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Flexible and electrically conductive nanocomposite films are essential for small, portable and even implantable electronic devices. Typically, such film synthesis and conductivity measurement are carried out sequentially. As a result, optimization of filler loading and size/morphology characteristics with respect to film conductivity is rather tedious and costly. Here, freshly-made Ag nanoparticles (nanosilver) are made by scalable flame aerosol technology and directly deposited onto polymeric (polystyrene and poly(methyl methacrylate)) films during which the resistance of the resulting nanocomposite is measured in situ. The formation and gas-phase growth of such flame-made nanosilver, just before incorporation onto the polymer film, is measured by thermophoretic sampling and microscopy. Monitoring the nanocomposite resistance in situ reveals the onset of conductive network formation by the deposited nanosilver growth and sinternecking. The in situ measurement is much faster and more accurate than conventional ex situ four-point resistance measurements since an electrically percolating network is detected upon its formation by the in situ technique. Nevertheless, general resistance trends with respect to filler loading and host polymer composition are consistent for both in situ and ex situ measurements. The time lag for the onset of a conductive network (i.e., percolation) depends linearly on the glass transition temperature (Tg) of the host polymer. This is attributed to the increased nanoparticle-polymer interaction with decreasing Tg. Proper selection of the host polymer in combination with in situ resistance monitoring therefore enable the optimal preparation of conductive nanocomposite films.

Particle–cell interactions in physiological media are important in determining the fate and transport of nanoparticles and biological responses to them. In this work, these interactions are assessed in real time using a novel atomic force microscopy (AFM) based platform. Industry-relevant CeO2 and Fe2O3 engineered nanoparticles (ENPs) of two primary particle sizes were synthesized by the flame spray pyrolysis (FSP) based Harvard Versatile Engineering Nanomaterials Generation System (Harvard VENGES) and used in this study. The ENPs were attached on AFM tips, and the atomic force between the tip and lung epithelia cells (A549), adhered on a substrate, was measured in biological media, with and without the presence of serum proteins. Two metrics were used to assess the nanoparticle cell: the detachment force required to separate the ENP from the cell and the number of bonds formed between the cell and the ENPs. The results indicate that these atomic level ENP–cell interaction forces strongly depend on the physiological media. The presence of serum proteins reduced both the detachment force and the number of bonds by approximately 50% indicating the important role of the protein corona on the particle cell interactions. Additionally, it was shown that particle to cell interactions were size and material dependent., ACS Sustainable Chemistry & Engineering, 2 (7), ISSN:2168-0485

Particle-particle interactions in physiological media are important determinants for nanoparticle fate and transport. Herein, such interactions are assessed by a novel atomic force microscopy (AFM)-based platform. Industry-relevant CeO2, Fe2O3, and SiO2 nanoparticles of various diameters were made by the flame spray pyrolysis (FSP)-based Harvard Versatile Engineering Nanomaterials Generation System (Harvard VENGES). The nanoparticles were fully characterized structurally and morphologically, and their properties in water and biological media were also assessed. The nanoparticles were attached on AFM tips and deposited on Si substrates to measure particle-particle interactions. The corresponding force was measured in air, water, and biological media that are widely used in toxicological studies. The presented AFM-based approach can be used to assess the agglomeration potential of nanoparticles in physiological fluids. The agglomeration potential of CeO2 nanoparticles in water and RPMI 1640 (Roswell Park Memorial Institute formulation 1640) was inversely proportional to their primary particle (PP) diameter, but for Fe2O3 nanoparticles, that potential is independent of PP diameter in these media. Moreover, in RPMI+10% Fetal Bovine Serum (FBS), the corona thickness and dispersibility of the CeO2 are independent of PP diameter, while for Fe2O3, the corona thickness and dispersibility were inversely proportional to PP diameter. The present method can be combined with dynamic light scattering (DLS), proteomics, and computer simulations to understand the nanobio interactions, with emphasis on the agglomeration potential of nanoparticles and their transport in physiological media.

Filler nanoparticles greatly enhance the performance of polymers and minimize filler content in the resulting nanocomposites. At the same time, they challenge the manufacturing of such nanocomposites by filler agglomeration and non-uniform spatial distribution. Here, multifunctional nanocomposite films are made by capitalizing on flame-synthesis of ceramic or metal filler nanoparticles followed by rapid, in situ deposition on sacrificial substrates, resulting in a filler film with controlled porosity. The polymer is then spin-coated on the porous film that retained its stochastic but uniform structure, resulting in nanocomposites with homogeneous filler distribution and high filler-loading. By sequential repetition of this procedure, sophisticated, multilayer, free-standing, plasmonic- (Ag-Fe2O3) and phosphorescent-superparamagnetic (Y2O3:Eu3+- Fe2O3) actuators are made by precisely tuning the polymer thickness between each functional nanostructured layer. These actuators are quite flexible, have fast response times, and exhibit superior superparamagnetism due to their high filler content and homogeneous spatial distribution.

Proton-coupled electron transfer (PCET) reactions involve the transfer of a proton and an electron and play an important role in a number of chemical and biological processes. Here, we describe a novel phenomenon, plasmon-enhanced PCET, which is manifested using SiO2-coated Ag nanoparticles functionalized with gallic acid (GA), a natural antioxidant molecule that can perform PCET. These GA-functionalized nanoparticles show enhanced plasmonic response at near-IR wavelengths, due to particle agglomeration caused by the GA molecules. Near-IR laser irradiation induces strong local hot-spots on the SiO2-coated Ag nanoparticles, as evidenced by surface enhanced Raman scattering (SERS). This leads to plasmon energy transfer to the grafted GA molecules that lowers the GA-OH bond dissociation enthalpy by at least 2 kcal mol(-1) and therefore facilitates PCET. The nanoparticle-driven plasmon-enhancement of PCET brings together the so far unrelated research domains of nanoplasmonics and electron/proton translocation with significant impact on applications based on interfacial electron/proton transfer.

Polymer nanocomposite films with nanoparticle-specific properties are sought out in novel functional materials and miniaturized devices for electronic and biomedical applications. Sensors, capacitors, actuators, displays, circuit boards, solar cells, electromagnetic shields and medical electrodes rely on flexible, electrically conductive layers or films. Scalable synthesis of such nanocomposite films, however, remains a challenge. Here, flame aerosol deposition of metallic nanosliver onto bare or polymer-coated glass substrates followed by polymer spin-coating on them leads to rapid synthesis of flexible, free-standing, electrically conductive nanocomposite films. Their electrical conductivity is determined during their preparation and depends on substrate composition and nanosilver deposition duration. Accordingly, thin (500 nm) and flexible nanocomposite films are made having conductivity equivalent to metals (e.g. 5 × 10(4) S cm(-1)), even during repetitive bending.

Silver (Ag) nanoparticles dispersed in an amorphous silica (SiO2) matrix or coated by a SiO2 layer were synthesized by flame spray pyrolysis (FSP). The coated nanoparticles were produced by using a modified enclosed FSP setup, in which the SiO2 precursor was injected through a ring above the FSP nozzle at various burner-ring-distances (BRDs), after the core Ag nanoparticles had been formed. The produced nanoparticles were characterized by XRD, BET, TEM and UV/vis analysis. The Ag particle size was possible to be controlled by tuning the FSP parameters. For the SiO2 coated nanoparticles, larger Ag core sizes were obtained for higher BRDs. All the produced nanoparticles exhibited the characteristic plasmon resonance frequency of Ag nanoparticles.

Silver (Ag) nanoparticles dispersed in an amorphous silica (SiO2) matrix or coated by a SiO2 layer were synthesized by flame spray pyrolysis (FSP). The coated nanoparticles were produced by using a modified enclosed FSP setup, in which the SiO2 precursor was injected through a ring above the FSP nozzle at various burner-ring-distances (BRDs), after the core Ag nanoparticles had been formed. The produced nanoparticles were characterized by XRD, BET, TEM and UV/vis analysis. The Ag particle size was possible to be controlled by tuning the FSP parameters. For the SiO2 coated nanoparticles, larger Ag core sizes were obtained for higher BRDs. All the produced nanoparticles exhibited the characteristic plasmon resonance frequency of Ag nanoparticles.