Browsing by Author "Pradeep, Thalappil"
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- Dual emitting Ag35nanocluster protected by 2-pyrene imine thiol
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2020-10-25) Jana, Arijit; Chakraborty, Papri; Dar, Wakeel Ahmed; Chandra, Sourov; Khatun, Esma; Kannan, M. P.; Ras, Robin H.A.; Pradeep, ThalappilIn this communication, we present the synthesis of 2-pyrene imine thiol (2-PIT)-protected Ag35 nanoclusters using a ligand exchange-induced structural transformation reaction. The formation of the nanocluster and its composition were confirmed through several spectroscopic and electron microscopic studies. The UV-vis absorption spectrum showed a set of characteristic features of the nanocluster. This nanocluster showed blue emission under UV light due to pyrene to metal corecharge-transfer, and NIR emission due to charge-transfer within the metal core. This is the first report on dual emitting pyrene protected atomically precise silver nanoclusters. - Effects of Chloride Concentration on the Water Disinfection Performance of Silver Containing Nanocellulose-based Composites
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-12-01) Lehtonen, Janika; Hassinen, Jukka; Honkanen, Riina; Kumar, Avula Anil; Viskari, Heli; Kettunen, Anu; Pahimanolis, Nikolaos; Pradeep, Thalappil; Rojas, Orlando J.; Ikkala, OlliThe availability of microbially-safe drinking water is a challenge in many developing regions. Due to the well-known antibacterial effect of silver ions, materials used for their controlled release have been widely studied for point-of-use water disinfection. However, even if it is in principle known that chloride anions can suppress the antibacterial efficiency of silver, the majority of previous studies, surprisingly, have not focused on chloride concentrations relevant for freshwaters and thus for practical applications. Here, we prepared low-cost nanocellulose-aluminium oxyhydroxide nanocomposites functionalized with silver nanoparticles. Field samples obtained from Chennai, India were used as a guideline for choosing relevant chloride concentrations for the antibacterial studies, i.e., 10, 90, and 290 ppm. The antibacterial performance of the material against Escherichia coli and Bacillus subtilis was demonstrated and the influence of chloride concentration on the antibacterial effect was studied with E. coli. A 1 h contact time led to bacterial reductions of 5.6 log10, 2.9 log10, and 2.2 log10, respectively. This indicates that an increase of chloride concentration leads to a substantial reduction of antibacterial efficiency, even within chloride concentrations found in freshwaters. This work enables further insights for designing freshwater purification systems that utilize silver-releasing materials. - Fabrication of a Waterborne Durable Superhydrophobic Material Functioning in Air and under Oil
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2018-06) Baidya, Avijit; Das, Sarit Kumar; Ras, Robin H.A.; Pradeep, ThalappilA fundamental challenge in artificially structured/ chemically modified superhydrophobic surfaces is their poor chemical, mechanical, and structural robustness toward different mechanical abrasions. This limits their application potential in different fields of science and technology. Herein, a waterborne superhydrophobic material composed of clay particles is developed through a one-pot chemical modification in ambient conditions, forming durable micro-nano dual-structured coatings over a range of substrates, without adhesive. This chemical modification inverts the inherent hydrophilic nature of clay particles and provides an excellent superhydrophobic surface having a water contact angle >170° (±2°) and contact angle hysteresis <5° (±2°). The coating shows excellent durability against various induced damages and works efficiently both in air and within oils. The observed property is due to the controlled surface energy obtained by the incorporated chemical functionalities and enhanced surface roughness facilitated by the hydrophobic effect during slow evaporation of water from the coating material. Being a stable water dispersion, it enables large area coatings, thereby minimizing safety and environmental concerns. Use of this material to develop rugged waterproof-paper for paper-based technologies is also demonstrated. As clay is commercially available and economical, it is believed, this scalable organic-solvent-free superhydrophobic material will have a positive impact on various industries. - Ferrofluid Microdroplet Splitting for Population-Based Microfluidics and Interfacial Tensiometry
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2020-07) Latikka, Mika; Backholm, Matilda; Baidya, Avijit; Ballesio, Alberto; Serve, Amandine; Beaune, Grégory; Timonen, Jaakko V.I.; Pradeep, Thalappil; Ras, Robin H.A.Ferrofluids exhibit a unique combination of liquid properties and strong magnetic response, which leads to a rich variety of interesting functional properties. Here, the magnetic-field-induced splitting of ferrofluid droplets immersed in an immiscible liquid is presented, and related fascinating dynamics and applications are discussed. A magnetic field created by a permanent magnet induces instability on a mother droplet, which divides into two daughter droplets in less than 0.1 s. During the splitting process, the droplet undergoes a Plateau–Rayleigh-like instability, which is investigated using high-speed imaging. The dynamics of the resulting satellite droplet formation is shown to depend on the roughness of the supporting surface. Further increasing the field results in additional splitting events and self-assembly of microdroplet populations, which can be magnetically actuated. The effects of magnetization and interfacial tension are systematically investigated by varying magnetic nanoparticles and surfactant concentrations, and a variety of outcomes from labyrinthine patterns to discrete droplets are observed. As the splitting process depends on interfacial tension, the droplet splitting can be used as a measure for interfacial tension as low as 0.1 mN m−1. Finally, a population-based digital microfluidics concept based on the self-assembled microdroplets is presented. - Gold Au(I)6 Clusters with Ligand-Derived Atomic Steric Locking: Multifunctional Optoelectrical Properties and Quantum Coherence
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-04-18) Chandra, Sourov; Sciortino, Alice; Das, Susobhan; Ahmed, Faisal; Jana, Arijit; Roy, Jayoti; Li, Diao; Liljeström, Ville; Jiang, Hua; Johansson, Leena Sisko; Chen, Xi; Nonappa; Cannas, Marco; Pradeep, Thalappil; Peng, Bo; Ras, Robin H.A.; Sun, Zhipei; Ikkala, Olli; Messina, FabrizioAn atomically precise ultrasmall Au(I)6 nanocluster where the six gold atoms are complexed by three sterically interlocking stabilizing ligands is reported, allowing a unique combination of efficient third harmonic generation (THG), intense photoluminescence quantum yield (35%), ultrafast quantum coherence, and electron accepting properties. The reaction of 6-(dibutylamino)-1,3,5-triazine-2,4-dithiol (TRZ) with HAuCl4 leads to complexation by thiolation. However, intriguingly, another reduction step is needed to form the centrosymmetric Au(I)6TRZ3 clusters with the multifunctional properties. Here, ascorbic acid is employed as a mild reducing agent, in contrast to the classic reducing agents, like NaBH4 and NaBH3CN, which often produce mixtures of clusters or gold nanoparticles. Such Au(I)6 nanocluster films produce very strong THG response, never observed for nanoclusters. The clusters also produce brilliant single and multiphoton luminescence with exceptional stability. Density functional theory calculations and femtosecond transient absorption studies suggest ultrafast ligand-to-metal charge transfer, quantum coherence with long decoherence time 200–300 fs, and fast propagation of excitation from the core to the surrounding solvent. Finally, novel electron-accepting ground state properties allow p-doping of 2D field-effect transistor devices. Summarizing, the potential of ultrasmall sterically interlocked Au(I) clusters, i.e., complexes allowed by the new sequential reduction protocol, towards multifunctional devices, fast photoswitches, and quantum colloidal devices is shown. - Mixed-Monolayer-Protected Au25 Clusters with Bulky Calix[4]arene Functionalities
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2014) Hassinen, Jukka; Pulkkinen, Petri; Kalenius, Elina; Pradeep, Thalappil; Tenhu, Heikki; Hakkinen, Hannu; Ras, Robin H.A. - Near-Infrared Chiral Plasmonic Microwires through Precision Assembly of Gold Nanorods on Soft Biotemplates
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-02-11) Chakraborty, Amrita; Nonappa; Mondal, Biswajit; Chaudhari, Kamalesh; Rekola, Heikki; Hynninen, Ville; Kostiainen, Mauri A.; Ras, Robin H.A.; Pradeep, ThalappilDirecting the assembly of plasmonic nanoparticles into chiral superstructures has diverse applications including, chiroptical sensing, nonlinear optics, and biomedicine. Though soft template-mediated assemblies of both spherical and nonspherical gold nanoparticles have made significant progress, most approaches require sophisticated chemical synthesis or advanced methodologies. Besides, reports of structurally precise chiral plasmonic assemblies beyond nanoscale are limited. Here, we propose an efficient yet simple strategy to grow such precision assemblies up to mesoscale, which is beneficial for a broader community. Briefly, cationic gold nanorods (AuNRs) are allowed to systematically assemble along atomically precise, chiral, rodlike tobacco mosaic virus (TMV) particles via electrostatic attraction under ambient condition. This leads to spontaneous formation of helical hybrid microwires with high structural precision, as evidenced by cryogenic transmission electron microscopy and tomography. Resulting composite superstructures show a strong circular dichroism response at the plasmon wavelength of the AuNRs, which is supported by simulations using discrete dipole approximation. Further, chirality of the system is investigated at a single-microwire level using polarized dark-field scattering microscopy. An alternative chiral template, negatively charged colloidal cellulose nanocrystals, also arrange AuNRs into similar chiral microstructures. Thus, our report proposes a generic methodology to obtain chiral plasmonic response at the NIR region using inexpensive templates that will encourage the exploration of a wider range of nanoscale templates for creating hybrid mesostructures with emerging optoelectronic properties. - Organic Solvent-Free Fabrication of Durable and Multifunctional Superhydrophobic Paper from Waterborne Fluorinated Cellulose Nanofiber Building Blocks
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2017-11-28) Baidya, Avijit; Ganayee, Mohd Azhardin; Jakka Ravindran, Swathy; Tam, Kam Chiu; Das, Sarit Kumar; Ras, Robin H.A.; Pradeep, ThalappilIn view of a great demand for paper-based technologies, nonwettable fibrous substrates with excellent durability have drawn much attention in recent years. In this context, the use of cellulose nanofibers (CNFs), the smallest unit of cellulosic substrates (5-20 nm wide and 500 nm to several microns in length), to design waterproof paper can be an economical and smart approach. In this study, an eco-friendly and facile methodology to develop a multifunctional waterproof paper via the fabrication of fluoroalkyl functionalized CNFs in the aqueous medium is presented. This strategy avoids the need for organic solvents, thereby minimizing cost as well as reducing safety and environmental concerns. Besides, it widens the applicability of such materials as nanocellulose-based aqueous coatings on hard and soft substrates including paper, in large areas. Water droplets showed a contact angle of 160° (±2°) over these surfaces and rolled off easily. While native CNFs are extremely hydrophilic and can be dispersed in water easily, these waterborne fluorinated CNFs allow the fabrication of a superhydrophobic film that does not redisperse upon submersion in water. Incorporated chemical functionalities provide excellent durability toward mechanochemical damages of relevance to daily use such as knife scratch, sand abrasion, spillage of organic solvents, etc. Mechanical flexibility of the chemically modified CNF composed paper remains intact despite its enhanced mechanical strength, without additives. Superhydrophobicity induced excellent microbial resistance of the waterproof paper which expands its utility in various paper-based technologies. This includes waterproof electronics, currency, books, etc., where the integrity of the fibers, as demonstrated here, is a much-needed criterion. - Phosphorylated cellulose nanofibers exhibit exceptional capacity for uranium capture
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2020-12) Lehtonen, Janika; Hassinen, Jukka; Kumar, Avula Anil; Johansson, Leena Sisko; Mäenpää, Roni; Pahimanolis, Nikolaos; Pradeep, Thalappil; Ikkala, Olli; Rojas, Orlando J.We investigate the adsorption of hexavalent uranium, U(VI), on phosphorylated cellulose nanofibers (PHO-CNF) and compare the results with those for native and TEMPO-oxidized nanocelluloses. Batch adsorption experiments in aqueous media show that PHO-CNF is highly efficient in removing U(VI) in the pH range between 3 and 6. Gelling of nanofiber hydrogels is observed at U(VI) concentration of 500 mg/L. Structural changes in the nanofiber network (scanning and transmission electron microscopies) and the surface chemical composition (X-ray photoelectron spectroscopy) gave insights on the mechanism of adsorption. The results from batch adsorption experiments are fitted to Langmuir, Freundlich, and Sips isotherm models, which indicate a maximum adsorption capacity of 1550 mg/g, the highest value reported so far for any bioadsorbent. Compared to other metals (Zn, Mn, and Cu) and typical ions present in natural aqueous matrices the phosphorylated nanofibers are shown to be remarkably selective to U(VI). The results suggest a solution for the capture of uranium, which is of interest given its health and toxic impacts when present in aqueous matrices. - Photoconversion of Ag31 to Ag42 Initiated by Solvated Electrons
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-09-12) Jana, Arijit; Dar, Wakeel Ahmed; Jana, Sourav Kanti; Poonia, Ajay Kumar; Yadav, Vivek; Roy, Jayoti; Chandra, Sourov; Adarsh, Kumaran Nair Valsala Devi; Ras, Robin H. A.; Pradeep, ThalappilLight-matter interactions, especially in atomically precise nanomaterials, belong to an unexplored realm of research with potential benefits for the synthesis of materials. Here, we present an interesting light-activated expansion process of an Ag31 nanocluster to an Ag42 analogue, both clusters being protected with 6-(dibutylamino)-1,3,5-triazine-2, 4-dithiol (shortly, TRZ-H2) ligands. The conversion process was initially monitored through UV–vis, revealing that the violet-colored Ag31 got converted to greenish Ag42, exhibiting their characteristic absorption features. High-resolution mass spectrometric studies confirmed that the as-synthesized [Ag31(TRZ)10] with coexisting di- and monoanionic charged species in dichloromethane solution got converted to [Ag42(TRZ)13] with a dipositive charge state. Electrochemical studies revealed the photoresponsive nature of Ag31, and light illumination resulted in transient intermediate clusters covered with solvated electrons, which contributed to the core expansion. Ag31 is NIR-emitting, while Ag42 is red-emitting. The ultrafast transient absorption studies reveal that Ag42 has strikingly short excited-state carrier dynamics than Ag31. The stable excited-state carriers for Ag31 upon photoexcitation also underline the unique electronic characteristics responsible for such light-activated structural evolution. - Simple and Efficient Separation of Atomically Precise Noble Metal Clusters
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2014-12-16) Ghosh, Atanu; Hassinen, Jukka; Pulkkinen, Petri; Tenhu, Heikki; Ras, Robin H. A.; Pradeep, ThalappilThere is an urgent need for accessible purification and separation strategies of atomically precise metal clusters in order to promote the study of their fundamental properties. Although the separation of mixtures of atomically precise gold clusters Au25L18, where L are thiolates, has been demonstrated by advanced separation techniques, we present here the first separation of metal clusters by thin-layer chromatography (TLC), which is simple yet surprisingly efficient. This method was successfully applied to a binary mixture of Au25L18 with different ligands, as well as to a binary mixture of different cluster cores, Au-25 and Au-144, protected with the same ligand. Importantly, TLC even enabled the challenging separation of a multicomponent mixture of mixed-monolayer-protected Au-25 clusters with closely similar chemical ligand compositions. We anticipate that the realization of such simple yet efficient separation technique will progress the detailed investigation of cluster properties. - Strong and Elastic Membranes via Hydrogen Bonding Directed Self-Assembly of Atomically Precise Nanoclusters
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-08) Som, Anirban; Griffo, Alessandra; Chakraborty, Indranath; Hähl, Hendrik; Mondal, Biswajit; Chakraborty, Amrita; Jacobs, Karin; Laaksonen, Päivi; Ikkala, Olli; Pradeep, Thalappil; Nonappa2D nanomaterials have provided an extraordinary palette of mechanical, electrical, optical, and catalytic properties. Ultrathin 2D nanomaterials are classically produced via exfoliation, delamination, deposition, or advanced synthesis methods using a handful of starting materials. Thus, there is a need to explore more generic avenues to expand the feasibility to the next generation 2D materials beyond atomic and molecular-level covalent networks. In this context, self-assembly of atomically precise noble nanoclusters can, in principle, suggest modular approaches for new generation 2D materials, provided that the ligand engineering allows symmetry breaking and directional internanoparticle interactions. Here the self-assembly of silver nanoclusters (NCs) capped with p-mercaptobenzoic acid ligands (Na4Ag44-pMBA30) into large-area freestanding membranes by trapping the NCs in a transient solvent layer at air–solvent interfaces is demonstrated. The patchy distribution of ligand bundles facilitates symmetry breaking and preferential intralayer hydrogen bondings resulting in strong and elastic membranes. The membranes with Young's modulus of 14.5 ± 0.2 GPa can readily be transferred to different substrates. The assemblies allow detection of Raman active antibiotic molecules with high reproducibility without any need for substrate pretreatment. - Waterborne Fluorine-Free Superhydrophobic Surfaces Exhibiting Simultaneous CO2 and Humidity Sorption
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-01-01) Baidya, Avijit; Yatheendran, Anagha; Ahuja, Tripti; Sudhakar, Chennu; Das, Sarit Kumar; Ras, Robin H.A.; Pradeep, ThalappilRecent progress in the field of superhydrophobic materials has proven their potential to solve many problems of the contemporary society. However, the use of such materials to capture moisture and CO2 from air, to help reduce the impact of global climate change is not explored. In addition, most of the time, fabrication of these materials needs organic solvents and fluorinated molecules involving multiple steps that hinder the use of nonwettable materials in everyday life. Herein, a waterborne, fluorine-free, robust superhydrophobic material synthesized at room temperature through a one-step chemical-modification process is reported, which exhibits moisture and CO2 capturing capability. While covalently grafted low surface energy hydrocarbon molecules control the bulk superhydrophobicity, the incorporated amine functionalities facilitate moisture and CO2 adsorption as these molecules (H2O and CO2) can easily diffuse through hydrocarbon assemblies. Being polar, H2O molecules are observed to readily interact with amine groups and favor the adsorption process. Synthesized material shows an approximate CO2 adsorption of 480 ppm (10.90 mmol L−1) in ambient conditions having 75% humidity. Multifunctionality along with durability of this material will help expand the applications of superhydrophobic materials.