Shape and size engineered cellulosic nanomaterials as broad spectrum anti-microbial compounds

Investigation of Cellulose-Based Materials Applied in Life Sciences Using Laser Light Scattering Methods

This review emphasizes the practical importance of laser light scattering methods for characterizing cellulose and its derivatives. The physicochemical parameters like molecular weights, the radius of gyration, hydrodynamic radius, and conformation will be considered when the reproducibility of polymer behavior in solution is necessary for the subsequent optimization of the property profile of a designed product. Since there are various sources of cellulose, and the methods of cellulose extraction and chemical modification have variable yields, materials with variable molecular weights, and size polydispersity will often result. Later, the molecular masses will influence other physicochemical properties of cellulosic materials, both in solution and solid state. Consequently, the most rigorous determination of these quantities is imperative. In this regard, the following are presented and discussed in this review: the theoretical foundations of the light scattering phenomenon, the evolution of the specific instrumentation and detectors, the development of the detector-coupling techniques which include a light scattering detector, and finally, the importance of the specific parameters of polymers in solution, resulting from the data analysis of light scattering signals. All these aspects are summarized according to the chemical classification of the materials: celluloses, esters of cellulose, co-esters of cellulose, alkyl esters of cellulose, ethers of cellulose, and other heterogeneous cellulose derivatives with applications in life sciences.

Sequential Oxidation on Wood and Its Application in Pb2+ Removal from Contaminated Water

Raw wood was subjected to sequential oxidation to produce 2,3,6-tricarboxycellulose (TCC) nanofibers with a high surficial charge of 1.14 mmol/g in the form of carboxylate groups. Three oxidation steps, including nitro-oxidation, periodate, and sodium chlorite oxidation, were successfully applied to generate TCC nanofibers from raw wood. The morphology of extracted TCC nanofibers measured using TEM and AFM indicated the average length, width, and thickness were in the range of 750 ± 110, 4.5 ± 1.8, and 1.23 nm, respectively. Due to high negative surficial charges on TCC, it was studied for its absorption capabilities against Pb2+ ions. The remediation results indicated that a low concentration of TCC nanofibers (0.02 wt%) was able to remove a wide range of Pb2+ ion impurities from 5–250 ppm with an efficiency between 709–99%, whereby the maximum adsorption capacity (Qm) was 1569 mg/g with R2 0.69531 calculated from Langmuir fitting. It was observed that the high adsorption capacity of TCC nanofibers was due to the collective effect of adsorption and precipitation confirmed by the FTIR and SEM/EDS analysis. The high carboxylate content and fiber morphology of TCC has enabled it as an excellent substrate to remove Pb2+ ions impurities.

Cellulose Degradation by Calcium Thiocyanate

The dissolution process of cellulose aerogels is an important part of their production. However, if the cellulose is severely degraded during the dissolution process, the quality may be low. To evaluate the degradation of cellulose during the dissolution process using calcium thiocyanate, the hydrolysis and oxidation of cellulose were evaluated by the change in absolute molecular weight and by the changes in the content of carboxyl and carbonyl groups introduced into the cellulose hydroxyl group, respectively. A noteworthy hydrolysis phenomenon was found in the cellulose dissolution process. The rate of hydrolysis increased as the number of hydrates in calcium thiocyanate decreased and as the reaction temperature increased. In the case of the reaction with calcium thiocyanate containing six hydrates, the time to reach a 50% loss of the degree of polymerization of cellulose reduced from 196 to 47 min as the reaction temperature was increased from 100 to 120 °C; however, the effect on oxidation was not significant. The Brunauer-Emmett-Teller (BET) surface area reduced as the degree of cellulose polymerization decreased. Therefore, it is necessary to consider how the cellulose degradation occurring during the cellulosic dissolution process can affect the quality of the final cellulose aerogels.

Adsorption, Antibacterial and Antioxidant Properties of Tannic Acid on Silk Fiber

Natural bioactive compounds have received increasing attention in the functional modification of textiles. In this work, tannic acid was used to impart antibacterial and antioxidant functions to silk using an adsorption technique, and the adsorption properties of tannic acid on silk were studied. The adsorption quantity of tannic acid on silk increased with decreasing pH in the range of 3–7. The rates of the uptake of tannic acid by silk were well correlated to the pseudo-second-order kinetic model, and the calculated activation energy of adsorption was 93.49 kJ/mol. The equilibrium adsorption isotherms followed the Langmuir model. The adsorption rate and isotherm studies demonstrated that the chemical adsorption of tannic acid on silk occurred through the ion-ion interaction between tannic acid and silk. Tannic acid displayed good building-up properties on silk. The silk fabric treated with 0.5% tannic acid (relative to fabric weight) exhibited excellent and durable antibacterial properties. Moreover, the silk fabrics treated with 2% and 5% tannic acid had good and durable antioxidant properties. The treatment by tannic acid had less impact on the whiteness of the silk fabric. In summary, tannic acid can be used as a functional agent for preparing healthy and hygienic silk materials.

Cellulose modification and shaping – a review

This review aims to present cellulose as a versatile resource for the production of a variety of materials, other than pulp and paper. These products include fibers, nonwovens, films, composites, and novel derivatized materials. This article will briefly introduce the structure of cellulose and some common cellulose derivatives, as well as the formation of cellulosic materials in the micro- and nanoscale range. The challenge with dissolution of cellulose will be discussed and both derivatizing and nonderivatizing solvents for cellulose will be described. The focus of the article is the critical discussion of different shaping processes to obtain a variety of cellulose products, from commercially available viscose fibers to advanced and functionalized materials still at the research level.