Saturday June 2, 2018
F. Bou-Abdallah, Organizer
H. Fenniri, G. Papaefthymiou, Presiding
Session sponsored by Shimadzu
8:15 . Chemistry and nanotechnology: Particle surface modification for improved properties and applications. R.E. Partch
8:50 . Micromagnetic characterization of zinc ferrite nanoparticles produced by mechanochemical synthesis. G. Papaefthymiou, W. Vogel, A. Viescas
9:25 . Nanocatalysis: In situ and in operando studies. C. Zhong
10:15 . Photocatalytic performance of noble metal-modified TiO2: the concept of catalytic farming. J. Scaiano, A. Elhage, N. Marina, A. Lanterna
10:50 . Solution-based synthesis and applications of multi-functional nanoscale systems. S.S. Wong
11:25 . Engineering biomedical function in supramolecular nanomaterials. H. Fenniri
NENM 2:Chemistry and nanotechnology: Particle surface modification for improved properties and applications
Richard E. Partch, firstname.lastname@example.org. Clarkson University, Potsdam, New York, United States
Advancing requirements for composites having enhanced chemical, mechanical, medical and physical properties are being met by molecular modifications of both filler particles and the matrix they are placed in. The presenter has enjoyed making successful contributions to a wide variety of technical problems by employing aerosol and dispersion chemical techniques for particle synthesis and surface modification. Synthetic processes have been developed to prepare 1) core-shell encapsulated composite particles, and 2) molecularly functionalized particle surfaces. The compositions, sizes and shapes of the obtained solids vary widely. Examples will be cited of improved properties of a) medical imaging and lighting phosphors, b) abrasives for wafer polishing during chip manufacture, c) optical limiting carbon and metallic nanoparticles, d) energy saving copy machine composites, e) injectables for in vivo treatment of some overdosed chemicals and f) microcapsules for national security use.
NENM 3:Micromagnetic characterization of zinc ferrite nanoparticles produced by mechanochemical synthesis
Georgia Papaefthymiou Davis, email@example.com, William Vogel, Arthur Viescas. Villanova University, Villanova, Pennsylvania, United StatesFerrite nanoparticles have important applications in nanotechnology. Due to their superparamagnetic properties, these materials are considered as good candidates for a variety of potential applications, such as, ferrofluids, catalysts and for biomedical purposes. They can be produced through a variety of synthesis routes that may impact their physical properties. Their spinel crystallographic structure allows for magnetic property modification through the degree of inversion in iron occupancy of tetrahedral (A) versus octahedral crystallographic sites. Bulk ZnFe2O4 is known to possess zero degree of inversion, that is, all Zn2+ ions occupy tetrahedral sites, leaving all Fe3+ ions in octahedral sites. Bulk ZnFe2O4 is paramagnetic down to ~10 K, where a paramagnetic to antiferromagnetic phase transition is observed. In contrast, ZnFe2O4 nanoparticles are magnetic at much higher temperature, due to cation redistribution at the nanoscale. In this study, zinc ferrite nanoparticles were prepared mechanochemically through high energy ball milling of commercially available ZnO and α-Fe2O3 powders. Non-zero degree of inversion was observed via Mössbauer Spectroscopy, confirming cation redistribution relative to the bulk. Analysis of Mössbauer hyperfine parameters over the temperature range of 4.2 K < T < 300 K examined the internal magnetism and magnetic relaxation phenomena present in these nanoparticles. These parameters probe the role that mechanical stress may play in determining the magnetic properties of the nanoparticles due to trapped, non-equilibrium crystallographic structures and oxygen vacancies, as compared to other established chemical synthetic routes.
NENM 4:Nanocatalysis: In situ and in operando studies
Chuanjian Zhong, firstname.lastname@example.org. Dept of Chemistry, State University of New York at Binghamton, Binghamton, New York, United States
The highly-dynamic nature of nanostructured catalysts in catalytic and electrocatalytic reactions requires fundamental understanding of the detailed surface sites and the nanostructures under the reaction conditions or simultaneous measurements of catalytic properties and catalyst structures. This presentation will discuss recent results of our studies of several types of nanoparticle and nanowire catalysts in catalytic oxidation of carbon monoxide and hydrocarbons and in electrocatalytic oxygen reduction and alcohol oxidation reactions. Examples will highlight the use of diffuse reflectance infrared Fourier transform spectroscopy and high energy x-ray diffraction coupled with atomic pair distribution function analysis for in situ and in operando characterizations of platinum- and palladium-based binary and ternary alloy or core-shell nanoparticles and nanowires in the reactions. Insights into the correlation of the catalytic or electrocatalytic synergies with the size, shape, composition, and surface sites will be discussed.
NENM 5:Photocatalytic performance of noble metal-modified TiO2: the concept of catalytic farming
J Scaiano, email@example.com, Ayda Elhage, Nancy Marina, Anabel Lanterna. Chemistry, University of Ottawa, Ottawa, Ontario, Canada
Visible-light-mediated photo-redox catalysis has emerged as a valuable concept in organic synthesis to induce selective organic transformations avoiding the undesired photo degradation of organic molecules under UV exposure. Titanium dioxide (TiO2) has been widely explored as an alternative heterogeneous photoredox catalyst. Heterogeneous photo-catalysis is a promising technology providing both facile catalyst separations, and potential reuse. The main disadvantage of the use of pure nanometric TiO2 as a photocatalyst is the large band gap (>3.1eV) of this semiconductor that can only absorb UV light (<400 nm). Decorating TiO2 with metals such as Pd, Au or Cu, among others, can overcome this problem as the resulting materials usually absorb light in the visible region.
We present here our efforts to develop hybrid catalysts based on TiO2 decorated with noble metal or metal oxide nanoparticles, with emphasis on palladium, which can be suitable catalysts for different organic transformation under mild conditions. The first example involves Pd/PdO NPs-doped TiO2 catalyst, known as an efficient photo-catalyst for olefin hydrogenation in the absence of H2 gas upon UV irradiation. Its photocatalytic activity can be tuned in favour of hydrogenation or isomerization of benzyl-substituted alkenes simply by changing the irradiation wavelength. The isomerization can be thermally induced in air or driven by visible light irradiation at room temperature under Argon atmosphere, while switching to UV irradiation leads to efficient hydrogenation. The versatility of the catalyst is also tested for Sonogashira and Ullmann couplings.
The use of heterogeneous catalysis has advantages compared to the homogeneous counterparts, such as easy catalyst separation and reusability. However, one of the main challenges yet to solve, is to ensure good performance after the first catalytic cycles. Active catalytic species being poisoned or inactivated during the catalytic process is the main reason behind the loss of catalytic efficiency. We propose a different approach in order to extend the catalyst lifetime based on the crop rotation system used in agriculture. Thus, the catalyst is used alternating different catalytic reactions, which in turn reactivate the catalyst surface, extending its reusability, preserving its selectivity and efficiency. As an example, different organic reactions (crops) were selected and catalyzed by the same catalyst during target-molecule rotation.
NENM 6:Solution-based synthesis and applications of multi-functional nanoscale systems
Stanislaus S. Wong, firstname.lastname@example.org. SUNY Stony Brook, Stony Brook, New York, United StatesOur group is fundamentally interested in the design of a series of multi-functional nanoscale systems using diverse and generalizable solution-based strategies. In this presentation, we focus on the synthesis and characterization of metal-containing nanostructures with relevant control over chemical composition, size, shape, purity, morphology, and crystallinity. In particular, we describe advances in the use of solution-based methodologies to generate novel functional nanoscale architectures (including composite heterostructures) with the objective of gaining valuable insights into designing interesting nanomaterials for primarily energy-related applications, such as light harvesting and fuel cells.
NENM 7:Engineering biomedical function in supramolecular nanomaterials
Hicham Fenniri, email@example.com. Chemical Engineering, Northeastern University , Boston, Massachusetts, United States
Supramolecular 1D nanostructures have far reaching applications in chemistry, biology and materials science, owing in part to the ability to correlate properties and function with the nature of the individual building blocks. Among 1D nanostructures are cylindrical architectures generated from the stacking of homo-modular or heteromodular rosettes formed through hydrogen bonding acceptor (A)-donor (D) interactions. Many examples of different sizes of rosettes including hexameric have been showcased in the literature, a few of which have demonstrated further stacking into cylindrical architectures such as nanowires or nanofibers. The molecular chemistry and supramolecular chemical biology of the pyrimido[4,5-d]pyrimidine shown in Fig. 1A and its analogues will be discussed here. This heterocycle, termed the G/\C motif herein, features a self-complementary triad of the ADD hydrogen bonding arrays of guanine (G) and DAA hydrogen bonding arrays of cytosine (C). In water, this motif undergoes an entropically driven, self organization process to form hexameric rosettes maintained by 18 hydrogen bonds (Fig. 1B). Since the redundant NH group in the cytosine ring is functionalized, the molecule is less prone to pyrimidine-hydroxypyrimidine tautomerism, thereby effectively locking the DAA array for rosette formation, regardless of the solvent. Once these rosettes are generated, they then organize through π-stacking, van der Waals interactions and solvophobic effects to form discrete tubular architectures called rosette nanotubes (RNTs) that have an inner channel diameter of ca. 1.1 nm (Fig. 1C). These materials have shown unusual optical, chiroptical, and biological properties in solution as well as excellent thermal stability and mechanical resilience under shear force. This talk will focus on the molecular and supramolecular design and characterization of various RNT classes; in particular recent applications in targeted drug and RNA delivery for pancreatic cancer therapy therapy.