Colloidal Approach Research Articles

Revealing Intrinsic Functionalization, Structure, and Photo-Thermal Oxidation in Hexagonal Antimonene.

Antimonene is one of the more exciting members of the post-graphene family with promising applications in optoelectronics, energy storage and conversion, catalysis, sensing or biomedicine. Efforts have been focused on developing a large-scale production route, and indeed, through a colloidal approach, high-quality few-layers antimonene (FLA) hexagons have been recently obtained. However, their oxidation behavior remains unexplored, as well as their interface, inner structure, and photothermal properties. Herein, it is revealed that the hexagons have an intrinsic surface functionalization with alkyl thiols that protects the core of the hexagonal flake against oxidation, and displayed inner defects related to the crystal formation during synthesis, as confirmed by cross-sectional scanning transmission electron microscopy energy dispersive X-ray spectroscopy (STEM-EDX) and temperature-dependent X-ray photoelectron spectroscopy (XPS) and selected area electron diffraction (SAED) analysis. A comprehensive study of temperature and laser power-dependent Raman spectroscopy on varying FLA hexagon thicknesses is carried out. Thinner flakes (<20nm) exhibited a blueshift and intensity decrease, contrasting with thicker ones resembling typical exfoliated flakes with a redshift. This work addresses a literature gap, providing insights into hexagonal FLA structure and characterization, and highlighting the influence of surface functional groups on oxidation behavior. Additionally, it emphasizes the potential of antimonene hexagons as building blocks for 2D heterostructures, including combinations with antimonene oxides and other 2D materials.

Plasmonic Particle Integration into Near-Infrared Photodetectors and Photoactivated Gas Sensors: Toward Sustainable Next-Generation Ubiquitous Sensing.

Current challenges in environmental science, medicine, food chemistry as well as the emerging use of artificial intelligence for solving problems in these fields require distributed, local sensing. Such ubiquitous sensing requires components with 1) high sensitivity, 2) power efficiency, 3) miniaturizability, and 4) the ability to directly interface with electronic circuitry, i.e., electronic readout of sensing signals. Over the recent years, several nanoparticle-based approaches have found their way into this field and have demonstrated high performance. However, challenges remain, such as the toxicity of many of today's narrow bandgap semiconductors for NIR detection and the high energy consumption as well as low selectivity of state-of-the-art commercialized gas sensors. With their unique light-matter interaction and ink-based fabrication schemes, plasmonic nanostructures provide potential technological solutions to these challenges, leading also to better environmental performance. In this perspective recent approaches of using plasmonic nanoparticles are discussed for the fabrication of NIR photodetectors and light-activated, energy-efficient gas sensing devices. In addition, new strategies implying computational approaches are pointed out for miniaturizable spectrometers, exploiting the wide spectral tunability of plasmonic nanocomposites, and for selective gas sensors, utilizing dynamic light activation. The benefits of colloidal approaches for device fabrication are discussed with regard to technological advantages and environmental aspects, which are barely considered so far.

(Invited) Plasmonic and Electrochemical Approaches to the Synthesis of Tailored Catalyst Materials

The development of novel photo- and electrocatalytic processes requires the design of catalyst materials that are specifically optimized to take advantage of these driving forces. This talk will describe approaches developed in our lab for (1) using visible light stimulus to control the structure of plasmonically responsive and hybrid materials and (2) using electrodeposition to grow shape-controlled nanostructures on electrode surfaces. In the first case, the reduction of more catalytically active metals onto plasmonically active metals requires fine control over competing reductive and oxidative chemical processes. Differentially modulating the rates of these reactions using only chemical and thermal parameters can be prohibitively challenging. However, excitation of the plasmon resonance of the growing nanoparticles using visible light can yield hybrid structures that are not accessible via standard colloidal approaches. In the second case, while particles synthesized in colloidal solution can be processed and cast onto electrodes, this adds an additional fabrication step—increasing time and cost—and faces challenges in controlling particle dispersion on the surface. Meanwhile, direct chemical reduction-based synthesis of well-defined nanoparticles on electrodes has proven difficult. We have developed an integrated electrochemical approach that enables directed synthesis of shaped nanoparticles on electrode surfaces. Our approach links metal nanoparticle synthesis with real-time monitoring of chemical changes in the reaction solution using a combination of colloidal particle synthesis, electrochemical particle synthesis, and electrochemical measurements. This provides a pathway for the directed adaptation of the extensive library of existing shaped colloidal nanoparticle syntheses to growth on a surface—something that remains a non-trivial challenge.

Depletion Flocculation of High Internal Phase Pickering Emulsion Inks: A Colloidal Engineering Approach to Develop 3D Printed Porous Scaffolds with Tunable Bioactive Delivery.

Flocculation is a type of aggregation where the surfaces of approaching droplets are still at distances no closer than a few nanometers while still remaining in close proximity. In a high internal-phase oil-in-water (O/W) emulsion, the state of flocculation affects the bulk flow behavior and viscoelasticity, which can consequently control the three-dimensional (3D)-printing process and printing performance. Herein, we present the assembly of O/W Pickering high-internal-phase emulsions (Pickering-HIPEs) as printing inks and demonstrate how depletion flocculation in such Pickering-HIPE inks can be used as a facile colloidal engineering approach to tailor a porous 3D structure suitable for drug delivery. Pickering-HIPEs were prepared using different levels of cellulose nanocrystals (CNCs), co-stabilized using "raw" submicrometer-sized sustainable particles from a biomass-processing byproduct. In the presence of this sustainable particle, the higher CNC contents facilitated particle-induced depletion flocculation, which led to the formation of a mechanically robust gel-like ink system. Nonetheless, the presence of adsorbed particles on the surface of droplets ensured their stability against coalescence, even in such a highly aggregated system. The gel structures resulting from the depletion phenomenon enabled the creation of high-performance printed objects with tunable porosity, which can be precisely controlled at two distinct levels: first, by introducing voids within the internal structure of filaments, and second, by generating cavities (pore structures) through the elimination of the water phase. In addition to printing efficacy, the HIPEs could be applied for curcumin delivery, and in vitro release kinetics demonstrated that the porous 3D scaffolds engineered for the first time using depletion-flocculated HIPE inks played an important role in 3D scaffold disintegration and curcumin release. Thus, this study offers a unique colloidal engineering approach of using depletion flocculation to template 3D printing of sustainable inks to generate next-generation porous scaffolds for personalized drug deliveries.

White Roman Goose Feather-Inspired Unidirectionally Inclined Conical Structure Arrays for Switchable Anisotropic Self-Cleaning.

White Roman goose (Anser anser domesticus) feathers, comprised of oriented conical barbules, are coated with gland-secreted preening oils to maintain a long-term nonwetting performance for surface swimming. The geese are accustomed to combing their plumages with flat bills in case they are contaminated with oleophilic substances, during which the amphiphilic saliva spread over the barbules greatly impairs their surface hydrophobicities and allows the trapped contaminants to be anisotropically self-cleaned by water flows. Particularly, the superhydrophobic behaviors of the goose feathers are recovered as well. Bioinspired by the switchable anisotropic self-cleaning functionality of white Roman geese, superhydrophobic unidirectionally inclined conical structures are engineered through the integration of a scalable colloidal self-assembly technology and a colloidal lithographic approach. The dependence of directional sliding properties on the shape, inclination angle, and size of conical structures is systematically investigated in this research. Moreover, their switchable anisotropic self-cleaning functionalities are demonstrated by Sudan blue II/water (0.01%) separation performances. The white Roman goose feather-inspired coatings undoubtedly offer a new concept for developing innovative applications that require directional transportation and the collection of liquids.

Versatile Nanoring Fabrication Assisted by Hole-mask Colloidal Lithography.

Nanomaterials shaped as rings are interesting nanostructures with control of the materials properties at the nanoscale. Nanoring plasmonic resonators provide tunable optical resonances in the near-infrared with application in sensing. Fabrication of nanorings can be carried out via top-down approaches based on electron beam lithography with high control of the ring size parameters but at high cost. Alternatively, fabrication via self-assembly approaches has a higher speed/lower cost but at the cost of control of ring parameters. Current colloidal lithography approaches can provide nanoring fabrication over large areas but only of specific materials and a select set of rings (large ring diameters or small rings with ultrathin walls). We extend Hole-mask Colloidal Lithography to use ring shaped holes, allow the deposition of arbitrary materials, and allow the independent tuning of ring-wall thickness over a large range of values. We present a generic approach for the fabrication of nanorings formed from a range of materials including low cost (e.g., Cu, Al) and nonplasmonic (e.g., W) materials and with control of ring wall thickness and diameter allowing tuning of ring parameters and materials for applications in nanooptics and beyond.

Colloidal Zeta Potential Modulation as a Handle to Control the Crystallization Kinetics of Tin Halide Perovskites for Photovoltaic Applications.

Tin halide perovskites (THPs) have demonstrated exceptional potential for various applications owing to their low toxicity and excellent optoelectronic properties. However, the crystallization kinetics of THPs are less controllable than its lead counterpart because of the higher Lewis acidity of Sn2+, leading to THP films with poor morphology and rampant defects. Here, a colloidal zeta potential modulation approach is developed to improve the crystallization kinetics of THP films inspired by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. After adding 3-aminopyrrolidine dihydro iodate (APDI2) in the precursor solution to change the zeta potential of the pristine colloids, the total interaction potential energy between colloidal particles with APDI2 could be controllably reduced, resulting in a higher coagulation probability and a lower critical nuclei concentration. In situ laser light scattering measurements confirmed the increased nucleation rate of the THP colloids with APDI2. The resulting film with APDI2 shows a pinhole-free morphology with fewer defects, achieving an impressive efficiency of 15.13 %.

Colloidal Zeta Potential Modulation as a Handle to Control the Crystallization Kinetics of Tin Halide Perovskites for Photovoltaic Applications

AbstractTin halide perovskites (THPs) have demonstrated exceptional potential for various applications owing to their low toxicity and excellent optoelectronic properties. However, the crystallization kinetics of THPs are less controllable than its lead counterpart because of the higher Lewis acidity of Sn2+, leading to THP films with poor morphology and rampant defects. Here, a colloidal zeta potential modulation approach is developed to improve the crystallization kinetics of THP films inspired by the classical Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) theory. After adding 3‐aminopyrrolidine dihydro iodate (APDI2) in the precursor solution to change the zeta potential of the pristine colloids, the total interaction potential energy between colloidal particles with APDI2 could be controllably reduced, resulting in a higher coagulation probability and a lower critical nuclei concentration. In situ laser light scattering measurements confirmed the increased nucleation rate of the THP colloids with APDI2. The resulting film with APDI2 shows a pinhole‐free morphology with fewer defects, achieving an impressive efficiency of 15.13 %.

Elucidating Local Structure and Positional Effect of Dopants in Colloidal Transition Metal Dichalcogenide Nanosheets for Catalytic Hydrogenolysis.

Tailoring nanoscale catalysts to targeted applications is a vital component in reducing the carbon footprint of industrial processes; however, understanding and controlling the nanostructure influence on catalysts is challenging. Molybdenum disulfide (MoS2), a transition metal dichalcogenide (TMD) material, is a popular example of a nonplatinum-group-metal catalyst with tunable nanoscale properties. Doping with transition metal atoms, such as cobalt, is one method of enhancing its catalytic properties. However, the location and influence of dopant atoms on catalyst behavior are poorly understood. To investigate this knowledge gap, we studied the influence of Co dopants in MoS2 nanosheets on catalytic hydrodesulfurization (HDS) through a well-controlled, ligand-directed, tunable colloidal doping approach. X-ray absorption spectroscopy and density functional theory calculations revealed the nonmonotonous relationship between dopant concentration, location, and activity in HDS. Catalyst activity peaked at 21% Co:Mo as Co saturates the edge sites and begins basal plane doping. While Co prefers to dope the edges over basal sites, basal Co atoms are demonstrably more catalytically active than edge Co. These findings provide insight into the hydrogenolysis behavior of doped TMDs and can be extended to other TMD materials.

Emerging Era in Colloidal Carriers Approach for Enhanced Transdermal Drug Delivery

Abstract: Colloidal carriers are a promising type of carriers which play a crucial role in transdermal drug delivery and other topical applications. These carriers are usually present in the microscopic size, which offers different methods to enclose and deliver a diverse range of dynamic substances such as medicines, genes, and lipids. They offer distinct advantages by mimicking the natural structure of the skin's lipid bilayers using lipids and allowing the incorporation of different active compounds through the use of polymers. Recently, more advanced technology like artificial intelligence (AI) and machine learning (ML) has been adopted in the pharmaceutical field. The incorporation of artificial intelligence and machine learning techniques in colloidal carriers holds immense promise in revolutionizing the domain of drug delivery and nanomedicine. Machine learning algorithms can undergo training with the use of extensive datasets containing information on drug behavior within the human body, which can predict drug response within the body. Additionally, AI can be employed to anticipate various processes, thereby resulting in an enhanced delivery of medication using carriers. Many studies have shown the use of machine learning (ML) and artificial intelligence (AI) for optimizing the drug-carrying capacity via colloidal carriers. The present review concentrates on various categories of innovative colloidal vehicles in transdermal administration, alongside their penetration technique, benefit, and mechanism in the integumentary system. Outcomes from the different researches are critically assessed and showcase the potential of colloidal carriers to augment the penetration of drugs through the stratum corneum while minimizing adverse effects on the entire system with improved therapeutic effectiveness in various diseases.

Hierarchically Periodic Macroporous Niobium Oxide Architecture for Enhanced Hydrogen Evolution.

The fabrication of periodic macroporous (PM) in Nb2O5 via morphological control is crucial for improving the photocatalytic hydrogen evolution efficiency. In this study, Nb2O5 with PM is synthesized using a straightforward colloidal crystal templating approach. This material features an open, interconnected macroporous architecture with nanoscale walls, high crystallinity, and substantial porosity. Extensive characterization reveals that this hierarchically structured Nb2O5 possesses abundant surface active sites and is capable of capturing light effectively, facilitating rapid mass transfer and diffusion of reactants and markedly suppressing the recombination of photoexcited charge carriers. Macroporous Nb2O5 exhibits superior water-splitting hydrogen evolution performance compared with its bulk and commercial counterparts, achieving a hydrogen production rate of 405µmol g-1 h-1, surpassing that of bulk Nb2O5 (B-Nb2O5) and commercial Nb2O5 (C-Nb2O5) by factors of 5 and 33, respectively. This study proposes an innovative strategy for the design of hierarchically structured PM, thereby significantly advancing the hydrogen evolution potential of Nb2O5.

The more the merrier: optimizing monomer concentration for supersaturation controlled synthesis of stable ultra-small CsPbBr3 nanocrystals for blue emission.

Synthesis of strongly quantum confined and emissive CsPbBr3 perovskite nanocrystals with sizes <4 nm has proven challenging owing to fast nucleation and rapid growth. In this work, ultra-small blue-emitting (∼461 nm) CsPbBr3 nanocrystals with an average particle size of 3.2 nm are synthesized via a high-temperature (170 °C) colloidal approach by controlling the supersaturation reaction conditions. Our approach yielded stable nanocrystals with uniform size, shape, and excellent color purity, making them promising for blue light emitting diode (LED) applications.

Fluorination of antimonene hexagons.

Fluorination of two-dimensional (2D) antimonene hexagons synthesized through a colloidal bottom-up approach has been explored using microwave-induced plasma and reactive ion etching fluorination strategies through the generation of CF4. The stability of the fluorine bond has been corroborated through DFT calculations. This work paves the way for further halogen-derivative modifications of heavy 2D pnictogens.

Degenerately doped metal oxide nanocrystals for infrared light harvesting: insight into their plasmonic properties and future perspectives.

The tuneability of the localized surface plasmon resonance (LSPR) of degenerately doped metal oxide (MOX) nanocrystals (NCs) over a wide range of the infrared (IR) region by controlling NC size and doping content offers a unique opportunity to develop a future generation of optoelectronic and photonic devices like IR photodetectors and sensors. The central aim of this review article is to highlight the distinctive and remarkable plasmonic properties of degenerately or heavily doped MOX nanocrystals by reviewing the comprehensive literature reported so far. In particular, the literature of each MOX NC, i.e. ZnO, CdO, In2O3, and WO3 doped with different dopants, is discussed separately. In addition to discussion of the most commonly used colloidal synthesis approaches, the ultrafast dynamics of charge carriers in NCs and the extraction of LSPR-assisted hot-carriers are also discussed in detail. Finally, future prospective applications of MOX NCs in IR photodetectors and photovoltaic (PV) self-powered chemical sensors are also presented.

From cubane-assembled Mn-oxo clusters to monodispersed manganese oxide colloidal nanocrystals.

The assemblies of [M4O4] (M = metal) cubanes represent a fascinating class of materials for a variety of application fields. Although such a structural characteristic is relatively common in small molecules and in extended bulk solids, high nuclearity clusters composed of multiple [M4O4] units as their backbones are rare. In this work, we report two new Mn-oxo clusters, MnII 8MnIII 10O10(OOCMe)12(OMe)14(py)2 ([Mn18-Ac]) and MnII 4MnIII 14O14(OOCCMe3)8(OMe)14(MeOH)5(py) ([Mn18-Piv]), whose core structures are assemblies of either 6- or 7-cubanes in different packing patterns, which have been unambiguously revealed by single crystal X-ray diffraction technique. The cubane-assembled structural features can be deemed as the embryonic structures of the bulk manganese oxide. Herein, this report demonstrates the first case study of utilizing Mn-oxo clusters as precursors for the preparation of manganese oxide nanocrystals, which has never been explored before. Through a simple colloidal synthetic approach, high-quality, monodisperse Mn3O4 nanocrystals can be readily prepared by employing both precursors, while their morphologies were found to be quite different. This work confirms that the structural similarity between precursors and nanomaterials is instrumental in affording more kinetically efficient pathways for materials formation, and the structure of the precursor has a significant impact on the morphology of final nanocrystal products.

Interplay between the oxidation process and cytotoxic effects of antimonene nanomaterials.

Pnictogen nanomaterials have recently attracted researchers' attention owing to their promising properties in the field of electronic, energy storage, and nanomedicine applications. Moreover, especially in the case of heavy pnictogens, their chemistry allows for nanomaterial synthesis using both top-down and bottom-up approaches, yielding materials with remarkable differences in terms of morphology, size, yield, and properties. In this study, we carried out a comprehensive structural and spectroscopic characterization of antimony-based nanomaterials (Sb-nanomaterials) obtained by applying different production methodologies (bottom-up and top-down routes) and investigating the influence of the synthesis on their oxidation state and stability in a biological environment. Indeed, in situ XANES/EXAFS studies of Sb-nanomaterials incubated in cell culture media were carried out, unveiling a different oxidation behavior. Furthermore, we investigated the cytotoxic effects of Sb-nanomaterials on six different cell lines: two non-cancerous (FSK and HEK293) and four cancerous (HeLa, SKBR3, THP-1, and A549). The results reveal that hexagonal antimonene (Sb-H) synthesized using a colloidal approach oxidizes the most and faster in cell culture media compared to liquid phase exfoliated (LPE) antimonene, suffering acute degradation and anticipating well-differentiated toxicity from its peers. In addition, the study highlights the importance of the synthetic route for the Sb-nanomaterials as it was observed to influence the chemical evolution of Sb-H into toxic Sb oxide species, playing a critical role in its ability to rapidly eliminate tumor cells. These findings provide insights into the mechanisms underlying the dark cytotoxicity of Sb-H and other related Sb-nanomaterials, underlining the importance of developing therapies based on controlled and on-demand nanomaterial oxidation.

Layered 2D material heterostructures – a colloidal perspective

The development and ongoing discovery of 2D materials and their optical and electronic properties led to interest in the stacking of different 2D materials into layered heterostructures, giving rise to a number of colloidal approaches.

Operando and Dynamic XAS Studies of Metal-Support Interactions of Iridium-Based Catalysts for Oxygen Evolution Reaction (OER) in Proton Exchange Membrane Water Electrolysis (PEMWE)

Iridium (Ir) is an important electrocatalyst material for the oxygen evolution reaction (OER) in acidic media. However, high loadings of very costly and scarce Ir are needed to achieve sufficient performance in proton exchange membrane water electrolysis (PEMWE). [1] To establish a large-scale green hydrogen economy based on PEMWE in the near future, the Ir loading needs to be further reduced. In the last decades, promising Ir-based catalyst strategies has been developed to improve the OER activity by controlling the size of Ir nanoparticles (NPs) [2] and tuning the electronic interactions of the Ir NPs with the catalyst support material, referred to as strong metal support interaction (SMSI). The latter has frequently been observed for heterogeneous catalysts (e.g. Au NPs supported on titanium oxide [3]), while the SMSI for Ir-based OER electrocatalysts is poorly understood to date.This study focuses on operando and dynamic X-ray absorption spectroscopy (XAS) analysis of Ir NPs deposited on three support materials: graphitized carbon (C), titanium oxide (TiO2) and antimony-doped tin oxide (ATO). The surfactant-free Ir NPs with controlled size of around 1 nm were obtained by a colloidal approach in low-boiling point alcohols. [2, 4] Afterwards, the Ir NPs were homogeneously distributed on different support materials with similar loadings and particle sizes confirmed by TEM and XRD. Solute components from the aged catalyst materials (Ir and/or support material) in the electrolyte solution were determined by ICP-OES, while the solid catalyst powders were analysed by TGA and µ-XRF. Our first/initial electrochemical results by recording cyclic voltammetry (CV) profiles show that after the immobilization the Ir NPs obtained from the same batch are strongly oxidized on TiO2, while a metallic character of the Ir is still observed on the C and ATO. The OER mass activity of 120±8 A/gIr for Ir/C is 2-times higher than for Ir/TiO2 (60±6 A/gIr) and 1.2-times higher than for Ir/ATO (95±4 A/gIr) at 1.5 VRHE,iR-free and 25 °C obtained from rotating disc electrode (RDE) setup.Operando and dynamic Ir LIII edge XANES measurements during the cycling from 0.06 to different upper potentials (0.8, 1.0, 1.2, 1.4 and 1.6 VRHE) at 2 mV/s were performed in acidic media at the SuperXAS (X10DA) beamline, Switzerland. All measurements were carried out using a home-made spectro-electrochemical flow-cell. Principal component analysis (PCA) of Quick-XANES data confirmed the tendencies of the formation of irreversible Irz+ species on TiO2 even at low upper potentials, while ATO and C tend to retain the metallic character of the Ir NPs. From the PCA, two independent components were identified to describe the changes in the series of XANES data. The compositions of these components were then analyzed using linear combination fitting (LCF).For 60 wt.% Ir/C, the cycling up to 1.4 VRHE shows two components with 50:25:25 wt.% of Ir0:Ir3+:Ir4+ and 42:0:58 wt.% of Ir0:Ir3+:Ir4+ obtained from the PCA and LCF analysis. During the cycling, the ratios of these components change gradually. In spite of the strong hysteresis behavior, we observed that the ratio between both components reverses to the initial state. In other words, only the component with 42:0:58 wt.% of Ir0:Ir3+:Ir4+ is present at 1.4 VRHE, while the other component is dominant at lower anodic potential.In the same experiment, the analysis of our data for 60 wt% Ir/ATO using PCA indicates two independent components with 74:11:15 wt.% of Ir0:Ir3+:Ir4+ and 70:0:30 wt.% of Ir0:Ir3+:Ir4+. The cycling up to 1.4 VRHE shows similar behavior like 60 wt.% Ir/C.Although the same batch of colloidal Ir NPs were used for the immobilization, the PCA and LCF analysis for 60 wt.% Ir/TiO2 reveal two components with high content of Ir4+ species, more precisely 36:64 wt.% of Ir0:Ir4+ and 2:98 wt.% of Ir0:Ir4+. The cycling up to 1.4 VRHE shows mainly a reversible behavior due to high content of Ir4+ species on TiO2. With increasing anodic potential, the content of metallic Ir further decreases and the main component with almost only Ir4+ species is stable at 1.4 VRHE. In the backward direction, the reduction to metallic Ir takes place to small extent. Therefore, the component with 36:64 wt.% of Ir0:Ir4+ is mainly present at 0.06 VRHE.In summary, our PCA and LCF analysis of the operando and dynamic Quick-XANES data provide further insights into the electronic structure of Ir species and the mechanism of the complex metal-support interaction for Ir NPs immobilized on C, ATO and TiO2.

Antibacterial Aerogels-Based Membranes by Customized Colloidal Functionalization of TEMPO-Oxidized Cellulose Nanofibers Incorporating CuO.

An innovative colloidal approach is proposed here to carry out the customized functionalization of TEMPO-Oxidized Cellulose Nanofibers (CNF) incorporating non-noble inorganic nanoparticles. A heterocoagulation process is applied between the delignified CNF and as-synthetized CuO nanoparticles (CuO NPs) to formulate mixtures which are used in the preparation of aerogels with antibacterial effect, which could be used to manufacture membranes, filters, foams, etc. The involved components of formulated blending, CNF and CuO NPs, were individually obtained by using a biorefinery strategy for agricultural waste valorization, together with an optimized chemical precipitation, assisted by ultrasounds. The optimization of synthesis parameters for CuO NPs has avoided the presence of undesirable species, which usually requires later thermal treatment with associated costs. The aerogels-based structure, obtained by conventional freeze-drying, acted as 3D support for CuO NPs, providing a good dispersion within the cross-linked structure of the nanocellulose and facilitating direct contact of the antibacterial phase against undesirable microorganisms. All samples showed a positive response against Escherichia coli and Staphylococcus aureus. An increase of the antibacterial response of the aerogels, measured by agar disk diffusion test, has been observed with the increase of CuO NPs incorporated, obtaining the width of the antimicrobial "halo" (nwhalo) from 0 to 0.6 and 0.35 for S. aureus and E. coli, respectively. Furthermore, the aerogels have been able to deactivate S. aureus and E. coli in less than 5 h when the antibacterial assays have been analyzed by a broth dilution method. From CNF-50CuO samples, an overlap in the nanoparticle effect produced a decrease of the antimicrobial kinetic.

Green Colloidal Synthesis of MoS2 Nanoflakes.

Currently, two approaches dominate the large-scale production of MoS2: liquid-phase exfoliation, referred to as the top-down approach, and bottom-up colloidal synthesis from molecular precursors. Known colloidal synthesis approaches utilize toxic precursors. Here, an alternative green route for the bottom-up synthesis of MoS2 nanoflakes (NFs) is described. The NFs were synthesized by colloidal synthesis using [Mo(CH3COO)2]2 and a series of sulfur (S)-precursors including thioacetamide (TAA), 3-mercaptopropionic acid (3-MPA), l-cysteine (L-CYS), mercaptosuccinic acid (MSA), 11-mercaptoundecanoic acid (MUA), 1-dodecanethiol (DDTH), and di-tert-butyl disulfide (DTBD). While TAA, an S-precursor most commonly used for MoS2 NF preparation, is a known carcinogen, the other investigated S-precursors have low or no known toxicity. High-resolution scanning transmission electron microscopy (HR-STEM) and grazing incidence wide-angle X-ray scattering (GIWAXS) confirmed that in all cases, the syntheses yielded single-layer MoS2 NFs with lateral sizes smaller than 15 nm and a well-defined crystal structure. Electronic absorption and Raman spectra showed characteristic features associated with the MoS2 monolayers. The evolution of the absorption spectra of the growth solution during the syntheses reveals how the kinetics of the NF formation is affected by the S-precursor as well as the nature of the coordinating ligands.