Characterization of surfaces (AFM, ATR, Water Contact Angle) Creation of the dextran layer Characterization with optical microscopy and AFM.

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1 BA semester project: 1. Characterization of flat surfaces. The goal of this project is to analyze the surface properties of a Si/SiO2 wafer after the functionalization with hydrophilic and hydrophobic molecules. Characterization of surfaces (AFM, ATR, Water Contact Angle) Contact: Marta Mameli marta.mameli@epfl.ch 2. Optimized method for creation of dextran support layer The aim of this project is the development of an optimized method for creating a thin (<10nm) homogenous layer of polymer (dextran) covalently bound to the surface of glass. This layer will subsequently be used a support for lipid bilayers so as to mimic the cytosqueleton. Creation of the dextran layer Characterization with optical microscopy and AFM. Contact: Kislon Voitchovsky kislon.voitchovsky@epfl.ch

2 Masters semester project: 1. Contact angle for anisotropic amphiphilic nanoparticles Nanoparticles covered with self- assembled monolayers (SAMS) are being extensively studied due to its implications in electronics, optics, biology, or just as building blocks for more complex materials (supracrystals and molecular colloids). SAMS of mixtures of ligands can be used to cover metallic nanoparticles and provide them with different and combine functionalities. These mixtures of ligands can be arranged in: a complete- mixed state, in circular narrow domains or stripes [1], or forming two (Janus) or more patches giving rise too anisotropic nanoparticles [2, 3]. The study of the surface nanostructuration of small nanoparticles is limited to techniques such as STM that are limited to few nanoparticles and can measure only the upper surface of the particles that lye on a substrate. There is a clear need of macroscopic measurements that complement the microscopy techniques and that give average values of the properties of the nanoparticles. One of these techniques is Contact- Angle that can be used to measure surface properties giving direct measurements of the hydrophobicity of a surface (interfacial energy). Here we propose the study of the anisotropy nanoparticles covered with self- assembled monolayers of two different ligands, one hydrophobic and one hydrophilic (amphiphilic nanoparticles) using contact angle as a characterization method. The project consists on the creation of layers of nanoparticles with a vertical orientation (using Langmuir- Blodgett deposition) and with a disordered orientation (using spincasting), and measure the hydrophobicity of them using contact angle measurements. Fig1: Langmuir- Blodgett deposition of amphiphilic Janus nanoparticles in two different orientations. References: 1. Jackson, A.M., J.W. Myerson, and F. Stellacci, Spontaneous assembly of subnanometre-ordered domains in the ligand shell of monolayer-protected nanoparticles. Nature Materials, (5): p Glotzer, S.C. and M.J. Solomon, Anisotropy of building blocks and their assembly into complex structures. Nature Materials, (8): p Perro, A., et al., Design and synthesis of Janus micro- and nanoparticles. Journal of Materials Chemistry, (35-36): p Contact: Javier Reguera javier.reguera@epfl.ch

3 2. Development of an analysis method for scanning probe microscopy (SPM) images The goal of this project is the development of a flexible analysis method (developed typically in Matlab, Igor or equivalent environment) able to analyze and extract meaningful information from SPM images (AFM and STM). Typical SPM images can be difficult to interpret because of the way they are created: through nanoscale local interactions between a probe and a sample. Consequently, the image depends on the nature and the range of the interactions exploited, and a direct correlation between the image and the structure of the sample is not always straightforward. In such cases, additional information about the image/imaging condition is required. Here we propose to develop a tool capable of identifying local structure in the sample (e.g. one type of molecule) from SPM images, and making use of the additional information available (e.g. types of molecules presents, nature of the SPM interaction, possible presence of a solvent, scan direction, etc) Figure 1: Image of the surface of calcite (CaCO3) obtained by AFM in liquid (left). The brighter spots are oxygen atoms. This interpretation is not obvious from the atomic structure of calcite, represented in a cartoon (right) with the oxygen atoms in red, the carbon in black and the calcium in green. The main points of the project are: Identification of the different atoms or molecules on a known surface taking into account additional knowledge available Identification of possible image deformation effects (drift) for a known structure Identification of molecules self- assembled onto curve surfaces (nanoparticles) Simple calculations from the data derived (e.g. nearest- neighbors distance, symmetry) Contact: Kislon Voitchovsky kislon.voitchovsky@epfl.ch

4 3. Synthesis and Characterization of functionalized silica nanoparticles. The goal of this project is to synthetize a batch of functionalized silica nanoparticles that can be suitable for a large range of biological purposes. The student will have to synthetize and characterize one or two dynamic libraries to use for the functionalization of silica nanoparticles that will be characterize in size and composition (Fig 1). Figure 1. Generic scheme for the synthesis of functionalized silica nanoparticles Techniques involved: Classical organic chemistry for the synthesis of the libraries members. Synthesis of functionalized nanoparticles Characterization of the libraries (NMR, UV- vis, Fluorescence). Characterization of nanoparticles (NMR, AFM, TEM, DLS) Contact: Marta Mameli marta.mameli@epfl.ch

5 4. Synthesis and Characterization of silica nanoparticles. Silica nanoparticles are versatile platform with many intrinsic features, such as low toxicity. In the past decades a lot of methods have been used for the synthesis of doped, mesoporus, functionalized particles. The goal of this project is to combine the different synthetic method (view an example in Fig. 1) in order to find the best way to easily obtain small and monodisperse nanoparticles ( 10 nm, doped and not- doped) Figure 1. Strategies for the synthesis of silica nanoparticles. a) Stöber van Blaaderen method; b) reverse microemulsion or water-in-oil method; c) synthesis of silica-core/peg-shell nanoparticles according to Ref 1. Techniques involved: Classical organic chemistry for the synthesis of the silica nanoparticles. Characterization of nanoparticles (NMR, AFM, TEM, DLS) References [1] S. Zanarini, E. Rampazzo, S. Bonacchi, R. Juris, M. Marcaccio, M. Montalti, F. Paolucci, L. Prodi, J. Am. Chem. Soc. 2009, 131, Contact: Marta Mameli marta.mameli@epfl.ch

6 5. Synthesis of water-soluble gold nanoparticles with low polydespersity. Gold nanoparticles covered with a self- assembled monolayer of two dislike ligands such as 11- mercapto- 1- undecanesulphonate (MUS) and octanethiol (OT) have shown really interesting properties such as cell penetration behavior. 1 The properties of these nanoparticles clearly dependent on parameters such as ligand ratio, size or polydispersity, being the last one related to the synthetic methods available. Recently it has bee discovered in our group that these particles can be synthesized by a different method like the proposed by Stucky 2 using mixtures of solvents and producing less polydisperse nanoparticles. However the polydispersity depends on variables such as temperature synthesis concentration or ratio between solvents. Here we proposed the study of those variables in the synthesis of more monodisperse nanoparticles. The candidate should perform different synthesis of gold nanoparticles varying the different synthesis parameters and characterize the size and size distribution of the particles using transmission electron microscopy and image analysis software. (1) Verma, A.; Uzun, O.; Hu, Y. H.; Hu, Y.; Han, H. S.; Watson, N.; Chen, S. L.; Irvine, D. J.; Stellacci, F. Nature Materials 2008, 7, 588. (2) Zheng, N.; Fan, J.; Stucky, G. D. Journal of the American Chemical Society 2006, 128, Contact: Javier Reguera javier.reguera@epfl.ch

7 Masters project: 1. Synthesis and Characterization of Dynamic Libraries and Study of their arrangements on flat and curved surfaces. The goal of this project is to develop dynamic libraries taking advantages of the principles of Dynamic Combinatorial Chemistry and to use them for functionalize flat surfaces and/or silica nanoparticles. The libraries have to be composed by two members that can interact in a reversible way between them. The first members will contain a silane group that will react covalently with the surface and a mobile group for the interaction with the second members. Playing with the length and the chemical composition of the second members, we aim to observe different type of arrangements on the silica surfaces as well as we already observed on gold (Fig.1). Figure 1. Examples of arrangement of a mixture of ligand on gold surfaces Techniques involved: Classical organic chemistry for the synthesis of the libraries members. Synthesis of functionalized nanoparticles and functionalization of flat surfaces. Characterization of the libraries (NMR, UV- vis, Fluorescence). Characterization of flat surfaces and nanoparticles (NMR, AFM, TEM, DLS, ATR, Water Contact Angle, Ellipsometry) Contact: Marta Mameli marta.mameli@epfl.ch

8 2. Z-potential in mixtures of oppositely charged nanoparticles with surface nanostructuration. Nanoparticles covered with self- assembled monolayers (SAMS) are being extensively studied due to its implications in electronics, optics, biology, or just as building blocks for more complex materials (supracrystals and molecular colloids). Recently supracrystals composed of oppositely charged nanoparticles have shown to form diamond- like lattices 1 when they are coprecipitated in a titration experiment. In addition it has been seen with Z- potential that this coprecipitation occurs for charges compensation of 1:1, differently that microparticles or ionic molecules. 2 Fig 1: Z- Potential and UV- Vis absorbance of a coprecipitation of two oppositely charged nanoparticles showing that the decrease in absorbance indicating the precipitation occurs for values of 0 Z- potential, i.e. for charge compensation. MUA Stands for Mercaptoundecano- acid, and TMA for Trimethyl amine undecane thiol. (Image from ref: 2 ). Our group has shown that nanoparticles covered with binary mixtures of dislike ligands show a surface arrangement in narrow domains or stripes. 3 These surface nanostructure provide the nanoparticle with different properties, such as low non- specific adsorption of proteins, 3 cell- penetration 4 or non- monotonic interfacial energy. 5 Here we propose to study the coprecipitation of surface- nanostructured nanoparticles (striped nanoparticles) using Z- potential and UV- Vis spectroscopy. A deviation in the coprecipitation regarding the completely homogeneous nanoparticles would be a clear consequence or the nano- organization on the surface of the nanoparticles. The candidate would need to synthesize the nanoparticles and perform titration experiments with Z- potential and UV- Vis absorption. References: (1) Kalsin, A. M.; Fialkowski, M.; Paszewski, M.; Smoukov, S. K.; Bishop, K. J. M.; Grzybowski, B. A. Science 2006, 312, 420. (2) Kalsin, A. M.; Kowalczyk, B.; Smoukov, S. K.; Klajn, R.; Grzybowski, B. A. Journal of the American Chemical Society 2006, 128, (3) Jackson, A. M.; Myerson, J. W.; Stellacci, F. Nature Materials 2004, 3, 330. (4) Verma, A.; Uzun, O.; Hu, Y. H.; Hu, Y.; Han, H. S.; Watson, N.; Chen, S. L.; Irvine, D. J.; Stellacci, F. Nature Materials 2008, 7, 588. (5) Kuna, J. J.; Voitchovsky, K.; Singh, C.; Jiang, H.; Mwenifumbo, S.; Ghorai, P. K.; Stevens, M. M.; Glotzer, S. C.; Stellacci, F. Nature Materials 2009, 8, 837. Contact: Javier Reguera javier.reguera@epfl.ch

9 3. Size fractionation and hydrodynamic characterization of striped gold nanoparticles. Gold nanoparticles are novel materials that have a wide variety of applications in solar cells, nanophotonics/plasmonics, catalysis, and medicine. It has been demonstrated that wide variety of materials properties depend critically on the size of the NP. However wet chemical synthetic methods for nanoparticle fabrication mostly result in polydisperse size distributions, especially NPs coated with a mixture of ligands on their surface. Thus there is a need for post- synthesis size fractionation of NPs. This can be accomplished by density gradient ultracentrifugation. Figure 1. (Left) AUC data of gold nanoparticle size and density distribution. (Right) TEM micrographs of pre- and post-fractionation of mixed-ligand coated gold nanoparticles Following hydrodynamic characterization of a population of gold NPs by analytical ultracentrifugation (Fig. 1), 1 the student will develop a rigorous method for reproducible fractionation of gold nanoparticles (NPs). There will be some room for preference in this project, as many steps and types of instrumentation are required to go from from nanoparticle synthesis to fractionation and subsequent characterization. Techniques involved: Analytical Ultracentrifugation (AUC). Chemical synthesis of mixed- ligand nanoparticles. Characterization of nanoparticles (NMR, TEM, DLS, UV/VIS). Fractionation through density gradient centrifugation and purification. [1] R. Carney, J.Y. Kim, H. Qian, R. Jin, H. Mehenni, F. Stellacci, & O.M. Bakr, Nature Comm. 2011, 2, 335. Contact: Randy Carney randy.carney@epfl.ch