TY - JOUR
AU1 - Aso,, Kohei
AU2 - Shigematsu,, Koji
AU3 - Yamamoto,, Tomokazu
AU4 - Matsumura,, Syo
AB - Abstract In situ sequential high-resolution observations were performed on gold nanorods under near-infra-red pulsed laser irradiation using a high-voltage electron microscope attached to a pulsed laser illumination system. The original nanorods were single crystals; the longer axes were oriented along [001]. Under laser light irradiation with λ = 1064 nm with an average intensity per pulse of 980 or 490 J/m2, the shape of the nanorods changed from rod to barrel surrounded by the {111} and {001} facets, while the original single-crystalline structure was maintained. The side surfaces with <110> direction were reconstructed into zig–zag fine structures consisting of narrow {111} facets. The temporal evolution of the volume and surface area during irradiation was evaluated based on the images, assuming that the particles have a rotational symmetry along their longer axes. The surface area was stepwise decreased during the shape change using pulse shots of 980 J/m2 while the volume was maintained. On the other hand, several repeated shots were required to induce the shape change when the averaged intensity was reduced to 490 J/m2 per pulse. In addition to the surface area, the volume was reduced under the latter condition during the shape change due to the evaporation of atoms. The quantitative analysis of the temporal changes indicates the heterogeneity of the atomic excitation or heating of gold nanorods induced by pulsed laser illumination. nanorods, laser light irradiation, high-voltage electron microscopy, in situ observation, high-resolution electron microscopy Introduction Gold nanorods have attracted great interest in scientific and engineering fields due to their characteristic optical properties [1–3]. The anisotropic rod shape of gold nanorods results in two light absorption peaks associated with the longitudinal and transverse modes of localised surface plasmon resonance in their optical absorbance spectra [4]. The light absorption heats up the nanorods through electron–phonon coupling, transforming their shapes [5–8]. Transmission electron microscopy (TEM) revealed that the gold nanorods change from rod shape to various shapes, such as spheres, singular Φ-shapes and elongated rods, when irradiated with pulsed laser light [9–11]. To understand such an interaction between the materials and light on the nanoscale, we connected a pulsed laser light illumination system to a high-voltage electron microscope (HVEM) [12]. Using this laser-HVEM, we observed the in situ morphological and structural change of gold nanorods in response to near-infra-red pulsed laser irradiation [12]. First, the laser pulse effectively rendered the nanorods more spherical; however, this effect diminished after additional shots because the energy transfer from a laser pulse to the nanorods decreases as the longitudinal SP band is blue-shifted by the reduced aspect ratio of the rod [4,13]. Recently, we also obtained atomic-resolution high-angle annular dark-field scanning TEM images of individual gold nanorods before and after pulsed laser irradiation using a TEM instrument with a spherical aberration corrector. These images revealed that a nanorod changes its structure after pulsed laser irradiation to a multiple twinned particle with large displacements of gold atoms near multiple twin junctions [14]. In the present study, we made in situ sequential high-resolution observations of the gradual shape change of gold nanorods under laser irradiation with moderate intensity, where the rods maintain their original single-crystalline structure. The results are expected to promote the understanding of the interaction between the nanorods and laser light. Experimental The gold nanorods used in this study were produced in a hexadecyltrimethylammonium bromide (CTAB) micellar solution with a photochemical method (products of the Dai Nihon Toryo Co. Ltd., Japan) [15]. The nanorods were synthesised to have an ~50 nm long axis and 10 nm diameter. The optical absorption spectrum of the nanorod solution shows peak maxima at wavelengths of 520 and 980 nm. The CTAB micelles were removed by centrifuging the aqueous solution for 10 min at 2 × 104g (g is the magnitude of gravitational acceleration). One drop of the solution was placed onto a Quantifoil™ carbon film of sample-supporting mesh, which had been rendered hydrophilic by exposure to Ar ions in a plasma cleaner. In situ high-resolution observations were made in an HVEM equipped with a laser irradiation system [12]. Laser light pulses generated by an yttrium aluminium garnet (YAG) laser (Quantel YAG 981 C) were introduced to the HVEM (JEM-1300NEF) via optical equipment consisting of mirrors and lenses. The wavelength of the laser pulses was 1064 nm and the pulse duration was 6–8 ns, repeating at 10 Hz. Based on measurements using a PIN photodiode in the specimen chamber, the averaged intensity per pulse in this experiment was 980 or 490 J/m2 over a specimen illumination area with 500 μm diameter. It should be noted that the laser intensities mentioned above are averaged over the illuminated area with a Gaussian-like intensity variation and do not exactly correspond to the values of local observation areas of orders of several tens of nanometres in the HVEM. Hereafter, we call conditions with higher and lower intensities H and L, respectively. The HVEM with an acceleration voltage of 1250 kV was used to acquire high-resolution TEM (HRTEM) images. Results and discussion Figure 1 shows the results of pulse-by-pulse sequential observations of a nanorod under condition H. The nanorod in Fig. 1a has a length of 40 nm, width of 8.5 nm and a aspect ratio of 4.7 before laser irradiation. The rod was confirmed to be a single crystal with its long axis along [001] because there were no defect contrasts such as twins or stacking faults. Both of the side edges are quite smooth, suggesting flat surfaces. Previous studies showed that the side surfaces of nanorods synthesised in CTAB have habit tendencies to {100} and {110} [16,17]. The outer shape of the particle after experiencing one shot of laser pulse changed; the length shortened to 30 nm and the width increased to 11 nm, which corresponds to an aspect ratio of 2.7 (Fig. 1b). The contrast in the interior of the nanorod did not change during laser irradiation; thus, the nanorod maintained a single-crystalline structure. As shown in Fig. 1c, after the second laser pulse shot, the shape changed to a barrel shape with a length of 22 nm, a width of 16.5 nm and a aspect ratio of 1.3. The particle became thicker in the radial direction and shortened in the direction of the long axis. Some atoms at the top of the rod were likely to be excited and migrate to the side while maintaining the original single-crystalline structure. The original {110} facet on the side surface disappeared, while the {111} and {001} facets became pronounced. Zig–zag fine structures consisting of {111} facets can be observed in a close-up view of the side. Previous in situ environmental TEM experiments revealed that the surface morphology of gold depends on the gas atmosphere; it is isotopically rounded in air but faceted and surrounded by {111} and {001} in a vacuum or CO atmosphere [18,19]. Ab initio calculations indicated that the surface energy of {111} is ~70% of the surface energy of {110} in vacuum [20]. Because the direction cosine between the {111} and {110} planes is 0.82, the zig–zag structure with {111} surfaces is stabilised by the reduction of the total surface energy against the increase in the surface area. Thus, the observed shape change due to laser shots can be explained in terms of the habit of the surface facet, reducing the total surface energy. In contrast to the surface morphological change, the particle interior maintains the single-crystalline state during the shape change. It is believed that the particle centre did not experience a molten state. Fig. 1. View largeDownload slide HRTEM images of a nanorod under pulsed laser irradiation at an average intensity per pulse of 980 J/m2. The nanorod before irradiation (a), after irradiation with one pulse shot (b) and after irradiation with two pulse shots (c). Fig. 1. View largeDownload slide HRTEM images of a nanorod under pulsed laser irradiation at an average intensity per pulse of 980 J/m2. The nanorod before irradiation (a), after irradiation with one pulse shot (b) and after irradiation with two pulse shots (c). A similar sequential observation was made under condition L with weaker repetitive pulse illumination. Figure 2 shows the results. Here, the shape change took place in almost the same manner as in the previous case but more gradually. A higher repetition of pulsed shots was required to change the shape. Figure 3 shows enlarged views of the side surfaces of the rectangle regions surrounded by white lines in Fig. 2a, c and f. It is notable that the original, flat {110} side surface changed into a zig–zag fine structure with narrow {111} and {100} facets. Fig. 2. View largeDownload slide Sequential HRTEM images of a nanorod irradiated with a pulsed laser at an average intensity of 490 J/m2 per pulse. Before irradiation (a) and after irradiation with 20 pulses (b), 80 pulses (c), 120 pulses (d), 240 pulses (e) and 1000 pulses (f). Fig. 2. View largeDownload slide Sequential HRTEM images of a nanorod irradiated with a pulsed laser at an average intensity of 490 J/m2 per pulse. Before irradiation (a) and after irradiation with 20 pulses (b), 80 pulses (c), 120 pulses (d), 240 pulses (e) and 1000 pulses (f). Fig. 3. View largeDownload slide Magnified images of the rectangle regions in Fig. 2. (a–c) Fig. 2a, c and f, respectively. Fig. 3. View largeDownload slide Magnified images of the rectangle regions in Fig. 2. (a–c) Fig. 2a, c and f, respectively. The length, width and aspect ratio of the particles were plotted as a function of the pulse sequence number in Fig. 4. Figure 4a shows that only one or two shots of the pulsed laser under condition H effectively changed the gold nanorod shape to a more isotropic shape with an aspect ratio of nearly one. On the other hand, as shown in Fig. 4b, the shape change proceeded much more gradually in the case of condition L. Up to 240 pulses were required to reach a barrel-like shape with an aspect ratio of nearly one. Further shots under the latter condition did not lead to further shape changes, which is due to the blue shift of the absorption peak to a shorter wavelength with the reduction of the aspect ratio. Fig. 4. View largeDownload slide Temporal changes of the length (dashed lines), width (chain lines) and aspect ratio (solid lines): (a) under condition H and (b) under condition L. Fig. 4. View largeDownload slide Temporal changes of the length (dashed lines), width (chain lines) and aspect ratio (solid lines): (a) under condition H and (b) under condition L. The rotational surface and volume integrals of the image outlines around the long axes were used to evaluate the temporal changes of the surface area Si (nm2) and volume Ni (atoms) with the pulse sequential number i ⁠: Si=p2∑lπdi(l) (1) Ni=ρp3∑lπ(di(l)2)2, (2) where p (nm/pixel) is the pixel size of the image, di(l) is the diameter at a position l (pixel) along the [001] long axis and ρ = 59 (atoms/nm3) is the atom density per volume of gold. Even if the bottom surface of a nanoparticle becomes partially flat on the carbon support with a wetting angle of 150° for gold [21], it influences only 1% and 3% of the surface area and volume, respectively. In addition, the error caused by the observed zig–zag structure was roughly estimated to be <7%. Figure 5 presents the results. After one and two shots with the pulsed laser under condition H, the surface area decreased almost linearly to 85% and 70% of the initial state, respectively, as shown in Fig. 5a. The surface reduction rate was estimated to be 160 nm2/pulse. The slight increase of the volume observed in Fig. 5c is unrealistic; it is most likely due to a rough approximation of the rotational symmetry in contrast to the habit tendency of the surface. The volume should be regarded as maintained. In contrast, both Si and Ni decrease almost linearly with increasing pulse sequential number i up to 240 under condition L, reaching almost half of the initial state after 240 shots. This indicates that on average ~290 atoms were removed from the particle by each shot of the pulsed laser. It is believed that a few atoms on the surface were removed after experiencing the liquid state, that is, they evaporated. Figure 5b and c confirms that the changes become less pronounced with further shooting, probably due to the blue shift of the absorption peak. Fig. 5. View largeDownload slide Temporal changes of the surface area (a and b) and volume (c and d) of the nanoparticles as function of the laser light pulses: (a and c) under condition H and (b and d) under condition L. Fig. 5. View largeDownload slide Temporal changes of the surface area (a and b) and volume (c and d) of the nanoparticles as function of the laser light pulses: (a and c) under condition H and (b and d) under condition L. As schematically shown in Fig. 6, we evaluated how many atoms participated in the shape change induced by the laser pulses by comparing the shapes and volumes before and after the shots. If the shapes at both steps are compared based on their centres of the mass, the mismatched portions can be regarded as volume migrated by laser light. The atoms in the dark blue area in Fig. 6b are considered to have effectively become mobile and, then, migrated to the light blue area during shape transformation. The numbers of atoms in the former and latter areas are hereafter referred to as Nid and Nim ⁠, respectively. If ∆Ni=Nid−Nim>0 ⁠, the number of atoms is considered to have been evaporated by the pulsed shot i. The parameters Nid and Nim were evaluated to be ~38,000 for both shots i = 1 and 2 under condition H; then, ∆Ni~0 ⁠. The migrated volume corresponds to 28% of the whole atoms in the particle. As shown in Fig. 5a, the surface area has been estimated to be 1070 and 900 nm2 before and after the shot i = 1, respectively. Therefore, the number of atoms on the outermost surface is ~12 000 and 10 000, respectively, because the areal density of the surface atoms is roughly 11 atoms/nm2 for gold. The above-mentioned amounts of Nid~Nim~38000 suggest that on average 3–4 atomic skin layers became mobile. However, as shown in Fig. 4a, the length was reduced by ~10 nm based on each shot. The thickness of the dark blue portions with Nid/2 atoms should be 5 nm, corresponding to 25 layers of (002) atomic planes, which is much larger than the average skin thickness mentioned above. A larger volume than the migrated one is likely to have become mobile just after the pulsed shot; however, some parts of it were recovered without migration in the following cooling stage. It should be noted that the decrement in the length of 10 nm by one shot is comparable to the dimension of the original width, that is, 8.5 nm. If the atoms would be excited within a uniform depth from the surface, almost all atoms should become mobile, even in a very short period of time and the single-crystalline state of the original orientation could no longer be maintained, which is inconsistent with the present result. Therefore, the above-mentioned results suggest that the pulsed laser excites atoms more strongly in the tip end portions of the nanorod. In addition, the spherical curvature of the tip surface accelerates the evacuation of atoms from the tip portions due to the enhanced surface tension. Fig. 6. View largeDownload slide Estimation of the mobile and migrated volumes Nid and Nim ⁠. (a) Images of the same particle before and after laser shots. The cross indicates the centre of mass. (b) Overlay of the two images. The grey line shows the main axis of rotational integration. (c) Nid and Nim after the rotational integration. Fig. 6. View largeDownload slide Estimation of the mobile and migrated volumes Nid and Nim ⁠. (a) Images of the same particle before and after laser shots. The cross indicates the centre of mass. (b) Overlay of the two images. The grey line shows the main axis of rotational integration. (c) Nid and Nim after the rotational integration. On the other hand, condition L was so weak that significant shape transformation was recognised after several pulse shots, although the average nominal intensity of the laser illumination was half of that of condition H. The average values of Nim and ∆Ni are plotted in Fig. 7 for periods between i1 and i2. The migrated volume Nim is ~620 atoms per pulse in the earliest stage up to 20 shots and, then, decreases almost exponentially with further increase of the sequential shot number, approaching zero. In contrast, ~300 atoms, which corresponds to ~3% of atoms on the outermost surface, were evaporated per pulse over a relatively longer period up to 240 shots. The latter result indicates that the surface atoms were continuously excited, even after the surface atomic migration was effectively attenuated. This suggests that the deformability is not only determined by the whole absorption energy, mostly depending on the aspect ratio, but also by the local curvature of the outer surface. Evaporation can also take place under condition H. However, the number of evaporated atoms is too small to be detected after only one and two shots under condition H. Fig. 7. View largeDownload slide Volume of the migrated (solid lines) and evaporated atoms (dashed line) versus the laser irradiation under condition L. Fig. 7. View largeDownload slide Volume of the migrated (solid lines) and evaporated atoms (dashed line) versus the laser irradiation under condition L. Baffou et al. numerically investigated the heat generation in gold nanoparticles when illuminated at plasmonic resonance using Green’s dyadic method [6]. Their results clearly showed that the energy absorption and peak wavelength depend on the aspect ratio of the nanorod and the excitation or heat generation is mostly localised in the surface layers. However, they also showed that the temperature very quickly becomes almost uniform due to the large heat conductivity in spite of localised heterogeneous heat generation. They estimated the spatial variation of the temperature to be only 0.1 K throughout the nanoparticle in the steady state. On the other hand, molecular dynamics (MD) calculations suggest a melting point of gold nanoparticles of ~1200–1300 K and that a surface melting point is ~90% of the melting point [22,23]. It is indicated that the surface diffusion of a nanorod becomes pronounced above ~400 K [24]. In addition, MD simulations conducted by Opletal et al. [25] showed that the single-crystalline state of a gold nanorod can be maintained under shot heating in nanosecond order up to ~800 K, while the higher temperature leads to the formation of planer stacking faults. The pulse duration of 6–8 ns in the present study can be generally regarded to be sufficiently longer than the relaxation time to induce thermalisation of plasmonic electron excitation through electron–phonon coupling interactions. If the results of the simulation studies mentioned above are considered, the nanorods would have been heated homogeneously to a moderate temperature <800 K, even under condition H in the present study. However, the present results indicate heterogeneous transformation behaviour, as mentioned above. The localised enhancement in the plasmonic excitation and/or atom migration should be considered also to understand the present results, in addition to the quasi-uniform temperature raise by laser illumination. Summary In the present study, in situ sequential high-resolution observations were made on single-crystalline gold nanorods under pulsed laser irradiation in vacuum using an HVEM with an illumination system, including a pulsed infra-red laser. The gold nanorods transformed from a rod shape with the main long axis along [001] to a barrel-like shape surrounded by {111} and {001} faceted surfaces if the single-crystalline state was maintained. The stepwise volume changes due to the pulsed shots indicate that the tip portions are preferentially excited and migrate during the shape change. Acknowledgement The authors are indebted to Mr. Hiroshi Maeno at the Ultramicroscopy Research Center, Kyushu University, for technical support. Funding Grant-in Aid for Scientific Research B from Japan Society for the Promotion of Science (JSPS) (25289221 and 18H01830). References 1 Jain P K , Huang X , El-Sayed I H , and El-Sayed M A ( 2008 ) Noble metals on the nanoscale: optical and photothermal properties and some applications in imaging, sensing, biology, and medicine . Acc. Chem. Res. 41 : 1578 – 1586 . Google Scholar Crossref Search ADS PubMed 2 Alkilany A M , Thompson L B , Boulos S P , Sisco P N , and Murphy C J ( 2012 ) Gold nanorods: their potential for photothermal therapeutics and drug delivery, tempered by the complexity of their biological interactions . Adv. Drug Deliv. Rev. 64 : 190 – 199 . Google Scholar Crossref Search ADS PubMed 3 Pérez-Juste J , Pastoriza-Santos I , Liz-Marzán L M , and Mulvaney P ( 2005 ) Gold nanorods: synthesis, characterization and applications . Coord. Chem. Rev. 249 : 1870 – 1901 . Google Scholar Crossref Search ADS 4 Link S , Mohamed M B , and El-Sayed M A ( 1999 ) Simulation of the optical absorption spectra of gold nanorods as a function of their aspect ratio and the effect of the medium dielectric constant . J. Phys. Chem. B 103 : 3073 – 3077 . Google Scholar Crossref Search ADS 5 Baffou G , and Quidant R ( 2013 ) Thermo-plasmonics: using metallic nanostructures as nano-sources of heat . Laser Photon. Rev. 7 : 171 – 187 . Google Scholar Crossref Search ADS 6 Baffou G , Quidant R , and Girard C ( 2009 ) Heat generation in plasmonic nanostructures: Influence of morphology . Appl. Phys. Lett. 94 : 5 – 8 . Google Scholar Crossref Search ADS 7 Fales A M , Vogt W C , Pfefer J , and Ilev I K ( 2017 ) Quantitative evaluation of nanosecond pulsed laser-induced photomodification of plasmonic gold nanoparticles . Sci. Rep. 7 : 1 – 11 . Google Scholar Crossref Search ADS PubMed 8 González-Rubio G , Díaz-Núñez P , Rivera A , Prada A , Tardajos G , González-Izquierdo J , Bañares L , Llombart P , Macdowell L G , Palafox M A , Liz-Marzán L M , Peña-Rodríguez O , and Guerrero-Martínez A ( 2017 ) Femtosecond laser reshaping yields gold nanorods with ultranarrow surface plasmon resonances . Science 358 : 640 – 644 . Google Scholar Crossref Search ADS PubMed 9 Horiguchi Y , Honda K , Kato Y , Nakashima N , and Niidome Y ( 2008 ) Photothermal reshaping of gold nanorods depends on the passivating layers of the nanorod surfaces . Langmuir 24 : 12026 – 12031 . Google Scholar Crossref Search ADS PubMed 10 Link S , Burda C , Mohamed M B , Nikoobakht B , and El-Sayed M A ( 1999 ) Laser photothermal melting and fragmentation of gold nanorods: energy and laser pulse-width dependence . J. Phys. Chem. A 103 : 1165 – 1170 . Google Scholar Crossref Search ADS 11 Link S , Burda C , Nikoobakht B , El-Sayed M A A , Link S , Burda C , Nikoobakht B , El-Sayed* M A , Link S , Burda C , Nikoobakht B , and El-Sayed M A A ( 2000 ) Laser-induced shape changes of colloidal gold nanorods using femtosecond and nanosecond laser pulses . J. Phys. Chem. B 104 : 6152 – 6163 . Google Scholar Crossref Search ADS 12 Sumimoto N , Nakao K , Yamamoto T , Yasuda K , Matsumura S , and Niidome Y ( 2014 ) In situ observation of structural transformation of gold nanorods under pulsed laser irradiation in an HVEM . Microscopy 63 : 261 – 268 . Google Scholar Crossref Search ADS PubMed 13 Hu M , Chen J , Li Z-Y , Au L , Hartland G V , Li X , Marquez M , and Xia Y ( 2006 ) Gold nanostructures: engineering their plasmonic properties for biomedical applications . Chem. Soc. Rev. 35 : 1084 . Google Scholar Crossref Search ADS PubMed 14 Aso K , Shigematsu K , Yamamoto T , and Matsumura S ( 2016 ) Detection of picometer-order atomic displacements in drift-compensated HAADF-STEM images of gold nanorods . Microscopy 65 : 391 – 399 . Google Scholar Crossref Search ADS PubMed 15 Niidome Y , Nishioka K , Kawasaki H , and Yamada S ( 2003 ) Rapid synthesis of gold nanorods by the combination of chemical reduction and photoirradiation processes; morphological changes depending on the growing processes . Chem. Commun. 18 : 2376 – 2377 . Google Scholar Crossref Search ADS 16 Goris B , Bals S , Van den Broek W , Carbó-Argibay E , Gómez-Graña S , Liz-Marzán L M , and Van Tendeloo G ( 2012 ) Atomic-scale determination of surface facets in gold nanorods . Nat. Mater. 11 : 930 – 935 . Google Scholar Crossref Search ADS PubMed 17 Katz-boon H , Walsh M , Dwyer C , Mulvaney P , Funston A M , and Etheridge J ( 2015 ) Stability of crystal facets in gold nanorods . Nano Lett. 15 : 1635 – 1641 . Google Scholar Crossref Search ADS PubMed 18 Uchiyama T , Yoshida H , Kuwauchi Y , Ichikawa S , Shimada S , Haruta M , and Takeda S ( 2011 ) Systematic morphology changes of gold nanoparticles supported on CeO2 during Co oxidation . Angew. Chemie - Int. Ed. 50 : 10157 – 10160 . Google Scholar Crossref Search ADS 19 Fujita T , Guan P , McKenna K , Lang X , Hirata A , Zhang L , Tokunaga T , Arai S , Yamamoto Y , Tanaka N , Ishikawa Y , Asao N , Yamamoto Y , Erlebacher J , and Chen M ( 2012 ) Atomic origins of the high catalytic activity of nanoporous gold . Nat. Mater. 11 : 775 – 780 . Google Scholar Crossref Search ADS PubMed 20 Galanakis I , Bihlmayer G , Bellini V , Papanikolaou N , Zeller R , Blügel S , and Dederichs P H ( 2002 ) Broken-bond rule for the surface energies of noble metals . EPL 58 : 751 . Google Scholar Crossref Search ADS 21 Ricci E , and Novakovic R ( 2001 ) Wetting and surface tension measurements on gold alloys . Gold Bull. 34 : 41 – 49 . Google Scholar Crossref Search ADS 22 Gan Y , and Jiang S ( 2013 ) Ultrafast laser-induced premelting and structural transformation of gold nanorod . J. Appl. Phys. 113 : 073507 . Google Scholar Crossref Search ADS 23 Essajai R , and Hassanain N ( 2018 ) Molecular dynamics study of melting properties of gold nanorods . J. Mol. Liq. 261 : 402 – 410 . Google Scholar Crossref Search ADS 24 Wang Y , Teitel S , and Dellago C ( 2005 ) Surface-driven bulk reorganization of gold nanorods . Nano Lett. 5 : 2174 – 2178 . Google Scholar Crossref Search ADS PubMed 25 Opletal G , Grochola G , Chui Y H , Snook I K , and Russo S P ( 2011 ) Stability and transformations of heated gold nanorods . J. Phys. Chem. C 115 : 4375 – 4380 . Google Scholar Crossref Search ADS © The Author(s) 2018. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Sequential transmission electron microscopy observation of the shape change of gold nanorods under pulsed laser light irradiation
JF - Microscopy
DO - 10.1093/jmicro/dfy136
DA - 2019-04-01
UR - https://www.deepdyve.com/lp/oxford-university-press/sequential-transmission-electron-microscopy-observation-of-the-shape-LysvqC2INs
SP - 174
VL - 68
IS - 2
DP - DeepDyve
ER -