R. Kamarudheen, G. Castellanos Gonzalez, L. P. J. Kamp, H. J. H. Clercx, and A. Baldi
Quantifying photothermal and hot charge carrier effects in plasmon-driven nanoparticle syntheses

M. Parente, S. Sheikholeslami, G. V. Naik, J. Dionne, and A. Baldi
Equilibration of Photogenerated Charge Carriers in Plasmonic Core@Shell Nanoparticles

F. Hayee, T. C. Narayan, N. Nadkarni, A. Baldi, A. L. Koh, M. Z. Bazant, R. Sinclair, and J. A. Dionne
In-situ visualization of solute-driven phase coexistence within individual nanorods
Nature Communications 9, 1775

Nanorods are promising components of energy and information storage devices that rely on solute-driven phase transformations, due to their large surface-to-volume ratio and ability to accommodate strain. Here we investigate the hydrogen-induced phase transition in individual penta-twinned palladium nanorods of varying aspect ratios with ~3 nm spatial resolution to understand the correlation between nanorod structure and thermodynamics. We find that the hydrogenated phase preferentially nucleates at the rod tips, progressing along the length of the nanorods with increasing hydrogen pressure. While nucleation pressure is nearly constant for all lengths, the number of phase boundaries is length-dependent, with stable phase coexistence always occurring for rods longer than 55 nm. Moreover, such coexistence occurs within individual crystallites of the nanorods and is accompanied by defect formation, as supported by in situ electron microscopy and elastic energy calculations. These results highlight the effect of particle shape and dimension on thermodynamics, informing nanorod design for improved device cyclability.



T. C. Narayan*, F. Hayee*, A. Baldi*, A.-L. Koh, R. Sinclair, and J. A. Dionne
Direct visualization of hydrogen absorption dynamics in individual palladium nanoparticles
Nature Communications 8, 14020

Many energy storage materials undergo large volume changes during charging and discharging. The resulting stresses often lead to defect formation in the bulk, but less so in nanosized systems. Here, we capture in real time the mechanism of one such transformation—the hydrogenation of single-crystalline palladium nanocubes from 15 to 80 nm—to better understand the reason for this durability. First, using environmental scanning transmission electron microscopy, we monitor the hydrogen absorption process in real time with 3 nm resolution. Then, using dark-field imaging, we structurally examine the reaction intermediates with 1 nm resolution. The reaction proceeds through nucleation and growth of the new phase in corners of the nanocubes. As the hydrogenated phase propagates across the particles, portions of the lattice misorient by 1.5%, diminishing crystal quality. Once transformed, all the particles explored return to a pristine state. The nanoparticles’ ability to remove crystallographic imperfections renders them more durable than their bulk counterparts.



T. C. Narayan*, A. Baldi*, A.-L. Koh, R. Sinclair, and J. A. Dionne
Reconstructing solute-induced phase transformations within individual nanocrystals
Nature Materials 15, 768–774 (Press: Stanford NewsFOM

Strain and defects can significantly impact the performance of functional nanomaterials. This effect is well exemplified by energy storage systems, in which structural changes such as volume expansion and defect generation govern the phase transformations associated with charging and discharging. The rational design of next-generation storage materials therefore depends crucially on understanding the correlation between the structure of individual nanoparticles and their solute uptake and release. Here, we experimentally reconstruct the spatial distribution of hydride phases within individual palladium nanocrystals during hydrogen absorption, using a combination of electron spectroscopy, dark-field imaging, and electron diffraction in an environmental transmission electron microscope. Our technique offers unprecedented insight into nanoscale phase transformations in reactive environments and can be extended to a variety of functional nanomaterials.




J. A. Dionne, A. Baldi, B. Baum, C.-S. Ho, V. Jankovic, G. V. Naik, T. C. Narayan, J. A. Scholl, and Y. Zhao
Localized fields, global impact: Industrial applications of resonant plasmonic materials
MRS Bulletin 40, 1138-1145 (2015)

This article highlights recent industrially relevant advances in plasmonics, including plasmonic materials and devices for energy; for medical sensing, imaging, and therapeutics; and for information technology. Some of the most exciting industrial applications include solar-driven water purifi ers, cell phone Raman spectrometers, high-density holographic displays, photothermal cancer therapeutics, and nanophotonic integrated circuits. We describe the fundamental scientific concepts behind these and related technologies, as well as the successes and challenges associated with technology transfer.




A. Baldi*, T. C. Narayan*, A.-L. Koh, and J. A. Dionne
In situ detection of hydrogen-induced phase transitions in individual palladium nanocrystals
Nature Materials 13, 1143-1148 (2014) (Press: Stanford NewsFOM NewsPhys.orgC2W)

Many energy- and information-storage processes rely on phase changes of nanomaterials in reactive environments. Here, we detect the phase transitions of individual ​palladium nanocrystals during ​hydrogen absorption and desorption, using in situ electron energy-loss spectroscopy in an environmental transmission electron microscope. Our results provide a general framework for monitoring phase transitions in individual nanocrystals in a reactive environment and highlight the importance of single-particle approaches for the characterization of nanostructured materials.


Previously published articles

S. de Man, M. Gonzalez-Silveira, D. Visser, R. Bakker, H. Schreuders, A. Baldi, B. Dam, and R. Griessen
Combinatorial method for direct measurements of the intrinsic hydrogen permeability of separation membrane materials
Journal of Membrane Science 444, 70-76 (2013) 

L. Mooij, A. Baldi, C. Boelsma, K. Shen, M. Wagemaker, Y. Pivak, H. Schreuders, R. Griessen, and B. Dam
Interface Energy Controlled Thermodynamics of Nanoscale Metal Hydrides
Advanced Energy Materials 1 (5), 754-758 (2011) 

C. Platzer-Björkman, T. Mongstad, J.-P. Maehlen, A. Baldi, S. Karazhanov, and A. Holt
Deposition of magnesium hydride thin films using radio frequency reactive sputtering
Thin Solid Films 519 (18), 5949-5954 (2011) 

A. Baldi and B. Dam
Thin film metal hydrides for hydrogen storage applications
Journal of Materials Chemistry 21, 4021-4026 (2011) 

V. Palmisano, M. Filippi, A. Baldi, M. Slaman, H. Schreuders, and B. Dam
An optical hydrogen sensor based on a Pd-capped Mg thin film wedge
International Journal of Hydrogen Energy 35 (22), 12574-12578 (2010) 

M. Gonzalez-Silveira, R. Gremaud, A. Baldi, H. Schreuders, B. Dam, and R. Griessen
Effect of H-induced microstructural changes on pressure-optical transmission isotherms for Mg–V thin films
International Journal of Hydrogen Energy 35 (13), 6959-6970 (2010) 

A. Baldi, G. K. Pálsson, M. Gonzalez-Silveira, H. Schreuders, M. Slaman, J. H. Rector, G. Krishnan, B. J. Kooi, G. S. Walker, M. W. Fay, B. Hjörvarsson, R. J. Wijngaarden, B. Dam, and R. Griessen
Mg/Ti multilayers: Structural and hydrogen absorption properties
Physical Review B 81, 224203 (2010) 

H. Leegwater, H. Schut, W. Egger, A. Baldi, B. Dam, and S. W. H. Eijt
Divacancies and the hydrogenation of Mg-Ti films with short range chemical order
Applied Physics Letters 96, 121902 (2010) 

A. Baldi, V. Palmisano, M. Gonzalez-Silveira, Y. Pivak, M. Slaman, H. Schreuders, B. Dam, and R. Griessen
Quasifree Mg–H thin films
Applied Physics Letters 95, 071903 (2009) 

A. Baldi, M. Gonzalez-Silveira, V. Palmisano, B. Dam, and R. Griessen
Destabilization of the Mg-H system through elastic constraints
Physical Review Letters 102, 226102 (2009) 

A. Baldi, R. Gremaud, D. M. Borsa, C. P. Baldé, A. M. J. Van der Eerden, G. L. Kruijtzer, P. E. De Jongh, B. Dam, and R. Griessen
Nanoscale composition modulations in MgyTi1−yHx thin film alloys for hydrogen storage
International Journal of Hydrogen Energy 34 (3), 1450-1457 (2009) 

A. Baldi, D. M. Borsa, H. Schreuders, J. H. Rector, T. Atmakidis, M. Bakker, H. A. Zondag, W. G. J. van Helden, B. Dam, and R. Griessen
Mg–Ti–H thin films as switchable solar absorbers
International Journal of Hydrogen Energy 33 (12), 3188-3192 (2008) 

R. Gremaud, A. Baldi, M. Gonzalez-Silveira, B. Dam, and R. Griessen
Chemical short-range order and lattice deformations in MgyTi1−yHx thin films probed by hydrogenography
Physical Review B 77, 144204 (2008) 

D. M. Borsa, R. Gremaud, A. Baldi, H. Schreuders, J. H. Rector, B. Kooi, P. Vermeulen, P. H. L. Notten, B. Dam, and R. Griessen
Structural, optical, and electrical properties of MgyTi1−yHx thin films
Physical Review B 75, 205408 (2007) 

D. M. Borsa, A. Baldi, M. Pasturel, H. Schreuders, B. Dam, R. Griessen, P. Vermeulen, P. H. L. Notten
Mg–Ti–H thin films for smart solar collectors
Applied Physics Letters 88, 241910 (2006) 

A. Baldi, F. Di Pascasio, D. Gozzi
H2 cold plasma on Pd/H system at low hydrogen pressure
Applied Physics Letters 89, 051918 (2006) 

* equal author contribution