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1. Nanoimprint Lithography for Next-Generation Carbon Nanotube-Based Devices

   https://doi.org/10.3390/nano14121011  

   Fialkova, Svitlana; Yarmolenko, Sergey; Krishnaswamy, Arvind; Sankar, Jagannathan; Shanov, Vesselin; Schulz, Mark J; Desai, Salil (June 2024, Nanomaterials)

   This research reports the development of 3D carbon nanostructures that can provide unique capabilities for manufacturing carbon nanotube (CNT) electronic components, electrochemical probes, biosensors, and tissue scaffolds. The shaped CNT arrays were grown on patterned catalytic substrate by chemical vapor deposition (CVD) method. The new fabrication process for catalyst patterning based on combination of nanoimprint lithography (NIL), magnetron sputtering, and reactive etching techniques was studied. The optimal process parameters for each technique were evaluated. The catalyst was made by deposition of Fe and Co nanoparticles over an alumina support layer on a Si/SiO2 substrate. The metal particles were deposited using direct current (DC) magnetron sputtering technique, with a particle ranging from 6 nm to 12 nm and density from 70 to 1000 particles/micron. The Alumina layer was deposited by radio frequency (RF) and reactive pulsed DC sputtering, and the effect of sputtering parameters on surface roughness was studied. The pattern was developed by thermal NIL using Si master-molds with PMMA and NRX1025 polymers as thermal resists. Catalyst patterns of lines, dots, and holes ranging from 70 nm to 500 nm were produced and characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Vertically aligned CNTs were successfully grown on patterned catalyst and their quality was evaluated by SEM and micro-Raman. The results confirm that the new fabrication process has the ability to control the size and shape of CNT arrays with superior quality. 

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2. A Hybrid Process for Printing Pure and High Conductivity Nanocrystalline Copper and Nickel on Flexible Polymeric Substrates

   https://doi.org/10.1038/s41598-019-55640-7  

   Bhuiyan, Md Emran Hossain; Behroozfar, Ali; Daryadel, Soheil; Moreno, Salvador; Morsali, Seyedreza; Minary-Jolandan, Majid (December 2019, Scientific Reports)

   Abstract Printing functional devices on flexible substrates requires printing of high conductivity metallic patterns. To prevent deformation and damage of the polymeric substrate, the processing (printing) and post-processing (annealing) temperature of the metal patterns must be lower than the glass transition temperature of the substrate. Here, a hybrid process including deposition of a sacrificial blanket thin film, followed by room environment nozzle-based electrodeposition, and subsequent etching of the blanket film is demonstrated to print pure and nanocrystalline metallic (Ni and Cu) patterns on flexible substrates (PI and PET). Microscopy and spectroscopy showed that the printed metal is nanocrystalline, solid with no porosity and with low impurities. Electrical resistivity close to the bulk (~2-time) was obtained without any thermal annealing. Mechanical characterization confirmed excellent cyclic strength of the deposited metal, with limited degradation under high cyclic flexure. Several devices including radio frequency identification (RFID) tag, heater, strain gauge, and temperature sensor are demonstrated. 

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3. A systematic study of naphthyridine-derived ligands for well-defined silver(I) dimers

   https://doi.org/10.1039/D5DT01626F  

   Bavaresco, Sofia Teixeira; Marquard, Nina P; Miura-Stempel, Emily; Mohsen, Mariana G; Campbell, Michael G (September 2025, Dalton Transactions)

   Dinuclear silver(I) complexes have recently gained attention for potential applications in visible light photochemistry. Our group has demonstrated that strong visible light absorption can occur in silver(I) dimers featuring redox-active naphthyridine diimine (NDI) ligands, resulting from a combination of close silver–silver interactions and low-lying ligand π* orbitals. A shortcoming of this previous work is that the sliver-NDI complexes displayed fluxional behavior due to rapid ligand exchange in solution; the ability to produce silver(I) dimers with targeted properties that maintain well-defined structures in solution remains an unmet challenge. Here, we describe the synthesis and characterization of a series of silver(I) dimers with naphthyridine-derived ligands, in which the ligand scaffold is systematically varied in order to determine structure/property relationships. We find that truncation of the NDI framework into an asymmetric “L-shaped” design results in a family of ligands that reliably produce structurally analogous silver(I) dimers. Ligands that maintain the π-conjugation of the iminopyridine motif consistently give silver(I) dimers with visible light absorption due to metal–metal to ligand charge transfer (MMLCT) transitions, and introduction of anionic (X-type) sites further increases stability in solution. 

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4. A window on first-stars models from studies of dwarf galaxies and galactic halo stars

   Venkatesan, Aparna (June 2018, American Astronomical Society, AAS Meeting)

   Dwarf galaxies dominate the local universe by number and are predicted to be even more dominant at early times, with many having large star formation rates per unit mass. The cosmological role of dwarf galaxies in the metal enrichment and the reionization of the universe is an important but unresolved problem at present. Nearby low-mass galaxies are much more accessible observationally for detailed study and may be local analogs of the types of galaxies that hosted the first-light sources relevant for reionization. I will share recent results on UV studies of the escaping radiation from nearby low-mass starforming galaxies, as well as the tantalizing similarities in element abundance patterns between local dwarf galaxies and the latest data compilations on extremely metal-poor stars in galactic halos. I will highlight trends of interest in a variety of individual elements at values of [Fe/H] between -7 and -3, including alpha-elements, elements originating mostly in intermediate-mass stars, lithium, titanium, and r-process elements. These trends constrain not only models of the first stars and their supernovae, but provide a window into the physical conditions in early galaxies and when metal-free star formation may have ceased in the early universe.This work was supported by the University of San Francisco Faculty Development Fund, and NSF grant AST-1637339. We thank the Aspen Center for Physics, where some of this work was conducted, and which is supported by National Science Foundation grant PHY-1607611. 

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5. Relaxation dynamics in see-saw shaped Dy( iii ) single-molecule magnets

   https://doi.org/10.1039/D0QI01007C  

   Harriman, Katie L.; Murillo, Jesse; Suturina, Elizaveta A.; Fortier, Skye; Murugesu, Muralee (December 2020, Inorganic Chemistry Frontiers)

   null (Ed.)

   Utilizing a terphenyl bisanilide ligand, two Dy( iii ) compounds [K(DME) n ][L Ar Dy(X) 2 ] (L Ar = {C 6 H 4 [(2,6- i PrC 6 H 3 )NC 6 H 4 ] 2 } 2− ), X = Cl ( 1 ) and X = I ( 2 ) were synthesized. The ligand imposes an unusual see-saw shaped molecular geometry leading to a coordinatively unsaturated metal complex with near-linear N–Dy–N (avg. 159.9° for 1 and avg. 160.4° for 2 ) angles. These compounds exhibit single-molecule magnet (SMM) behavior with significant uniaxial magnetic anisotropy as a result of the transverse coordination of the bisanilide ligand which yields high energy barriers to magnetic spin reversal of U eff = 1334 K/927 cm −1 ( 1 ) and 1278 K/888 cm −1 ( 2 ) in zero field. Ab initio calculations reveal that the dominant crystal field of the bisanilide ligand controls the orientation of the main magnetic axis which runs nearly parallel to the N–Dy–N bonds, despite the identity of the halide ligand. Analysis of the relaxation dynamics reveals a ca. 14-fold decrease in the rate of quantum tunneling of the magnetisation when X = I ( 2 ). Most notably, the relaxation times were on average 5.6× longer at zero field when the heavier group 17 congener was employed. However, no direct evidence of a heavy atom effect on the Orbach relaxation was obtained as the height of the barrier is defined by the dominant bisanilide ligand. 

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