Chemistry Faculty Research and Publications
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Item Open Access Research Update: Density functional theory investigation of the interactions of silver nanoclusters with guanine(2017-02-01) Dale, B. B.; Senanayake, R. D.; Aikens, Christine M.; cmaikens; Aikens, Christine M.Bare and guanine-complexed silver clusters Agnz (n = 2-6; z = 0-2) are examined using density functional theory to elucidate the geometries and binding motifs that are present experimentally. Whereas the neutral systems remain planar in this size range, a 2D-3D transition occurs at Ag5+ for the cationic system and at Ag42+ for the dicationic system. Neutral silver clusters can bind with nitrogen 3 or with the pi system of the base. However, positively charged clusters interact with nitrogen 7 and the neighboring carbonyl group. Thus, the cationic silver-DNA clusters present experimentally may preferentially interact at these sites. © 2017 Author(s).Item Open Access Detection of extremely low concentration waterborne pathogen using a multiplexing self-referencing SERS microfluidic biosensor(2017-02-14) Wang, C.; Madiyar, F.; Yu, C. X.; Li, Jun; junli; Li, JunBackground: It is challenging to achieve ultrasensitive and selective detection of waterborne pathogens at extremely low levels (i.e., single cell/mL) using conventional methods. Even with molecular methods such as ELISA or PCR, multi-enrichment steps are needed which are labor and cost intensive. In this study, we incorporated nano-dielectrophoretic microfluidic device with Surface enhanced Raman scattering (SERS) technique to build a novel portable biosensor for easy detection and characterization of Escherichia coli O157:H7 at high sensitivity level (single cell/mL). Results: A multiplexing dual recognition SERS scheme was developed to achieve one-step target detection without the need to separate target-bound probes from unbound ones. With three different SERS-tagged molecular probes targeting different epitopes of the same pathogen being deployed simultaneously, detection of pathogen targets was achieved at single cell level with sub-species specificity that has not been reported before in single-step pathogen detection. Conclusion: The self-referencing protocol implements with a Nano-dielectrophoretic microfluidic device potentially can become an easy-to-use, field-deployable spectroscopic sensor for onsite detection of pathogenic microorganisms.Item Open Access Gaussian and non-Gaussian fluctuations in pure classical fluids(2017-03-06) Naleem, Nawavi; Ploetz, Elizabeth A.; Smith, Paul E.; pesmith; Smith, Paul E.The particle number, energy, and volume probability distributions in the canonical, isothermal-isobaric, grand canonical, and isobaric-isenthalpic ensembles are investigated. In particular, we consider Gaussian and non-Gaussian behavior and formulate the results in terms of a single expression valid for all the ensembles employing common, experimentally accessible, thermodynamic derivatives. This is achieved using Fluctuation Solution Theory to help manipulate derivatives of the entropy. The properties of the distributions are then investigated using available equations of state for fluid water and argon. Purely Gaussian behavior is not observed for any of the state points considered here. A set of simple measures, involving thermodynamic derivatives, indicating non-Gaussian behavior is proposed. Ageneral expression, valid in the high temperature limit, for small energy fluctuations in the canonical ensemble is provided. Published by AIP Publishing.Item Open Access Fluctuation solution theory of pure fluids(2017-03-01) Ploetz, Elizabeth A.; Pallewela, Gayani N.; Smith, Paul E.; pesmith; Smith, Paul E.Fluctuation Solution Theory (FST) provides an alternative view of fluid thermodynamics in terms of pair fluctuations in the particle number and excess energy observed for an equivalent open system. Here we extend the FST approach to provide a series of triplet and quadruplet particle and excess energy fluctuations that can also be used to help understand the behavior of fluids. The fluctuations for the gas, liquid, and supercritical regions of three fluids (H2O, CO2, and SF6) are then determined from accurate equations of state. Many of the fluctuating quantities change sign on moving from the gas to liquid phase and, therefore, we argue that the fluctuations can be used to characterize gas and liquid behavior. Further analysis provides an approach to isolate contributions to the excess energy fluctuations arising from just the intermolecular interactions and also indicates that the triplet and quadruplet particle fluctuations are related to the pair particle fluctuations by a simple power law for large regions of the phase diagram away from the critical point. Published by AIP Publishing.Item Open Access Frustrated pretransitional phenomena in aperiodic composites(2016-11-11) Mariette, C.; Frantsuzov, Ilya; Wang, Bo; Guerin, L.; Rabiller, P.; Hollingsworth, Mark D.; Toudic, B.; mdholl; Hollingsworth, Mark D.This paper reports on symmetry breaking in the aperiodic inclusion compound n-octadecane/urea and its isotopomer n-octadecane/urea-d(4). The high-symmetry phase is described by a hexagonal rank-4 superspace group. Pretransitional phenomena in this crystallographic superspace reveal competing short-range-ordering phenomena within the high-symmetry phase. Very high-resolution diffraction data show that critical scattering appears at inequivalent points within the four-dimensional Brillouin zone, although the first phase transition at T-c1 near 158 K implies the condensation at only one of those points. The resulting superspace group remains of dimension 4. Two other phase transitions are reported at T-c2 = 152.8(4) K and T-c3 = 109(4) K in n-octadecane/urea-d(4). The two low-symmetry phases that arise are described by rank-5 superspace groups.Item Open Access Incorporating I-131 into a PAMAM (G5.0) dendrimerconjugate: design of a theranostic nanosensor for medullary thyroid carcinoma(2017-03-14) He, R.; Wang, H.; Su, Y.; Chen, C.; Xie, L.; Chen, L.; Yu, J.; Toledo, Y.; Abayaweera, G. S.; Zhu, G.; Bossmann, Stefan H.; sbossman; Bossmann, Stefan H.We report the synthesis and purification of a targeting probe for Medullary Thyroid Carcinoma (MTC) by incorporating I-131 into PAMAM (G5.0) dendrimers. Both the I-131 labeled control dendrimer (I-131-PAMAM (G5.0) without attached targeting peptide) and the MTC-targeting dendrimer (I-131-PAMAM (G5.0) attached to VTP (vascular targeting peptide)) were labeled with the radioisotope I-131 by applying the iodogen method. The resulting G5.0 dendrimers were purified by means of ultracentrifugation. The labelling efficiencies and radiochemical purities vs. time were determined by paper chromatography. The radiolabeling efficiencies of I-131-PAMAM (G5.0) and I-131-PAMAM (G5.0) were 93 +/- 1% and 85 +/- 2%, respectively. I-131-PAMAM (G5.0) did exhibit small, but significant changes in radiochemical purity as a function of time after labelling. The highest observed highest purity was 82 +/- 2%. I-131-PAMAM (G5.0)VTP did display larger changes in radiochemical purity as a function of time after labelling, maximally 80 +/- 2%. The stability of the two probes and their binding behavior to the human medullary thyroid cancer cell line (TT) were observed in vitro. Compared to the negative control group (consisting of (NaI)-I-131), the TT cell binding rate of 131I-PAMAM (G5.0)-VTP was significantly increased at 48 h and 72 h (P < 0.01). The TT cell binding rate of I-131-PAMAM (G5.0)-VTP at 48 h and 72 h was not significantly different when compared to the positive control group (I-131-PAMAM (G5.0) group) (P > 0.05). These findings have been confirmed by performing MTT assays. These results confirm earlier findings, which demonstrated fast uptake of PAMAM (G5.0) by various cell types.Item Open Access Correlation of the plasmon-enhanced photoconductance and photovoltaic properties of core-shell Au@TiO2 network(2016-08-30) Yang, Yiqun Q.; Wu, Judy; Li, Jun; junli; Li, JunThis study reveals the contribution of hot electrons from the excited plasmonic nanoparticles in dye sensitized solar cells (DSSCs) by correlating the photoconductance of a core-shell Au@TiO2 network on a micro-gap electrode and the photovolatic properties of this material as photoanodes in DSSCs. The distinct wavelength dependence of these two devices reveals that the plasmon-excited hot electrons can easily overcome the Schottky barrier at Au/TiO2 interface in the whole visible wavelength range and transfer from Au nanoparticles into the TiO2 network. The enhanced charge carrier density leads to higher photoconductance and facilitates more efficient charge separation and photoelectron collection in the DSSCs. Published by AIP Publishing.Item Open Access Rapid Nanoparticle Synthesis by Magnetic and Microwave Heating(2016-05-06) Chikan, Viktor; McLaurin, Emily J.; vchikan; mclaurin; Chikan, Viktor; McLaurin, Emily J.Traditional hot-injection (HI) syntheses of colloidal nanoparticles (NPs) allows good separation of the nucleation and growth stages of the reaction, a key limitation in obtaining monodisperse NPs, but with limited scalability. Here, two methods are presented for obtaining NPs via rapid heating: magnetic and microwave-assisted. Both of these techniques provide improved engineering control over the separation of nucleation and growth stages of nanomaterial synthesis when the reaction is initiated from room temperature. The advantages of these techniques with preliminary data are presented in this prospective article. It is shown here that microwave assisted heating could possibly provide some selectivity in activating the nanomaterial precursor materials, while magnetic heating can produce very tiny particles in a very short time (even on the millisecond timescale), which is important for scalability. The fast magnetic heating also allows for synthesizing larger particles with improved size distribution, therefore impacting, not only the quantity, but the quality of the nanomaterials.Item Open Access On the Conflicting Estimations of Pigment Site Energies in Photosynthetic Complexes: A Case Study of the CP47 Complex(2016-06-02) Reinot, Tonu; Chen, Jinhai H.; Kell, Adam; Jassas, Mahboobe; Robben, Kevin C.; Zazubovich, V.; Jankowiak, Ryszard; ryszard; Jankowiak, Ryszard; Reinot, Tonu; Chen, Jinhai H.; Kell, Adam; Jassas, Mahboobe; Robben, Kevin C.We focus on problems with elucidation of site energies (E-0(n)) for photosynthetic complexes (PSCs) in order to raise some genuine concern regarding the conflicting estimations propagating in the literature. As an example, we provide a stern assessment of the site energies extracted from fits to optical spectra of the widely studied CP47 antenna complex of photosystem II from spinach, though many general comments apply to other PSCs as well. Correct values of E-0(n) for chlorophyll (Chl) a in CP47 are essential for understanding its excitonic structure, population dynamics, and excitation energy pathway(s). To demonstrate this, we present a case study where simultaneous fits of multiple spectra (absorption, emission, circular dichroism, and nonresonant hole-burned spectra) show that several sets of parameters can fit the spectra very well. Importantly, we show that variable emission maxima (690-695 nm) and sample-dependent bleaching in nonresonant hole-burning spectra reported in literature could be explained, assuming that many previously studied CP47 samples were a mixture of intact and destabilized proteins. It appears that the destabilized subpopulation of CP47 complexes could feature a weakened hydrogen bond between the 13(1)-keto group of Chl29 and the PsbH protein subunit, though other possibilities cannot be entirely excluded, as discussed in this work. Possible implications of our findings are briefly discussed.Item Open Access Engineered Nanomedicine with Alendronic Acid Corona Improves Targeting to Osteosarcoma(2016-11-08) Nguyen, Thi D.T.; Pitchaimani, Arunkumar; Aryal, Santosh; saryalWe engineered nanomedicine with the stealth corona made up of densely packed bone seeking ligand, alendronic acid. In a typical nanoconstruct, alendronic acid is conjugated with hydrophilic head moiety of phospholipid that has an ability to self-assemble with hydrophobic polymeric core through its hydrophobic long carbon-chain. Proposed nanomedicine has three distinct compartments namely; poly(l-lactic-co-glycolic acid) polymeric core acting as a drug reservoir and skeleton of the nanoconstruct, phospholipid monolayer covers the core acting as a diffusion barrier, and a densely packed alendronic acid corona acting as a stabilizer and targeting moiety. Thus engineered nanomedicine attain spherical entity with ~90 ± 6 nm having negative zeta potential, −37.7 ± 2 mV, and has an ability to load 7 ± 0.3 wt% of doxorubicin. In-vitro bone targeting efficiency of nanomedicine was studied using hydroxyapatite crystals as a bone model, and found significant accumulation of nanoparticle in the crystals. Moreover, cellular internalization studies with mouse osteosarcoma confirm the selectivity of nanomedicine when compared to its internalization in non-targeted mouse melanoma. This nanomedicine shows prolong stability in serum and deliver the drug into the cell exhibiting an IC50 of 3.7 μM. Given the strong interacting property of alendronic acid with bone, the proposed nanomedicine hold promises in delivering drug to bone microenvironment.Item Open Access Graphene/GaSe-Nanosheet Hybrid: Towards High Gain and Fast Photoresponse(2016-01-18) Lu, R. T.; Liu, J. W.; Luo, H. F.; Chikan, Viktor; Wu, J. Z.; vchikanWhile high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications. In this paper we report a graphene/GaSe nanosheets hybrid photodetector, in which GaSe nanosheets provide a favorable geometric link to graphene conductive layer through van Der Waals force. After a vacuum annealing process, a high gain in exceeding 107 has been obtained simitaneously with a dynamic response time of around 10 ms for both light on and off. We attribute the high performance to the elimination of possible deep charge traps, most probably at the graphene/GaSe nanosheets interface. This result demonstrates high photoconductive gain and fast photoresponse can be achieved simultaneously and a clean interface is the key to the high performance of these hybrid devices.Item Open Access Early breast cancer screening using iron/iron oxide-based nanoplatforms with sub-femtomolar limits of detection(2016-03-07) Udukala, D. N.; Wang, H. W.; Wendel, S. O.; Malalasekera, A. P.; Samarakoon, Thilani Nishanthika; Yapa, A. S.; Abayaweera, G.; Basel, M. T.; Maynez, P.; Li, Ping; Higgins, Daniel A.; Gadbury, Gary; Troyer, Deryl L.; Bossmann, Stefan H.; pli; higgins; gadbury; troyer; sbossmanProteases, including matrix metalloproteinases (MMPs), tissue serine proteases, and cathepsins (CTS) exhibit numerous functions in tumor biology. Solid tumors are characterized by changes in protease expression levels by tumor and surrounding tissue. Therefore, monitoring protease levels in tissue samples and liquid biopsies is a vital strategy for early cancer detection. Water-dispersable Fe/Fe3O4-core/shell based nanoplatforms for protease detection are capable of detecting protease activity down to sub-femtomolar limits of detection. They feature one dye (tetrakis(carboxyphenyl) porphyrin (TCPP)) that is tethered to the central nanoparticle by means of a protease-cleavable consensus sequence and a second dye (Cy 5.5) that is directly linked. Based on the protease activities of urokinase plasminogen activator (uPA), MMPs 1, 2, 3, 7, 9, and 13, as well as CTS B and L, human breast cancer can be detected at stage I by means of a simple serum test. By monitoring CTS B and L stage 0 detection may be achieved. This initial study, comprised of 46 breast cancer patients and 20 apparently healthy human subjects, demonstrates the feasibility of protease-activity-based liquid biopsies for early cancer diagnosis.Item Open Access Is there any point in making co-crystals?(2015-07-15) Aakeröy, Christer B.; aakeroyItem Open Access Long-range modulation of a composite crystal in a five-dimensional superspace(2015-05-05) Guerin, L.; Mariette, C.; Rabiller, P.; Huard, M.; Ravy, S.; Fertey, P.; Nichols, S. M.; Wang, B.; Mannsfeld, S. C. B.; Weber, T.; Hollingsworth, Mark D.; Toudic, B.; mdhollItem Open Access Cu2S3 complex on Cu(111) as a candidate for mass transport enhancement(2015-01-22) Walen, H.; Liu, D. J.; Oh, J.; Lim, H.; Evans, J. W.; Aikens, Christine M.; Kim, Y.; Thiel, P. A.; cmaikensItem Open Access Probing environment fluctuations by two-dimensional electronic spectroscopy of molecular systems at temperatures below 5 K(2015-04-21) Rancova, O.; Jankowiak, Ryszard J.; Abramavicius, D.; ryszardItem Open Access Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers(2015-03-04) Reppert, M.; Kell, A.; Pruitt, T.; Jankowiak, Ryszard J.; ryszardItem Open Access Experimental triplet and quadruplet fluctuation densities and spatial distribution function integrals for liquid mixtures(2015-03-05) Ploetz, E. A.; Smith, Paul E.; pesmithItem Open Access Nested Helmholtz coil design for producing homogeneous transient rotating magnetic fields(2015-03-03) Podaru, G.; Moore, J.; Dani, R. K.; Prakash, Punit; Chikan, Viktor; vchikan; prakashpItem Open Access Experimental triplet and quadruplet fluctuation densities and spatial distribution function integrals for pure liquids(2015-01-26) Ploetz, E. A.; Karunaweera, S.; Smith, Paul E.; pesmith
