School of Chemistry - Research Publications
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ItemNo Preview AvailableUltrasonics in polymer science: applications and challengesSantha Kumar, ARS ; Padmakumar, A ; Kalita, U ; Samanta, S ; Baral, A ; Singha, NK ; Ashokkumar, M ; Qiao, GG (Elsevier BV, 2023-07-01)Ultrasonic waves in a liquid media generate both chemical and mechanistic effects that are actively used to perform chemical reactions, polymer synthesis, nanoparticle synthesis, colloids, food processing and so on. The application of sonochemistry in polymer science has been an interesting topic of research in the recent years. Ultrasonication acts as an external stimulus to initiate free radical polymerization (FRP) by the homolysis of the solvent, thereby generating radicals. The recent utilization of high frequency ultrasound (>100 KHz) for polymer synthesis has evoked new interest in the use of sonochemistry in the field of polymer chemistry, especially in chain growth polymerization reactions including reversible-deactivation radical polymerization (RDRP) techniques and novel applications. This review presents the principles of sonochemisty and the fundamental aspects governing the cavitation process and the radical generation process. A historical overview of the development of ultrasound-assisted polymerization with a focus on chain-growth polymerizations operating under pseudo-“living” conditions including nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP) and reversible addition–fragmentation chain transfer (RAFT) polymerization is provided. The utilization of ultrasound in polymer applications such as hydrogels, biomedical nanostructures, drug delivery, nanocomposite synthesis is also discussed. Unlike conventional FRP, ultrasound-initiated polymerization does not involve any external toxic chemical initiators, adds temporal control to the polymerization process, offers excellent control over the molecular weight and the microstructure of the final polymers, etc. The ultrasound assisted polymerization is a novel, clean and green technology, which can be investigated further by coupling with thermo-, mechano- or photochemical stimuli or flow chemistry. It has the potential to be scaled up into an industrial process.
ItemFundamentals and comprehensive insights on pulsed laser synthesis of advanced materials for diverse photo- and electrocatalytic applications.Theerthagiri, J ; Karuppasamy, K ; Lee, SJ ; Shwetharani, R ; Kim, H-S ; Pasha, SKK ; Ashokkumar, M ; Choi, MY (Springer Science and Business Media LLC, 2022-08-10)The global energy crisis is increasing the demand for innovative materials with high purity and functionality for the development of clean energy production and storage. The development of novel photo- and electrocatalysts significantly depends on synthetic techniques that facilitate the production of tailored advanced nanomaterials. The emerging use of pulsed laser in liquid synthesis has attracted immense interest as an effective synthetic technology with several advantages over conventional chemical and physical synthetic routes, including the fine-tuning of size, composition, surface, and crystalline structures, and defect densities and is associated with the catalytic, electronic, thermal, optical, and mechanical properties of the produced nanomaterials. Herein, we present an overview of the fundamental understanding and importance of the pulsed laser process, namely various roles and mechanisms involved in the production of various types of nanomaterials, such as metal nanoparticles, oxides, non-oxides, and carbon-based materials. We mainly cover the advancement of photo- and electrocatalytic nanomaterials via pulsed laser-assisted technologies with detailed mechanistic insights and structural optimization along with effective catalytic performances in various energy and environmental remediation processes. Finally, the future directions and challenges of pulsed laser techniques are briefly underlined. This review can exert practical guidance for the future design and fabrication of innovative pulsed laser-induced nanomaterials with fascinating properties for advanced catalysis applications.
ItemUltrasonic Processing of Food Waste to Generate Value-Added ProductsWu, Y ; Yao, S ; Narale, BA ; Shanmugam, A ; Mettu, S ; Ashokkumar, M (MDPI, 2022-07-01)Ultrasonic processing has a great potential to transform waste from the food and agriculture industry into value-added products. In this review article, we discuss the use of ultrasound for the valorisation of food and agricultural waste. Ultrasonic processing is considered a green technology as compared to the conventional chemical extraction/processing methods. The influence of ultrasound pre-treatment on the soluble chemical oxygen demand (SCOD), particle size, and cell wall content of food waste is first discussed. The use of ultrasonic processing to produce/extract bioactives such as oil, polyphenolic, polysaccharides, fatty acids, organic acids, protein, lipids, and enzymes is highlighted. Moreover, ultrasonic processing in bioenergy production from food waste such as green methane, hydrogen, biodiesel, and ethanol through anaerobic digestion is also reviewed. The conversion of waste oils into biofuels with the use of ultrasound is presented. The latest developments and future prospective on the use of ultrasound in developing energy-efficient methods to convert food and agricultural waste into value-added products are summarised.
ItemThe physical, mechanical, thermal and barrier properties of starch nanoparticle (SNP)/polyurethane (PU) nanocomposite films synthesised by an ultrasound-assisted process.Hakke, VS ; Landge, VK ; Sonawane, SH ; Uday Bhaskar Babu, G ; Ashokkumar, M ; M M Flores, E (Elsevier BV, 2022-08)This article reports on the ultrasound-assisted acid hydrolysis for the synthesis and evaluation of starch nanoparticles (SNP) as nanofillers to improve the physical, mechanical, thermal, and barrier properties of polyurethane (PU) films. During the ultrasonic irradiation, dropwise addition of 0.25 mol L-1 H2SO4 was carried out to the starch dispersion for the preparation of SNPs. The synthesized SNPs were blended uniformly within the PU matrix using ultrasonic irradiation (20 kHz, 220 W pulse mode). The temperature was kept constant during the synthesis (4 °C). The nanocomposite coating films were made with a regulated thickness using the casting method. The effect of SNP content (wt%) in nanocomposite coating films on various properties such as morphology, water vapour permeability (WVP), glass transition temperature (Tg), microbial barrier, and mechanical properties was studied. The addition of SNP to the PU matrix increased the roughness of the surface, and Tg by 7 °C, lowering WVP by 60% compared to the PU film without the addition of SNP. As the SNP concentration was increased, the opacity of the film increased. The reinforcement of the SNP in the PU matrix enhanced the microbial barrier of the film by 99.9%, with the optimal content of SNP being 5%. Improvement in the toughness and barrier properties was observed with an increase in the SNP content of the film.
Sonosynthesis of nanobiotics with antimicrobial and antioxidant propertiesZhu, H ; Wen, Q ; Bhangu, SK ; Ashokkumar, M ; Cavalieri, F (ELSEVIER, 2022-05-10)Transforming small-molecule antibiotics into carrier-free nanoantibiotics represents an opportunity for developing new multifunctional therapeutic agents. In this study, we demonstrate that acoustic cavitation produced by high-frequency ultrasound transforms the antibiotic doxycycline into carrier-free nanobiotics. Upon sonication for 1 h at 10-15 W cm-3, doxycycline molecules underwent hydroxylation and dimerization processes to ultimately self-assemble into nanoparticles of ∼100-200 nm in size. Micrometer sized particles can be also obtained by increasing the acoustic power to 20 W cm-3. The nanodrugs exhibited antioxidant properties, along with antimicrobial activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacterial strains. Our results highlight the feasibility of the ultrasound-based approach for engineering drug molecules into a nanosized formulation with controlled and multiple bio-functionalities.
ItemLysozyme microspheres incorporated with anisotropic gold nanorods for ultrasound activated drug deliveryBhargawa, B ; Sharma, V ; Ganesh, M-R ; Cavalieri, F ; Ashokkumar, M ; Neppolian, B ; Sundaramurthy, A (ELSEVIER, 2022-05-04)We report on the fabrication of lysozyme microspheres (LyMs) incorporated with gold nanorods (NRs) as a distinctive approach for the encapsulation and release of an anticancer drug, 5-Fluorouracil (5-FU). LyMs with an average size of 4.0 ± 1.0 µm were prepared by a sonochemical method and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR). The LyMs were examined using hydrophobic (nile red) as well as hydrophilic (trypan blue) dyes under confocal laser scanning microscopy (CLSM) to obtain information about the preferential distribution of fluorescent molecules. Notably, the fluorescent molecules were accumulated in the inner lining of LyMs as the core was occupied with air. The encapsulation efficiency of 5-FU for LyMs-NR was found to be ∼64%. The drug release from control LyMs as well as LyMs incorporated with NRs was investigated under the influence of ultrasound (US) at 200 kHz. The total release for control LyMs and LyMs incorporated with gold NRs was found to be ∼70 and 95% after 1 h, respectively. The density difference caused by NR incorporation on the shell played a key role in rupturing the LyMs-NR under US irradiation. Furthermore, 5-FU loaded LyMs-NR exhibited excellent anti-cancer activity against the THP-1 cell line (∼90% cell death) when irradiated with US of 200 kHz. The enhanced anti-cancer activity of LyMs-NR was caused by the transfer of released 5-FU molecules from bulk to the interior of the cell via temporary pores formed on the surface of cancer cells, i.e., sonoporation. Thus, LyMs-NR demonstrated here has a high potential for use as carriers in the field of drug delivery, bio-imaging and therapy.
ItemNo Preview AvailableUltrasonic microencapsulation of oil-soluble vitamins by hen egg white and green tea for fortification of foodZhu, H ; Mettu, S ; Cavalieri, F ; Ashokkumar, M (ELSEVIER SCI LTD, 2021-03-10)We report the microencapsulation of oil soluble vitamins (A, D and E) using a one pot ultrasonic process and raw egg white proteins as a shell material. Green tea catechin/iron complex coating method was further developed to impart UV filtering property to the microcapsules in order to protect the encapsulated nutrients from photodegradation. The microcapsules showed antibacterial properties and long shelf-life. The encapsulated vitamins were protected from degradation upon heating, UV irradiation, simulated storage/transit and cooking processes. The in-vitro digestion study showed that functional vitamin D can be potentially released in the gastrointestinal tract improving vitamin D availability by more than 2-fold compared to the free vitamin. The vitamin D microcapsules were highly stable and maintained their microstructures once incorporated into staple food products. The low-cost egg white shell encapsulated vitamins can improve the nutritional value of staple food products to combat maternal and child malnutrition.
ItemUltrasound-induced protein restructuring and ordered aggregation to form amyloid crystalsPathak, R ; Bhangu, SK ; Martin, GJO ; Separovic, F ; Ashokkumar, M (SPRINGER, 2022-05-16)Amyloid crystals, a form of ordered protein aggregates documented relatively recently, have not been studied as extensively as amyloid fibres. This study investigates the formation of amyloid crystals with low frequency ultrasound (20 kHz) using β-lactoglobulin, as a model protein for amyloid synthesis. Acoustic cavitation generates localised zones of intense shear, with extreme heat and pressure that could potentially drive the formation of amyloid structures at ambient bulk fluid temperatures (20 ± 1 °C). Thioflavin T fluorescence and electron microscopy showed that low-frequency ultrasound at 20 W/cm3 input power induced β-stacking to produce amyloid crystals in the mesoscopic size range, with a mean length of approximately 22 µm. FTIR spectroscopy indicated a shift towards increased intermolecular antiparallel β-sheet content. An increase in sonication time (0-60 min) and input power (4-24 W/cm3) increased the mean crystal length, but this increase was not linearly proportional to sonication time and input power due to the delayed onset of crystal growth. We propose that acoustic cavitation causes protein unfolding and aggregation and imparts energy to aggregates to cross the torsion barrier, to achieve their lowest energy state as amyloid crystals. The study contributes to a further understanding of protein chemistry relating to the energy landscape of folding and aggregation. Ultrasound presents opportunities for practical applications of amyloid structures, presenting a more adaptable and scalable approach for synthesis.
ItemA correlation between cavitation bubble temperature, sonoluminescence and interfacial chemistry - A minireview.Yusof, NSM ; Anandan, S ; Sivashanmugam, P ; Flores, EMM ; Ashokkumar, M (Elsevier BV, 2022-04)Ultrasound induced cavitation (acoustic cavitation) process is found useful in various applications. Scientists from various disciplines have been exploring the fundamental aspects of acoustic cavitation processes over several decades. It is well documented that extreme localised temperature and pressure conditions are generated when a cavitation bubble collapses. Several experimental techniques have also been developed to estimate cavitation bubble temperatures. Depending upon specific experimental conditions, light emission from cavitation bubbles is observed, referred to as sonoluminescence. Sonoluminescence studies have been used to develop a fundamental understanding of cavitation processes in single and multibubble systems. This minireview aims to provide some highlights on the development of basic understandings of acoustic cavitation processes using cavitation bubble temperature, sonoluminescence and interfacial chemistry over the past 2-3 decades.
ItemUltrasound-aided synthesis of gold-loaded boron-doped graphene quantum dots interface towards simultaneous electrochemical determination of guanine and adenine biomolecules.Kaimal, R ; Mansukhlal, PN ; Aljafari, B ; Anandan, S ; Ashokkumar, M (Elsevier BV, 2022-02)To acquire substantial electrochemical signals of guanine-GUA and adenine-ADE present in deoxyribonucleic acid-DNA, it is critical to investigate innovative electrode materials and their interfaces. In this study, gold-loaded boron-doped graphene quantum dots (Au@B-GQDs) interface was prepared via ultrasound-aided reduction method for monitoring GUA and ADE electrochemically. Transmission electron microscopy-TEM, Ultraviolet-Visible spectroscopy-UV-Vis, Raman spectroscopy, X-ray photoelectron spectroscopy-XPS, cyclic voltammetry-CV, and differential pulse voltammetry-DPV were used to examine the microstructure of the fabricated interfaceand demonstrate its electrochemical characteristics. The sensor was constructed by depositing the as-prepared Au@B-GQDs as a thin layer on a glassy carbon-GC electrode by the drop-casting method and carried out the electrochemical studies. The resulting sensor exhibited a good response with a wide linear range (GUA = 0.5-20 μM, ADE = 0.1-20 μM), a low detection limit-LOD (GUA = 1.71 μM, ADE = 1.84 μM), excellent sensitivity (GUA = 0.0820 µAµM-1, ADE = 0.1561 µAµM-1) and selectivity with common interferents results from biological matrixes. Furthermore, it seems to have prominentselectivity, reproducibility, repeatability, and long-lastingstability. The results demonstrate that the fabricated Au@B-GQDs/GC electrode is a simple and effective sensing platform for detecting GUA and ADE in neutral media at low potential as it exhibited prominent synergistic impact and outstanding electrocatalytic activity corresponding to individual AuNPs and B-GQDs modified electrodes.