Publications

Abstract Soft nanomaterials can form stimuli-responsive self-assembled structures with significant potential for pharmaceutical and biomedical applications. Polymer/surfactant (P/S) solutions and hydrogels, in particular, have drawn great interest for the development of effective delivery systems, yet molecular insight into these systems and their mechanisms of action is still needed. Here, we examine the colloidal properties of mixtures comprising the amino acid-derived surfactant 14Lys10 and the amphiphilic triblock copolymers Pluronic F127 and P84, which have distinct hydrophobic/hydrophilic balances. We hypothesized that the two F127/14Lys10 and P84/ 14Lys10 systems would show strong, complex associative behavior and this was indeed observed. Combined data from light and electron microscopy, differential scanning microcalorimetry, rheology and surface tension provide a comprehensive picture. At room temperature, the bio-inspired surfactant forms a gel network of entangled nano and micro-tubes that transitions into vesicles at 33 degrees C. The polymers form micelles upon heating. When mixed, the polymer significantly decreases the strength of the tube network and lowers the tube-to-vesicle transition temperature, with the effect strongly dependent on polymer concentration and hydrophobic/hydrophilic balance. Upon tube disassembly, evidence indicates the formation of mixed vesicles coexisting with mixed micelles. Molecular-level insights into the interactions and self-assembly phenomena are provided. This study opens avenues for rationally designing hybrid soft materials as advanced functional biomaterials in nano-medicine and pharmaceutics.

Abstract Polymeric hydrogels are traditionally employed as drug reservoirs in topical delivery, but they can also function as scaffolds for drug-loaded nanocarriers, enabling hybrid systems with enhanced performance. In this work, we report a thermo-adaptive hybrid hydrogel-composed of a block copolymer scaffold and a network of surfactant-based nano- and microtubes-which exhibits a mechanism herein termed inversely coupled thermogelation (ICT). The scaffold consists of Pluronic F127, a biocompatible triblock copolymer that transitions from micellar solution to a cubic liquid crystalline gel upon heating. The tubular network arises from the self-assembly of biomimetic lysine-derived surfactants. Crucially, when the block copolymer/surfactant hybrid is heated from 20 degrees C to 35 degrees C (approx. skin temperature), the surfactant tubes disassemble into micelles or vesicles, while the block copolymer forms the cubic phase. Accordingly, a tube-dominated gel evolves into a block copolymer-dominated gel through a gel-solution-gel sequence uniquely driven by the opposing thermal responses of the two constituents. This results in a hybrid system that is not only spreadable, self-healing, and mechanically robust, but also well-suited for sustained topical delivery. Imaging, calorimetry, and rheology provide detailed insights into the structure, phase transitions, and flow behavior of the hybrid system and its individual components. As a proof-of-concept, the gel enables slow, sustained release of a fluorescent model probe (carboxyfluorescein), exhibits excellent cytocompatibility, and promotes high cell internalization. Overall, this ICT-based strategy establishes a versatile and sustainable platform with strong potential for long-term topical drug delivery.

Abstract Stimuli-responsive surfactant self-assembly offers versatile opportunities to tailor colloidal structure and function through simple formulation strategies. Here, we report a photoresponsive catanionic vesicle system composed of the double-chained cationic surfactant didodecyldimethylammonium bromide (DDAB) and an anionic amphiphilic 2-hydroxychalcone derivative bearing a sulfonate headgroup (C8SCh). The self-assembly and phase behavior of the individual components and their mixtures are characterized, revealing a broad vesicle-forming compositional range. Notably, three molar fractions (xCh = 0.10, 0.20, and 0.80) yield dispersions composed exclusively of vesicles, enabling the formation of either positively or negatively charged vesicles using the same pair of molecular building blocks. Strong synergistic interactions between DDAB and C8SCh are evidenced by markedly reduced critical aggregation concentrations and negative interaction parameters. The incorporation of the chalcone photoswitch endows the vesicles with light responsiveness, inducing composition-dependent morphological rearrangements in both DDAB-rich and C8SCh-rich regimes. Under mildly acidic conditions (pH = 4.5), partial conversion of the chalcone to its flavylium form introduces an additional, independent stimulus that further modulates the structure of C8SCh-rich vesicles. This intrinsic charge tunability enables highly efficient, charge-selective electrostatic entrapment of both anionic and cationic molecular probes-carboxyfluorescein (CF) and doxorubicin (DOX), respectively-without the need for active loading strategies. Importantly, cargo release is selectively modulated by vesicle composition and external stimuli: light stimulation enhances the release of CF from DDAB-rich vesicles, while the combined action of acidification and irradiation significantly increases DOX release from C8SCh-rich vesicles. Overall, these results establish a simple catanionic system in which surface charge, morphology, and release behavior are jointly controlled by composition, light, and pH, offering a versatile and readily formulated platform with potential applications in controlled delivery.

Abstract Electrochemical energy conversion technologies are central to sustainable power generation, yet sluggish oxygen reduction reaction (ORR) kinetics remain a key limitation in alkaline fuel cells. Although Pt-based electrocatalysts are highly active, their cost and scarcity motivate the development of sustainable, carbon-based alternatives. Here, biochars derived from different parts of an abundant invasive plant, water hyacinth (WH), namely bulbs, wood and leaves, were prepared, screened, and evaluated as ORR electrocatalysts. Among them, bulb-derived biochar (WHB) showed the highest potential, and nitrogen doping produced the most pronounced enhancement. N-doped WHB exhibited an onset potential of 0.85 V, a limiting current density of-3.19 mA center dot cm-2, an electron transfer number of nO2 = 3.16 and a Tafel slope of 57 mV center dot dec-1, approaching Pt/C in activity metrics. XPS and Raman analyses linked these improvements to favorable nitrogen speciation-particularly graphitic N-and increased structural disorder. In parallel, layer-by-layer (LbL) hybridization with multi-walled carbon nanotubes (MWNTs) provided complementary insight into structure-performance relationships. Hybridization improved ORR activity when the base material was pristine WHB (among the nanocomposites, 3:1 WHB:N-MWNT performed best, with Eonset 1/4 0.81 V, jL =-3.37 mA center dot cm-2, nO2 = 3.12, and TS = 76 mV center dot dec-1), consistent with effective integration of porous biochar and conductive nanotube pathways. In contrast, adding MWNTs to already highly active N-WHB reduced performance, likely due to dilution of catalytic sites and disruption of active interfaces. Overall, this study demonstrates invasive biomass as a viable feedstock for high-performance, Pt-free ORR catalysts and highlights when chemical tuning versus hybrid assembly is most beneficial for catalyst design.

Abstract A comprehensive thermodynamic and supramolecular characterization was conducted on a series of phenanthroline-based organic semiconductors and related derivatives, including 1,10-phenanthroline (PHEN), neocuproine (DMPHEN), bathophenanthroline (BPHEN), and bathocuproine (BCP), to elucidate how systematic molecular substitution affects their stability, volatility, and optoelectronic properties. Heat capacity and phase-transition studies, including vapor-pressure measurements, provided a consistent thermodynamic framework for these materials. Analysis of heat capacities revealed that methyl and phenyl groups contribute independently and additively, supporting transferable models for predicting thermal behavior. Thermogravimetric analysis showed that phenyl substitution enhances thermal stability (BPHEN, BCP), whereas methyl substitution slightly decreases it. Differential scanning calorimetry revealed distinct phase behaviors: PHEN is sensitive to hydration, DMPHEN exhibits polymorphism, BPHEN tends to form a glass, and BCP crystallizes reproducibly. Sublimation studies using Knudsen effusion coupled with a quartz crystal microbalance yielded enthalpic and entropic parameters clarifying volatility trends. Complementary supramolecular analysis identified the key pi-pi stacking, C-H & centerdot;& centerdot;& centerdot;N and C-H & centerdot;& centerdot;& centerdot;pi interactions underlying crystal cohesion. UV-vis spectroscopy further provided the band gap energies, which are relevant to optoelectronic performance. By correlating thermodynamic data with supramolecular organization and molecular structure, this study establishes a rigorous framework for the rational design and processing of phenanthroline derivatives in robust and efficient organic electronic devices.

Abstract A systematic investigation of thin films of pyridinium-based ionic liquids (ILs), [C n py][NTf2] (n = 2-9), deposited via physical vapor deposition on ITO and Au/ITO substrates is presented, providing the first comprehensive study of vacuum-deposited films within this homologous series. The influence of evaporation temperature, deposition rate, alkyl chain length, and substrate on thin-film morphology, nucleation and coalescence dynamics, interfacial behavior, and film structure was examined using SEM, optical microscopy, FTIR, and XPS. SEM analyses reveal that higher evaporation temperatures, which increase the deposition rate, lead to larger droplets and enhanced coalescence, resulting in larger microstructures. A comparison of the film morphologies across the IL series shows that longer cation alkyl chains further enhance lateral spreading and wetting, particularly on Au substrates. An odd-even effect on the morphological characteristics of the films is observed across the series, reflecting subtle differences in interfacial interactions. Moreover, a clear distinction in wetting behavior between short- and long-chain pyridinium ILs is evident, consistent with trends previously reported for imidazolium-based ILs. FTIR spectra comparing bulk and thin IL films confirm that the ILs retain their chemical integrity upon film formation. XPS measurements support the morphological observations, highlighting that ILs comprising longer alkyl chains achieve more complete surface coverage. The results of this work provide fundamental insights into the interplay between the cation alkyl chain length of pyridinium-based ILs, substrate interactions, and film formation dynamics, offering guidance for the rational design of IL films for functional surface applications.

Abstract This work investigates the potential of betaine as a substitute for choline chloride in the formation of polyol-based DES. The solid-liquid equilibrium (SLE) phase diagrams of binary mixtures of betaine with one polyol (ethylene glycol, 1,3-propanediol, glycerol, meso-erythritol, xylitol, or sorbitol) were studied across the entire composition range. Experimental measurements of the phase diagrams were limited by the thermal degradation of betaine and by the boiling points or high viscosities of some polyols. Overall, betaine exhibited negative deviations from ideality, while most polyols displayed near-ideal behaviour. COSMO-RS, a thermodynamic model, satisfactorily predicts these deviations from ideality and the observed phase behaviour. Mixtures of betaine and polyols yielded a narrower liquid-phase window for room-temperature applications than the corresponding choline chloride systems. The cross-association of betaine with polyols is more favourable than its self-association, and stronger interactions between the polyols and betaine than with choline chloride are expected, leading to more negative deviations; thus, the smaller melting temperature depression must result from a higher enthalpy of fusion of betaine than that of choline chloride.

Abstract The biphasic transfer of Eu(NO3)3 by trioctylphosphine oxide (TOPO) diluted in a molecular diluent or as a component of a hydrophobic eutectic solvent (HES) was studied by two-phase isothermal titration calorimetry and complemented by XAS, FTIR, and NMR spectroscopy. In HES, the solvent intermolecular interactions introduce an enthalpic penalty, which is overcompensated by a reduction of the entropic cost of Eu(III) phase transfer, resulting in enhanced metal partitioning.

Abstract Hydroponics is an advanced agricultural technique that involves growing plants without soil. Instead, plants are cultivated in a nutrient-rich water solution that provides all the essential minerals they need to thrive, allowing plants to grow either with their roots directly in the solution or supported by inert substrates like pine bark, coconut husk fiber, and rice husk. The solid waste generated from hydroponic cultivation is valuable due to its low cost, abundance, biodegradability, and renewability. These residues are rich in lignocellulosic materials, which can be extracted and refined to produce cellulose and nanocellulose (NC). In this work, cellulose and nanocellulose were extracted from residues of coconut husk fiber and a mixture of pine bark and coconut husk fiber, used in tomato and strawberry hydroponics, respectively. The residues were ground, washed, and chemically treated to obtain cellulose and NC. The chemical process involved several stages: (i) acid treatment, alkaline treatment, and bleaching to isolate cellulose, and (ii) acid hydrolysis followed by ultrasonication to obtain NC. Both materials underwent characterization using various techniques such as TGA, DSC, XRD and FTIR-ATR, which confirmed very low levels of lignin and hemicellulose. Morphological characterization through SEM revealed the presence of micro- and nano-crystals in the cellulose and NC samples, respectively, highlighting the effectiveness of the extraction method. The high purity and quality of the extracted materials make them competitive with commercially available products, suitable for applications in healthcare, food packaging, and automotive industries, while supporting recycling and reuse principles.

Abstract Extensive research has focused on films formed by pure ionic liquids (ILs). However, growing interest in IL mixtures and their synergistic properties presents new opportunities for targeted applications and fundamental scientific investigations. This study explores the morphology of films composed of mixtures of two ILs, [C2C1im][OTf] and [C8C1im][OTf], co-deposited via physical vapor deposition (PVD)/vacuum thermal evaporation. The primary objective was understanding how varying the IL ratio influences droplet formation, surface coverage, and overall film structure. Thin-film growth was examined on glass substrates coated with indium tin oxide (ITO) and ITO/glass surfaces coated with metallic films (Au and Ag). Film morphology was characterized using optical and high-resolution scanning electron microscopy (SEM), while elemental composition was analyzed via X-ray photoelectron spectroscopy (XPS). The results show that IL mixture morphology is strongly influenced by both IL composition and substrate type. Increasing [C8C1im][OTf] content led to larger microstructures due to improved wetting, particularly on Au surfaces, resulting in nearly fully coalesced films. Metallic surfaces near ITO significantly impacted droplet behavior, with ILs exhibiting a strong affinity for metals, especially when the long-chain IL dominated the mixture. The IL-assisted crystallization of rubrene, a high-performance organic semiconductor (OSC) that typically exhibits poor crystallinity when deposited via PVD, highlights the potential of IL mixtures to enhance organic film quality. X-ray diffraction (XRD) confirmed that [C2C1im][OTf] and [C8C1im][OTf] mixtures significantly improved rubrene crystallinity, demonstrating their potential to create an optimal environment for OSC solubility and crystallization.