Porous Nanoparticle Films Research Articles

Mass and density determination of porous nanoparticle films using a quartz crystal microbalance

A method is presented to directly measure the mass output of an impaction printer coupled with a spark ablation generator. It is based on a quartz crystal microbalance and shown to be reliable in quantifying mass deposition rate. Here, the method is demonstrated with an Au nanoparticle aerosol synthesized under several spark ablation and deposition settings. Changes in the deposition rate in response to changed synthesis conditions follow the spark ablation models on generation rate made in previous studies, validating this novel measurement method. In combination with the volume of a deposit, a good estimate of the film porosity can be made. The Au nanoparticle films synthesized here have a low porosity of 0.18 due to extensive restructuring and compaction on impact with the substrate. The porosity is found to be insensitive to deposition settings and is constant throughout the film. The simplicity and low cost of a quartz crystal microbalance setup make this an accessible method to determine porosity in porous thin films.

Elucidating the role of electrophoretic mobility for increasing yield in the electrophoretic deposition of nanomaterials

HypothesisCatalysts, chemical, gas, and bio- sensing devices fabricated from porous nanoparticle films show better performance and sensitivity than their bulk material counterparts because of their high specific surface area. Electrophoretic deposition (EPD) technique is a cost-effective, fast, versatile, and easy to perform method to fabricate porous nanoparticle films. However, conventional EPD is currently limited by the fact that the deposition rate decreases with time, resulting in an eventual plateau in the deposit yield. Here, we sought to overcome this limitation by establishing and leveraging the critical role of the particle’s electrophoretic mobility in EPD kinetics. ExperimentsTo identify the impact of electrophoretic mobility on EPD yield we used alumina nanoparticles suspended in ethanol as a model system. Changes in particle mobility were monitored via changes in the effective pH (pHe) of the suspension during EPD. We also developed a new suspension replenish EPD approach that allows us to maintain near-constant particle mobility and particle concentration with time thereby increasing yield. FindingsWe observed that in conventional EPD the particle mobility of the alumina nanoparticles decreased with time, resulting in a halting of deposition. Further, using the suspension replenish EPD, we observed a linear increase in the mass of the deposited film with time, overcoming the plateau limitation of conventional EPD.

Reaction pathways and optoelectronic characterization of single-phase Ag2ZnSnS4 nanoparticles

Abstract

Fabrication of condensate microdrop self-propelling porous films of cerium oxide nanoparticles on copper surfaces.

Condensate microdrop self-propelling (CMDSP) surfaces have attracted intensive interest. However, it is still challenging to form metal-based CMDSP surfaces. We design and fabricate a type of copper-based CMDSP porous nanoparticle film. An electrodeposition method based on control over the preferential crystal growth of isotropic nanoparticles and synergistic utilization of tiny hydrogen bubbles as pore-making templates is adopted for the in situ growth of cerium oxide porous nanoparticle films on copper surfaces. After characterizing their microscopic morphology, crystal structure and surface chemistry, we explore their CMDSP properties. The nanostructure can realize the efficient ejection of condensate microdrops with sizes below 50 μm.

Thin film fabricated from solution-dispersible porous hyperbranched conjugated polymer nanoparticles without surfactants

Porous hyperbranched conjugated polymer nanoparticles with an average particle size of 20-60 nm and a specific surface area of 225 m(2) g(-1) have been prepared through Suzuki polymerization in a miniemulsion, which could be stably dispersed in common organic solvents after complete removal of surfactants. Furthermore, a simple spin-coating method for the preparation of homogeneous transparent thin films of the nanoparticle has been developed. Bright blue emission of the porous nanoparticle films could be reversibly quenched by nitroaromatics with enhanced sensitivity compared to dense films of the linear conjugated polymer analogue.

Forming-free resistive switching memories based on titanium-oxide nanoparticles fabricated at room temperature

In this work, we present symmetric metal-insulator-metal bipolar memristors based on room-temperature deposition of charged titanium-oxide nanoparticles formed in vacuum by a physical process. One of the most striking features of these devices is that they do not require a forming step, which is to be related to protrusions of the top electrode material inside the intrinsically porous nanoparticle films. Furthermore, we report that deposition under substrate biasing conditions strongly affects the structural and electrical properties of the produced titanium oxide nanoparticle films including their bipolar switching behaviour.

Structural and chemical characterization of SnO2-based nanoparticles as electrode material in Li-ion batteries

Improvement of long-term stability of electrode materials in Li-ion batteries requires a detailed understanding of influence of synthesis parameters on surface chemistry and on properties. Therefore, bare SnO2 and core/shell nanoparticles with SnO2 core and a hydrocarbon shell are synthesized in an Ar/20% O2 microwave plasma, deposited as porous nanoparticle films in situ on heated Ni-substrates, and finally assembled as anodes in Swagelok cells. In a comprehensive study, we investigate structure, particle size, chemistry, morphology, and water content of the nanoparticles using X-ray diffraction, transmission electron microscopy, specific surface area analysis, and coulometric water titration. The thicknesses of the nanoparticle films and their surface chemistry are investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. SnO2 nanoparticles are crystalline, with a tetragonal cassiterite structure. Primary particle sizes around 3 nm are reached for the bare SnO2 particles, 5–8 nm for the cores of the core/shell nanoparticles. A minimum microwave power of 900 W is necessary to synthesize SnO2 nanoparticles without precursor residuals as pristine SnO2 particles for the subsequent coating step. In the coating step increasing hydrocarbon content can be correlated with increasing carbon-precursor feeding rate. Water uptake, stemming either from the process, or due to atmospheric contamination, can successfully be reduced by a thermal treatment. The still remaining water is a function of specific surface area. Finally, bare SnO2 versus core/shell nanoparticles are compared regarding the influence of the shell on the electrochemical properties. The principal improved functionality of the developed anodes in Swagelok cells is demonstrated.

Highly porous TiO2 films for dye sensitized solar cells

Highly porous nanoparticle films were investigated as alternative working electrode morphology for the synthesis of dye sensitized solar cells (DSSCs). These films were rapidly assembled by flame synthesis and direct aerosol deposition of TiO2 nanoparticles with high specific surface area. Structural–functional analysis of their properties revealed that the film porosity is a key parameter greatly determining the resulting energy conversion efficiency (η). In fact, aerosol deposition at low substrate temperatures (∼100 °C) led to very high porosity (ε = 98%) and weak film cohesion. These films were easily resuspended upon immersion in the dye and/or electrolyte solutions resulting in very poor performances (η = 0.08%). In contrast, allowing for partial nanoparticle sintering by deposition at moderate temperatures (∼400 °C) decreased the film porosity from 98 to 95% leading to higher mechanical stability and partially preserving the large surface required for dye adsorption. As a result, these films had drastically higher current density (12.2 mA cm−2) and overall performances (η = 5%) representing an 8 times improvement with respect to the best reported for similar highly porous morphologies. Remarkably, their conversion efficiency decreased only slightly with increasing film thickness reaching 4.6% at 128 µm. This unique attribute suggests that high film porosity may inhibit recombination losses enabling utilization of thick films with enhanced light absorption properties.

Volatile Organic Compound Sensing by Gold Nanoparticles Capped with Calix[4]arene Ligand

Abstract Gold nanoparticles capped with calix[4]arene ligands have been designed and synthesized for highly sensitive and selective VOC sensing. Mass sensors coated with porous nanoparticle films displayed a good response toward toluene gas.