Magnetic aerogels from FePt and CoPt3 directly from organic solution

Here the synthesis of magnetic aerogels from iron platinum and cobalt platinum nanoparticles is presented. The use of hydrazine monohydrate as destabilizing agent triggers the gelation directly from organic solution, and therefore a phase transfer to aqueous media prior to the gelation is not necessary. The aerogels were characterized through Transmission Electron Microscopy, Scanning Electron Microscopy, Powder X-Ray Diffraction Analysis and Argon Physisorption measurements to prove the formation of a porous network and define their compositions. Additionally, magnetization measurements in terms of hysteresis cycles at 5 K and 300 K (M-H-curves) as well as zero field cooled-field cooled measurements (ZFC-FC measurements) of the dried colloids and the respective xero- and aerogels were performed, in order to analyze the influence of the gelation process and the network structure on the magnetic properties

Photoluminescence Lifetime Based Investigations of Linker Mediated Electronic Connectivity Between Substrate and Nanoparticle

The evolution of systems based on nanoparticles as the main component seems to be a self-accelerating process during the last five decades. Hence, an overview across this field gets more and more challenging. It is sometimes rewarding to focus on the fundamental physical phenomenon of the electronic interconnection between the different building blocks of the obtained devices. Therefore, the investigation of charge transport among the utilized particles and their substrate is one of the mandatory steps in the development of semiconductor nanoparticle based devices like e.g., sensors and LEDs. The investigation of the influence of tunneling barriers on the properties of nanoparticle-functionalized surfaces is a challenging task. The different basic influences on the charge transport dynamics are often difficult to separate from each other. Non-invasive and easily viable experiments are still required to resolve the charge distributing mechanisms in the systems. In the presented work, we want to focus on thin and transparent indium tin oxide (ITO) layers covered glass slides since this substrate is frequently utilized in nanoelectronics. CdSe/CdS nanorods (NRs) are applied as an optically addressable probe for the electronic surface states of the conductive glass. The presented experimental design provides the proof of electronic interconnections in ITO coated glass/linker/NR electrodes via easy reproducible functionalization and polishing experiments. UV/Vis absorption and photoluminescence (PL) lifetime measurements revealed changes in the optical properties caused by differences in the charge carrier dynamics between the system. Our work is focused on the modification of charge carrier dynamics due to the application of linker molecules with different functional groups like (3-mercaptopropyl)methoxysilane (MPTMS) and (3-aminopropyl)trimethoxysilane (APTMS). The presented observations are explained with a simple kinetic model

Patterning of Nanoparticle‐Based Aerogels and Xerogels by Inkjet Printing

Nanoparticle-based voluminous 3D networks with low densities are a unique class of materials and are commonly known as aerogels. Due to the high surface-to-volume ratio, aerogels and xerogels might be suitable materials for applications in different fields, e.g. photocatalysis, catalysis, or sensing. One major difficulty in the handling of nanoparticle-based aerogels and xerogels is the defined patterning of these structures on different substrates and surfaces. The automated manufacturing of nanoparticle-based aerogel- or xerogel-coated electrodes can easily be realized via inkjet printing. The main focus of this work is the implementation of the standard nanoparticle-based gelation process in a commercial inkjet printing system. By simultaneously printing semiconductor nanoparticles and a destabilization agent, a 3D network on a conducting and transparent surface is obtained. First spectroelectrochemical measurements are recorded to investigate the charge–carrier mobility within these 3D semiconductor-based xerogel networks

Electronic transport in CdSe nanoplatelet based polymer fibres

One of the most significant objectives in the field of nanotechnology is the transfer of specific properties of smaller nanoparticle building blocks into larger units. In this way, nanoscopic properties can be linked to the macroscopic addressability of larger systems. Such systems might find applications in fields like photoelectrochemical sensing or solar energy harvesting. Our work reports on the novel synthesis of hybrid semiconductor/polymer fibres, which are based on stacks of 4 monolayer (ML) thick CdSe nanoplatelets (NPLs) encapsulated into a polymer shell. The polymer encapsulation not only enables the water transfer of the NPL stacks but also allows the preparation of photoelectrodes by linking the fibres to surface modified indium tin oxide (ITO) glass slides. By applying electrochemical techniques like intensity modulated photocurrent spectroscopy (IMPS), it was possible to prove the motion of charge carriers inside the nanoplatelet stacks and by this the electronic addressibility of them

Spectroelectrochemical Investigation of the Charge Carrier Kinetics of Gold-Decorated Cadmium Chalcogenide Nanorods

The interfacial transfer of charge carriers across the semiconductor nanoparticle/electrolyte boundary is an elementary process for applications such as photoelectrochemical sensing and photocatalysis. This mechanism is investigated for systems based on complex shaped semiconductor and metal-semiconductor nano-heteroparticles. In the present work the influence of the presence of a CdSe domain within the CdS nanorod as well as the influence of gold domain decoration is investigated spectroelectrochemically. Therefore, the mentioned nanoparticles are linked to transparent indium tin oxide (ITO) glass slides via (3-mercaptopropyl)trimethoxysilane (MPTMS). This preparation yields sub-monolayers of the particles. External photocurrent quantum efficiency spectra are measured in the range from λ=350–650 nm. Intensity-modulated photocurrent spectroscopy (IMPS) and electrochemical impedance spectroscopy (EIS) measurements are applied to the samples in order to reveal and explain the differences of the electrochemical kinetics between the four different particle types (CdS, CdSe/CdS, CdS−Au, and CdSe/CdS−Au nanorods). We demonstrate that the presence of gold domains affects the carrier dynamics of various involved processes. An equivalent circuit model is derived and fitted to the impedance data to explain changes of the kinetics in the system

Nanoplatelet cryoaerogels with potential application in photoelectrochemical sensing

Semiconductor nanoparticle based porous 3D assemblies are interesting materials for various applications in the fields of photovoltaics, catalysis, or optical sensing. For use as photoelectrodes in photoelectrochemical sensors they need to be characterised by a high porosity, a good photostability, and a high charge carrier mobility. Our work reports on the preparation of cryoaerogel photoelectrodes based on CdSe nanoplatelets and their photoelectrochemical characterisation by means of linear sweep voltammetry (LSV) and intensity modulated photocurrent spectroscopy (IMPS). The obtained open-pored cryoaerogel films were observed to produce much higher photocurrents than comparable drop-cast films. By means of IMPS, the performance differences could be linked to the occurrence of charge carrier movement, which could solely be proven for the cryoaerogels. In a proof-of-principle experiment, the potential of the prepared photoelectrodes for application in photoelectrochemical sensing was moreover demonstrated