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Start Over Author "Rojas, Orlando J." Publisher american chemical society
311 results on '"Rojas, Orlando J."'

12. Mechanisms of Strain-Induced Interfacial Strengthening of Wet-Spun Filaments

Author

Guo, Tianyu, Wan, Zhangmin, Yu, Yan, Chen, Hui, Wang, Zhifeng, Li, Dagang, Song, Junlong, Rojas, Orlando J., Jin, Yongcan, Nanjing Forestry University, University of British Columbia, Yangzhou University, Bio-based Colloids and Materials, Department of Bioproducts and Biosystems, Aalto-yliopisto, and Aalto University

Subjects
axial orientation, interfacial strengthening, wet drawing, General Materials Science, carbon nanotube, reversible torsion
Abstract

openaire: EC/H2020/788489/EU//BioELCell Funding Information: This work was supported by the National Natural Science Foundation of China (Grant Nos. 31730106, 31770623, 31670555), the Canada Excellence Research Chair initiative (CERC-2018-00006), and Canada Foundation for Innovation (Project number 38623), as well as the European Research Council (ERC), under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 788489). T.G. would like to acknowledge the financial support from China Scholarship Council (CSC). The authors thank Dr. Zhifeng Wang of the Test Center at Yangzhou University for technical assistance. Publisher Copyright: © 2021 American Chemical Society. All rights reserved. We investigate the mechanism of binding of dopamine-conjugated carboxymethyl cellulose (DA-CMC) with carbon nanotubes (CNTs) and the strain-induced interfacial strengthening that takes place upon wet drawing and stretching filaments produced by wet-spinning. The filaments are known for their tensile strength (as high as 972 MPa and Young modulus of 84 GPa) and electrical conductivity (241 S cm-1). The role of axial orientation in the development of interfacial interactions and structural changes, enabling shear load bearing, is studied by molecular dynamics simulation, which further reveals the elasto-plasticity of the system. We propose that the reversible torsion of vicinal molecules and DA-CMC wrapping around CNTs are the main contributions to the interfacial strengthening of the filaments. Such effects play important roles in impacting the properties of filaments, including those related to electrothermal heating and sensing. Our findings contribute to a better understanding of high aspect nanoparticle assembly and alignment to achieve high-performance filaments.

Published
2022

21. Quantification of cellulase activity using the quartz crystal microbalance technique

Author

Hu, Gang, Heitmann, John A., Jr., and Rojas, Orlando J.

Subjects
Quartz crystals -- Properties, Biomass -- Research, Biotechnology -- Research, Equilibrium (Physics) -- Research, Enzymes -- Properties, Cellulose -- Properties, Crystals -- Properties, Chemistry
Abstract

The development of more efficient utilization of biomass has received increased attention in recent years. Cellulases play an important role in processing biomass through advanced biotechnological approaches. Both the development and the application of cellulases require an understanding of the activities of these enzymes. A new method to determine the activity of cellulase has been developed using a quartz crystal microbalance (QCM) technique. We compare the results from this technique with those from the IUPAC (International Union of Pure and Applied Chemistry) dinitrosalicylic acid (DNS) standard method and also from biccinchoninic acid and ion chromatography methods. It is shown that the QCM technique provides results closer to those obtained by measuring the actual reducing sugars. The elimination of the use of color development in the standard redox methods makes the QCM platform easier to implement; it also allows more flexibility in terms of the nature of the substrate. Finally, validation of the proposed method was carded out by relating the crystallinity of different substrates to the cellulase activity. Numerical values of cellulase activities measured with the QCM method showed that celluloses with higher crystallinity indices were hydrolyzed slower and to a lower extent than those of lower crystallinity indices for the cellulase mixtures examined.

Published
2009

24. Charge Matters

Author

Otoni, Caio G., Queirós, Marcos V.A., Sabadini, Julia B., Rojas, Orlando J., Loh, Watson, Bio-based Colloids and Materials, Universidade Estadual de Campinas, Department of Bioproducts and Biosystems, Aalto-yliopisto, and Aalto University

Abstract

openaire: EC/H2020/788489/EU//BioELCell We report on electrostatically complexed materials bearing advanced functions that are not possible for other assemblies. The fundamentals of electrostatic association between oppositely charged polyelectrolytes and colloidal particles are introduced together with the conditions needed for complexation, including those related to ionic strength, pH, and hydration. Related considerations allow us to control the properties of the formed complexes and to develop features such as self-healing and underwater adhesion. In contrast to assemblies produced by typical hydrophobic and chemical interactions, electrostatic complexation leads to reversible systems. A state-of-the-art account of the field of electrostatically complexed materials is provided, including those formed from biomolecules and for salt-controlled rheology, underwater adhesiveness, and interfacial spinning. Finally, we present an outlook of electrostatic complexation from the colloidal chemistry perspective.

Published
2020

25. Modulation of Physicochemical Characteristics of Pickering Emulsions

Author

Zhou, Hualu, Lv, Shanshan, Liu, Jinning, Tan, Yunbing, Muriel Mundo, Jorge L., Bai, Long, Rojas, Orlando J., McClements, David Julian, University of Massachusetts, Bio-based Colloids and Materials, Department of Bioproducts and Biosystems, Aalto-yliopisto, and Aalto University

Subjects
endocrine system, nanochitin, technology, industry, and agriculture, nanoparticles, Pickering emulsions, heteroaggregation, complex mixtures, eye diseases, nanocellulose
Abstract

Mixed Pickering emulsions were prepared by blending anionic nanocellulose-stabilized lipid droplets with cationic nanochitin-stabilized lipid droplets. Changes in the surface potential, particle size, shear viscosity, and morphology of the mixed emulsions were characterized when the droplet mixing ratio was varied. Emulsion properties could be tailored by altering the pH and mixing ratio. Surface potential measurements suggested that the nanochitin-coated lipid droplets adsorbed to the surfaces of the nanocellulose-coated lipid droplets, thereby dominating the overall electrical characteristics of the mixed emulsions. As a result, the mixed emulsions had better stability to coalescence than the single emulsions containing only nanocellulose-coated lipid droplets. Our results suggest that the physicochemical properties, shelf life, and functional performance of Pickering emulsions may be modulated by blending different kinds of particle-stabilized lipid droplets together.

Published
2020

29. Lignins as Emulsion Stabilizers

Author

Rojas, Orlando J., primary, Bullón, Johnny, additional, Ysambertt, Fredy, additional, Forgiarini, Ana, additional, Salager, Jean-L., additional, and Argyropoulos, Dimitris S., additional

Published
2007
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