Showing papers by "Orlando J. Rojas published in 2018"
TL;DR: There is an emerging quest for lightweight materials with excellent mechanical properties and economic production, while still being sustainable and functionalizable, which could form the basis of the future bio economy for energy and material efficiency.
Abstract: There is an emerging quest for lightweight materials with excellent mechanical properties and economic production, while still being sustainable and functionalizable. They could form the basis of the future bioeconomy for energy and material efficiency. Cellulose has long been recognized as an abundant polymer. Modified celluloses were, in fact, among the first polymers used in technical applications; however, they were later replaced by petroleum-based synthetic polymers. Currently, there is a resurgence of interest to utilize renewable resources, where cellulose is foreseen to make again a major impact, this time in the development of advanced materials. This is because of its availability and properties, as well as economic and sustainable production. Among cellulose-based structures, cellulose nanofibrils and nanocrystals display nanoscale lateral dimensions and lengths ranging from nanometers to micrometers. Their excellent mechanical properties are, in part, due to their crystalline assembly via hydrogen bonds. Owing to their abundant surface hydroxyl groups, they can be easily modified with nanoparticles, (bio)polymers, inorganics, or nanocarbons to form functional fibers, films, bulk matter, and porous aerogels and foams. Here, some of the recent progress in the development of advanced materials within this rapidly growing field is reviewed.
446 citations
TL;DR: Recent progress in advanced nanostructures synthesized from biomass resources for the oxygen reduction reaction (ORR) is reviewed and the resulting electrocatalytic activity and durability are introduced and compared to those from conventional Pt/C-based Electrocatalysts.
Abstract: Recent progress in advanced nanostructures synthesized from biomass resources for the oxygen reduction reaction (ORR) is reviewed. The ORR plays a significant role in the performance of numerous energy-conversion devices, including low-temperature hydrogen and alcohol fuel cells, microbial fuel cells, as well as metal-air batteries. The viability of such fuel cells is strongly related to the cost of the electrodes, especially the cathodic ORR electrocatalyst. Hence, inexpensive and abundant plant and animal biomass have become attractive options to obtain electrocatalysts upon conversion into active carbon. Bioresource selection and processing criteria are discussed in light of their influence on the physicochemical properties of the ORR nanostructures. The resulting electrocatalytic activity and durability are introduced and compared to those from conventional Pt/C-based electrocatalysts. These ORR catalysts are also active for oxygen or hydrogen evolution reactions.
331 citations
TL;DR: In this paper, cellulose nanofibrils (CNF) were used to induce depletion stabilization of oil-in-water Pickering emulsions formed by interfacial adsorption of another type of nanocellulose, namely, cellulose nano-stals (CNC).
220 citations
TL;DR: In this article, a cellulose nanomaterial (cellulose nanocrystals, CNC) was employed as solid support for the nucleation of silver and gold nanoparticles via solid-state synthesis.
Abstract: Heterogeneous catalysis has played a critical role in environmental remediation, for example, in processes that generate toxic streams. Thus, there is an ever-increasing need for green, cost-effective routes to synthesize highly active catalysts. In this study, a cellulose nanomaterial (cellulose nanocrystals, CNC) was employed as solid support for the nucleation of silver and gold nanoparticles via solid-state synthesis. The process involved solvent-free reduction in ambient conditions of metal precursors on the surface of CNC and in the presence of ascorbic acid. Surface plasmon resonance and X-ray diffraction indicated the successful formation of the metal nanoparticles, in the form of organic–inorganic hybrids. A strong hydrogen bonding was observed between CNC and the metal nanoparticles owing to the high density of hydroxyl groups in CNC, as determined by Fourier transform infrared spectroscopy. Electron microscopies indicated that the silver and gold precursors formed nanoparticles of hexagonal and...
103 citations
01 Jan 2018
TL;DR: A review of recent work shows that considerable progress has been achieved in addressing these issues and that there is potential to use cellulosic nano-components in a wide range of high-tech applications as discussed by the authors.
Abstract: Because of their wide abundance, their renewable and environmentally benign nature, and their outstanding mechanical properties, a great deal of attention has been paid recently to cellulosic nanofibrillar structures as components in nanocomposites. A first major challenge has been to find efficient ways to liberate cellulosic fibrils from different source materials, including wood, agricultural residues, or bacterial cellulose. A second major challenge has involved the lack of compatibility of cellulosic surfaces with a variety of plastic materials. The water-swellable nature of cellulose, especially in its non-crystalline regions, also can be a concern in various composite materials. This review of recent work shows that considerable progress has been achieved in addressing these issues and that there is potential to use cellulosic nano-components in a wide range of high-tech applications.
94 citations
TL;DR: The functional properties imparted by LAE, a highly effective molecule against food pathogens and spoilage organisms, open new opportunities in food, cosmetics, and pharmaceutical applications, where the presence of CNC plays a critical role in achieving synergistic effects with LAE.
89 citations
TL;DR: The technical, financial, and market assessment represent the basis for R&D planning and efforts to lower the risk related to expected industrialization efforts and identify potential LMNPs applications from a financial perspective.
Abstract: Lignin micro- and nanoparticles (LMNPs) synthesized from side-streams of pulp and paper and biorefinery operations have been proposed for the generation of new, high-value materials. As sustainable alternatives to particles of synthetic or mineral origins, LMNPs viability depends on scale-up, manufacturing cost, and applications. By using experimental data as primary source of information, along with industrial know-how, we analyze dry and spherical LMNPs obtained by our recently reported aerosol/atomization method. First, a preliminary evaluation toward the commercial production of LMNPs from industrial lignin precursors is presented. Following, we introduce potential LMNPs applications from a financial perspective. Mass and energy balances, operating costs, and capital investment are estimated and discussed in view of LMNPs scalability prospects. The main potential market segments identified (from a financial perspective) include composite nanofillers, solid foams, emulsion stabilizers, chelating agents...
82 citations
TL;DR: It is demonstrated that the light transport in membranes of pure cellulose nanofibrils (CNFs) can be controlled to achieve bright whiteness in structures only a few micrometer thick, in contrast to other materials, such as paper, which require hundreds of micrometers to achieve a comparable appearance.
Abstract: The understanding of the interaction between light and complex, random structures is the key for designing and tailoring the optical appearance and performance of many materials that surround us, ranging from everyday consumer products, such as those for personal care, paints, and paper, to light diffusers used in the LED-lamps and solar cells. Here, it is demonstrated that the light transport in membranes of pure cellulose nanofibrils (CNFs) can be controlled to achieve bright whiteness in structures only a few micrometers thick. This is in contrast to other materials, such as paper, which require hundreds of micrometers to achieve a comparable appearance. The diffusion of light in the CNF membranes is shown to become anomalous by tuning the porosity and morphological features. Considering also their strong mechanical properties and biocompatibility, such white coatings are proposed as a new application for cellulose nanofibrils.
79 citations
TL;DR: In this article, seven selected Eucalyptus varieties grown under the same conditions were collected to investigate the relationships between specie type and cellulose composition as well as structural and thermo-chemical properties.
Abstract: Seven selected Eucalyptus varieties grown under the same conditions were collected to investigate the relationships between specie type and cellulose composition as well as structural and thermo-chemical properties. This systematic investigation used E. badjensis, E. benthamii, E. dunnii, E. globulus, E. nitens, E. smithii and two hybrids, E. nitens × E. globulus, from which holocellulose and alpha-cellulose were isolated. The results indicated no significant correlation between the molecular fingerprints and higher order structural features (crystallinity via X-ray diffraction, CrI XRD). Compared to the cellulosic source, the same techniques revealed higher CrI for the isolated holocellulose. The opposite applied to the CrI of alpha-cellulose. CrI spanned the range between 39 and 55%, and crystallite sizes spanned 1.8–4.4 nm range. The cellulose from the Eucalyptus samples displayed distinctive chemical fingerprints and thermal degradation (thermogravimetric analysis, TGA), the latter of which occurred in a wide range of temperature, between 338 and 369 °C. Most remarkably, a significant correlation was observed between CrI XRD and TGA from the wood samples. Moreover, the thermal degradation of alpha-cellulose correlated strongly with the crystallite size. In wood and holocellulose samples, E. badjensis and E. smithii showed the lowest CrI and thermal degradation of cellulose, while En × Eg hybrids showed the highest values. Alpha-cellulose from E. dunni underwent the highest thermal degradation and E. smithii displayed the highest CrI. Such differences are expected to be relevant to the processing and quality of cellulose derivatives, a subject that is yet to be evaluated.
69 citations
TL;DR: In this article, a simple yet customizable process is described to finely engineer the morphology of BC in all (x, y, z) directions, enabling new advanced functionalities, by using hydrophobic particles and superhydrophobized surfaces.
Abstract: Biomass-based nanomaterials such as bacterial cellulose (BC) are one of the most promising building blocks for the development of sustainable materials with the potential to outperform their conventional, synthetic, counterparts. The formation of BC occurs at the air–water interface, which has been exploited to engineer materials with finely controlled microtopographical features or simple three-dimensional morphologies for a wide range of applications. However, a high degree of control over the 3D morphology of BC films across several length scales (micro to macro) has not yet been achieved. Herein, we describe a simple yet customizable process to finely engineer the morphology of BC in all (x, y, z) directions, enabling new advanced functionalities, by using hydrophobic particles and superhydrophobized surfaces. This results in hollow, seamless, cellulose-based objects of given shapes and with sizes from ca. 200 μm to several centimeters. We demonstrate some of the unique properties of the process and the resulting objects via post-fabrication merging (biowelding), by in situ encapsulation of active cargo and by multi-compartmentalization for near limitless combinations, thus extending current and new applications for example in advanced carbon materials or regenerative medicine.
68 citations
TL;DR: A review of the most recent methods of treating or dissolving cellulose, and its derivatives to form polymer films or membranes for a variety of applications is given in this article, where the success of the Lyocell process as well as the amine/metal thiocyanate solvent blends of cellulose and other polysaccharides like starch, chitosan, and other natural polymers are also elaborated.
Abstract: Cellulose has been used as a raw material for the manufacture of membranes and fibers for many years. This review gives the background of the most recent methods of treating or dissolving cellulose, and its derivatives to form polymer films or membranes for a variety of applications. Indeed, some potential applications of bacterial cellulose, nanofibrillar cellulose (NFC) for films showing enhanced barrier characteristics are reviewed as well as the utilization of cellulose nanonocrystals (CNC) for production of highly oriented super strong films or thin films is discussed. Because of the success of the Lyocell process as well as the amine/metal thiocyanate solvent blends of cellulose and other polysaccharides like starch, chitosan, and other natural polymers. Consequently, the use of cellulose (or its derivatives) and another polysaccharide dissolved as a blend is also elaborated. It is our hope that the reader will want to follow up and investigate these new systems and use them to develop end u...
TL;DR: This work investigates multifunctional composite films synthesized with cellulose nanofibers (CNFs) and poly(vinyl alcohol) (PVA) and indicates promising applications, for example, in active packaging.
TL;DR: In this article, two common lignin sources (kraft and alkali lignins) were used as renewable and easily degradable particulate templates for the preparation of hollow polymeric capsules.
TL;DR: It is shown that high AVF and more extensive phase separation in CNC suspensions resulted in large, long-range ordered chiral nematic domains in dried films, more pronounced for the suspensions that were closer to equilibrium prior to drying.
TL;DR: The system that underwent the slowest coagulation rate (CNF/GG in ethanol) displayed a limited CNF orientation but achieved an intermediate level of mechanical resistance, owing to the strong core/shell interfacial affinity.
Abstract: A continuous and scalable method for the wet spinning of cellulose nanofibrils (CNFs) is introduced in a core/shell configuration. Control on the interfacial interactions was possible by the choice of the shell material and coagulant, as demonstrated here with guar gum (GG) and cellulose acetate (CA). Upon coagulation in acetone, ethanol, or water, GG and CA formed supporting polymer shells that interacted to different degrees with the CNF core. Coagulation rate was shown to markedly influence the CNF orientation in the filament and, as a result, its mechanical strength. The fastest coagulation noted for the CNF/GG core/shell system in acetone led to an orientation index of ∼0.55 (Herman's orientation parameter of 0.40), Young's modulus of ∼2.1 GPa, a tensile strength of ∼70 MPa, and a tenacity of ∼8 cN/tex. The system that underwent the slowest coagulation rate (CNF/GG in ethanol) displayed a limited CNF orientation but achieved an intermediate level of mechanical resistance, owing to the strong core/shell interfacial affinity. By using CA as the supporting shell, it was possible to spin CNF into filaments with high water absorption capacity (43 g water/g dry filament). This was explained by the fact that water (used as the coagulant for CA) limited the densification of the CNF core structure, yielding filaments with high accessible area and pore density.
TL;DR: MC/CNC hybrid networks offer materials with tunable rheological properties and access to liquid crystalline properties at low CNC concentrations and enthalpic binding between CNCs and MC with the latter comprising aqueous, molecularly dispersed polymer chains that lead to looser and less birefringent material.
TL;DR: Overall, stratified coatings comprising nano- and microparticles derived from lignin are expected to open opportunities for multifunctional structures that can be designed and predicted on the basis of experimental Péclet numbers and computational order.
Abstract: Polydisperse smooth and spherical biocolloidal particles were suspended in aqueous media and allowed to consolidate via evaporation-induced self-assembly. The stratification of the particles at the solid–air interface was markedly influenced, but not monotonically, by the drying rate. Cross-sectional imaging via electron microscopy indicated a structured coating morphology that was distinctive from that obtained by using particles with a mono- or bimodal distribution. Segregation patterns were found to derive from the interplay of particle diffusion, interparticle forces, and settling dynamics. Supporting our experimental findings, computer simulations showed an optimal drying rate for achieving maximum segregation. Overall, stratified coatings comprising nano- and microparticles derived from lignin are expected to open opportunities for multifunctional structures that can be designed and predicted on the basis of experimental Peclet numbers and computational order.
TL;DR: The shear and extensional rheology of aqueous suspensions of cellulose nanofibrils (CNF) were investigated under dynamic and steady flow fields as mentioned in this paper.
TL;DR: A generalized approach to synthesize aerogels that allows remarkable control over its mechanical properties is introduced and is a novel and generic solution to achieving full control of aerogel development, which up to now has been an intractable challenge.
Abstract: We introduce a generalized approach to synthesize aerogels that allows remarkable control over its mechanical properties. The Hansen solubility parameters are used to predict and regulate the swelling properties of the precursor gels and, consequently, to achieve aerogels with tailored density and mechanical properties. As a demonstration, crosslinked organogels were synthesized from cellulose esters to generate aerogels. By determination of Hansen's Relative Energy Difference, it was possible to overcome the limitations of current approaches that solely rely on the choice of precursor polymer concentration to achieve a set of aerogel properties. Hence, from a given concentration, aerogels were produced in a range of mass densities, from 25 to 113 mg/cm3. Consequently, it was possible to tailor the stiffness, toughness and compressive strength of the aerogels, in the ranges between 14-340, 4-103 and 22-373 kPa, respectively. Additionally, unidirectional freeze-drying introduced pore alignment in aerogels with honeycomb morphologies and anisotropy. Interestingly, when the swelling of the polymeric gel was arrested in a non-equilibrium state, it was possible to gain additional control of the property space. The proposed method is a novel and generic solution to achieving full control of aerogel development, which up to now has been an intractable challenge.
TL;DR: A relationship of a higher BC production rate (provoked by ethanol and acetic acid adding) and changes in BC properties is demonstrated, which is the mechanism that provokes those changes.
TL;DR: N nanostructuring thymol in the biogenic silica endowed systems with controlled, responsive release promoting remarkable, high and localized biocidal activity is explored.
Abstract: Biocides are essential for crop protection, packaging and several other biosystem applications. Therein, properties such as tailored and controlled release are paramount in the development of sustainable biocide delivery systems. We explore the self-similar nano-organized architecture of biogenic silica particles to achieve high biocide payload. The high surface area accessibility of the carrier allowed us to develop an efficient, low energy loading strategy, reaching significant dynamic loadings of up to 100 mg·g−1. The release rate and responsiveness were tuned by manipulating the interfaces, using either the native hydroxyl surfaces of the carrier or systems modified with amines or carboxylic acids in high density. We thoroughly evaluated the impact of the carrier-biocide interactions on the release rate as a function of pH, ionic strength and temperature. The amine and carboxyl functionalization strategy led to three-fold decrease in the release rate, while higher responsiveness against important agro-industrial variables. Key to our discoveries, nanostructuring thymol in the biogenic silica endowed systems with controlled, responsive release promoting remarkable, high and localized biocidal activity. The interfacial factors affecting related delivery were elucidated for an increased and localized biocidal activity, bringing a new light for the development of controlled release systems from porous materials.
TL;DR: Filaments display a remarkable stretchability and ultrahigh toughness, both surpassing the values of all reported nanocellulose-based filaments, and retain 90% of these properties after long-term immersion in water, solving the main challenge of the lack of wet strength that is otherwise observed for filaments synthesized from nano celluloses.
Abstract: Heterogeneous acetylation of wood fibers is proposed for weakening their interfibrillar hydrogen bonding, which facilitates their processing into micro- and nanocelluloses that can be further used to synthesize filaments via wet-spinning. The structural (SEM, WAXD), molecular (SEC), and chemical (FTIR, titration) properties of the system are used to propose the associated reaction mechanism. Unlike the homogeneous acetylation, this method does not alter the main morphological features of cellulose fibrils. Thus, we show for the first time, the exploitation of synergies of compositions simultaneously comprising dissolved cellulose esters and suspended cellulose micro- and nanofibrils. Such colloidal suspension forms a co-continuous assembly with a matrix that interacts strongly with the micro- and nanofibrils in the dispersed phase. This facilitates uninterrupted and defect-free wet-spinning. Upon contact with an antisolvent (water), filaments are easily formed and display a set of properties that set them apart from those reported so far for nanocelluloses: a remarkable stretchability (30% strain) and ultrahigh toughness (33 MJ/m3), both surpassing the values of all reported nanocellulose-based filaments. All the while, they also exhibit competitive stiffness and strength (6 GPa and 143 MPa, respectively). Most remarkably, they retain 90% of these properties after long-term immersion in water, solving the main challenge of the lack of wet strength that is otherwise observed for filaments synthesized from nanocelluloses.
TL;DR: A low-temperature and versatile methodology is employed to structure nanoparticles into controlled morphologies from biogenic silica, used as a main building block, together with cellulose nanofibrils, which promote cohesion, and the resultant superstructures resist extremely high mechanical loading without catastrophic failure.
Abstract: In parallel with important technological advances, nanoparticles have brought numerous environmental and toxicological challenges due to their high mobility and nonspecific surface activity. The hazards associated with nanoparticles can be significantly reduced while simultaneously keeping their inherent benefits by superstructuring. In this study, a low-temperature and versatile methodology is employed to structure nanoparticles into controlled morphologies from biogenic silica, used as a main building block, together with cellulose nanofibrils, which promote cohesion. The resultant superstructures are evaluated for cargo loading/unloading of a model, green biomolecule (thymol), and for photo-accessibility and mobility in soil. The bio-based superstructures resist extremely high mechanical loading without catastrophic failure, even after severe chemical and heat treatments. Additionally, the process allows pre and in situ loading, and reutilization, achieving remarkable dynamic payloads as high as 90 mg g-1 . The proposed new and facile methodology is expected to offer a wide range of opportunities for the application of superstructures in sensitive and natural environments.
TL;DR: In this paper, photo-induced thiol-yne click coupling was applied to nanocellulose films and paper to develop micro-patterned surfaces via UV lithography, endowing the substrates with thin hydrophilic channels and hydrophobic boundaries between neighboring water droplets, as small as 100mm in width.
Abstract: We report a facile approach to tailor the wettability of ligno-cellulosic substrates via photo-induced thiol–yne click coupling. First, cellulosic surfaces were functionalized with 4-pentynoic acid to introduce terminal alkyne moieties for the subsequent photo-induced coupling in heterogeneous phase. Next, the (primed) surfaces were reacted with various thiol-containing molecules to systematically tailor the surface energy. Finally, the method was applied to nanocellulose films and paper to develop micro-patterned surfaces via UV lithography, endowing the substrates with thin hydrophilic channels (~ 250 μm thickness) and hydrophobic boundaries between neighboring water droplets, as small as 100 μm in width. Overall, we propose thiol-click as a facile method toward spatially-resolved wetting that enables paper-based electronics in smart labels and point-of-care bioplatforms.
TL;DR: In this paper, two concurrent formation mechanisms are suggested based on the structures revealed by confocal microscopy imaging for white fleck formation in reconstituted milk obtained from spray-dried, fat-containing dairy powders.
TL;DR: In this paper, the authors modified lignin with silicon-containing vinyl groups via a highly efficient silylation reaction that achieved ∼30% substitution of the hydroxyl units.
Abstract: We modified lignin, a renewable biomacromolecule with high carbon density, with silicon-containing vinyl groups via a highly efficient silylation reaction that achieved ∼30% substitution of lignin’s hydroxyl units. This exothermic process was carried out in the melt state, in situ, in a reactive extruder. 1H, 13C, and 31P NMR and FTIR confirmed the success of the silylation and were used to access the reactivity of the vinyl silylated lignin for copolymerization with polyacrylonitrile (PAN). Copolymers of the unmodified lignin and PAN were also produced as a reference. Importantly, the rheological behaviors of the copolymers of lignin and PAN were suitable for application in surface coating and films that were not possible if lignin or physical mixtures of lignin and PAN were used. Glass surfaces were treated via solution casting followed by oven drying, yielding films that were evaluated regarding their morphology (SEM) and thermal properties (TGA and DSC). The films produced with copolymers based on vin...
03 Aug 2018
TL;DR: Light is shed on the transformation of aqueous dispersions of CNFs into filaments that are suited for controlled interactions with water via concurrent hydrolysis and condensation reactions in CVD, while maintaining the moisture buffering capacity and breathability of related structures.
Abstract: Colloidal dispersions of cellulose nanofibrils (CNFs) are viable alternatives to cellulose II dissolutions used for filament spinning. The porosity and water vapor affinity of CNF filaments make them suitable for controlled breathability. However, many textile applications also require water repellence. Here, we investigated the effects of postmodification of wet-spun CNF filaments via chemical vapor deposition (CVD). Two organosilanes with different numbers of methyl substituents were considered. Various surface structures were achieved, either as continuous, homogeneous coating layers or as three-dimensional, hairy-like assemblies. Such surface features reduced the surface energy, which significantly affected the interactions with water. Filaments with water contact angles of up to 116° were obtained, and surface energy measurements indicated the possibility of developing amphiphobicity. Dynamic vapor sorption and full immersion experiments were carried out to inquire about the interactions with water, ...
TL;DR: A harmonic analysis of surface wrinkles and folds on submicron colloidal particles, obtained using an aerosol flow route, with small radius and high crust thickness-to-radius ratio, indicates a possible axial or planar alignment attributed to the directionality of the surface corrugations.
Abstract: Wrinkling of colloidal particles alter a wide variety of interfacial properties but quantitative topographical descriptions have been explored experimentally to a very limited extent. In this study, we present a harmonic analysis of surface wrinkles and folds on submicron colloidal particles, obtained using an aerosol flow route, with small radius ( 0.1). The particle surface coordinates were mapped in their entirety using cryo-electron tomography and subsequently reconstructed using spherical harmonics, allowing a spectral topographical description of the instability patterns and the identification of their surface modes by lateral wavelength. Wrinkled and crumpled particles showed a similar surface roughness spectrum, wherein differences were found most noticeable in the large wavelength region. The analysis of preferred directions of harmonic frequencies indicated a possible axial or planar alignment attributed to the directionality of the surface corrugations. The employed characterization methodology can further the study of topographical influences on colloidal interactions.
06 Mar 2018