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Silver nano-entities through ultrafast double ablation in aqueous media for surface enhanced Raman scattering and photonics applications
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10.1063/1.4792483
/content/aip/journal/jap/113/7/10.1063/1.4792483
http://aip.metastore.ingenta.com/content/aip/journal/jap/113/7/10.1063/1.4792483

Figures

Image of FIG. 1.
FIG. 1.

(a) Mechanism of multiple/double ablation as a result of over writing for substrates SS-1 and SS-2. The separation between the scans was much less than the beam waist, (b) For SS-3, SS-4 ablation was carried out with separation more than beam waist.

Image of FIG. 2.
FIG. 2.

Depiction of nanoparticles fabricated by pulsed (∼2 ps, 800 nm) laser ablation of Ag metal immersed in double distilled water (a) TEM image of well dispersed Ag nanospheres formed in colloidal water (NP-1), (b) Size distribution histogram of Ag nanoparticles in NP-1 showing an average size near of 13 nm, (c) TEM image of Ag nanospheres in NP-2, (d) Size distribution histogram Ag nanoparticles in NP-2 exhibited an average size of 17 nm. The scale bar in (a) and (c) is 100 nm.

Image of FIG. 3.
FIG. 3.

Depiction of nanoparticles fabricated by pulsed (∼2 ps, 800 nm) laser ablation of Ag metal immersed in double distilled water. (a) TEM image of well dispersed Ag nanospheres formed in colloidal water (NP-3), (b) size distribution histogram of Ag nanoparticles in NP-3 depicting an average size of 6 nm, (c) TEM image of Ag nanospheres in NP-4, (d) size distribution histogram Ag nanoparticles in NP-4 demonstrated an average size of 7 nm. The scale bar in (a) and (c) is 50 nm.

Image of FIG. 4.
FIG. 4.

(a) HRTEM image of the Ag nanoparticles formed shows the clear view of lattice planes observed at a characteristic separation 2.2 Å (diameter of the ring very next to the central maxima in the electron diffraction pattern) corresponding to the plane of Ag crystal (111). Right (b-e) – depictions of selective area electron beam diffraction patterns from the fabricated Ag nanoparticles in NP-1, NP-2, NP-3, and NP-4, respectively, confirming the polycrystalline nature of Ag nanocrystals. The scale bar in (a) is 5 nm.

Image of FIG. 5.
FIG. 5.

(a) UV-Vis extinction spectra of Ag nanoparticles prepared in water (I) NP-1with SPR peak at 412 nm, (II) NP-2 with SPR peak at 417 nm, (III)NP-3 with SPR peak at 407 nm, (IV) NP-4 with SPR peak at 407 nm, (b) red curve depicts the variation of SPR peak with respect to line separation, blue curve depicts the average Ag particle size versus line separation.

Image of FIG. 6.
FIG. 6.

Open aperture Z-scan curves obtained for (a) Ag colloids NP-1 with varying input intensities I00 = 83 GW/cm2 (open circles), I00 = 138 GW/cm2 (stars). Blue, red colors represent low intensity, high intensities, respectively, (b) closed aperture Z-scan curves obtained for Ag colloids NP-1 at peak intensity 28 GW/cm2, (c) open aperture Z-scan curves obtained for Ag colloids NP-2 with varying input intensities I00 = 83 GW/cm2 (open circles), I00 = 138 GW/cm2 (stars), and (d) closed aperture Z-scan curves obtained for Ag colloids NP-2 at peak intensity 28 GW/cm2. Solid lines are the theoretical fits.

Image of FIG. 7.
FIG. 7.

UV-Vis reflectance spectra of the Ag substrates SS-1 (red, solid curve), SS-2 (blue, short dash-dot curve), SS-3 (green, dashed curve), and SS-4 (violet, dash-dot curve). A small hump (inset) near 340 nm confirmed the formation of nanostructures on SS-1 and SS-2. For the other two cases, no nanostructures were found.

Image of FIG. 8.
FIG. 8.

FESEM images of the laser exposed portions in Ag substrate in water (a, b) dome like structures formed on the substrate SS-1 because of the over wring and its closer view, (c, d) surface morphology of SS-2 shows the dome like structures. Closer view images show the fabricated Ag NPs grains on the substrate. The scale bar in (a), (b), and (c) is 2 μm while in (d) it is 200 nm.

Image of FIG. 9.
FIG. 9.

FESEM images of the laser exposed portions of Ag substrate in water for (a) SS-3, fabricated at a line sparation of 50 μm,(b) SS-4, fabricated at a line sparation of 75 μm. The scale bar in (a) and (b) is 200 nm.

Image of FIG. 10.
FIG. 10.

Raman signals recorded from R6G molecules (12 μΜ) in methanol (a) with micro Raman spectrometer (excitation at 532 nm). Red, blue spectra represent the enhanced Raman signatures of R6G from SS-1 and SS-2, respectively (b)with bulk Raman spectrometer (excitation at 785 nm). Black spectrum was from Ag plain surface. Red, blue spectra represent the enhanced Raman signatures of R6G from SS-1 and SS-2. Signal collection time for both spectrometers was 5 seconds.

Image of FIG. 11.
FIG. 11.

Fluence versus Raman intensity enhancement observed from R6G adsorbed on the Ag substrates with excitation at (a) 532 nm (b) 785 nm. Symbols are experimental data points while lines are only a guide to the eye.

Image of FIG. 12.
FIG. 12.

FESEM images [closer view of the structure] of the laser exposed portions in Ag substrate in water prepared for diffrerent laser fluences (a) 4 J/cm2, (b) 8 J/cm2, (c) 12 J/cm2, and (d) 16 J/cm2. The images depict fabricated grains of Ag NPs on the substrate. The scale bar in (a) and (d) is 100 nm and for (b) and (c) it is 200 nm.

Image of FIG. 13.
FIG. 13.

(a) Micro-Raman spectra of adsorbed RDX molecules (excitation at 532 nm) in acetonitrile. The maximum enhancement of Raman signal was observed at pulse energy 150 μJ (fluence of 12 J/cm2). (b) Bulk Raman spectra of the adsorbed RDX (excitation at 785 nm) in acetonitrile. The maximum enhancement of Raman signal was observed at pulse energy of 200 μJ (fluence of 16 J/cm2). More signatures were observed with 785 nm excitation compared to 532 nm excitation. For both, the cases time of integration was 5 s.

Image of FIG. 14.
FIG. 14.

Fluence versus Raman intensity enhancement observed from RDX adsorbed on the Ag substrates with excitation at 532 nm (a) 2255 cm−1 and 2005 cm−1 modes (b) 2947 cm−1 mode. Maximum enhancement was observed for the fluence 12 J/cm2. Symbols are experimental data points while lines are only a guide to the eye.

Image of FIG. 15.
FIG. 15.

Fluence versus Raman intensity enhancement for RDX Ag substrates with excitation at 785 nm for (a) 379 cm−1, 600 cm−1, 710 cm−1, and 856 cm−1 modes (b) 1008 cm−1, 1078 cm−1, 1136 cm−1, and 1240 cm−1 modes (c) 1314 cm−1, 1393 cm−1, 1457 cm−1, and 1560 cm−1 modes. Maximum enhancement was observed for fluence of 16 J/cm2 in most of the cases.

Tables

Generic image for table
Table I.

Observed active Raman modes of Rhodamine 6G adsorbed on Ag substrates SS-1 and SS-2 and their corresponding intensity enhancement obtained using excitation at 532 nm and 785 nm. Signal was collected for 5 seconds.

Generic image for table
Table II.

Raman modes of RDX in ACN (∼50 mM) adsorbed on different Ag substrates. Corresponding intensity enhancements are listed. Excitation wavelength was 785 nm. Signal was collected for 5 seconds.

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/content/aip/journal/jap/113/7/10.1063/1.4792483
2013-02-21
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Silver nano-entities through ultrafast double ablation in aqueous media for surface enhanced Raman scattering and photonics applications
http://aip.metastore.ingenta.com/content/aip/journal/jap/113/7/10.1063/1.4792483
10.1063/1.4792483
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