Browsing by Author "Hati, Sumon"

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    Design of Anisotropically Shaped Plasmonic Nanocrystals from Ultrasmall Sn-Decorated In2O3 Nanoclusters Used as Seed Materials
    (American Chemical Society, 2022-12-07) Davis, Gregory A., Jr.; Prusty, Gyanaranjan; Hati, Sumon; Lee, Jacob T.; Langlais, Sarah R.; Zhan , Xun; Sardar, Rajesh; Chemistry and Chemical Biology, School of Science
    Ultrasmall inorganic nanoclusters (<2.0 nm in diameter) bridge the gap between individual molecules and large nanocrystals (NCs) and provide the critical foundation to design and prepare new solid-state nanomaterials with previously unknown properties and functions. Herein, for the first time, we report the monodispersed colloidal synthesis and successful isolation of metastable, rhombohedral-phase, <2.0 nm indium oxide (In2O3) nanoclusters. Ultrasmall nanocluster formation is controlled by a kinetically driven growth process, as evaluated through the variation of metal-to-passivating ligand concentrations. Although <2.0 nm-diameter In2O3 nanoclusters are synthesized in the presence of tin (Sn) precursors, they do not display typical localized surface plasmon resonance (LSPR) properties, which are commonly observed in Sn-doped In2O3 (Sn:In2O3) NCs. Our Raman and X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy (HRTEM) analyses support the existence of Sn-decorated In2O3 nanoclusters, where Sn complexes reside on the surface of the nanocluster as Z-type ligands, as opposed to the formation of Sn:In2O3 nanoclusters, which behave as wide band gap (∼5.5 eV) nanomaterials. The experimentally determined band gap is in good agreement with the theoretical effective mass calculations. The newly synthesized Sn-decorated, 1.7 nm-diameter In2O3 nanoclusters are further used as reactive monomers for the seeded growth synthesis of bcc-phase, plasmonic Sn:In2O3 NCs via ex situ injection of In precursors without the addition of any Sn precursors. The LSPR peak of Sn:In2O3 NCs, which appear to form nanoflower assemblies, is tunable in the 1800–4000 nm region and possibly even the deep-IR region. In addition to altering the size and assembly of the spherical Sn:In2O3 NCs by introducing different amounts of indium acetylacetonate, injection of indium chloride precursors in the reaction mixture results in the formation of rod-shaped NCs. Surprisingly, Sn-decorated, <1.5 nm-diameter In2O3 nanoclusters do not grow into large plasmonic Sn:In2O3 NCs. Taken together, the results presented here contribute to the fundamental understanding of the surface free energy of ultrasmall metal oxide nanoclusters and further advance the knowledge on the phase transformation and growth of plasmonic NCs.
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    Enhancing Nonfouling and Sensitivity of Surface-Enhanced Raman Scattering Substrates for Potent Drug Analysis in Blood Plasma via Fabrication of a Flexible Plasmonic Patch
    (ACS, 2021-01) Masterson, Adrianna N.; Hati, Sumon; Ren, Greta; Liyanage, Thakshila; Manicke, Nicholas E.; Goodpaster, John V.; Sardar, Rajesh; Chemistry and Chemical Biology, School of Science
    Surface-enhanced Raman scattering (SERS) is an ultrasensitive analytical technique, which is capable of providing high specificity; thus, it can be used for toxicological drug assay (detection and quantification). However, SERS-based drug analysis directly in human biofluids requires mitigation of fouling and nonspecificity effects that commonly appeared from unwanted adsorption of endogenous biomolecules present in biofluids (e.g., blood plasma and serum) onto the SERS substrate. Here, we report a bottom-up fabrication strategy to prepare ultrasensitive SERS substrates, first, by functionalizing chemically synthesized gold triangular nanoprisms (Au TNPs) with poly(ethylene glycol)-thiolate in the solid state to avoid protein fouling and second, by generating flexible plasmonic patches to enhance SERS sensitivity via the formation of high-intensity electromagnetic hot spots. Poly(ethylene glycol)-thiolate-functionalized Au TNPs in the form of flexible plasmonic patches show a twofold-improved signal-to-noise ratio in comparison to triethylamine (TEA)-passivated Au TNPs. Furthermore, the plasmonic patch displays a SERS enhancement factor of 4.5 ×107. Utilizing the Langmuir adsorption model, we determine the adsorption constant of drugs for two different surface ligands and observe that the drug molecules display stronger affinity for poly(ethylene glycol) ligands than TEA. Our density functional theory calculations unequivocally support the interaction between drug molecules and poly(ethylene glycol) moieties. Furthermore, the universality of the plasmonic patch for SERS-based drug detection is demonstrated for cocaine, JWH-018, and opioids (fentanyl, despropionyl fentanyl, and heroin) and binary mixture (trace amount of fentanyl in heroin) analyses. We demonstrate the applicability of flexible plasmonic patches for the selective assay of fentanyl at picogram/milliliter concentration levels from drug-of-abuse patients’ blood plasma. The fentanyl concentration calculated in the patients’ blood plasma from SERS analysis is in excellent agreement with the values determined using the paper spray ionization mass spectrometry technique. We believe that the flexible plasmonic patch fabrication strategy would be widely applicable to any plasmonic nanostructure for SERS-based chemical sensing for clinical toxicology and therapeutic drug monitoring.
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    Inorganic–Organic Interfacial Electronic Effects in Ligand-Passivated WO3–x Nanoplatelets Induce Tunable Plasmonic Properties for Smart Windows
    (ACS, 2022-07-06) Lee, Jacob T.; Das, Debabrata; Davis, Gregory A., Jr.; Hati, Sumon; Ramana, C. V.; Sardar, Rajesh; Chemistry and Chemical Biology, School of Science
    Transition-metal oxide (TMO) nanocrystals (NCs), displaying localized surface plasmon resonance (LSPR) properties, are an emerging class of nanomaterials due to their high stability, high earth abundance, and wide range of spectral responses covering the near-to-far infrared region of the solar spectrum. Although surface passivating ligands are ubiquitous to colloidal NC-based research, the role of ligands, specifically the impact of their chemical structure on the dielectric and LSPR properties of TMO NC films, has not been investigated in detail. Here, we report for the first time the chemical effects at the metal–ligand (inorganic–organic) interfaces influencing the optical constants and LSPR properties of thin films comprising highly oxygen-deficient, sub-stoichiometric, LSPR-active tungsten oxide (WO3–x) nanoplatelets (NPLs). We studied ligands with two different types of binding head groups, aromatic conjugation, and short and long hydrocarbon chains. Using density functional theory calculations, we determine that the changes in the interfacial dipole moments and polarizability control the permittivity at the interface, resulting in the alteration of dielectric and LSPR properties of ligand-passivated NPL in thin nanocrystalline films. The photochromic properties of WO3–x NPL passivated with different ligands in thin films have also been investigated to highlight the impact of interfacial permittivity caused by the chemical structures of passivating ligands. Taken together, this study provides a fundamental understanding of emerging properties at the metal–ligand interface that could be further optimized for energy efficiency in smart windows.
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    β Cell microRNAs Function as Molecular Hubs of Type 1 Diabetes Pathogenesis and as Biomarkers of Diabetes Risk
    (bioRxiv, 2023-06-15) Syed, Farooq; Krishnan, Preethi; Chang, Garrick; Langlais, Sarah R.; Hati, Sumon; Yamada, Kentaro; Lam, Anh K.; Talware, Sayali; Liu, Xiaowen; Sardar, Rajesh; Liu, Jing; Mirmira, Raghavendra G.; Evans-Molina, Carmella; Pediatrics, School of Medicine
    MicroRNAs (miRNAs) are small non-coding RNAs that play a crucial role in modulating gene expression and are enriched in cell-derived extracellular vesicles (EVs). We investigated whether miRNAs from human islets and islet-derived EVs could provide insight into β cell stress pathways activated during type 1 diabetes (T1D) evolution, therefore serving as potential disease biomarkers. We treated human islets from 10 cadaveric donors with IL-1β and IFN-γ to model T1D ex vivo. MicroRNAs were isolated from islets and islet-derived EVs, and small RNA sequencing was performed. We found 20 and 14 differentially expressed (DE) miRNAs in cytokine- versus control-treated islets and EVs, respectively. Interestingly, the miRNAs found in EVs were mostly different from those found in islets. Only two miRNAs, miR-155-5p and miR-146a-5p, were upregulated in both islets and EVs, suggesting selective sorting of miRNAs into EVs. We used machine learning algorithms to rank DE EV-associated miRNAs, and developed custom label-free Localized Surface Plasmon Resonance-based biosensors to measure top ranked EVs in human plasma. Results from this analysis revealed that miR-155, miR-146, miR-30c, and miR-802 were upregulated and miR-124-3p was downregulated in plasma-derived EVs from children with recent-onset T1D. In addition, miR-146 and miR-30c were upregulated in plasma-derived EVs of autoantibody positive (AAb+) children compared to matched non-diabetic controls, while miR-124 was downregulated in both T1D and AAb+ groups. Furthermore, single-molecule fluorescence in situ hybridization confirmed increased expression of the most highly upregulated islet miRNA, miR-155, in pancreatic sections from organ donors with AAb+ and T1D.