Sunhee Kim's research while affiliated with University of Pittsburgh and other places

Publications (10)

Article
The influence of water vapor on the surface diffusion behavior of pyridine adsorbed on powdered MgO surfaces has been studied by Fourier transform IR (FTIR) absorption spectroscopy. It has been found that the introduction of water vapor significantly increases the pyridine surface diffusion coefficient. FTIR spectra showed that water vapor converte...
Article
The molecular transport of pyridine through nanosized MgO particles has been investigated by Fourier transform IR spectroscopy. Two regimes of chemisorbed pyridine diffusion are observed. A fast diffusion process is associated with pyridine bound to nondefective smooth MgO(100) facets which exhibit an activation energy barrier of 35.7 kJ mol−1 for...
Article
The effect of triethylenediamine (TEDA) (also named 1,4-diazabicyclo [2.2.2]octane, DABCO) on the adsorption of ClCN on a γ-Al2O3 absorbent has been investigated. Both Fourier transform infrared (FTIR) and theoretical studies indicate that no direct interaction between amine groups of TEDA and ClCN molecules takes place. Instead, we found that TEDA...
Article
FTIR spectroscopy has been used to monitor the transport of CO to the Pt cores of Pt@CoO nanoparticles forming CO/Pt species. It was found that external Pt sites are not present on the outer surfaces of the approximately 10 nm diameter nanostructures and that CO transports to Pt adsorption sites by an activated surface diffusion process through the...
Article
The adsorption and vibrational properties of chemisorbed HCN on Lewis acid sites, Lewis base sites, and Brønsted Al-OH acid sites on a partially hydroxylated [gamma]-Al2O3 surface have been obtained by a combination of FTIR and density functional theory studies. The vibrational modes from the molecular and dissociative adsorption of HCN were assign...
Article
A new method to study the diffusion properties of molecules into porous materials using transmission IR spectroscopy is employed. A measurement of the diffusion of the 2-chloroethylethyl sulfide (2-CEES) molecule into two types of gamma-Al2O3 powder is performed, showing that the diffusion rate into subnanometer crystallite particle size gamma-Al2O...
Article
The coadsorption of CO and triethylenediamine (TEDA) (also called 1,4-diazabicyclo[2.2.2]octane, DABCO) on a high-area gamma-Al2O3 surface has been investigated with use of transmission FTIR spectroscopy. It has been found that TEDA binds more strongly to both Lewis acid sites and to Brønsted Al-OH sites than does CO. Competition experiments indica...
Article
The adsorption of triethylenediamine (TEDA) on Lewis acid (Al(3+)) sites of the highly dehydroxylated Al(2)O(3) surface has been observed by FT-IR spectroscopy. This was done by monitoring the competitive adsorption of TEDA and CO on the Al(3+) sites. A stoichiometric replacement of Al(3+)-CO species was observed as Al(3+)-TEDA surface species were...
Article
The adsorption of triethylenediamine (TEDA) at 300 K is observed to occur via hydrogen bonding to isolated Al-OH groups on the surface of partially dehydroxylated high area gamma-Al(2)O(3) powder. This form of bonding results in +0.3 to +0.4% blue shifts in the CH(2) scissor modes at 1455 cm(-1) and a -0.4% red shift in the CN skeletal mode at 1060...
Article
The hydrogen bonding of the triethylenediamine (TEDA) molecule to isolated Al-OH groups on partially dehydroxylated high area gamma-Al(2)O(3) powder has been studied using transmission IR spectroscopy. It has been found that TEDA adsorbs both singly and as multiple species to single Al-OH groups in clearly separable equilibrium stages of adsorption...

Citations

... The latter can be bound to the surface via C or N atom, thus demonstrating linkage isomerism, previously established for CO molecules. Such two forms of HCN dissociative adsorption were reported for silica [20] and alumina [22]. It should be added that HCN molecule itself exists in two isomeric forms, HCN and HNC. ...
... In the most common neutralization technologies use is made of mixtures that consist of nanoparticles of such metal oxides as MgO, CaO, ZnO, SrO, TiO 2 , Al 2 O 3 , CuO, Fe 2 O 3 with grain diameters ranging from a few nanometers to several dozen micrometers . The nanocrystalline MgO with grains of a 4 µm diameter and a specific surface exceeding 500 m 2 /g is characterized by a particularly large surface and activity [14][15][16][17][18]30,34]. Reducing the size of nanocrystallites causes a significant increase in the share of surface atoms, including those occupying edge and corner places, particularly as their network defects comprise the active sites of the oxide neutralizer [34]. ...
... The increase of Knudsen diffusion into porous media at the onset of desorption has been demonstrated experimentally (Ballinger et al. 1989). Outward diffusion of an adsorbate through MgO powders with nanosized interparticle voids showed both a fast and a slow diffusion channel, suggestive of bonding on two types of sites, and thermal desorption followed a symmetric TPD curve unlike a first-order curve (Kim et al. 2009, their Figure 4). We suggest that these experimental results are similar to our findings that desorption from a powder is slower than an exponential decay of the adsorbate reservoir even for well-defined sites. ...
... One such possibility is the reaction of SO or SO 2 on the dust grain surface to form tetratomic [Al, S, O 2 ] molecules. Kim et al. 2007 demonstrated a similar formation mechanism for AlCN and AlNCO on an Al 2 O 3 surface. An additional formation mechanism for this system of molecules is gas-phase chemical reaction, such as Al + SO 3 → AlSO 2 + O or AlO + SO 2 → AlSO 2 + O. Finally, radiative association processes such as AlO + SO or Al + SO 2 may occur with [Al, S, O 2 ] molecules as an intermediate; however, radiative combination is a less efficient process than chemical reaction either in the gas phase or on a surface. ...
... 38 In the presence of HA and FA, the amount of surface hydroxyl groups increased aer the PSMPs adsorption of As(III), more so in the presence of HA as compared to FA because the molecular weight, structural complexity, and number of oxygencontaining functional groups are higher on HA. 39 Aer adsorption, the FTIR band associated with hydroxyl group vibrations was red-shied to a lower energy, indicating that the energy required for the vibration of the hydroxyl group is less and the group is less stable. 40 Thus, considering that the adsorption of metal ions is related to the chemical functions of oxygen on the adsorbent, 41 we speculate that As(III) may interact with the surface -OH of PSMPs. ...
... With the goal of evaluating the transport dynamics of CWAs in Zr-based MOFs, our research efforts began by developing a method for monitoring molecular transport under pristine conditions. Our approach, adapted from Kim et al., 46 utilized in situ infrared (IR) spectroscopy operating under ultrahigh vacuum (UHV) conditions to monitor changes that occur during exposure, diffusion, and desorption of the analytes of interest within porous materials, specifically Zr-based MOFs. 30,46−48 Initial diffusion studies were performed on UiO-66 with a series of linear and aromatic hydrocarbons to validate the method. ...
... As for the reason why Metal/Al 2 O 3 was selected as the co-milling regent of MCT of HCB, many previous studies demonstrated its effectiveness in the organic pollutants treatment from their excellent adsorption and chemical composition properties [48][49][50][51][52]. HCB was selected as the model pollutant due to its universality, typical symmetry and polysubstitution. ...
... Apart from above mentioned multifunctional materials, Al 2 O 3 , as a catalyst and/or catalyst support used in organic pollutants elimination has been endowed heightened interests owing to its large surface and pore volume (Li et al., 2010;Lu et al., 2017). In addition, among multiple kinds of Al 2 O 3 crystalline forms, g-Al 2 O 3 , attributed to its specific defective spinel structure, processes large amounts of surface-adsorbed oxygen species, Brønsted and Lewis acid sites (Kim et al., 2005;Liu et al., 2017c;Lu et al., 2017). Given that, Lu et al. (2017) successfully synthesized micro/nano-g-Al 2 O 3 rod-like fibers to perform the gaseous degradation of 1chloronaphthalene (CN-1), and the proposed mechanism is shown in Fig. S1. ...
... For instance, Pt@CoO yolk@shell CNHSs were found to exhibit the typical catalytic activity of Pt for the hydrogenation of ethylene. Dedicated experiments revealed that, because of their small sizes, the molecular reactants and byproducts could approach the surface of the buried Pt core by permeating through the porous CoO shell [189,193]. Encouraged by the success of prototypical biological assays, in which FePt@CoS 2 and Co@Au yolk@shell CNHSs were proven to act as effective killers for cancer cells [165] and as carriers for gene delivery [187], respectively, FePt@Fe 3 O 4 yolk@shell CNHSs were assessed for their potential as MRI contrast agents and as anticancer drugs [188]. ...