Self-assembly of block copolymers (BCPs) is an alternative patterning technique that promises high resolution and density multiplication with lower costs. The defectivity of the resulting nanopatterns remains too high for many applications in microelectronics and is exacerbated by small variations of processing parameters, such as film thickness, and fluctuations of solvent vapor pressure and temperature, among others. In this work, a solvent vapor annealing (SVA) flow-controlled system is combined with design of experiments (DOE) and machine learning (ML) approaches. The SVA flow-controlled system enables precise optimization of the conditions of self-assembly of the high Flory–Huggins interaction parameter (χ) hexagonal dot-array forming BCP, poly(styrene-b-dimethylsiloxane) (PS-b-PDMS). The defects within the resulting patterns at various length scales are then characterized and quantified. The results show that the defectivity of the resulting nanopatterned surfaces is highly dependent upon very small variations of the initial film thicknesses of the BCP, as well as the degree of swelling under the SVA conditions. These parameters also significantly contribute to the quality of the resulting pattern with respect to grain coarsening, as well as the formation of different macroscale phases (single and double layers and wetting layers). The results of qualitative and quantitative defect analyses are then compiled into a single figure of merit (FOM) and are mapped across the experimental parameter space using ML approaches, which enable the identification of the narrow region of optimum conditions for SVA for a given BCP. The result of these analyses is a faster and less resource intensive route toward the production of low-defectivity BCP dot arrays via rational determination of the ideal combination of processing factors. The DOE and machine learning-enabled approach is generalizable to the scale-up of self-assembly-based nanopatterning for applications in electronic microfabrication.
Bisphenol–based cyanide sensing: Selectivity, reversibility, facile synthesis, bilateral “OFF-ON” fluorescence, C2ν structural and conformational analysis
Z. Ullah, P. A. Sonawane, T. S. Nguyen, M. Garai, D. G. Churchill, C. T. Yavuz
A structurally characterized novel dual–pocketed tetra–conjugated bisphenol–based chromophore (fluorescence = 652 nm) was synthesized in gram scale in ~90% yield from its tetraaldehyde. Highly selective, naked-eye detection of CN− (DMSO/H2O) was confirmed by interferent testing. A detection limit of 0.38 µM, within the permissible limit of CN− concentration in drinking water was achieved as mandated by WHO. The “reversibility” study shows potential applicability and reusability of Sen. Moreover, cost-effective and on-site interfaces, application tools such as fabricated cotton swabs, plastic Petri dishes, and filter papers further demonstrated the specific selectivity of Sen for the toxic CN−. In addition, an easily available and handy smartphone-assisted “Color Picker” app was utilized to help estimate the concentration of CN− ion present. A dual phenol deprotonation mechanism is active and supported by 1H NMR spectroscopic data and DFT calculation results.
Extensive Screening of Solvent-linked Porous Polymers through Friedel-Crafts Reaction for Gas Adsorption
V. Rozyyev, Y. Hong, M. S. Yavuz, D. Thirion, C. T. Yavuz
Scalability, cost, and feasibility of porous structures in gas capture are prerequisites for emerging materials to be promising in the industry. Herein, a simpler variant of Friedel−Crafts’ synthesis of highly porous covalent organic polymers (COPs) based on an unprecedented solvent-mediated crosslinking is presented. Alkyl chlorides behave as both solvents and linkers in the presence of AlCl3. Studies on three classes of 18 different monomers using dichloromethane, chloroform, and 1,2-dichloroethane lead to producing 29 new COPs (124−152). Polymers are characterized by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, elemental composition analysis, scanning electron microscope (SEM), thermogravimetric analysis (TGA), and porosity analyzer. The synthesized COPs exhibit structures from nonporous to highly porous morphologies with Brunauer–Emmett–Teller (BET) surface areas as high as 1685 m2 g−1. These COPs show high gas uptake toward CO2 (up to 4.71 mmol g−1 at 273 K, 1.1 bar), CH4 (up to 1.31 mmol g−1 at 273 K, 1.1 bar), and H2 (up to 2.02 wt% at 77 K, 1.1 bar). The findings point to significant potential in producing sustainable porous materials through simple and scalable methodology developed here.
Alkyl-linked porphyrin porous polymers for gas capture and precious metal adsorption
Y. Hong§, V. Rozyyev§, C. T. Yavuz. §: Equal contribution
In gas adsorption and metal recovery, inexpensive and covalently bonded porous polymers offer industrial feasibility, despite the challenge of having reactive functionalities while maintaining porosity. Herein, three highly porous covalent organic polymers (COPs), COP-210, COP-211, and COP-212, with porphyrin functionalities that are readily synthesized by a Friedel–Crafts reaction using chlorinated solvents as linkers are reported. The polymers exhibit competitive adsorption capacities for CO₂, H2, and CH4. Their porphyrin sites proved particularly effective in precious metal recovery, where COPs exhibit high selectivity toward gold, platinum, palladium, and silver. Analysis reveals that reductive metal capture is prevalent for gold and silver. Platinum is also captured through a combination of reduction and chelation. The gold adsorption capacities are 0.901–1.250 g g−1 with fast adsorption kinetics at low pH. COP-212 selectively recovers 95.6% of gold from actual electronic waste (e-waste) collected from junkyards. The results show that the inexpensive and scalable porous porphyrin polymers offer great potential in gas capture, separation, and precious metal recovery.
Reaction: Porous Organic Polymers for Uranium Capture
Cafer T. Yavuz received his PhD from Rice University in 2008 with a
Welch scholarship under the supervision of Vicki Colvin. He then
worked as a postdoctoral scholar at the University of California,
Santa Barbara, with Galen Stucky. He started his independent
group in 2010 at KAIST, Korea. He is currently a professor of chemistry at the King Abdullah University of Science and Technology in
Saudi Arabia. His research focuses on the design and synthesis of
nanoscale and porous materials for applications in energy and
the environment. He uses fine chemistry in confined spaces to
enable rapid and targeted transformations of CO₂, methane, and
water.
Asynchronous double Schiff base formation of pyrazole porous polymers for selective Pd recovery
M. Garai§, M. Mahato§, Y. Hong, V. Rozyyev, U. Jeong, Z. Ullah, C. T. Yavuz
Pyrazole-linked covalent organic polymer is synthesized using an asynchronous double Schiff base from readily available monomers. The one-pot reaction features no metals as a building block or reagent, hence facilitating the structural purity and industrial scalability of the design. Through a single-crystal study on a model compound, the double Schiff base formation is found to follow syn addition, a kinetically favored product, suggesting that reactivity of the amine and carbonyls dictate the order and geometry of the framework building. The highly porous pyrazole polymer COP-214 is chemically resistant in reactive conditions for over two weeks and thermally stable up to 425 °C in air. COP-214 shows well-pronounced gas capture and selectivities, and a high CO₂/N₂ selectivity of 102. The strongly coordinating pyrazole sites show rapid uptake and quantitative selectivity of Pd (II) over several coordinating metals (especially Pt (II)) at all pH points that are tested, a remarkably rare feature that is best explained by detailed analysis as the size-selective strong coordination of Pd onto pyrazoles. Density functional theory (DFT) calculations show energetically favorable Pd binding between the metal and N-sites of COP-214. The polymer is reusable multiple times without loss of activity, providing great incentives for an industrial prospect.
Metal Oxide Supported Catalyst for Dry Reforming and Method of Preparing Syngas Using the Same
App# 10-2016-0100271 and 10-2017-0099675, 2016.
C. T. Yavuz, Y. Song, E. Ozdemir
he present invention relates to: a dry reforming catalyst in which an active material is impregnated on the surface of a metal oxide support, wherein the active material is surrounded by a surfactant; a method for preparing the same; and a method for preparing a synthetic gas by using the catalyst. Since the surfactant on the surface of the active material prevents sintering of the active material and a phenomenon of covering the active surface with carbon, the dry reforming catalyst exhibits high activity for a long time at a high temperature without using a noble metal, thereby being useful in the preparation of a synthesis gas.
Electroless for efficient recovery of the adsorbed noble metal in the porphyrin polymer-coated porous method
App # 10-2017-0170184 and 10-2018-0129227 and 10-2018-0162181, 2017.
C. T. Yavuz, Y. Hong
he present invention relates to a porous porphyrin polymer and a method for recovering precious metal elements using the same, wherein the porous porphyrin polymer of chemical formula 1, having high selectivity and adsorptivity with respect to precious metal elements, can be applied to the recovery of precious metal elements from a metal leachate of electronic product waste, river water or sea water.
Novel heterogeneous organic catalyst with pyridyl salicylimine for selective cyclic carbonate formation
App # 10-2019-0021112, 2019.
C. T. Yavuz, S. Subramanian
he present invention relates to a heterogeneous organic catalyst with pyridyl salicylimine and a method for producing a cyclic carbonate using the same. More particularly, it is possible to selectively and continuously synthesize a cyclic carbonate from carbon dioxide and epoxy compounds by using a heterogeneous organic polymer with a novel pyridyl salicylimine functional group as a catalyst, under a relatively mild condition of normal pressure and mild temperature, without additives such as a solvent or a cocatalyst.
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