Добірка наукової літератури з теми "Control surface nano-functionalization"

This short communication presents a simple method of preparation of thin-metal nano-platelets utilizing metal sputtering and lift-off photolithography. The method offers complete control over size, shape and properties of nano-platelets of sub-micrometer thickness. Platelets with a thickness of 50–200 nm and with defined arbitrary shapes and sizes in the range of 15–300 μm were prepared from single or multiple metal layers by magnetron sputtering. Deposition of different metals in layers enabled fabrication of bi- or tri-metallic platelets with a magnetic core and differently composed surfaces. Highly reflective nano-platelets with a magnetic core allowed manipulation by magnetic fields, while different metallic surfaces served for functionalization by selected molecules. Submicron thin nano-platelets are extremely light (e.g., ~20 ng for a 100 μm × 100 μm × 0.1 μm gold nano-platelet) so that they can be attached to surfaces by only a few chemical bonds. At the same time their area is sufficiently large for simple optical recognition of their shape which is intended to label various characteristics depending on the specific surface functionalization of the given shape.

Trifluoropropyl-trichlorosilane reagents were used to tailor the surface chemistry of porous nano-structured thin films fabricated using glancing angle deposition (GLAD). GLAD produces high surface area films of isolated columnar structures and provides complete control over the film morphology. Here, the chemical tunability of these GLAD films was investigated using solution and vapor-phase surface functionalization methods. All films were characterized using scanning electron microscopy, X-ray photoelectron spectroscopy and advancing aqueous contact angle measurements. Our results indicate that the surface chemistry of the GLAD films was effectively changed after functionalization by either approaches. We also note that vapor-phase functionalization provides more consistent results and eliminates the need for organic solvents, making it an ideal method for tailoring the surface properties of GLAD films for specific applications.

Cells are the smallest living units of a human body’s structure and function, and their behaviors should not be ignored in human physiological and pathological metabolic activities. Each cell has a different scale, and presents distinct responses to specific scales: Vascular endothelial cells may obtain a normal function when regulated by the 25 µm strips, but de-function if the scale is removed; stem cells can rapidly proliferate on the 30 nm scales nanotubes surface, but stop proliferating when the scale is changed to 100 nm. Therefore, micro and nano scales play a crucial role in directing cell behaviors on biomaterials surface. In recent years, a series of biomaterials surface with micro and/or nano scales, such as micro-patterns, nanotubes and nanoparticles, have been developed to control the target cell behavior, and further enhance the surface biocompatibility. This contribution will introduce the related research, and review the advances in the micro/nano scales for biomaterials surface functionalization.

DNA SAMs have received a lot of research interest recently as a suitable platform for modern biosensors. However, there are some shortcomings that remain to be addressed, such as uneven coverage of monolayer, or the spacing between the DNA strands that is hard to control. Here, we present DNA nanostructured cubes as an improved platform for DNA SAM based sensors. The DNA nano-cubes allow for a precise control of ssDNA spacing on the surface and have a great functionalization possibility. We have modified the nanostructures to include thiolated surface anchor and a fluorescence reporter. Cubes were deposited gold electrode via Au-S bonds and analyzed, using AFM and in-situ fluorescence microscopy.

Functionalization of a surface with biomimetic nano-/micro-scale roughness (wires) has attracted significant interests in surface science and engineering as well as has inspired many real-world applications including anti-fouling and superhydrophobic surfaces. Although methods relying on lithography include soft-lithography greatly increase our abilities in structuring hard surfaces with engineered nano-/micro-topologies mimicking real-world counterparts, such as lotus leaves, rose petals, and gecko toe pads, scalable tools enabling us to pattern polymeric substrates with the same structures are largely absent in literature. Here we present a robust and simple technique combining anodic aluminum oxide (AAO) templating and vacuum-assisted molding to fabricate nanowires over polymeric substrates. We have demonstrated the efficacy and robustness of the technique by successfully fabricating nanowires with large aspect ratios (>25) using several common soft materials including both cross-linking polymers and thermal plastics. Furthermore, a model is also developed to determine the length and molding time based on nanowires material properties (e.g., viscosity and interfacial tension) and operational parameters (e.g., pressure, vacuum, and AAO template dimension). Applying the technique, we have further demonstrated the confinement effects on polymeric crosslinking processes and shown substantial lengthening of the curing time.

Two-dimensional poly(dimethylsiloxane) (PDMS) films with wavy patterns were studied in order to investigate reversible and irreversible wetting effects. Pre-strained, surface oxidized layers of PDMS were used to form relieved wavy geometries, on which hydrophobic functionalization was carried out in order to produce irreversible wetting effects. Wavy-patterned PDMS films showed time-dependent reversible wetting effects. The degree of surface wettability could be tuned by the choice of wavy groove geometries. And the groove geometries were controlled via O2 plasma treatment and mechanical pre-straining. The pre-strained, buckled PDMS films were applied to the fabrication of hydrophobic polystyrene nano-patterns using colloidal self-assembly, where the colloids were arrayed in two-dimensional way. The wavy polystyrene films were found to be more hydrophobic relative to flat polystyrene films. The grooving methodology used in this study could be applied to enhancing the hydrophobicity of other types of polymeric thin films, eliminating the need for chemical treatment.

Texturing can be used to functionalize the surface of plastic parts and, in particular, to modify the interaction with fluids. Wetting functionalization can be used for microfluidics, medical devices, scaffolds, and more. In this research, hierarchical textures were generated on steel mold inserts using femtosecond laser ablation to transfer on plastic parts surface via injection molding. Different textures were designed to study the effects of various hierarchical geometries on the wetting behavior. The textures are designed to create wetting functionalization while avoiding high aspect ratio features, which are complex to replicate and difficult to manufacture at scale. Nano-scale ripples were generated over the micro-scale texture by creating laser-induced periodic surface structures. The textured molds were then replicated by micro-injection molding using polypropylene and poly(methyl methacrylate). The static wetting behavior was investigated on steel inserts and molded parts and compared to the theoretical values obtained from the Cassie–Baxter and Wenzel models. The experimental results showed correlations between texture design, injection molding replication, and wetting properties. The wetting behavior on the polypropylene parts followed the Cassie–Baxter model, while for PMMA, a composite wetting state of Cassie–Baxter and Wenzel was observed.

Dendrimers are novel three dimensional, hyperbranched globular nano polymeric architectures. Attractive features like nanoscopic size, narrow polydispersity index and excellent control over molecular structure afford dendrimers with ideal drug delivery ability through encapsulating drugs in their interior or covalently conjugating drugs on their surfaces. The adaptable surface functionalization ability enables covalent conjugation of various targeting molecules onto the surface of dendrimers, thereby allowing for generation of various multifunctional nanodevices for targeted drug delivery applications. Drug delivery researchers are especially enthusiastic about possible utility of dendrimers as drug delivery tool. However, to get the maximum benefits of these novel class macromolecules, a research by collaboration is very much essential. Finally, it is one of the youngest and exciting fields of polymer researches where all branches of science can take part and hence, deserves more intensive attention. Keywords: Dendrimers, Drug Delivery, Targeting, Dual Drug Loading, PAMAM

The large surface areas and interlayer gaps of 2D materials enable surface functionalization and intercalation as effective post-synthesis design knobs to tune the properties of 2D materials using ions, atoms, and organic molecules. For complete engineering control, detailed understanding of the interactions between the 2D materials and the molecules adsorbed on 2D materials surface or between the 2D materials and the intercalants is necessary. I will first discuss surface functionalization to tune the electrical properties of 2D materials. We developed an experimental approach to quantitatively measure the doping powers of organic electron donors (OEDs) to monolayer MoS2. Using novel and previously studied OEDs, we demonstrate experimentally that the measured doping power is a sensitive function of molecule’s reduction potential, size, surface coverage, and orientation to 2D materials [1, 2]. I will then discuss electrochemical intercalation into 2D materials to induce novel phases that were previously undetected and to study heterointerface effects on the intercalation induced phase transition [3, 4]. We discover new structural phases in Td-WTe2 and T’-MoTe2 with lithium intercalation and these new phases are semiconducting even though the initial WTe2 and MoTe2 are semimetallic and lithium ions donate electrons to the host materials. In the lithium intercalation-induced phase transition from the 2H to 1T’ phase of MoS2, we show that the nucleation of the 1T’ phase proceeds via heterogeneous nucleation where the nature of heterointerface dictates the thermodynamics of the phase transition. For these studies, multi-modal, in-situ probes were necessary to track the changes in the structure-property relation of the layered materials as a function of intercalation. [1] Advanced Electronic Materials 7, 2000873 (2021). [2] Nano Letters 22, p.4501 (2022). [3] ACS Applied Materials & Interfaces 13, p.10603-10611 (2021). [4] Advanced Materials 34, 2200861 (2022).

In general, nano-emulsions are submicron droplets composed of liquid oil phase dispersed in liquid aqueous bulk phase. They are stable and very powerful systems when it regards the encapsulation of lipophilic compounds and their dispersion in aqueous medium. On the other hand, when the properties of the nano-emulsions aim to be modified, e.g. for changing their surface properties, decorating the droplets with targeting ligands, or modifying the surface charge, the dynamic liquid / liquid interfaces make it relatively challenging. In this study, we have explored the development of nano-emulsions which were not anymore stabilized with a classical low-molecular weight surfactant, but instead, with an amphiphilic polymer based on poly(maleic anhydride-alt-1-octadecene) (PMAO) and Jeffamine®, a hydrophilic amino-terminated PPG/PEG copolymer. Using a polymer as stabilizer is a potential solution for the nano-emulsion functionalization, ensuring the droplet stabilization as well as being a platform for the droplet decoration with ligands (for instance after addition of function groups in the terminations of the chains). The main idea of the present work was to understand if the spontaneous emulsification –commonly performed with nonionic surfactants– can be transposed with amphiphilic polymers, and a secondary objective was to identify the main parameters impacting on the process. PMAO was modified with two different Jeffamine®, additionally different oils and different formulation conditions were evaluated. As a control, the parent monomer, octadecyl succinic anhydride (OSA) was also modified and studied in the similar way as that of polymer. The generated nano-emulsions were mainly studied by dynamic light scattering and electron microscopy, that allows discriminating the crucial parameters in the spontaneous process, originally conducted with polymers as only stabilizer.

L'assemblage de nanoparticules (NPs) couplées a suscité un grand intérêt ces dernières années, en vue d'application dans la détection de composés chimiques (molécule, explosifs, drogues,') appartenant au domaine de la spectroscopie Raman exaltée de surface (SERS) par exemple. Récemment, le couplage de structures périodiques de nanoparticules métalliques NPs a permis de mettre en avant des résonances dites résonances collectives de surface (SLR) résultant du couplage entre les modes plasmon de surface localisé et les modes de diffraction. Ces résonances se caractérisent par une largeur spectrale très fine impliquant une forte exaltation du champ électrique au voisinage des nanoparticules. Dans cette thèse, nous proposons une étude expérimentale vérifiée par le biais de modélisations par la méthode des Différences Finies dans le Domaine Temporel (FDTD), des résonances plasmoniques individuelles et collectives de surfaces supportées par des réseaux périodiques de NPs métalliques élaborés par la technique lithographie électronique. La première partie de cette thèse, mets en évidence les principales caractéristiques optiques, de la NP unique à l'assemblage de NPs en réseau périodique. Ce chapitre est illustré de quelques exemples tirés de la littérature sur l'excitation de ces plasmons de surface, pour engendrer une fonctionnalisation localisée de surface. Dans un deuxième temps, une étude approfondie sur l'amélioration des conditions de morphologie des substrats plasmoniques, en vue d'améliorer le greffage moléculaire au niveau des NPs, est présentée. Puis, nous présentons les résultats obtenus pour une méthode de greffage chimique, mise en place au laboratoire, et qui permet la visualisation directe des modes de réseau, par greffage de films moléculaires organiques dérivés de sels de diazonium, en excitant des modes SLRs. Enfin, la dernière partie porte sur l'étude des réseaux binaires de nanoparticules qui ont révélé l'émergence de deux modes plasmoniques hybrides, provenant de l'asymétrie du motif élémentaire. Nous avons ensuite mené, à l'aide de notre stratégie de greffage, une étude sur la fixation de molécules uniquement dans les zones de maximum d'exaltions des champs électriques en excitant tantôt dans le mode symétrique, tantôt, dans le mode anti-symétrique. Pendant ce doctorat, ces travaux de recherche ont permis une nette amélioration de la compréhension et du contrôle de la localisation du dépôt à l'échelle de la nanoparticule. C'est sur cette base solide qu'il est envisageable d'associer des matériaux déjà connus pour leurs propriétés optiques remarquables (NPs métalliques, boîtes quantiques 'QD), avec un polymère thermosensible (le pNIPAM), permettant un contrôle actif et réversible de l'exaltation (ou l'inhibition) de l'émission de lumière par les QDs, à l'échelle de la NP métallique. Un tel contrôle permettrait une avancée majeure des performances optiques des QDs incorporés dans des composants optiques
The assembly of coupled nanoparticles (NPs) has aroused great interest in recent years, with a view to applications in the detection of chemical compounds (molecules, explosives, drugs,...) belonging to the field of surface exalted Raman spectroscopy (SERS) for example. Recently, the coupling of periodic structures of metallic nanoparticles NPs has allowed to highlight resonances called surface collective resonances (SLR) resulting from the coupling between localized surface plasmon modes and diffraction modes. These resonances are characterized by a very fine spectral width implying a strong exaltation of the electric field in the vicinity of the nanoparticles. In this thesis, we propose an experimental study verified by means of Finite Difference Time Domain (FDTD) modeling, of individual and collective plasmonic resonances of surfaces supported by periodic arrays of metallic NPs elaborated by the electron lithography technique. The first part of this thesis, highlights the main optical characteristics, from the single NP to the assembly of NPs in periodic array. This chapter is illustrated with some examples from the literature on the excitation of these surface plasmons, to generate a localized surface functionalization. In a second step, an in-depth study on the improvement of the morphology conditions of the plasmonic substrates, in order to improve the molecular grafting at the level of the NPs, is presented. Then, we present the results obtained for a chemical grafting method, implemented in the laboratory, which allows the direct visualization of lattice modes, by grafting organic molecular films derived from diazonium salts, by exciting SLRs modes. Finally, the last part deals with the study of binary arrays of nanoparticles which revealed the emergence of two hybrid plasmonic modes, originating from the asymmetry of the elementary pattern. We then carried out, with the help of our grafting strategy, a study on the attachment of molecules only in the regions of maximum exaltions of the electric fields by exciting sometimes in the symmetric mode, sometimes in the anti-symmetric mode. During this PhD, these research works have allowed a clear improvement of the understanding and control of the deposition localization at the nanoparticle scale. It is on this solid basis that it is possible to associate materials already known for their remarkable optical properties (metallic NPs, quantum dots -QDs), with a thermosensitive polymer (pNIPAM), allowing an active and reversible control of the exaltation (or inhibition) of light emission by QDs, at the scale of the metallic NP. Such a control would allow a major advance in the optical performances of QDs incorporated in optical components