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The presence of contaminants in water is a subject of paramount importance nowadays, which can make water improper to human consumption even when these contaminants are present at very low concentrations, causing health issues and economic losses. In this work, we evaluated the performance of nanocomposites based on nylon 6,6/chitosan electrospun nanofibers modified by cellulose nanowhiskers combined with functional materials like silver nanoparticles, gold nanoparticles, and reduced graphene oxide to be used as sensing layers of an electronic tongue (e-tongue) to detect Isoborneol. This compound, found in some plants and essential oils, is used as a natural repellent and also to produce many other chemicals. Additionally, its chemical structure is related to that of 2-methylisoborneol, a critical pollutant in aqueous media. The synergism between the nanomaterials combined with electrospun nanofibers could be verified by the enhancement of the charge transference ability. Additionally, electrical capacitance data measured with the impedimetric e-tongue were treated by Principal Component Analysis (PCA), and revealed the sensing system was able to discriminate samples contaminated with Isoborneol at nanomolar concentrations. Moreover, the electronic tongue system could detect Isoborneol in real water samples under different concentrations.

Active food packaging systems promote better food quality and/or stability, such as by releasing antimicrobial agents into food. Advantages of adding antimicrobials to the packaging material instead of into the bulk food include controlled diffusion, reduced antimicrobial contents, and improved cost effectiveness. Nanostructured antimicrobials are especially effective due to their high specific surface area. The present review is focused on recent advances and findings on the main nanostructured antimicrobial packaging systems for food packaging purposes. Several kinds of nanostructures, including both inorganic particles and organic structures, have been proven effective antimicrobials by different mechanisms of action and with different application scopes. Moreover, there are systems containing nanocarriers to protect antimicrobials and deliver them in a controlled fashion. On the other hand, scientific data about migration of nanostructures onto food and their toxicity are still limited, requiring special attention from researchers and regulation sectors.

In this study, gelatin, a biocompatible, collagen-derived protein, was combined with clove essential oil (CEO) and hydrotalcite ([Mg-Al-CO3]-LDH) nanoplates (D ∼ 100 nm) as an attempt to develop new antimicrobial wound dressings. CEO-loaded gelatin films covering different hydrotalcite contents (0.5–5.0 wt.%) were obtained by solution casting and characterized by light microscopy, FTIR and UV–vis spectroscopies, tensile and optical tests, water contact angle (WCA) determinations, and disc diffusion assays. CEO formed emulsified morphologies with gelatin over the entire hydrotalcite content range. Hydrotalcite contents larger than 2.5 wt.% were key for retain CEO in the gelatin matrix, which ensured antimicrobial activity for the films against Staphylococcus aureus and Escherichia coli. The UV barrier and mechanical properties of gelatin were significantly increased by CEO and further sustained upon hydrotalcite addition. All the composite films were regarded as hydrophilic materials (WCA

Made available in DSpace on 2021-06-25T10:56:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Mangoes are usually wasted by consumers due to a physiological disorder known as Internal breakdown (IB). In this study, Palmer mangoes affected by IB were valorized by turning into edible films by continuous solution casting. The films were produced using mango pulps with different IB levels, being 0 (no IB), 2 (1/3–2/3 of IB-affected pulp) and 3 (more than 2/3 of IB-affected pulp), and pectin as a matrix former. The influence of IB level on the physicochemical composition of mango pulps was assessed by pH, soluble solid content, and fiber content analyses. Continuous casting allowed for high productivity of edible films with natural mango color attributes. The films obtained from mango pulps with the highest IB level displayed lowest thickness and water vapor permeability, and largest elongation and opacity, in addition to exhibiting a short composting time (10 days). The physical properties of mango edible films are influenced by the pulp physiochemical composition which changes with IB progression. Department of Food and Nutrition São Paulo State University (UNESP), Rod. Araraquara Jaú, Km 01 – S/n Brazilian Agricultural Research Corporation Embrapa Instrumentation, XV de Novembro Street, 1452 Department of Agronomy Federal University of Paraná (UFPR), Pioneiro Street, 2153 Department of Materials Engineering (DEMa) Federal University of São Carlos (UFSCar), Rod. Washington Luis, Km 235, 310 Department of Food and Nutrition São Paulo State University (UNESP), Rod. Araraquara Jaú, Km 01 – S/n FAPESP: 2018/07860–9 FAPESP: 2018/24612-9 FAPESP: 2019/13656-8

Cellulose nanocrystals (CNCs)-reinforced gelatin (Gel) films are appealing candidates for biodegradable packaging. However, tailoring the physical properties of Gel/CNCs films by control of pH and film-forming drying temperature continues unstudied. Here, we described the influence of pH on the physical properties of Gel/CNCs films covering different CNCs contents. The interactions between CNCs and Gel were studied by assessing the ζ-potential of Gel/CNCs suspensions under acidic (pH 3), Gel isoelectric point (pI, pH 6) and alkaline (pH 8) conditions. pH 3 promotes the electrostatic attraction, while pH 8 favors the electrostatic repulsion in the Gel-CNCs pair, increasing the suspension viscosity in both cases. The addition of 0.5 wt% CNCs decreased the water vapor permeability (WVP) of the Gel/CNCs films by 68% under electrostatic attractive forces and by 39% at the gelatin pI. The addition of 5 wt% CNCs at pH 3 resulted in the formation of complex coacervates, which decreased the mechanical properties and increased the WVP of Gel/CNCs films. Increasing pH above the Gel pI remarkedly increased the gelatin renaturation as triple helices, which was found to be key for increasing by 152% and 56% the Young's modulus and tensile strength, respectively, of the Gel/CNCs films with 0.5 wt% CNCsFilm-forming drying temperatures had an inverse effect on the triple helix content, and, consequently, on the physical properties of the Gel/CNCs films. These findings denote that modulating pH, CNCs amount, and drying temperature is a suitable strategy for tailoring the properties of nanocellulose-reinforced gelatin films for an extended range of food packaging applications.

Nanotechnology has provided innovative solutions to guarantee sustainable energy and maintain a clean environment for the future. In this regard, 1D nanostructured materials, such as nanofibers, are very attractive, especially for the development of economic and environmentally friendly approaches for wastewater treatment. Recently, Solution Blow Spinning (SBS) has appeared as a powerful fiber forming technique with several advantages compared to the traditional electrospinning method. Herein, we present the fabrication of composite membranes using solution blow spun poly(methylmethacrylate) nanofibers wrapped with reduced graphene oxide (PMMA-rGO) to adsorb methylene blue (MB), which is a typical dye used in the printing and dyeing industry. The dye adsorption kinetics and isotherm follow the pseudo-second-order and the Langmuir models, respectively. The π–π stacking interactions were considered to be the major driving force for the spontaneous adsorption of MB and the maximum adsorption capacity was 698.51 mg g−1 according to Langmuir fitting. The developed nanocomposite shows great potential for decolorizing dyeing wastewater aimed at industrial and environmental remediation applications.

Poly(lactic acid) (PLA) is a biodegradable polymer that exhibits high elastic modulus, high mechanical strength, and feasible processability. However, high cost and fragility hinder the application of PLA in food packaging. Therefore, this study aimed to develop flexible PLA/acetate and PLA/chitosan films with improved thermal and mechanical properties without the addition of a plasticizer and additive to yield extruder compositions with melt temperatures above those of acetate and chitosan. PLA blends with 10, 20, and 30 wt% of chitosan or cellulose acetate were processed in a twin-screw extruder, and grain pellets were then pressed to form films. PLA/acetate films showed an increase of 30 °C in initial degradation temperature and an increase of 3.9 % in elongation at break. On the other hand, PLA/chitosan films showed improvements in mechanical properties as an increase of 4.7 % in elongation at break. PLA/chitosan film which presented the greatest increase in elongation at break proved to be the best candidate for application in packaging.

This paper reports on a study of highly filled composites of polypropylene (PP) and 75% by weight sugarcane bagasse fiber with and without alkali treatment and with and without coupling agent (SEBS-g-MA). Composites were prepared using a Rheomix600 mixer connected to a HAAKE torque rheometer. The thermal and mechanical behavior of these composites were investigated by thermogravimetry (TGA), differential Scanning Calorimetry (DSC), flexural tests, impact tests and scanning electron microscopy. Scanning electron microscopy (SEM) images taken from sugarcane bagasse fibers showed enhancements in the fiber's surface topography after the surface treatment process. The FTIR, TGA and SEM results for the fibers showed that the alkali treatment modified the fiber surface as well as the chemical composition. The impact test results showed a good potential of SEBS-g-MA as coupling agent and impact modifier in highly filled composites, increasing by more than 100% the impact strength of the composite as compared to those without the coupling agent. Scanning electron microscopy showed that addition of coupling agent improved the interfacial adhesion between the fibers and polypropylene.

The reuse of the solid residues generated in the production of second-generation (2G) ethanol to obtain high-value products is a potential strategy for improving the economic and environmental viability of the overall process. This study evaluated the feasibility of using the residual solids remaining after the enzymatic hydrolysis of sugarcane bagasse for the production of cellulose nanocrystals (CNC), a valuable bionanomaterial. To this end, sugarcane bagasse subjected to steam explosion (SEB) or liquid hot water (LHWB) pretreatment was hydrolysed using different loadings of a commercial cellulase cocktail. Samples of SEB and LHWB were hydrolysed enzymatically, resulting in glucose releases close to 40 g/L, which would be suitable for producing 2G ethanol by microbial fermentation. The solid residues after the enzymatic hydrolysis step presented cellulose contents of up to 54 %, indicating that a significant amount of recalcitrant crystalline cellulose remained available for subsequent use. These solid residues were purified and submitted to acid hydrolysis, resulting in the successful formation of CNC with crystallinity close to 80 %, lengths of 193–246 nm and diameters of 14–18 nm. The CNC produced presented morphology, dimensions, physical-chemical characteristics, thermal stability and crystallinity within the ranges reported for this type of material. Moreover, the enzyme loading or the type of hydrothermal pretreatment process employed here showed no significant effects on the CNC obtained, indicating that these variables could be flexibly adjusted according to specific interests.

Efficient use of the entire lignocellulosic biomass is important for biorefinery sustainability, especially considering the extraction of high value-added products, such as nanocellulosic materials. This work investigates the feasibility of using sugarcane straw as a feedstock to obtain lignocellulose nanocrystals (LCNCs). Together with bagasse, the straw is a residue from the processing of sugarcane in the ethanol/sugar mills, but its effective use remains to be further studied. An organosolv pretreatment process was first applied to the straw for partial removal of the lignin and hemicellulose contents (reductions of 72.2 and 62.1 %, respectively) and to increase the surface area (observed by scanning electron microscopy and atomic force microscopy). Acid hydrolysis carried out for different reaction times, with or without mechanical treatment, resulted in high yields of sugarcane straw LCNCs (40–64 % of the total mass). X-ray diffraction analyses showed that the crystallinity of the LCNCs increased from 65 to 80 %, with an estimated average elementary crystallite size of 3.3 nm. The aspect ratios of the LCNCs were determined by AFM and ranged from 18.0–30.1. The onset of thermal degradation of the LCNCs occurred between 145 and 191 °C. The findings demonstrated the effective extraction of cellulose nanocrystals with residual lignin from sugarcane straw, opening the possibility of obtaining high value-added nanomaterials and contributing to the sustainability of future lignocellulosic biomass biorefineries.

Miniaturized and inexpensive sensing platforms remains an important goal for the field-deployable monitoring of toxic gases. In this work, we report a disposable ethanol sensor based on nanochitin-composite containing chitin nanowhiskers/zinc oxide nanoparticles/polyaniline (ChitNW-ZnO/PANI) produced via solution casting method. The as-prepared material was fully characterized by transmission electron microscopy, atomic force microscopy, contact angle measurements, mechanical tests, thermogravimetric analysis and X-ray diffraction, confirming its successful preparation and revealing its morphology, microstructure and composition. Such nanocomposite showed enhanced ethanol sensing performance at room temperature, in which quantitative analysis was obtained in the range 20–100 ppm with a detection limit of 17 ppm (S/N = 3). We further validated that common potential interfering agents were not misidentified with ethanol. The development of such a unique nanochitin-based composite as a disposable sensor is a great step ahead in flexible and wearable electronics having potential applications in different fields such as biomedical and biotechnological engineering, security and internet of things (IoT).

This study aims at assessing the potential use of cellulose pulp in MgO-water slurries with potential for precast composites. These systems for composites applications envisage encapsulating CO2 when exposed to fast carbonation. The effect of cellulose fibers was evaluated on samples after the drainage of MgO-cellulose-water slurries. Different cellulose mass fractions were added into MgO-water suspensions – up to 30 wt% – to study the MgO hydration during the first 96 h. Afterward, the carbonation of the hydrated products for 6 and 12 h was evaluated. The addition of cellulose, after hydration, increases the sample porosity, where Mg(OH)2 is the main crystalline phase and only minor traces of unreacted MgO are found. MgO-H2O systems after hydration do not present any binding capacity given the low density and high apparent porosity of the clusters. However, XRD and TG analyses show that exposing samples to a rich CO2 environment promotes the formation of nesquehonite (MgCO3·3H20), which significantly reduces the porosity induced by the cellulose hygroscopy. This reduction in porosity is greater for samples with cellulose fibers because of the greater content of nesquehonite produced in samples with cellulose. Besides, cellulose fibers are covered with nesquehonite nanocrystals after carbonation. By adding cellulose to water-MgO suspensions yields lighter products with promising potential for fiber-cement applications. Moreover, the addition of cellulose contributes to the encapsulation of CO2 in building materials through the Mg(OH)2 carbonation.

Considerable effort has been devoted to improving the properties of PVDF (polyvinylidene fluoride), arguably the most technologically important piezoelectric polymer. Electrospinning has been found to be a particularly effective method of producing PVDF nanofibers with superior piezoelectric properties due to the resulting exceptionally high fraction of the piezoelectrically active crystalline β‐phase. It is typically assumed that the high external electric fields applied during electrospinning enhance the formation of this β‐phase, with the confused literature offering various unsatisfactory mechanistic explanations. However, by comparing PVDF nanofibers produced by two different processes (electrospinning and blowspinning), we show that the electric field is entirely unnecessary; indeed, the crystallization dynamics are principally driven by the applied mechanical stress, as evidenced by structurally identical 200 nm diameter PVDF fibers produced with and without external electric fields.

The objective of this study was to prepare pectin films (PEC) activated by copaiba oil (CP) nanoemulsions (NE). CP-NE were added to film-forming formulations based on pectin and then dried into films by continuous casting. Chemical, morphological, thermal, mechanical and antimicrobial properties were studied in addition to biodegradability by the respirometer test. In general, the nanoemulsions were suitably dispersed in the PEC matrix, both phases showing good interaction and compatibility. The nanoemulsions caused large changes in PEC, such as increased roughness with oil concentration, gradual reduction of the elastic modulus and tensile strength, increased elongation at break, and antimicrobial activity against S. aureus and E. coli. Another important observation was the maintenance of the biodegradation profile of the films after the addition of CP-NE. In conclusion, the active pectin film manufactured with CP emulsions showed great potential for active food packaging and is a promising alternative to reduce environmental impacts.

Polyurethanes have been widely used in a wide variety of applications that benefit our everyday life. However, in the present scenario, it is urgent to find solutions towards more sustainable polymeric systems that can be more biodegradable and less dependent on non-renewable feedstocks. The present work proposes a thorough structural investigation of polyurethane materials based on the use of two small eco-friendly reactants: glycerol and urea. The results with glycerol demonstrated a preferential reactivity of MDI with primary alcohol terminals, except when the diisocyanate was in excess, which resulted in crosslinking formation (shown in 13C NMR). Urea-based materials displayed superior thermal stability, associated with higher crystallinity and intermolecular forces, as observed in TGA, XRD, and FTIR. Overall, the structural characteristics support the potential of biodegradability of the studied polyurethanes and polyureas.

In this study, continuous casting is proposed as a suitable approach to scale up the production of gelatin-cellulose nanocrystals (CNCs) bionanocomposites. The processing conditions and bionanocomposite properties were established based on the ζ-potential and gelatin content, and CNCs concentration, respectively. Gelatin film-forming solution at 20 wt% was required for proper continuous casting processing, leading to a productivity of 0.20 m2 film/min, which was at least 1000-fold higher than that of the classical bench casting. The gelatin-CNCs bionanocomposites displayed transparency, flexibility, and improved UV-barrier and thermal properties. Adding only 0.5 wt% of CNCs resulted in an increase of 77 % and 48 % in the tensile strength and Young’s modulus of gelatin, respectively. Comparison with previous nanocellulose-based nanocomposites pointed out the relatively superior performance of the gelatin-CNCs bionanocomposites obtained by continuous casting for various applications, including flexible food packaging.

The arising of global energy crisis and tremendous risk of climate change has drastically endangered the survival and development of human society, which certainly demand for modern technologies that require high-performance materials with superior properties. In this context, nanotechnology has emerged as a powerful tool for the scientific community to the design and development of engineered materials. In particular, nanomaterials derived from biomass (plants or plant-based) resources are gaining much attention by governments, industries, and academia owing to their low-cost, environmental compatibility, and replacement capability for petroleum-derived products for energy and environmental applications. Meanwhile, it is desirable that the development of novel materials from the natural resources that meet our daily needs and at the same time environmental-friendly in nature. This chapter provides a comprehensive understanding for obtaining renewable nanomaterials from natural biomass precursors for energy and environmental applications. Three different nanomaterials (i) cellulose nanostructures, (ii) starch nanocrystals (SNC), and (iii) carbon nanostructures along with their recent advancement in energy and environmental applications are figured out.

The environmental impact caused by the excessive amount of synthetic packaging used in modern society imposes serious demands for biodegradable plastic materials made from renewable sources. Among the natural polymers, starch has been considered as one of the most promising candidates for future materials because of its attractive combination of price, abundance, and thermoplastic behavior, in addition to its biodegradability. Within this context, this chapter provides a comprehensive review of starch-based edible films and coatings by describing the characteristics of the polymer matrix, methods of film formation, and their properties and potential applications, as well as the influence of the addition of different components into these materials. It also outlines the main current technological advances and future trends in this area.

The threat caused by drug-resistant pathogens represents a great concern to several economic sectors. This issue has intensified the development of more efficient antimicrobial products that could be safe not only for medical, pharmaceutical, water disinfection and food applications but also for reduced environmental impact. Nanotechnology now emerges as a powerful tool for scientists and engineers to develop engineered nanomaterials with remarkable antimicrobial activity. The potential of engineered nanomaterials is now certain to benefit different areas, such as medicine, food, pharmaceutical, and agriculture, once higher antimicrobial effectiveness implies in reduced content of antimicrobial compounds, thereby reducing cytotoxicity effects as well as environmental impact to different forms of life. This chapter summarizes the most recent achievements on antimicrobial engineered nanomaterials intended for better medicine, cosmetics, environmental, and food applications with emphasis on (i) new silver-based hybrid nanomaterials, (ii) new bioinspired antimicrobial nanoparticles, (iii) new antimicrobial nanostructures derived from layered minerals, (iv) recent developments on antimicrobial polymer nanocomposites, and finally (v) some recent trends in nanotechnological antimicrobial products available at the European market. The remarkable importance of antimicrobial engineered nanomaterials emerges from the combination of different nanomaterials so that main advantages of each are built together into new, revolutionary systems capable of solving the pathogen infection issue.

Made available in DSpace on 2018-11-26T17:54:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Ministry of Science, Technology, and Innovation (MCTI/SISNANO) The ever-growing environmental concern arising from the unrestricted exploitation of fossil sources for the massive production of non-biodegradable materials encourages research on alternative renewable resources. We herein pave the route for the production of biodegradable biocomposites made up of carrot minimal processing waste (CMPW) by optimizing its combination with hydroxypropyl methylcellulose (HPMC) and high-pressure microfluidized cellulose fibers, which played ligand and mechanical reinforcement roles, respectively. Ternary mixture designs established mathematical models aimed at structure-composition-property correlations, allowing their mechanical performances to be innovatively predicted without the need for further experiments. The optimized formulation comprised 33 wt.% CPMW and led to biodegradable biocomposites featuring ca. 30 MPa of tensile strength, ca. 3% elongation at break, and ca. 2 GPa of Young's modulus, properties which are suitable for food packaging applications. Finally, the film-forming protocol was successfully scaled-up through a continuous casting approach, allowing the production of 1.56 m(2) of biodegradable biocomposite in each hour. While scaling up did not affect film's barrier to moisture, it did impair its mechanical behavior. Embrapa Instrumentat, LNNA, Rua 15 Novembro,1452, BR-13560979 Sao Carlos, SP, Brazil Univ Fed Sao Carlos, Dept Mat Engn, PPG CEM, Rod Washington Luis,Km 235, BR-13565905 Sao Carlos, SP, Brazil Embrapa Trop Agroind, Rua Dra Sara Mesquita 2270, BR-60511110 Fortaleza, Ceara, Brazil Sao Paulo State Univ, FEIS, Dept Chem & Phys, Ave Brasil 56, BR-15385000 Ilha Solteira, SP, Brazil Sao Paulo State Univ, FEIS, Dept Chem & Phys, Ave Brasil 56, BR-15385000 Ilha Solteira, SP, Brazil FAPESP: 2013/14366-7 FAPESP: 2014/23098-9 CNPq: 303796/2014-6 Ministry of Science, Technology, and Innovation (MCTI/SISNANO): 402287/2013-4

Made available in DSpace on 2019-10-06T16:01:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-08-01. Added 1 bitstream(s) on 2021-07-15T15:05:15Z : No. of bitstreams: 1 S0104-14282018000400285.pdf: 1931837 bytes, checksum: 3c7de2f9006701cf537f74d2d6270727 (MD5) The non-isothermal decomposition kinetics of conductive polyaniline (PANI) and its derivatives, poly(o-methoxyaniline) (POMA) and poly(o-ethoxyaniline) (POEA), was investigated by thermogravimetric analysis (TGA), under inert and oxidative atmospheres, using Flynn-Wall-Ozawa's approach to assess the kinetic parameters of the decomposition process. The order of reaction was found to be dependent on the degree of conversion indicating that both the early and the later stages of polymer degradation were next the zero or pseudo zero order kinetics, whereas the intermediate stages follow a first order kinetics. The activation energy was found to be dependent on both the degree of conversion and PANI derivative. Activation energy values vary from 125 to 250 kJ/mol, to decompositions carried out under nitrogen, and 75 to 120 kJ/mol to oxidative atmosphere. Parent PANI presented the best thermal stability and suggesting that thermal stability is also influenced by derivatization and type of atmosphere used. Universidade Federal Do Acre-UFAC Campus Floresta Departamento de Física e Química-DFQ Universidade Estadual Paulista júlio de Mesquita Filho-UNESP Campus de Ilha Solteira Laboratório de Nanotecnologia para O Agronegócio-LNNA Centro Nacional de Pesquisa e Desenvolvimento de Instrumentacao Agropecuaria-CNPDIA Empresa Brasileira de Pesquisa Agropecuária-EMBRAPA Laboratório de Materiais e Biossistemas-LAMAB Universidade Federal da Paraíba-UFPB Departamento de Física e Química-DFQ Universidade Estadual Paulista júlio de Mesquita Filho-UNESP Campus de Ilha Solteira

In this paper, series of novel nanocomposite hydrogels based on polyacrylamide (PAAm), carboxymethylcellulose (CMC) and nanoclay were synthesized. Hydrophilic, kinetic, spectroscopic and morphological properties were investigated as function of their constituents. Spectroscopic properties confirmed the obtaining of the nanocomposites. It was also observed that the nanocomposites have walls of pores with a more rugged morphology compared with the morphology of the hydrogel without clay, contributing to repel the water molecules. Besides, the results showed that the velocity and quantity of water uptake may be controlled by adjusting of matrix rigidity, i.e., nanoclay content into polymeric matrix. This behavior is required to future application in agriculture fields, specifically as carrier vehicle in controlled release of agrochemicals. Thus, these nanocomposites have technological application.

Ammonia (NH3) gas is a prominent air pollutant that is frequently found in industrial and livestock production environments. Due to the importance in controlling pollution and protecting public health, the development of new platforms for sensing NH3 at room temperature has attracted great attention. In this study, a sensitive NH3 gas device with enhanced selectivity is developed based on zinc oxide nanofibers (ZnO NFs) decorated with poly(styrene sulfonate) (PSS) and operated at room temperature. ZnO NFs were prepared by electrospinning followed by calcination at 500 °C for 3 h. The electrospun ZnO NFs are characterized to evaluate the properties of the as-prepared sensing materials. The loading of PSS to prepare ZnO NFs/PSS composite is also optimized based on the best sensing performance. Under the optimal composition, ZnO NFs/PSS displays rapid, reversible, and sensitive response upon NH3 exposure at room temperature. The device shows a dynamic linear range up to 100 ppm and a limit of detection of 3.22 ppm and enhanced selectivity toward NH3 in synthetic air, against NO2 and CO, compared to pure ZnO NFs. Additionally, a sensing mechanism is proposed to illustrate the sensing performance using ZnO NFs/PSS composite. Therefore, this study provides a simple methodology to design a sensitive platform for NH3 monitoring at room temperature.

Solution blow spinning (SBS) is a recent technology to produce polymer micro- and nanofibers, including nanocomposites loaded with a wide range of nanoparticles. Because of its novelty, various studies about the properties of the produced materials are necessary, especially those related to material stability. In the present study, poly(lactic acid) (PLA)/titanium dioxide anatase (TiO2) nanocomposite fibers, with different TiO2 percentages, were produced by the SBS method. The spun nanocomposite fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry (DSC). Moreover, the photocatalytic degradation of Rhodamine B (RhB) dye and PLA degradation by UV-C lamps were investigated. SEM and TEM micrographs show that the SBS method produced PLA/TiO2 nanofibers with uniform morphology and without beads. The DSC analyses and X-ray diffraction patterns show that incorporation of TiO2 nanoparticles could influence the PLA nanocomposite crystallinity. PLA photocatalytic degradation experiments demonstrate that the weight loss of the polymer increases with an increase in TiO2 content. The present results indicate that the SBS method can be used to produce biodegradable nanocomposite fibers with good properties and potential applications.

Solution blow spinning (SBS) is a process to produce non-woven fiber sheets with high porosity and an extremely large amount of surface area. In this study, a Box–Behnken experimental design (BBD) was used to optimize the processing parameters for the production of nanofibers from polymer solutions consisting of poly(lactic acid) (PLA) dissolved in dimethyl carbonate. In addition, a comparative study between SBS fibers and cast film was performed to verify the influence of the SBS process on the crystallinity and thermal properties of PLA. The PLA concentration in polymer solutions was the most significant parameter affecting fiber diameter. The BBD analysis revealed that small diameter fibers were best obtained by a combination of 8 % w/v PLA concentration, 80 psi air pressure, and a feed rate of 50 µL min−1. The comparative study showed that both the SBS and the film casting processes increased the PLA crystallinity. However, the PLA films had a higher degree of crystallinity compared with the fibers made by the SBS process (39 and 17 %, respectively), which was attributed to the high shear created at the SBS nozzle inducing orientation and chain alignment. During the fiber formation, crystals formed with varied morphology including the α′-crystals, which have a less ordered structure and lower thermal stability compared to the α-crystals. The lower thermal stability of SBS fibers compared to the films can be explained by the lower degree of crystallinity and also by the higher surface area which can accelerate the weight loss process.

In this study, the performance of a glassy carbon electrode (GCE) modified with functionalized multi-walled carbon nanotubes (MWCNT) immobilized within a poly(allylamine hydrochloride) (PAH) film for the electrochemical determination of the catecholamines, levodopa (LD) and carbidopa (CD) is evaluated. The electrochemical behaviour of the MWCNT-PAH/GCE sensor was investigated via cyclic voltammetry. Under the optimum experimental conditions, the LD and CD analytes were determined by differential pulse voltammetry (DPV) using their oxidation redox processes at −24 mV and +490 mV (versus Ag/AgCl (3.0 mol L−1 KCl)), respectively. The obtained analytical curves were linear from 2.0 to 27 μmol L−1 for LD and from 2.0 to 23 μmol L−1 for CD, with limits of detection of 0.84 μmol L−1 for LD and 0.65 μmol L−1 for CD. The proposed DPV method was successfully employed for LD and CD determination in commercial pharmaceutical formulation samples, and the collected results were consistent with those obtained by the respective standard methods at a confidence level of 95%. In addition, the potentiality of the DPV method was tested for LD and CD quantification in human serum samples.

The development of novel and portable chemical sensors aimed at the food industry is of prime importance for food safety issues, and nanomaterial science can greatly contribute to this task. In this context, a careful choice of the sensing material is essential for achieving high performance sensor arrays, such as those employed in nanostructured electronic tongues (e-tongues). In the current work, an impedimetric e-tongue based on gold interdigitated microelectrodes (IDEs) modified with polyamide 6/polyaniline (PA6/PANI) electrospun nanofibers was developed, characterized and used to detect tetracycline (TC) residue in fat and skimmed milk samples. By analyzing the electrical resistance data collected by the e-tongue, which were treated by Principal Component Analysis (PCA), the e-tongue was able to identify the presence of TC residues (from 1 to 300 ppb) in fat and skimmed milk samples. The results obtained demonstrate the ability of the approach of modifying IDEs with conducting electrospun nanofibers to be used as sensing units in the e-tongue, aiming to analyze complex matrices such as milk without any prior pre-treatment.

Endocrine disruptor compounds (EDCs) are environmental pollutant chemicals that can affect the endocrine system of some organisms. Such compounds are excreted by humans and released into aquatic environments via sewage treatment plant. One example of EDC is 17α-ethinylestradiol (EE2), a synthetic estrogen widely used as oral contraceptive and considered a powerful estrogenic. Although there has been a deep concern about the EDC presence in surface and drinking waters, there are only a few works in the scientific literature regarding EE2 electrochemical detection. Here we present the development of a new nanostructured sensing platform aimed at the electrochemical detection of EE2. The platform was based on a fluorine doped tin oxide (FTO) electrode coated with nanostructured Layer-by-Layer (LbL) films of chitosan/multi-walled carbon nanotubes (Chi/CNTs). The physicochemical properties of the films were evaluated by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). Electrochemical characterization revealed a decrease in the film resistance as the number of bilayers increased from 1 to 3, as a direct consequence of the augment in the amount of conductive material (CNTs). Cyclic voltammetric measurements showed that the three bilayer electrode, namely FTO-(Chi/CNTs) 3 , are suitable to EE2 detection, through an irreversible and adsorption-controlled electrochemical oxidation process. Square Wave Voltammetry (SWV) yielded a linear response for EE2 detection in range from 0.05 to 20 μmol L − 1 , with a detection limit of 0.09 μmol L − 1 (S/N = 3). The sensor showed a good reproducibility with the relative standard deviation (RSD) equal to 3.2% and 6.6% to intra- and inter-electrode, respectively. Furthermore, the sensor platform showed to be suitable to EE2 selective electrochemical detection, with no significant interference from common interfering compounds. The concepts behind the EE2 electrochemical behavior can be potentially harnessed for designing new electrochemical sensors and biosensors with the architecture described here.

The disinfectant activity of poly(hexamethylene biguanide) (PHMB) has been explored in industrial applications, in agriculture and in food manipulation, but this biocide action is not completely understood. It is believed to arise from electrostatic interactions between the polyhexanide group and phosphatidylglycerol, which is the main phospholipid on the bacterial membrane. In this study, we investigated the molecular-level interactions between PHMB and dipalmitoyl phosphatidylglycerol (DPPG) in Langmuir monolayers that served as cell membrane models. PHMB at a concentration of 2 × 10 −4 g L −1 in a Theorell–Stenhagen at pH 3.0 and in a phosphate at pH 7.4 was used as a subphase to prepare the DPPG monolayers. Surface pressure–area isotherms showed that PHMB adsorbs and penetrates into the DPPG monolayers, expanding them and increasing their elasticity under both conditions examined. Results from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) indicated that PHMB induces disorder in the DPPG chains and dehydrates their C O groups, especially for the physiological medium. Overall, these findings point to hydrophobic interactions and dehydration being as relevant as electrostatic interactions to explain changes in membrane fluidity and permeability, believed to be responsible for the biocide action of PHMB.

The controlled-release of natural plant oils such as linalool is of interest in therapeutics, cosmetics, and antimicrobial and larvicidal products. The present study reports the release characteristics of linalool encapsulated at three concentrations (10, 15 and 20 wt.%) in poly(lactic acid) nanofibrous membranes produced by electrospinning and solution blow spinning (SBS) as well as the effect of linalool on fiber morphology and structural properties. PLA nanofibrous membranes were characterized by Scanning Electron Microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and contact angle measurements. The average diameters of the electrospun and solution blow spun nanofibers were similar, ranging from 176 to 240 nm. Linalool behaved as a plasticizer to PLA decreasing the glass transition temperature (Tg), melting point (Tm) and crystallization temperature (TC) of PLA. Curves of the release of linalool at 35 °C were non-linear, showing a clear biphasic pattern consistent with one or more Fickian release components. The time required to release 50% of linalool (t1/2) decreased with increasing linalool concentration. The range in t1/2 values for SBS nanofibers was higher (291-1645s) than the t1/2 values for electrospun fibers (76-575s).

Electronic tongue (e-tongue) sensors based on impedance spectroscopy have emerged as a potential technology to evaluate the quality and chemical composition of food, beverages, and pharmaceuticals. E-tongues usually employ transducers based on metal interdigitated electrodes (IDEs) coated with a thin layer of an active material, which is capable of interacting chemically with several types of analytes. IDEs are usually produced by photolithographic methods, which are time-consuming and costly, therefore, new fabrication technologies are required to make it more affordable. Here, we employed femtosecond laser ablation with pulse duration of 50 fs to microfabricate gold IDEs having finger width from 2.3 μm up to 3.2 μm. The parameters used in the laser ablation technique, such as light intensity, scan speed and beam spot size have been optimized to achieve uniform IDEs, which were characterized by optical and scanning electron microscopy. The electrical properties of gold IDEs fabricated by laser ablation were evaluated by impedance spectroscopy, and compared to those produced by conventional photolithography. The results show that femtosecond laser ablation is a promising alternative to conventional photolithography for fabricating metal IDEs for e-tongue systems.

Over the years there has been a significant increase in the manufacturing of silver nanoparticles-based products, mainly due to their antimicrobial activity, with application in medicine and textile and food industry. However, the inappropriate use and disposal of these materials can allow the entry of silver nanoparticles (AgNP) into the aquatic environment, with potential toxicological effects. In this study we used Pseudokirchneriella subcapitata, Artemia salina and Daphnia similis as model organisms to investigate the toxicity of PVA-stabilized AgNP at several concentration levels. AgNP were physico-chemically characterized by UV–vis spectroscopy, particle size distribution, zeta potential analyzes and Transmission Electron Microscopy (TEM). AgNP presented a maximum absorption at 400 nm and size range between 2 and 18 nm. Each specific organism was exposed to AgNP concentrations through standardized protocol. For P. subcapitata and A. salina the EC50 value found, 1.09 mg L−1 and 5.5 × 10−2 mg/L, respectively, were in accordance to previous results reported in the literature. However, for D. similis, the EC50 24–48 h values indicate a higher toxicity than other results reported for other daphnids.

Cellulose, the main component of plant cell walls, is a biopolymer widely used for industrial applications, including, food, paper and textile fabrication. More recently, hybrid materials composed of cellulose nanostructures and metal nanoparticles have been applied in diverse areas such as medical and pharmaceutical applications. In this work, cellulose-silver nanoparticles (AgNPs) hybrid material was synthesized and the influence of cellulose, employed as a stabilizer agent, was investigated. Specifically, cellulose whiskers (CCW) were extracted from commercial cotton fibers by acid hydrolysis route, while the AgNPs were synthesized by reducing silver salt using sodium citrate and/or sodium borohydride in the presence of CCW. The synthesized AgNPs/CCW nanocomposites were characterized in terms of morphology, chemical composition, surface charge and antibacterial properties. The varied synthetic routes generated AgNPs with different morphological characteristics in terms of size, shape and coalescence. The particularity of each sample resulted in distinct behaviors for the tested bacteria. Syntheses employing CCW resulted in AgNPs/CCW nanocomposites with controlled morphology and improved antibacterial effects against E. coli (Gram-negative) and S. aureus (Gram-positive), indicating CCW as a promising compound to be used in the syntheses of silver and other metal nanoparticles with controlled morphology and antibacterial properties.

The food packaging function has evolved from providing a barrier between food and the surrounding environment, to acquiring new functionalities such as the release of antimicrobials onto food surfaces. Materials containing nanostructured antimicrobials (either as nanoparticles directly added to the polymer matrix or included in nanocarriers such as nanocapsules) are especially effective, thanks to the high surface area:volume ratio, which enhances their surface reactivity. Several nanostructured antimicrobial systems have been proposed for food packaging applications, including both inorganic and organic additives. The present article covers findings on nanostructured antimicrobial systems applicable to food packaging, their mechanisms of action and potential applications.

While there have been many studies of fibers extracted from pineapple leaves as reinforcement in polymer composites, to date, only commercial varieties have been examined. This work aims to investigate the fibers from the leaves of a hybrid pineapple called Potyra as a mechanical reinforcement in a poly(lactic acid) (PLA) matrix. The fibers were pre-treated in a NaOH solution (1 wt%) and were incorporated into the PLA by a torque rheometer mixer followed by twin-screw extrusion. Samples of each composition were injected. The molded composites showed increases of tensile strength from 58.8 to 69.6 MPa, of Young?s modulus from 1.9 to 3.5 GPa, and of impact resistance from 28 to 44 J/m, and showed an increase of 58C in the heat deflection temperature (Abstract Figure). The measured tensile strength and Young?s modulus values are lower than the theoretical values obtained by micromechanics theory due to the pull-out of the matrix fiber and due to the orientation of the fibers in the composites. It was concluded that the pineapple hybrid fibers have potential for use as mechanical reinforcement in green composites. POLYM. COMPOS., 00:000?000, 2017. VC 2017 Society of Plastics Engineers Made available in DSpace on 2022-04-29T19:42:23Z (GMT). No. of bitstreams: 1 P-Polylatic-acid-composites-reinforced....pdf: 458131 bytes, checksum: 614f5bc0c1ab023ca47201d7d1cd71aa (MD5) Previous issue date: 2018

The use of nanomaterials as an electroactive medium has improved the performance of bio/chemical sensors, particularly when synergy is reached upon combining distinct materials. In this paper, we report on a novel architecture comprising electrospun polyamide 6/poly(allylamine hydrochloride) (PA6/PAH) nanofibers functionalized with multiwalled carbon nanotubes, used to detect the neurotransmitter dopamine (DA). Miscibility of PA6 and PAH was sufficient to form a single phase material, as indicated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), leading to nanofibers with no beads onto which the nanotubes could adsorb strongly. Differential pulse voltammetry was employed with indium tin oxide (ITO) electrodes coated with the functionalized nanofibers for the selective electrochemical detection of dopamine (DA), with no interference from uric acid (UA) and ascorbic acid (AA) that are normally present in biological fluids. The response was linear for a DA concentration range from 1 to 70 μmol L(-1), with detection limit of 0.15 μmol L(-1) (S/N = 3). The concepts behind the novel architecture to modify electrodes can be potentially harnessed in other electrochemical sensors and biosensors.

Vegetable fiber reinforced polymer composites have enormous potential to replace materials originated from non-renewable resources. For an adequate use of vegetable fibers as reinforcements, however, the relationships between technological properties and chemical, structural and morphological characteristics of the fibers must be fully understood. In this work, fibers from 12 different varieties of pineapple (Ananas genus) were characterized on their morphology, structure, chemical composition, mechanical and thermal properties. The elastic modulus ranged from 37 to 86 GPa, the tensile strength from 629 to 1309 MPa, and the onset oxidation temperature from 240 to 272 °C; indicating the potential of using all selected pineapple fibers as reinforcing fillers (depending on the polymer matrix and processing method). Direct correlations were observed between the thermo-mechanical properties of the fibers and their chemical features, such as holocellulose and cellulose contents, and also the cellulose crystallinity index. The mechanical properties showed an inversely proportional relation with the lignin content and diameter of the fiber bundle. These correlations provided indexes for the direct selection and/or for a genetic improvement program of the Ananas genus for the development of pineapples whose fibers may be adequate as mechanical reinforcement in polymer composite. An example of methodology is presented, aiming to help with materials selection within the group of vegetable fibers used in composites.

Heterostructured nanomaterials have attracted increasing interest because of their novel and distinct optical and electrical properties, finding applications in devices and chemical sensors. Here we report a new electrochemical platform based on the modification of fluorine doped tin oxide (FTO) electrodes with polyamide 6/polyaniline (PA6/PANI) electrospun nanofibers decorated with ZnO nanoparticles. The nanoparticles were synthesized by a co-precipitation method, followed by hydrothermal treatment; the route was optimized in order to obtain particles of small average diameter (45 nm). Polymeric nanofibers were obtained by the electrospinning technique and further subjected to ZnO modification by nanoparticle impregnation. SEM images confirmed the uniform distribution of ZnO nanoparticles adsorbed onto the nanofiber surface, the amount of which was estimated to be 4% w/w, according to thermal gravimetric analysis (TGA). According to the electrochemical characterization, an improvement in electron transfer kinetics and increase in electroactive area was observed for the ZnO-modified FTO electrode. The modified electrode was employed for monitoring hydrazine, and yielded a detection limit of 0.35 μmol L−1. Our results indicate that the novel sensing platform based on the adsorption of ZnO nanoparticles onto the surface of electrospun nanofibers can be potentially harnessed for electrochemical sensor and biosensor applications.

Edible films supplemented with active ingredients are promising for food packaging and preservation. Numerous plant essential oils present antimicrobial activity against pathogenic microorganisms, but their low solubility in water limits food-related applications. Emulsification is herein exploited as a means of improving the dispersion of such active substances in water, imparting increased functionality and reduced degradation. Lemongrass essential oil (LEO) was directly emulsified as dispersed phase into aqueous solutions of pectin, which was used together with Tween 80 as polymeric emulsifiers. LEO nano- and micro-sized droplets were added to film-forming formulations based on glycerol-plasticized cassava starch (TPS) and then dried into films by continuous casting. LEO contents in films relied upon microbiological assays to ensure antimicrobial activity. Films’ chemical composition, morphological, thermal, mechanical, and barrier properties, in addition to biodegradability in vegetal compost, were comprehensively studied. In general, emulsions were suitably dispersed within the TPS matrix, both phases showing good interaction and compatibility. Emulsification caused important changes in the TPS-based films, such as improved colorimetric attributes, thermal stability, barrier to moisture, and mechanical properties. Another key observation was the maintenance of the biodegradation profile in soil of TPS after the addition of LEO emulsions. Overall, the emulsification approach was successful in providing TPS films with multifunctionality by the supplementation of an active substance without negatively affecting its fundamental properties for food packaging applications.

Made available in DSpace on 2020-12-12T02:31:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The demand for bioplastics from renewable sources for a range of emerging applications has been as extensive as the efforts to find greener routes for their isolation from nature. Surfing this wave, we report on the production of flexible, optically semi-transparent onion-only bioplastics through different all-aqueous film-forming procedures encompassing hydrothermal, grinding, washing, and/or sieving pre-solvent casting steps. The onion bioplastics were extensively characterized targeting correlations among chemical structure, film-forming protocol, and film properties. HPLC evidenced insoluble carbohydrates/polysaccharides in all samples, though at different contents (11–44%) depending on processing, but washing lixiviated all soluble carbohydrates – the presence of ca. 14% of the latter in unwashed samples provided their films with reduced glass transition temperature – from 73–83 to 13 °C, as indicated by DSC; elastic modulus and tensile strength – from 1.5–3.2 GPa to 47 MPa and from 7–21 to 3 MPa, respectively; increased elongation at break – from 0.7–1.6% to 22%; and decreased contact angle with water – from 39-70° to 22° (in comparison with washed samples). Additionally, SEM provided morphological aspects; thermogravimetry indicated thermal stability profile; FTIR led to hydrogen bond energy [kJ] and distance [Å] as well as total crystallinity index (0.43–0.96), lateral order index (0.8–3.2), and hydrogen bonding intensity (13–4.7); and XRD determined the index of crystallinity (21–49%). Finally, the hydrophilic/hydrophobic nature, water barrier, and moisture sorption of the bioplastics were determined. Altogether, we herein depict the production of novel bioplastics made up exclusively of onion and used a range of characterization techniques to come up with relevant structure-processing-property correlations. São Paulo State University (UNESP) Institute of Chemistry Nanotechnology National Laboratory for Agriculture (LNNA) Embrapa Instrumentation University of Araraquara (Uniara) Laboratory of Biopolymers and Biomaterials (BIOPOLMAT) Chalmers University of Technology Department of Chemistry and Chemical Engineering São Paulo State University (UNESP) Institute of Chemistry FAPESP: 2014/23098-9 FAPESP: 2016/15504-2

The rising demand for bio-based materials to be used in food packaging has encouraged the development of novel, environmentally-friendly films. Fruit puree has the potential to be incorporated in the film-forming solution so that to produce edible films. The major components of plant essential oils (e.g., cinnamaldehyde) deliver antimicrobial properties against food pathogens and may be released by active films in an effort to replace synthetic preservatives. This work aimed at producing cinnamaldehyde nanoemulsions of different droplet sizes, as well as assessing the effect of papaya puree and cinnamaldehyde droplet diameter in the antimicrobial and physical-mechanical properties of high or low methylester pectin films. Increased stirring energies reduced droplet diameter. Papaya puree reduced films’ resistance and rigidity while increased extensibility and water vapor permeability. Cinnamaldehyde nanoemulsions balanced the plasticizing effect of papaya puree by increasing rigidity and decreasing extensibility and permeability to water vapor of pectin films. Also, cinnamaldehyde provided antimicrobial properties against Escherichia coli, Salmonella enterica, Listeria monocytogenes, and Staphylococcus aureus. The reduction on droplet diameter did not influence the physical-mechanical properties of the films, but remarkably improved bacterial inhibition due to the higher delivery of active compounds having increased surface areas. Antimicrobial edible films from renewable sources were successfully produced here, and the improved bacterial inhibition provided by the same cinnamaldehyde content with smaller nanodroplets may play an important role in reducing preservative content as required by consumers.

Nanoencapsulation is a process suitable for use in reducing degradation of instable components. In this study, chitosan and trimethyl chitosan with tripolyphosphate were used to nanoencapsulate vitamins C, B9, and B12. Analysis of the particle size showed that for a fix proportion of the polymer tripolyphosphate, the system showed a wide variation in size with the amount of added vitamins: e.g., for vitamin B9, the particle size varied from 150±5 nm to 809±150 nm. The zeta potential confirmed that trimethyl chitosan nanoparticles generally had a lower net positive charge (20 mV) than chitosan nanoparticles (40 mV). The encapsulation efficiency was found to be dependent on nanoparticle structure and vitamin solubility, with vitamin B9 the most efficiently encapsulated (approximately 40%). UV-Visible spectroscopy indicated different release profiles for vitamins C, B9, and B12 in a neutral PBS solution with release rates of 36%, 52%, and 16% after 2, 24, and 4 h, respectively. In conclusion the liberation was found to be slower in acidic media.

Made available in DSpace on 2015-11-03T15:30:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-07-01. Added 1 bitstream(s) on 2015-11-04T10:15:49Z : No. of bitstreams: 1 S0104-14282014000400012.pdf: 1300349 bytes, checksum: 1d7103f91d5d56f18ea2d6eb49d24b0e (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Neste trabalho, o objetivo foi produzir nanobiocompósitos biodegradáveis à base de pectina e nanoemulsão de canela que tenham propriedades satisfatórias para aplicação como embalagens ativas. Foram detalhados os procedimentos de preparação das nanoemulsões e incorporação dessas na matriz polimérica. Foi apresentada uma metodologia nova de análises dos melhores nanocompósitos através de um planejamento baseado em aspectos visuais que nos forneceu resultados interessantes. Os nanocompósitos obtidos foram analisados através de: medidas de espessura, solubilidade, propriedades mecânicas e microscopia eletrônica de varredura (MEV). Resultados das análises visuais mostraram que os nanocompósitos produzidos com concentração de pectina de 2% m/v e nanoemulsões preparadas com velocidade de agitação de 16000 rpm em 2 minutos mostraram melhores condições para serem aplicados como embalagens. Resultados de propriedades mecânicas demonstraram que nanocompósitos contendo nanoemulsões com tamanhos menores de gotículas apresentam maior resistência e elongação, além de serem menos solúveis. O controle dessas propriedades com a variação de tamanho médio das nanoemulsões torna esses materiais potencialmente viáveis, por exemplo, em embalagens ativas. In this study, the objective was to produce biodegradable nanobiocomposites based on pectin and cinnamon nanoemulsion having satisfactory properties for application as active packaging. Procedures for preparing and incorporating these nanoemulsions in the polymeric matrix are described. The nanocomposites were analyzed through: thickness measurements, solubility, mechanical properties and scanning electron microscopy (SEM). A subjective analysis indicated the nanocomposite made with pectin 2 % w/v and nanoemulsions prepared with stirring speed of 16000 rpm in 2 min was the most suitable for application in packaging. The nanocomposites containing nanoemulsions with smaller nanodroplets had greater strength and elongation, being less soluble. The control of these properties by varying the average size of the nanoemulsion makes these materials potentially viable, for example, for active packaging. Empresa Brasileira de Pesquisa Agropecuária, Laboratório Nacional de Nanotecnologia aplicada ao Agronegócio Universidade Estadual Paulista, Departamento de Física e Química, Faculdade de Engenharia de Ilha Solteira

Formulations of poly(lactic acid) (PLA) reinforced by curaua leaf fibers were prepared and characterized. This biocomposite has material characteristics such as biodegradability and renewability. This work aimed to develop a PLA/curaua leaf fiber composite as a sustainable biodegradable polymer composite. The PLA and composites were thermally, mechanically, and morphologically evaluated. The critical fiber length was studied to check its influence on the mechanical properties. Predictions of the Young's modulus were done to compare with the experimental data, having a reasonable agreement. The Young's modulus increased above 70%, and the impact strength increased 20% compared with the pure PLA. Thermal analysis showed that formulations with up to 20% by weight of fibers were more thermally stable. The fiber modified the crystallinity of the PLA matrix. The best overall balance of properties was attained in composites containing 15% curaua fiber. POLYM. COMPOS., 36:1520–1530, 2015. © 2014 Society of Plastics Engineers

Cellulose nanofibrils (CNF) were isolated from cotton microfibrils (CM) by acid hydrolysis and coated with polyaniline (PANI) by in situ polymerization of aniline onto CNF in the presence of hydrochloride acid and ammonium peroxydisulfate to produce CNF/PANI. Nanocomposites of natural rubber (NR) reinforced with CNF and CNF/PANI were obtained by casting/evaporation method. TG analyses showed that coating CNF with PANI resulted in a material with better thermal stability since PANI acted as a protective barrier against cellulose degradation. Nanocomposites and natural rubber showed the same thermal profiles to 200 °C, partly due to the relatively lower amount of CNF/PANI added as compared to conventional composites. On the other hand, mechanical properties of natural rubber were significantly improved with nanofibrils incorporation, i.e., Young’s modulus and tensile strength were higher for NR/CNF than NR/CNF/PANI nanocomposites. The electrical conductivity of natural rubber increased five orders of magnitude for NR with the addition of 10 mass% CNF/PANI. A partial PANI dedoping might be responsible for the low electrical conductivity of the nanocomposites.

A novel biodegradable polymer based on glycerol, succinic anhydride and maleic anhydride, poly(glycerol succinate-co-maleate), poly(GlySAMA), was synthesized by melt polycondensation and tested as a matrix for composites with nanocrystalline cellulose. This glycerol-based polymer is thermally stable as a consequence of its targeted cross-linked structure. To broaden its range of properties, it was specifically formulated with nanocrystalline cellulose (NCC) at concentrations of 1, 2 and 4 wt%, and showed improved mechanical properties with NCC. Specifically, the effect of reinforcement on mechanical properties, thermal stability, structure, and biodegradability was evaluated, respectively, by tensile tests and thermogravimetric analyses, X-ray diffraction and respirometry. The neat poly(GlySAMA) polymer proved flexible, exhibiting an elongation-to-break of 8.8 % while the addition of nanowhiskers (at 4 wt%) caused tensile strength and Young’s modulus to increase, 20 and 40 %, respectively. Stiffness improved without significantly decreasing thermal stability as measured by thermogravimetric analysis. Biodegradation tests indicated that all samples were degradable but NCC reduced the rate of biodegradation.

Electrospun fibers are explored as a new system for controlled drug delivery. Novel techniques capable of obtaining polymer nanofibers have been reported in the literature. They include solution blow spinning (SBS), which is a technique to produce polymer nanofibers in the same range as electrospinning, using pressurized gas instead of high voltage. The present study investigates release characteristics of diclofenac sodium encapsulated at three concentrations (5, 10, and 20% w/v) in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibers made by electrospinning and SBS and determines the drug’s effect on fiber morphology and structural properties. PHBV nanofibers were characterized using scanning electronic microscopy, differential scanning calorimetry, and X-ray diffraction, and the release profile was examined via UV-Vis spectrophotometry. Both electrospinning and SBS encapsulated diclofenac sodium in PHBV membranes efficiently and effectively. The profile of thein vitrorelease of diclofenac sodium was dependent on drug concentration and temperature. The drug reduced crystallinity and increased flexibility.

In order to investigate the incorporation of tannin from barbatimao bark in zein nanofibers obtained by electrospinning, it was studied the effect of addition of different contents of tannin in the properties of zein nanostructured membranes and their relationship with fiber morphology. It was confirmed the interaction occurring between the tannin and zein by thermal and microscopy analysis. Addition of tannins increased the glass transition temperature of the nanofibers, suggesting higher energy input for processing for example. SEM micrographs provided evidence of a homogeneous structure for the nanostructured membranes. X-ray analysis showed the presence of zein crystals in the nanofibers. This ongoing research confirms the possibility of incorporation of barbatimao tannin in the production of bio-nanofibers that will be studied for multi-purpose applications.