material, with very organized micropores and network of channels. Zeolites have been widely used in chemical processes as heterogeneous catalysts, both in the research and development stage of technology and in applications already established in industry, such as the catalytic cracking of petroleum. The synthesis of this material occurs through the hydrothermal method, which consists on the steps of gel synthesis, crystallization at autogenous pressure, separation of the precipitated material and subsequent heat treatment to remove the structure directing agents. During preparation of the synthesis gel, the composition of the material to be generated can be changed, by varying the Si/Al ratio (important parameter for zeolites) or by incorporating other metals into the crystalline structure, for example. It is also possible to vary the amount of synthesis water, which changes the solubility of the medium and also the autogenous pressure in the subsequent phase. In the crystallization step, the time and temperature in which nucleation and crystal growth occurs can be manipulated, altering the size of the crystallites formed. Finally, in the heat treatment step, the textural properties and the crystallinity can be altered by modifying the temperature, heating rate and calcination time. The possibility of altering the physical-chemical properties of the zeolites makes them very versatile materials for application in catalysis, making it possible to obtain materials with characteristics close to the ideal for specific processes. In this sense, zeolitic materials have been used as catalysts with acidic activity (property generated in the material structure itself), as supports for certain active phases in chemical reactions and even as active supports in photochemical reactions. Therefore, the aim of this chapter is to discuss the synthesis of zeolites through the hydrothermal method, with a focus on the manipulation of the synthesis conditions and their consequences on the physicochemical properties and the implications for the applications in different catalytic processes.

Since Alfred Werner published his work on coordination compounds in 1893, much progress has been made regarding this class of materials. Further studies evolved to the coordination polymers, among which the Metal-Organic Frameworks (MOFs), which are two- or three-dimensional coordination networks containing potentially empty cavities. Frequently, MOFs are crystalline materials with the coordination units repeating itself in an ordered manner in the structure, thus creating different topologies. However, synthetic parameters (pH, temperature, solvent) directly influence the kinetics and thermodynamics of the nucleation and growth of MOF crystals. In some cases, a material of low crystallinity may be formed, with short-range order. Most authors classify these compounds as Infinite Coordination Polymers (ICPs), Coordination Polymer Particles (CPPs) or Nanoscale Coordination Polymers (NCPs). Although not yet standardized by IUPAC, several articles, including recent review articles, name low-crystalline coordination polymers as ICPs. ICPs can show high tailorability regarding the particle size and morphology. They are usually obtained as micro- or nanoparticles, with spherical (mainly), cubic, rod-like and ring-like morphologies being reported. The major challenge in the study of ICPs lies in the structural elucidation, often performed by single crystal X-ray diffraction in crystalline MOFs. In this chapter, the synthetic routes, formation mechanisms, characterization techniques and potential applications of spherical ICP particles, such as in sensing, light-emitting devices, biomedicine, catalysis, gas sorption and separation, will be discussed.

Currently, graphitic carbon nitride (g-C₃N₄)-based materials are the centre of attention in chemistry and materials science because of their unique as well as fascinating properties, which are strongly desired for many technological applications. g-C₃N₄ is lamellar and composed of two-dimensional layers of carbon atoms naturally arranged in hexagonal networks. g-C₃N₄ is, therefore, analogous to graphene, but has nitrogen atoms bound through covalent bonds (sp²). This results in a stable, porous, heat-resistant polymeric semiconductor that is optically active under visible-light irradiation (and thus has excellent photocatalytic characteristics) as well as economically sustainable. The recent discovery of this new member of the graphene family is a crucial breakthrough, as there are only a few bi-dimensional organic solids. Hence, this chapter summarizes the current progress in the understanding of the synthesis and fundamental properties of g-C₃N₄-related materials.

The synthesis of new polymeric materials from the monomers is an arduous task, which does not always achieve the desired success. A very promising alternative that grows each year is the chemical modification of existing polymers. In this case, the polymer is one of the reagents of well-known properties and, through conventional chemical reactions, new functional groups can be inserted into the polymer chain, leading to a wide diversity of properties and applications for the new materials obtained. However, for the chemical modification reaction to succeed, it is critical that the polymer has reactive functional groups that can be used in chemical reactions. Polysaccharides are renewable, biodegradable and abundant natural polymers throughout the planet Earth, which have, on average, three hydroxyls in each repeating unit. With these characteristics, they have been extensively used in reactions of chemical modification, to reach biodegradable products, renewable sources and with important physicochemical properties for the industries. In this chapter, we will present different methodologies used in the synthesis of new materials from polysaccharides, as well as the study of their properties and technical feasibility of application in important sectors of the industry.

Organic semiconductors (OS) are applied in many electronic devices, for instance, OLEDs. The main advantages of these materials are focused in flexibility, high possibilities for structural changes and synthesis. The chemical structure of OS is based on a polymeric chain formed by π conjugated bonds, which act as charge carriers for conductive and optical properties. One of the most investigated polymeric structure is Poly(3,4-ethylenedioxythiophene) (PEDOT) due to its planar molecular structure. To investigate the charge bulk influence formed by \( \uppi \) conjugated bonds on excitation energy and band-gap of PEDOT were performed simulations in PM6, DFT and TD-DFT levels of theory. Consequently, Density of States (DOS) analysis showed an association between intermediary energy levels formed inside monomer band-gap and excitation energy profiles as essential factor to change electronic properties of PEDOT.

Modern society is dependent on different devices in which the fundamental behavior is deeply attached to the magnetic and electrical properties of the components used to build them. Until now, the development of new materials guarantees the improvement of the efficiency of these devices. However, new functionalized materials are necessary to the development of the next generation considering not only efficiency, but low environmental impact, durability, and low toxicity. One important concern is material weight and mild synthesis methods. In this sense, since the discovery of conducting polymers, in 1977, there are many and important applications of these materials. These compounds have as special properties the possibility to have their conductivity modulated between 10⁻⁶ up to 10³ S cm⁻¹. Besides, most of them are redox materials, meaning they can be reversibly changed between the reduced (dielectric) and oxidized states (semiconductor). On the other hand, fundamental aspects of their behavior are still a challenge to researchers of many areas due to the very drastic changes associated with the redox behavior, such as conductivity, spectral absorbance, ionic intercalation, volume change, and more recently, magnetic properties. Specifically, this chapter presents a review about those works which have investigated the magnetic properties, its correlation with synthesis methods and redox behavior as well as the morphological effect. The concern of this chapter is to analyze the different magnetic phases present in conducting polymers, in particularly, antiferromagnetic, ferromagnetic phases observed at room temperature in some of these materials, which open many possibilities for different applications.

Extensive research on ferrite-based materials and their application in field of electronics is of great importance in near future. In the last decade, several experiments have been conducted for developing different forms of ferrite-based materials through controlling its size, composition, and morphology. Such studies indicate that the chemical and physical properties of these materials can in principle be manipulated based on the desired application and are highly relevant from the technological point of view. However, the relationship between the closed structure and the composition of these advanced nanoscale materials is still debatable. In this chapter, the chemical structure of spinel ferrite nanoparticles has been studied using crystal engineering. It is quite evident that the change in the morphology of its particles and in the degree of defects alter their magnetic, optical and catalytic properties significantly. This makes these materials suitable for use in electronic devices such as high-density recording media and as a medical guide.