Julia Grothe

Graphene Quantum Dots-Capped Magnetic Mesoporous Silica Nanoparticles as a Multifunctional Platform for Controlled Drug Delivery, Magnetic Hyperthermia, and Photothermal Therapy.

A multifunctional platform is reported for synergistic therapy with controlled drug release, magnetic hyperthermia, and photothermal therapy, which is composed of graphene quantum dots (GQDs) as caps and local photothermal generators and magnetic mesoporous silica nanoparticles (MMSN) as drug carriers and magnetic thermoseeds. The structure, drug release behavior, magnetic hyperthermia capacity, photothermal effect, and synergistic therapeutic efficiency of the MMSN/GQDs nanoparticles are investigated. The results show that monodisperse MMSN/GQDs nanoparticles with the particle size of 100 nm can load doxorubicin (DOX) and trigger DOX release by low pH environment. Furthermore, the MMSN/GQDs nanoparticles can efficiently generate heat to the hyperthermia temperature under an alternating magnetic field or by near infrared irradiation. More importantly, breast cancer 4T1 cells as a model cellular system, the results indicate that compared with chemotherapy, magnetic hyperthermia or photothermal therapy alone, the combined chemo-magnetic hyperthermia therapy or chemo-photothermal therapy with the DOX-loaded MMSN/GQDs nanosystem exhibits a significant synergistic effect, resulting in a higher efficacy to kill cancer cells. Therefore, the MMSN/GQDs multifunctional platform has great potential in cancer therapy for enhancing the therapeutic efficiency.

Few-Layer Graphene Shells and Nonmagnetic Encapsulates: A Versatile and Nontoxic Carbon Nanomaterial

In this work a simple and scalable approach to coat nonmagnetic nanoparticles with few-layer graphene is presented. In addition, the easy processing of such nanoparticles to remove their core, leaving only the 3D graphene nanoshell, is demonstrated. The samples are comprehensively characterized, as are their versatility in terms of functionalization and as a material for electrochemical storage. Indeed, these 3D graphene nanostructures are easily functionalized much as is found with carbon nanotubes and planar graphene. Electrochemical investigations indicate these nanostructures are promising for stable long-life battery applications. Finally, initial toxicological investigations suggest no acute health risk from these 3D graphene nanostructures.

High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.

Metal deposition by electroless plating on polydopamine functionalized micro- and nanoparticles

A novel approach for the fabrication of metal coated micro- and nanoparticles by functionalization with a thin polydopamine layer followed by electroless plating is reported. The particles are initially coated with polydopamine via self-polymerization. The resulting polydopamine coated particles have a surface rich in catechols and amino groups, resulting in a high affinity toward metal ions. Thus, they provide an effective platform for selective electroless metal deposition without further activation and sensitization steps. The combination of a polydopamine-based functionalization with electroless plating ensures a simple, scalable, and cost-effective metal coating strategy. Silver-plated tungsten carbide microparticles, copper-plated tungsten carbide microparticles, and copper-plated alumina nanoparticles were successfully fabricated, showing also the high versatility of the method, since the polymerization of dopamine leads to the formation of an adherent polydopamine layer on the surface of particles of any material and size. The metal coated particles produced with this process are particularly well suited for the production of metal matrix composites, since the metal coating increases the wettability of the particles by the metal, promoting their integration within the matrix. Such composite materials are used in a variety of applications including electrical contacts, components for the automotive industries, magnets, and electromagnetic interference shielding.

Precursor strategies for metallic nano- and micropatterns using soft lithography†

Soft lithographic methods describe a set of printing methods which are widely used for the preparation of structured surfaces. Structured surfaces are essential components in the field of (opto-)electronic devices such as organic light emitting diodes, photovoltaics or organic field effect transistors. In recent years, crucial progress has been achieved in the development of patterned metal coatings for these applications. This review focusses on new strategies for soft lithographical printing of metal structures emphasizing the subtle interplay of printing techniques, metal precursor chemistry, and surface functionalization strategies.

Nanoimprint patterning of thin cadmium stannate films using a polymeric precursor route

The synthesis of cadmium stannate (Cd2SnO4 CTO) nanoparticle powders and the deposition and patterning of thin Cd2SnO4 films were achieved via a polymeric precursor approach. Conditions for the phase formation of the cubic spinel phase were evaluated, and for the first time the system was obtained in single phase powder form from a precursor system. Thin Cd2SnO4 films were prepared by spin coating the polymeric precursor solution followed by thermal treatment. Highly transparent and 20 nm thick films with a minimum sheet resistance of 110 Ohm were prepared. A thermal imprint process with PDMS molds was used for patterning of the films in the sub-micrometre range. Nanostructured CTO films are essential to improve structured electrodes in opto-electronic devices such as CdTe-based thin film solar cells.

Metal–Organic Framework/Graphene Quantum Dot Nanoparticles Used for Synergistic Chemo- and Photothermal Therapy

In this study, a simple one-pot method was used to prepare a multifunctional platform for synergistic chemo- and photothermal therapy,, which is composed of zeolitic imidazolate framework-8 (ZIF-8) as drug nanocarriers and the embedded graphene quantum dots (GQDs) as local photothermal seeds. The structure, drug release behavior, photothermal effect, and synergistic therapeutic efficiency of the ZIF-8/GQD nanoparticles were systematically investigated. Using doxorubicin (DOX) as a model anticancer drug, the results showed that monodisperse ZIF-8/GQD nanoparticles with a particle size of 50–100 nm could encapsulate DOX during the synthesis procedure and trigger DOX release under acidic conditions. The DOX-loaded ZIF-8/GQD nanoparticles could efficiently convert near-infrared (NIR) irradiation into heat and thereby increase the temperature. More importantly, with breast cancer 4T1 cells as a model cellular system, the results indicated that the combined chemo- and photothermal therapy with DOX-ZIF-8/GQD nanoparticles exhibited a significant synergistic effect, resulting in a higher efficacy to kill cancer cells compared with chemotherapy and photothermal therapy alone. Hence, ZIF-8/GQD nanoparticles would be promising as versatile nanocarriers for synergistic cancer therapy.

Semi-transparent silver electrodes for flexible electronic devices prepared by nanoimprint lithography

The preparation of mechanically flexible and optically transparent electronic circuits plays a key role in the development of next-generation display technologies. Silver nano-gratings are of particular interest due to their excellent conductivity and adjustable transmittance. Printed on polymeric substrates they are suitable for an application in flexible opto-electronic devices. Here, we present the preparation of a smart silver precursor system combining both the ability of cheap and scalable nanoimprint patterning and simple thermal silver reduction. Homogeneous silver line and grid patterns with line widths down to 400 nm are prepared using poly(dimethylsiloxane) stamps in a thermal nanoimprint lithography process. Relatively low process temperatures allow the film formation on polymeric substrates. Semi-transparent silver electrodes with a resistance of 2.8 ohm are patterned on polyimide foils to prepare flexible electro-luminescence devices. A detailed investigation of the precursors thermal decomposition behaviour as well as the resulting electrical and optical properties of the films is offered.

Preparation and microcontact printing of platinum and palladium thin films

Thin palladium and platinum films were prepared using a polymeric precursor method. For the first time, down to 30 nm thick films were achieved by this method. A precursor solution consisting of ethylene glycol, citric acid, a metal salt and the corresponding acid was deposited by spin coating onto various substrates. The thermal decomposition behavior of these precursors was characterized by thermal analysis methods. Dried and calcined films were characterized by XRD, UV-Vis and IR spectroscopy as well as resistance measurements to get more information about the film formation. The specific resistance of the phase pure platinum films was as low as 1.1 × 10−7 Ω m and that of the palladium films was as low as 6.0 × 10−7 Ω m. In addition, a platinum precursor was used for microcontact printing. Regular line patterns with widths between 800 nm and 15 μm were achieved, as could be shown by AFM and SEM.

Nanocomposites and Hybrid Materials

Within the last two decades nanocomposite materials have gained in importance not only in the academic world but also for industrial applications. The preparation of hybrid materials composed of inorganic nanoparticles in polymeric matrices allows for the development of completely new materials with unique qualities. For the successful preparation of polymer nanocomposites different techniques have been established, including melt processing, solution casting, and in situ processing techniques. The chapter will review the current progress in nanocomposite processing and will present a section of realized applications focusing on optical properties of transparent nanocomposites and specific features of clay composite materials.