Boron nitride and phonon polaritons

Phillips, C.; Gilburd, L.; Xu, X. G.; Walker, G. C. Surface and Volume Phonon Polaritons in Boron Nitride Nanotubes. J. Phys. Chem. Lett. 2019, 10, 4851–4856. doi: 10.1021/acs.jpclett.9b01829.

Wagner, M.; Jakob, D. S.; Horne, S.; Mittel, H.; Osechinskiy, S.; Phillips, C.; Walker, G. C.; Su, C.; Xu, X. G. Ultrabroadband Nanospectroscopy with a Laser-Driven Plasma Source. ACS Photonics 2018, 5, 1467–1475. doi: 10.1021/acsphotonics.7b01484

Jiang, J.-H.; Xu, X. G.; Gilburd, L.; Walker, G. C. Optical hot-spots in boron-nitride nanotubes at mid infrared frequencies: one-dimensional localization due to random-scattering. Opt. Express 2017, 25, 25059–25070. doi: 10.1364/OE.25.025059

Kim, K. S.; Trajanoski, D.; Ho, K.; Gilburd, L.; Maiti, A.; van der Velden, L.; de Beer, S.; Walker, G. C. The Effect of Adjacent Materials on the Propagation of Phonon Polaritons in Hexagonal Boron Nitride. J. Phys. Chem. Lett. 2017, 8, 2902–2908. doi: 10.1021/acs.jpclett.7b01048

Gilburd, L.; Kim, K. S.; Ho, K.; Trajanoski, D.; Maiti, A.; Halverson, D.; de Beer, S.; Walker, G. C. Hexagonal Boron Nitride Self-Launches Hyperbolic Phonon Polaritons. J. Phys. Chem. Lett. 2017, 8, 2158–2162. doi: 10.1021/acs.jpclett.7b00748

Gilburd, L.; Xu, X. G.; Bando, Y.; Golberg, D.; Walker, G. C. Surface Phonon Coupling within Boron Nitride Nanotubes Resolved by a Novel Near-Field Infrared Pump-Probe Imaging Technique. Microsc. Microanal. 2016, 22, 366–367. doi: 10.1017/S1431927616002683

Gilburd, L.; Xu, X. G.; Bando, Y.; Golberg, D.; Walker, G. C. Near-Field Infrared Pump–Probe Imaging of Surface Phonon Coupling in Boron Nitride Nanotubes. J. Phys. Chem. Lett. 2016, 7, 289–294. doi: 10.1021/acs.jpclett.5b02438

Xu, X. G.; Gilburd, L.; Bando, Y.; Golberg, D.; Walker, G. C. Defects and Deformation of Boron Nitride Nanotubes Studied by Joint Nanoscale Mechanical and Infrared Near-Field Microscopy. J. Phys. Chem. C 2016, 120, 1945–1951. doi: 10.1021/acs.jpcc.5b10670

Xu, X. G.; Jiang, J.-H.; Gilburd, L.; Rensing, R. G.; Burch, K. S.; Zhi, C.; Bando, Y.; Golberg, D.; Walker, G. C. Mid-infrared Polaritonic Coupling between Boron Nitride Nanotubes and Graphene. ACS Nano 2014, 8, 11305–11312. doi: 10.1021/nn504093g

Ghamsari, B. G.;  Xu, X. G.; Gilburd, L.; Walker, G. C.; Berini, P. Mid-infrared surface phonon polaritons in boron-nitride nanotubes. J. Opt. 2014, 16, 114008. doi: 10.1088/2040-8978/16/11/114008

Xu, X. G.; Ghamsari, B. G.; Jiang, J.-H.; Gilburd, L.; Andreev, G. O.; Zhi, C.; Bando, Y.; Golberg, D.; Berini, P.; Walker, G. C. One-dimensional surface phonon polaritons in boron nitride nanotubes. Nat. Commun. 2014, 5, 4782. doi: 10.1038/ncomms5782

Xu, X. G.; Tanur, A. E.; Walker, G. C. Phase Controlled Homodyne Infrared Near-Field Microscopy and Spectroscopy Reveal Inhomogeneity within and among Individual Boron Nitride Nanotubes. J. Phys. Chem. A 2013, 117, 3348–3354. doi: 10.1021/jp4008784

Tanur, A. E.; Wang, J.; Reddy, A. L. M.; Lamont, D. N.; Yap, Y. K.; Walker, G. C. Diameter-Dependent Bending Modulus of Individual Multiwall Boron Nitride Nanotubes. J. Phys. Chem. B 2013, 117, 4618–4625. doi: 10.1021/jp308893s

Reddy, A. L. M.; Gupta, B. K.; Narayanan, T. N.; Martí, A. A.; Ajayan, P. M.; Walker, G. C. Probing of Ni-Encapsulated Ferromagnetic Boron Nitride Nanotubes by Time-Resolved and Steady-State Photoluminescence Spectroscopy. J. Phys. Chem. C 2012, 116, 12803–12809. doi: 10.1021/jp210597m

Reddy, A. L. M.; Tanur, A. E.; Walker, G. C. Synthesis and hydrogen storage properties of different types of boron nitride nanostructures. Int. J. Hydrogen Energy 2010, 35, 4138–4143. doi: 10.1016/j.ijhydene.2010.01.072

A tool for infrared imaging at the nanoscale

Gilburd, L.; Xu, X. G.; Bando, Y.; Golberg, D.; Walker, G. C. Near-Field Infrared Pump–Probe Imaging of Surface Phonon Coupling in Boron Nitride Nanotubes. J. Phys. Chem. Lett. 2016, 7, 289–294. doi: 10.1021/acs.jpclett.5b02438

Xu, X. G.; Gilburd, L.; Walker, G. C. Phase stabilized homodyne of infrared scattering type scanning near-field optical microscopy. Appl. Phys. Lett. 2014, 105, 263104. doi: 10.1063/1.4905207

Xu, X.; Walker, G. C. Method to obtain absorption spectra from near-field infrared scattering using homodyne detection. US8646110B1, February 4, 2014.

Coupled plasmonic structures and their analogues

Walters, C. M; Pao, C.; Gagnon, B. P.; Zamecnik, C. R.; Walker, G. C. Bright Surface-Enhanced Raman Scattering with Fluorescence Quenching from Silica Encapsulated J-Aggregate Coated Gold Nanoparticles. Adv. Mater. 2018, 30, 1705381. doi: 10.1002/adma.201705381

Stewart, A. F.; Gagnon, B. P.; Walker, G. C. Forming End-to-End Chains of Gold Nanorods Using Porphyrins and Phthalocyanines. Langmuir 2015, 31, 6902–6908. doi: 10.1021/acs.langmuir.5b01323

Klinkova, A.; Thérien-Aubin, H.; Ahmed, A.; Nykypanchuk, D.; Choueiri, R. M.; Gagnon, B.; Muntyanu, A.; Gang, O.; Walker, G. C.; Kumacheva, E. Structural and Optical Properties of Self-Assembled Chains of Plasmonic Nanocubes. Nano Lett. 2014, 14, 6314–6321. doi: 10.1021/nl502746h

Stewart, A. F.; Lee, A.; Ahmed, A.; Ip, S.; Kumacheva, E.; Walker, G. C. Rational Design for the Controlled Aggregation of Gold Nanorods via Phospholipid Encapsulation for Enhanced Raman Scattering. ACS Nano 2014, 8, 5462–5467. doi: 10.1021/nn4044589

Pirotta, S.; Xu, X. G.; Delfan, A.; Mysore, S.; Maiti, S.; Dacarro, G.; Patrini, M.; Galli, M.; Guizzetti, G.; Bajoni, D.; Sipe, J. E.; Walker, G. C.; Liscidini, M. Surface-Enhanced Raman Scattering in Purely Dielectric Structures via Bloch Surface Waves. J. Phys. Chem. C 2013, 117, 6821–6825. doi: 10.1021/jp400223f

Zamecnik, C. R.; Ahmed, A.; Walters, C. M.; Gordon, R.; Walker, G. C. Surface-Enhanced Raman Spectroscopy Using Lipid Encapsulated Plasmonic Nanoparticles and J-Aggregates To Create Locally Enhanced Electric Fields. J. Phys. Chem. C 2013, 117, 1879–1886. doi: 10.1021/jp3117352

Kofke, M. J.; Waldeck, D. H.; Walker, G. C. Composite nanoparticle nanoslit arrays: a novel platform for LSPR mediated subwavelength optical transmission. Opt. Express 2010, 18, 7705–7713. doi: 10.1364/OE.18.007705

Particles for surface-enhanced Raman scattering for identifying cell surface proteins for biodiagnostics

Jankowski, A. P.; Pao, C.; Walker, G. C. Photonic Nanoparticles for Cellular and Tissular Labeling. In Comprehensive Nanoscience and Nanotechnology, 2nd ed.; Andrews, D., Nann, T., Lipson, R., Eds.; Academic Press: Cambridge, 2019. Accepted.

Ip, S.; MacLaughlin, C. M.; Joseph, M.; Mullaithilaga, N.; Yang, G.; Wang, C.; Walker, G. C. Dual-Mode Dark Field and Surface-Enhanced Raman Scattering Liposomes for Lymphoma and Leukemia Cell Imaging. Langmuir 2018. Article ASAP. doi: 10.1021/acs.langmuir.8b02313

MacLaughlin, C. M.; Mullaithilaga, N.; Yang, G.; Ip, S. Y.; Wang, C.; Walker, G. C. Surface-Enhanced Raman Scattering Dye-Labeled Au Nanoparticles for Triplexed Detection of Leukemia and Lymphoma Cells and SERS Flow Cytometry. Langmuir 2013, 29, 1908–1919. doi: 10.1021/la303931c

MacLaughlin, C. M.; Parker, E. P. K.; Walker, G. C.; Wang, C. Evaluation of SERS labeling of CD20 on CLL cells using optical microscopy and fluorescence flow cytometry. Nanomedicine 2013, 9, 55–64. doi: 10.1016/j.nano.2012.04.003

MacLaughlin, C. M.; Parker, E. P. K.; Walker, G. C.; Wang, C. Polymer-coated surface enhanced Raman scattering (SERS) gold nanoparticles for multiplexed labeling of chronic lymphocytic leukemia cells. In Frontiers in Biological Detection: Proc. SPIE 8212: From Nanosensors to Systems IV, San Franciso, CA, Jan. 2012; Miller, B. L., Fauchet, P. M., Eds.; SPIE: Bellingham, WA, 2012; 821203. doi: 10.1117/12.909192

Ip, S. Y.; MacLaughlin, C. M.; Mullaithilaga, N.; Joseph, M.; Wala, S.; Wang, C.; Walker, G. C. Lipid-encapsulation of surface enhanced Raman scattering (SERS) nanoparticles and targeting to chronic lymphocytic leukemia (CLL) cells. In Frontiers in Biological Detection: Proc. SPIE 8212: From Nanosensors to Systems IV, San Francisco, CA, Jan. 2012; Miller, B. L., Fauchet, P. M., Eds.; SPIE: Bellingham, WA, 2012; 821204. doi: 10.1117/12.909179

Ip, S.; MacLaughlin, C. M.; Gunari, N.; Walker, G. C. Phospholipid Membrane Encapsulation of Nanoparticles for Surface-Enhanced Raman Scattering. Langmuir 2011, 27, 7024–7033. doi: 10.1021/la200212c

Nguyen, C. T.; Nguyen, J. T.; Rutledge, S.; Zhang, J.; Wang, C.; Walker, G. C. Detection of chronic lymphocytic leukemia cell surface markers using surface enhanced Raman scattering gold nanoparticles. Cancer Lett. 2010, 292, 91–97. doi: 10.1016/j.canlet.2009.11.011

Ip, S.; MacLaughlin, C. M.; Nguyen, C. T.; Walker, G. C. Photonic Nanoparticles for Cellular and Tissular Labeling. In Comprehensive Nanoscience and Nanotechnology; Andrews, D., Scholes, G., Wiederrecht, G., Eds.; Academic Press: Cambridge, 2010, 59–104. doi: 10.1016/B978-0-12-374396-1.00076-3

Mechanics of cellular environments, including phospholipid bilayers

Alipour, E.; Halverson, D.; McWhirter, S.; Walker, G. C. Phospholipid Bilayers: Stability and Encapsulation of Nanoparticles. Annu. Rev. Phys. Chem. 2017, 68, 261–283. doi: 10.1146/annurev-physchem-040215-112634

Navab, R.; Strumpf, D.; To, C.; Pasko, E.; Kim, K. S.; Park, C. J.; Hai, J.; Liu, J.; Jonkman, J.; Barczyk, M.; Bandarchi, B.; Wang, Y. H.; Venkat, K.; Ibrahimov, E.; Pham, N.-A.; Ng, C; Radulovich, N.; Zhu, C.-Q.; Pintilie, M.; Wang, D.; Lu, A.; Jurisica, I.; Walker, G. C.; Gullberg, D.; Taso, M.-S. Integrin α11β1 regulates cancer stromal stiffness and promotes tumorigenicity and metastasis in non-small cell lung cancer. Oncogene 2015, 35, 1899–1908. doi: 10.1038/onc.2015.254

Sullan, R. M. A.; Shi, W.; Chan, H.; Li, J. K.; Walker, G. C. Mechanical stability of phase-segregated multicomponent lipid bilayers enhanced by PS-b-PEO diblock copolymers. Soft Matter 2013, 9, 6245–6253. doi: 10.1039/C3SM50855B

Kumachev, A.; Tumarkin, E.; Walker, G. C.; Kumacheva, E. Characterization of the mechanical properties of microgels acting as cellular microenvironments. Soft Matter 2013, 9, 2959–2965. doi: 10.1039/C3SM27400D

Velasco, D.; Chau, M.; Thérien-Aubin, H.; Kumachev, A.; Tumarkin, E.; Jia, Z.; Walker, G. C.; Monteiro, M.; Kumacheva, E. Nanofibrillar thermoreversible micellar microgels. Soft Matter 2013, 9, 2380–2383. doi: 10.1039/C2SM27796D

Li, J. K.; Li, I. T. S.; Walker, G. C.; Sullan, R. M. A.; Zou, S.; Sun, Y. Polymer Nanomechanics. In Polymer Science: A Comprehensive Reference; Matyjaszewski, K., Möller, M., Eds; Academic Press: Cambridge, 2012, 377–404. doi: 10.1016/B978-0-444-53349-4.00184-9

Raz, N.; Li, J. K.; Fiddes, L. K.; Tumarkin, E.; Walker, G. C.; Kumacheva, E. Microgels with an Interpenetrating Network Structure as a Model System for Cell Studies. Macromolecules 2010, 43, 7277–7281. doi: 10.1021/ma101231z

Sullan, R. M. A.; Li, J. K.; Hao, C.; Walker, G. C.; Zou, S. Cholesterol-Dependent Nanomechanical Stability of Phase-Segregated Multicomponent Lipid Bilayers. Biophys. J. 2010, 99, 507–516. doi: 10.1016/j.bpj.2010.04.044

Ip, S.; Li, J. K.; Walker, G. C. Phase Segregation of Untethered Zwitterionic Model Lipid Bilayers Observed on Mercaptoundecanoic-Acid-Modified Gold by AFM Imaging and Force Mapping. Langmuir 2010, 26, 11060–11070. doi: 10.1021/la100605t

New tools to characterize oligomers and aggregates of amyloidogenic peptides

Bhowmik, D.; MacLaughlin, C. M; Chandrakesan, M.; Ramesh, P.; Venkatramani, R.; Walker, G. C.; Maiti, S. pH changes the aggregation propensity of amyloid-β without altering the monomer conformation. Phys. Chem. Chem. Phys. 2014, 16, 885–889. doi: 10.1039/C3CP54151G

Paulite, M.; Blum, C.; Schmid, T.; Opilik, L.; Eyer, K.; Walker, G. C.; Zenobi, R. Full Spectroscopic Tip-Enhanced Raman Imaging of Single Nanotapes Formed from β-Amyloid(1–40) Peptide Fragments. ACS Nano 2013, 7, 911–920. doi: 10.1021/nn305677k

Paulite, M.; Fakhraai, Z.; Li, I. T. S.; Gunari, N.; Tanur, A. E.; Walker, G. C. Imaging Secondary Structure of Individual Amyloid Fibrils of a β₂-Microglobulin Fragment Using Near-Field Infrared Spectroscopy. J. Am. Chem. Soc. 2011, 133, 7376–7383. doi: 10.1021/ja109316p

Length scales of hydrophobic hydration

Mondal, J.; Halverson, D.; Li, I. T. S.; Stirnemann, G.; Walker, G. C.; Berne, B. J. How osmolytes influence hydrophobic polymer conformations: A unified view from experiment and theory. Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 9270–9275. doi: 10.1073/pnas.1511780112

Li, I. T. S.; Walker, G. C. Single Polymer Studies of Hydrophobic Hydration. Acc. Chem. Res. 2012, 45, 2011–2021. doi: 10.1021/ar200285h

Li, I. T. S.; Walker, G. C. Signature of hydrophobic hydration in a single polymer. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 16527–16532. doi: 10.1073/pnas.1105450108

Li, I. T. S.; Walker, G. C. Interfacial Free Energy Governs Single Polystyrene Chain Collapse in Water and Aqueous Solutions. J. Am. Chem. Soc. 2010, 132, 6530–6540. doi: 10.1021/ja101155h

Polymer self-assembly

Gonzalez-Alvarez, M. J.; Jia, L.; Guerin, G.; Kim, K. S.; An Du, V.; Walker, G.; Manners, I.; Winnik, M. A. How a Small Modification of the Corona-Forming Block Redirects the Self-Assembly of Crystalline–Coil Block Copolymers in Solution. Macromolecules 2016, 49, 7975–7984. doi: 10.1021/acs.macromol.6b01616

Feng, C.; Jose Gonzalez-Alvarez, M.; Song, Y.; Li, I.; Zhao, G.; Molev, G.; Guerin, G.; Walker, G. C.; Scholes, G. D.; Manners, I.; Winnik, M. A. Synthesis, self-assembly and photophysical properties of oligo(2,5-dihexyloxy-1,4-phenylene vinylene)-block-poly(ethylene glycol). Soft Matter 2014, 10, 8875–8887. doi: 10.1039/C4SM01402B

Jia, L.; Zhao, G.; Shi, W.; Coombs, N.; Gourevich, I.; Walker, G. C.; Guerin, G.; Manners, I.; Winnik, M. A. A design strategy for the hierarchical fabrication of colloidal hybrid mesostructures. Nat. Commun. 2014, 5, 3882. doi: 10.1038/ncomms4882

Molev, G.; Lu, Y.; Kim, K. S.; Majdalani, I. C.; Guerin, G.; Petrov, S.; Walker, G.; Manners, I.; Winnik, M. A. Organometallic–Polypeptide Diblock Copolymers: Synthesis by Diels–Alder Coupling and Crystallization-Driven Self-Assembly to Uniform Truncated Elliptical Lamellae. Macromolecules 2014, 47, 2604–2615. doi: 10.1021/ma402441y

Qian, J.; Lu, Y.; Chia, A.; Zhang, M.; Rupar, P. A.; Gunari, N.; Walker, G. C.; Cambridge, G.; He, F.; Guerin, G.; Manners, I.; Winnik, M. A. Self-Seeding in One Dimension: A Route to Uniform Fiber-like Nanostructures from Block Copolymers with a Crystallizable Core-Forming Block. ACS Nano 2013, 7, 3754–3766. doi: 10.1021/nn400124x

Wang, M.; Zhang, M.; Li, J.; Kumar, S.; Walker, G. C.; Scholes, G. D.; Winnik, M. A. Self-Assembly of Colloidal Quantum Dots on the Scaffold of Triblock Copolymer Micelles. ACS Appl. Mater. Interfaces 2010, 2, 3160–3169. doi: 10.1021/am100645j

Materials to reduce biofouling and the adhesive cements of marine organisms

Kim, K. S.; Gunari, N.; MacNeil, D.; Finlay, J.; Callow, M.; Callow, J.; Walker, G. C. Aqueous-Based Fabrication of Low-VOC Nanostructured Block Copolymer Films as Potential Marine Antifouling Coatings. ACS Appl. Mater. Interfaces 2016, 8, 20342–20351. doi: 10.1021/acsami.6b04629

Sarvothaman, M. K.; Kim, K. S.; Seale, B.; Brodersen, P. M.; Walker, G. C.; Wheeler, A. R. Dynamic Fluoroalkyl Polyethylene Glycol Co-Polymers: A New Strategy for Reducing Protein Adhesion in Lab-on-a-Chip Devices. Adv. Funct. Mater. 2015, 25, 506–515. doi: 10.1002/adfm.201402218

Grozea, C. M.; Li, I. T. S.; Grozea, D.; Walker, G. C. Microdomain Orientation of Diblock Copolymer Ultrathin Films Solvent Annealed at Low Temperatures. Macromolecules 2011, 44, 3901–3909. doi: 10.1021/ma102470v

Gunari, N.; Brewer, L. H.; Bennett, S. M; Sokolova, A.; Kraut, N. D.; Finlay, J. A.; Meyer, A. E.; Walker, G. C.; Wendt, D. E.; Callow, M. E.; Callow, J. A.; Bright, F. V.; Detty, M. R. The control of marine biofouling on xerogel surfaces with nanometer-scale topography. Biofouling 2011, 27, 137–149. doi: 10.1080/08927014.2010.548599

Finlay, J. A.; Bennett, S. M.; Brewer, L. H.; Sokolova, A.; Clay, G.; Gunari, N.; Meyer, A. E.; Walker, G. C.; Wendt, D. E.; Callow, M. E.; Callow, J. A.; Dettey, M. R. Barnacle settlement and the adhesion of protein and diatom microfouling to xerogel films with varying surface energy and water wettability. Biofouling 2010, 26, 657–666. doi: 10.1080/08927014.2010.506242

Tanur, A. E.; Gunari, N.; Sullan, R. M. A.; Kavanagh, C. J.; Walker, G. C. Insights into the composition, morphology, and formation of the calcareous shell of the serpulid Hydroides dianthus. J. Struct. Biol. 2010, 169, 145–160. doi: 10.1016/j.jsb.2009.09.008

Weinman, C. J.; Gunari, N.; Krishnan, S.; Dong, R.; Paik, M. Y.; Sohn, K. E.; Walker, G. C.; Kramer, E. J.; Fischer, D. A.; Ober, C. K. Protein adsorption resistance of anti-biofouling block copolymers containing amphiphilic side chains. Soft Matter 2010, 6, 3237–3243. doi: 10.1039/B925114F

Bennett, S. M.; Finlay, J. A.; Gunari, N.; Wells, D. D.; Meyer, A. E.; Walker, G. C.; Callow, M. E.; Callow, J. A.; Bright, F. V.; Detty, M. R. The role of surface energy and water wettability in aminoalkyl/fluorocarbon/hydrocarbon-modified xerogel surfaces in the control of marine biofouling. Biofouling 2009, 26, 235–246. doi: 10.1080/08927010903469676

Grozea, C. M.; Walker, G. C. Approaches in designing non-toxic polymer surfaces to deter marine biofouling. Soft Matter 2009, 5, 4088–4100. doi: 10.1039/B910899H

Grozea, C. M.; Gunari, N.; Finlay, J. A.; Grozea, D.; Callow, M. E.; Callow, J. A.; Lu, Z.-H.; Walker, G. C. Water-Stable Diblock Polystyrene-block-poly(2-vinyl pyridine) and Diblock Polystyrene-block-Poly(methyl methacrylate) Cylindrical Patterned Surfaces Inhibit Settlement of Zoospores of the Green Alga Ulva. Biomacromolecules 2009, 10, 1004–1012. doi: 10.1021/bm900065b

Sullan, R. M. A.; Gunari, N.; Tanur, A. E.; Chan, Y.; Dickinson, G. H.; Orihuela, B.; Rittschof, D.; Walker, G. C. Nanoscale structures and mechanics of barnacle cement. Biofouling 2009, 25, 263–275. doi: 10.1080/08927010802688095