Nonlinear Optical Response of Gold-Decorated Nanodiamond

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Non-Linear Optical Response of Gold-Decorated Nanodiamond Hybrids Dionysios Potamianos, Ioannis Papadakis, Eirini Kakkava, Athanasios B. Bourlinos, George Trivizas, Radek Zboril, and Stelios Couris J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.5b07065 • Publication Date (Web): 09 Oct 2015 Downloaded from http://pubs.acs.org on October 12, 2015

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The Journal of Physical Chemistry

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Non-linear Optical Response of Gold-decorated Nanodiamond Hybrids D. Potamianos,1,2 I. Papadakis,1,2 E. Kakkava,1,2 A. B. Bourlinos,3,4 G. Trivizas,3 R. Zboril4,*and S. Couris,1,2,*

1

2

Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology-Hellas (FORTH), 26504 Patras, Greece 3

4

Department of Physics, University of Patras, 26504 Patras, Greece

Physics Department, University of Ioannina, Ioannina 45110, Greece

Regional Centre of Advanced Technologies and Materials, Faculty of Science, Department of Physical Chemistry, Palacky University, Olomouc 77146, Czech Republic

* Corresponding authors: [email protected] and [email protected]

ACS Paragon Plus Environment


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Abstract Hybrids containing nanodiamonds with controllable content of gold nanoparticles (ND/Au) were prepared and characterized by XRD, TGA and TEM/HRTEM techniques including STEM-EDS chemical mapping. For the first time, the nonlinear optical response of the prepared ND/Au dispersions in DMF was investigated by means of the Z-scan technique using 35 ps, (532 and 1064 nm), and 40 fs (800 nm) laser excitations and is compared with that of neat nanodiamonds. The nanohybrids exhibited important nonlinear optical response, significantly larger than that of neat nanodiamonds under visible 35 ps laser excitation, while they were found to exhibit negligible nonlinear optical response when excited by 1064 nm, 35 ps or 800 nm, 40 fs laser pulses. Gold loading was found to affect significantly their non-linear optical properties therefore providing an easy mean of modulation of their non-linear optical response in view of different photonic and optoelectronic applications, such as optical limiters, optical switches, saturable absorbers etc.

Keyword: nanodiamonds, gold nanoparticles, hybrid materials, colloidal dispersions, nonlinear optical, Z-scan


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1. Introduction Nanodiamonds (NDs) represent an intriguing carbon allotrope which is obtained in powdered form by the detonation technique.1,2 The prime particles in these powders have nearly spherical shape (4-5 nm) and form fractal agglutinates that are few nanoparticles thick and several hundred nanometers long.3,4 This robust matrix provides an ideal platform for the deposition of various nanoparticles on the surface using wet chemistry. In this way a series of new hybrids can be foreseen suitable for catalysis, biomedicine or magnetic recording.5–7 Colloidal gold nanoparticles which have been used for centuries in art and decoration related applications due to the colors they exhibit upon interaction with light, possess tunable optical and electronic properties,8 which make them very attractive candidates in many fields including e.g. photovoltaics and sensors, therapeutic agents and drug delivery vehicles for biological and medical applications, electronic conductors and catalysis. The optical and electronic properties of gold nanoparticles are tunable, in principle, by changing their size, shape, surface chemistry and/or aggregation state.9-11 In general the interaction of gold nanoparticles with light depends strongly on their size, shape, surface functionalization and dielectric properties of their environment. In particular, it is known that gold nanoparticles exhibit a very intense localized surface plasmon resonance (LSPR) peak, tunable in the visible spectral region (i.e., between 520 and 600 nm) depending on the morphological and size characteristics of the nanoparticles. Besides, gold nanoparticles are known to exhibit important nonlinear optical (NLO) response under laser excitation which can be further enhanced by tuning the LSPR feature near the excitation wavelength, thus resulting in considerable amplification of the NLO response.12,13



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So far surface decoration of NDs with gold nanoparticles has resulted in hybrid materials with enhanced catalytic, photoacoustic, plasmonic and luminescence properties.14–16 Though the non-linear optical effects of gold nanoparticles and NDs17-20 have been studied in parallel, no report in the literature refers to the non-linear optical response of joined gold-ND hybrids. Along these lines, the present work represents the first study of NLO properties of gold-decorated NDs hybrids (ND/Au) dispersed in dimethylformamide (DMF). The hybrids were obtained by the borohydride reduction of aqueous gold salt solutions in presence of NDs, whereas colloidal dispersions were achieved by mild sonication of the solids in DMF. The materials were characterized by the XRD, TGA and TEM/HRTEM techniques. Finally, their NLO properties were studied by means of the z-scan technique under both 35 picosecond and 40 femtosecond laser excitation and the effect of the gold loading on the NLO response of the nanohybrids is investigated. In addition, the influence of the gold loading on the NLO refraction and absorption properties of the neat NDs is also studied. The obtained values of γ΄ (or Reχ(3)) can be compared to the already published data and a good agreement is observed.21,22

2. Experimental Materials: Dimethylformamide (DMF) (Aldrich), de-ionized water, commercial acetone, AuCl3 (Aldrich), crystalline diamond nanopowder NDs (Aldrich, 4-6 nm quasi-spherical nanoparticles), NaBH4 (Merck), sodium citrate (Aldrich). NDs dispersion in DMF: 50 mg NDs were suspended in 10 mL DMF by 2.5 h sonication in an ultrasound bath (130 W). The suspension was left in rest for several months in order to remove any solid particulates prior to collecting the supernatant colloid. The grey colloid contained ND agglomerates dispersed in DMF at concentration of 1.332 mg mL-1. It should be mentioned that


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DMF is considered an excellent solvent for dispersing various carbon allotropes by mild sonication, including graphene.23 In the present case the affinity of graphene monolayers present on the outer surface of NDs24 towards DMF are responsible for the stabilization of the dispersion. Colloidal gold: Colloidal gold was obtained by the Turkevich method through aqueous reduction of gold salts by citrate ions at 100 oC.25 Specifically, 2 mL aqueous solution of AuCl3 (1 mg mL1

) were added in 20 mL water. The solution was heated to boiling and 5 mL aqueous solution of

sodium citrate (2 mg mL-1) was rapidly added under vigorous stirring. A deep red colloid was formed after 15 min of boiling (1.203 mg mL-1). Based on TEM, the colloid contained nearly spherical gold nanoparticles with sizes ranging between 20 and 40 nm (Figure S1). ND/Au hybrids: 45 mg NDs were suspended by sonication in 20 mL H2O followed by the addition of 1 mL aqueous solution AuCl3 (10 mg mL-1). The suspension was stirred for 20 min and then 2 mL aqueous solution NaBH4 (15 mg mL-1) were added dropwise under vigorous stirring. The as-formed reddish-colored suspension was stirred for additional 30 min prior collecting the solid by centrifugation and washings with water and acetone. The reddish sample (ND/Au) was dried at room temperature for 24 h. The formation of gold nanoparticles in the ND support was verified by powdered XRD (Figure S2). According to TGA (Figure S3) the hybrid contained ca.10 % w/w Au with gold having no effect on the thermal properties of NDs. Nanodiamond hybrids with gold contents of 1% and 5% w/w were similarly prepared by adjusting the mass ratio of NDs to gold salt. ND/Au dispersions in DMF: 50 mg ND/Au (10 % Au) were suspended in 10 mL DMF by 2.5 h sonication in an ultrasound bath (130 W). The suspension was left in rest for few to several days in order to remove any solid particulates prior to collecting the supernatant colloid. The wine-



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reddish colloid contained gold-decorated ND agglomerates dispersed in DMF at concentration of 0.560 mg mL-1. Figure 1 shows some typical photos of the ND/Au and NDs dispersions in DMF. Such colloidal dispersions could be easily processed into thin film by spin coating or incorporated into polymers through solution processing towards the fabrication of polymer nanocomposites with non-linear optical properties.

Figure 1: Colloidal dispersions of ND/Au (10%) (left) and NDs (right) in DMF.

Similar wine-reddish dispersions in DMF were also obtained for the 1% and 5% ND/Au hybrids. Higher gold loadings on NDs surface were also possible (e.g., 20 %). However, this results in a higher degree of aggregation of the gold nanoparticles over the support. In addition, at higher loadings it is likely to observe particles residing outside the support (i.e. phase separation). Lastly, the resulting colloids tend to crash out faster than those reported in the paper due to the higher density of the hybrid particles. In a control experiment, borohydride reduction of AuCl3 in the absence of NDs followed by sonication of the derived gold nanoparticles in DMF resulted in no particle dispersion (e.g., gold sinks in DMF) and hence no coloration of the solvent. Therefore, it is the high affinity of the ND support towards DMF that makes possible the dispersion of ND/Au in the solvent.


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HRTEM studies of the dispersed hybrid showed nearly spherical gold nanoparticles, with diameters ranging between 6-20 nm (average: 6±1 nm), supported on the ND (4-6 nm) matrix (Figure 2). The corresponding size histogram is given in supporting information (Figure S4). For the better understanding of the elemental composition of the sample, the chemical mapping of the hybrid was performed by STEM-Energy Dispersive X-ray Spectroscopy (EDS) (Figure 2). As can be seen, gold is spread on the surface in small islands confirming the successful modification of NDs with Au nanoparticles and the successful formation of the ND/Au hybrids.

Figure 2: HRTEM portraits of NDs (a) and ND/Au (10 %) (b). ND matrix is composed of 5 nm sized nanodiamonds. The gold nanoparticles are seen as dark globular objects (8-25 nm) embedded on ND matrix. Chemical mapping of the ND/Au hybrid (10%) on the right demonstrates the distribution of Au nanoparticles (violet) over the ND matrix (green). Note that figure b and chemical mapping on the right refer to different sample’s areas.

Nonlinear optical measurements: For the study of the nonlinear optical properties of the ND/Au nanohybrids, the Z-scan technique was used.26 The Z-scan technique has become a very popular technique due to the fact that it allows the simultaneous determination of the nonlinear



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absorption and refraction of a sample in a single measurement. The Z-scan technique is a relatively simple experimental technique which basically measures the variation of the transmission of a sample as it moves through the focal plane of a focused laser beam, by two different experimental procedures. In the present work the nonlinear optical properties of the ND/Au hybrids were investigated under two different laser excitation regimes, namely under 35 ps and 40 fs laser excitation. In more details, two lasers have been employed, a 35 ps modelocked Nd:YAG laser operating at 1064 and/or 532 nm, at 10 Hz and a 40 fs Ti:Sapphire based laser system operating at 800 nm at 10 Hz. The details of the experimental setup and the full description of the analysis of the Z-scan measurements have been presented elsewhere27 and therefore only some necessary information will be reported here. Both laser beams were focused by means of a 200 mm focal length plano-convex quartz lens into the sample. The waist of the picosecond laser beam was determined to be 18 and 30 µm, for 532 and 1064 nm radiations respectively, using a CCD camera and taking images of the laser beam at several positions prior and after the focal level. Following a similar procedure the beam waist of the femtosecond laser was also determined and it was found to be 14 µm. The ND/Au nanohybrids and the pure ND were suspended in DMF (dimethylformamide) forming stable dispersions. The pure Au nanoparticles were dispersed in distilled water and samples with different concentrations were also prepared. The UV-Vis-NIR absorption spectra of all prepared samples were measured regularly in order to ensure their stability. The samples were put in 1 mm thick quartz cells which were mounted on a computer controlled motorized stage, moving through the focal plane along the propagation direction of the focused laser beam, thus experiencing different intensity at each position, the maximum intensity occurring at about the focal plane. The transmitted through the sample beam was divided into two equal parts by means


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of a 50:50 beam splitter, each part driven into one of the two arms of the experimental setup, providing the so-called “open-” and “closed-aperture” Z-scans. Each of these Z-scans was showing the variation of the normalized transmission of a sample, in two different ways. In the “open-aperture” one, the transmitted laser beam was totally collected after the sample and was measured by means of a photomultiplier (PMT). According to the Z-scan theoretical assumptions, the sample transmission can be described by the following equation (1):  β Ι 0 Leff / (1 + z 2 z02 )  Τ=∑ ( m + 1)3 2 m=0 ∞

m

(1)

where β is the nonlinear absorption coefficient, I0 is the on-axis peak irradiance, Leff is the effective thickness of the sample given by the following relation: Leff = (1 − e−a0 L ) a0 , where a 0 is the absorption coefficient at the laser wavelength and L is the sample’s length. The parameter z 0 is the Rayleigh length and m is an integer. From the fitting of the “open-aperture” Z-scan by equation (1) the nonlinear absorption coefficient β can be obtained. Then, the imaginary part of the third-order nonlinear susceptibility χ(3), the Imχ(3), can be easily calculated from the following relation: (3) Im χ1111 (esu ) =

10 −7 c 2 n02 β 96π 2ω

(2)

where c is the speed of light given in cm s-1, n0 is the refractive index and ω is the frequency of the incident beam in s-1. During the “closed-aperture” Z-scan transmission measurement, the transmitted through the sample laser beam is measured, after it has passed through narrow pinhole placed in the farfield. This measurement can provide information about the nonlinear refractive index parameter γ'. In particular, in the case where the nonlinear absorption is negligible, then the “closed-



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aperture” Z-scan recording can allow the straightforward determination of γ'. In the case of nonnegligible nonlinear absorption, its effect on the nonlinear refraction can be removed by dividing the “closed-aperture” Z-scan with the “open-aperture” one, the resultant transmission curve called “divided” Z-scan. The “closed-aperture” and the “divided” Z-scans are characterized by a transmission peak followed by a valley or by a valley followed by a transmission peak, indicative of self-defocusing or self-focusing behavior respectively. In other words, the nonlinear refractive behavior of the sample around the focal plane where it experiences the highest incident laser intensity is similar to that of a negative or positive lens respectively. Then, the nonlinear refractive parameter γ' of the sample can be obtained from the measurement of the transmission difference, ∆ΤP−V , between the peak (p) and the valley (v) of the normalized transmission curve, resulting from the “divided” Z-scan measurement using the following equation:

0.406 ∆ΤP −V 2 k0 Ι 0 Leff

γ '=

(3)

where γ' is the nonlinear refractive index parameter and k 0 is the laser light wavenumber. The real part of the third-order nonlinear susceptibility χ(3), the Reχ(3), can be then calculated from the following relation:

Re χ

(3) 1111

10−6 c n0 γ' ( esu ) = 480 π 2

(4)

Finally, the nonlinear refractive index n2 can be calculated according to the following equation:  cn  n2 (esu ) =  0  γ '( m 2 / W )  40π 

3. Results and discussion


(5)

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In Figure 3, some representative UV-Vis-NIR absorption spectra of different concentration dispersions of neat NDs, Au colloidal nanoparticles and ND/Au nanohybrids are presented. As can be seen, the neat NDs UV-Vis-NIR absorption spectra were found featureless, the NDs dispersions being highly transparent both in the visible and near-infrared spectral regions while that of Au colloidal nanoparticles were exhibiting the characteristic spectral feature at about 550 nm which is attributed to the well-known localized surface plasmon resonance (LSPR) peak, both in agreement with previously reported absorption spectra respectively.28,29 This characteristic LSPR feature of Au colloidal nanoparticles is also clearly distinguishable at the UV-Vis-NIR absorption spectra of the ND/Au nanohybrids shown in Figure 3 (right), superimposed on the featureless spectrum of neat NDs.30 In the same Figure, the effect of the Au load on the intensity of the LSPR peak, at about 550 nm, is clearly observable for the 1, 5 and 10% ND/Au samples. In fact, the increase of Au loading is followed by the corresponding increase of the LSPR peak.

Figure 3: UV-Vis-NIR absorption spectra of NDs and Au nanoparticles (left), and ND/Au hybrids with different Au loading (w/w).



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Figure 4 illustrates “open-” and “divided” Z-scans obtained under 35 ps, 532 nm laser excitation. As can be seen from the upper series of “open-aperture” Z-scans, the ND/Au hybrids were found to exhibit sizable reverse saturable absorption (RSA) in contrast to the pure NDs’ dispersions (without any gold nanoparticles), which exhibited negligible nonlinear absorption. Furthermore, the nonlinear absorption of the ND/Au nanohybrids was found to vary with the gold loading, indicating unambiguously that the source of the observed NLO response of the hybrids is directly related to the Au nanoparticles attached on the surface of the nanodiamonds. Finally, the Au colloids (without any ND support) were found to exhibit important saturable absorption. This is a direct consequence of the resonant excitation conditions occurring, since the laser excitation wavelength was in full resonance with their plasmonic feature.

Figure 4: “Open-aperture” (a, b, c) and “divided” Z-scan (d, e, f) of ND/Au (10%) and NDs in DMF and Au nanoparticles in distilled water under 532 nm, 35 ps laser excitation.


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Concerning the nonlinear optical refraction of the nanohybrids, as depicted in Figure 4(d), the “divided Z-scan of the ND/Au dispersion were found to exhibit a “valley-peak” configuration, characteristic of self-focusing behavior, i.e., positive nonlinear refraction. However, Z-scan measurements performed on different concentration dispersions revealed a clear decrease of the experimental ∆Τp-v values of the dispersions increasing the concentration of the nanohybrids as shown in Figure 5. Such a behavior is typical of opposite sign NLO refraction between the solute and the solvent, i.e. the ND/Au hybrids and DMF.31 In order to further confirm this finding and determine the magnitude of the NLO refractive index parameter γ' similar measurements were performed for neat DMF and the distilled water, which was employed for the dispersion of the gold colloids. More in detail, both DMF and water were found to exhibit “divided” Z-scans with the characteristic “valley-peak” configuration (not shown here), suggesting self-focusing behavior, i.e., positive nonlinear refraction, in good agreement with other previous literature reports.32 In a similar way, the neat NDs and the Au colloids were also found exhibiting opposite sign nonlinear refraction compared to the solvents used, i.e., DMF and water respectively. This situation has been also confirmed experimentally from the decreasing trend of the ∆Τp-v values of the dispersions as the concentration of the nanoparticles was increased. In Figure 5, the variation of the ∆Τp-v parameter as a function of the incident laser energy, for three different concentration dispersions of the 10% w/w ND/Au sample is presented. As shown, for all studied samples (Figure S5) a good linear correlation was obtained, confirming both the quality of the measurements and the presence of the third-order nonlinear refraction phenomena according to the Z-scan theory. From the slopes of the straight lines, which correspond to the linear best fits of the experimental data, the nonlinear refractive parameter γ'



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was calculated after having taken into account the contribution of the solvent. The obtained nonlinear optical parameters, i.e. the NLO absorption coefficient β, and the NLO refractive parameter γ' together with the corresponding imaginary and real parts of the third-order nonlinear susceptibility χ(3) of the ND/Au nanohybrids, the NDs and the Au nanoparticles are all included and presented in Table 1.

Figure 5: Variation of the ∆Τp-v with the laser energy, under 35 ps, 532 nm laser excitation of the 10% w/w ND/Au nanohybrids.

Then, the nonlinear optical response of the ND/Au nanohybrids under infrared (1064 nm), 35 ps laser excitation was studied (Figure S6). However, all the different concentration ND/Au nanohybrids dispersions which were prepared revealed rather negligible nonlinear optical response. Even, the nanohybrids with the highest Au loading (i.e. 10% w/w Au), exhibited insignificant nonlinear optical response. Similarly, the dispersions of the neat NDs did not reveal any measurable nonlinear optical response. In contrast to the above, the dispersions of the colloidal gold were found to exhibit “valley-peak” transmittance configuration, with the water


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not contributing to this response for infrared excitation, suggesting self-focusing behavior. In fact, the gold colloids exhibited sizeable positive nonlinear refraction, while they did not presented any nonlinear absorption under the present experimental conditions. It is interesting, that although the Au colloidal dispersions possess important saturable absorption under visible excitation, no measurable nonlinear absorption was observed under infrared excitation conditions. This finding is rather surprising, since, in principle, two-photon induced nonlinear absorption should be observable under the sufficiently high laser intensity used in the present experiments. The lack of any observable nonlinear absorption of the gold colloids under 1064 nm, 35 ps laser excitation despite the various experimental conditions tried (i.e., laser intensity, concentration of gold colloid, etc.) could be attributed to the very low two-photon absorption cross section of this process. Finally, the investigation of the NLO response of the ND/Au nanohybrids was performed using 40 fs, 800 nm laser excitation. However, the nanohybrids were found to exhibit negligible NLO response, not distinguishable from that of the solvent (i.e. DMF), despite the various concentration samples studied, implying a rather low value of nonlinearity under these excitation conditions. In Figure 6, the obtained results are presented, where it becomes evident that the response of the nanohybrids is not distinguishable from that of DMF (Figure S7). Separate measurements of the NLO response of the solvent DMF using 40 fs, 800 nm laser excitation have shown that DMF exhibited only (positive sign) NLO refraction and insignificant NLO absorption under the laser intensities employed, with the magnitude of its Reχ(3)) to be about (10.1±0.2)10-16 esu. However, recently, in a study concerning the optical limiting behavior of dispersions of several different nano-carbon based materials,33 under 120 fs, 800 nm laser pulses, some similar neat NDs have been investigated. In this study, it was reported that the water



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suspensions of NDs exhibited saturable absorption behavior. Although the femtosecond laser intensities used in this study and in the present work are very similar, i.e. around (1-3)×1015 W/cm2, the concentrations of the studied dispersions were very different. In fact, the concentrations used in the present work are about 100 times lower. This can certainly explain the lack of observation of saturable absorption behavior in the present study.

Figure 6: Dependence of the ∆Τp-v parameter versus the laser energy, under 40 fs, 800 nm laser excitation for the 10% w/w ND/Au hybrid sample.

In order to make easier the comparison of the nonlinear optical response of the different ND/Au nanohybrids and the other nanoparticles determined in the present work, the deduced third-order nonlinear susceptibility, χ(3), values have been divided by the respective concentration C and the resultant quantity, χ(3)/C, has been added in the last column of Table 1, corresponding to a figure of merit of the strength of the nonlinear optical response of each nanoparticle. So, it becomes more evident now, that the gold loading in the ND/Au nanohybrids plays a key role in determining their nonlinear optical response. In fact, it becomes apparent that the nonlinear optical response of the three differently gold loaded ND/Au samples, scale with the gold content.


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More specifically, the sample loaded with 10% w/w Au was found to exhibit a |χ(3)|/C value of ~0.9×10-13 esu·ml·mg-1, while the 5% and the 1% w/w ND/Au samples exhibited ~0.6×10-13and ~0.27×10-13 esu·ml·mg-1 respectively. A similar situation was found to hold for the nonlinear absorption of the ND/Au hybrids. Again, the quantity Imχ(3)/C (not shown in Table 1) was found to be strongly dependent on the Au loading. Hence, it is confirmed that the use of Au nanoparticles to decorate the surface of the NDs can be an efficient tool for modulating both the nonlinear refraction and absorption of the ND/Au nanohybrids, towards the realization of tailor made materials for potential applications in photonics and opto-electronics.

4. Conclusions Nanohybrids based on nanodiamond support (4-6 nm) with controllable gold loading (1, 5 and 10 %) were prepared and their nonlinear optical properties were studied. The nonlinear optical response of ND/Au hybrids could be easily and efficiently tailored by modulating the gold loading, thus making them attractive for photonic and optoelectronic applications. The dispersions of the ND/Au nanohybrids were found to exhibit important negative sign nonlinear refraction (i.e. self-defocusing) and reverse saturable absorption under visible 35 ps laser pulses, while they did not exhibit significant NLO response under infrared (1064 nm) 35 ps laser excitation. Gold-decoration resulted in enhancement of the NLO refraction of the nanohybrids compared to neat NDs, while it gave rise to important NLO absorption which was absent before, in the case of neat NDs. In contrast, the excitation of NDs and ND/Au nanohybrids with 40 fs, 800 nm laser pulses did not reveal any measurable nonlinear optical response. Overall, the method presented here is of general character and could be expanded to silver and palladium nanoparticles on nanodiamonds.



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Supporting Information S1. TEM image of the neat gold nanoparticles. S2. XRD pattern of the ND/Au hybrid (10% Au). S3. TGA/DTA analysis of ND/Au hybrid (10% Au). S4. Size histogram based on TEM for ND/Au hybrid (10% Au). S5. Variation of ∆Τp-v under 35 ps, 532 nm laser excitation of the 5%, 1% w/w ND/Au nanohybrids, NDs and Au. S6. Variation of ∆Τp-v under 35 ps, 1064 nm laser excitation of the 5 Au nanoparticles. S7: Z-scan recordings of ND/Au (10%) and DMF under 800 nm, 40 fs laser excitation.

This material is available free of charge via the Internet at http://pubs.acs.org.

Acknowledgements We gratefully acknowledge the support bythe Ministry of Education, Youth and Sports of the Czech Republic (LO1305), and Greek Nationalfunds through the Operational Program ‘‘Education and Lifelong Learning’’ of the National Strategic Reference Framework (NSRF)Research Funding Program: THALIS and HERAKLEITOUS II. The authors thank Klara Cepe for microscopic analyses.

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Table 1: Nonlinear optical parameters of the ND/Au nanohybrids, neat NDs and Au colloids under 35 ps, 532 and 1064 nm laser excitation. 532 nm, 35 ps Sample

γ'

n2

Reχ(3)

β

Imχ(3)

|χ(3)|

|χ(3)|/c

(mg ml-1)

(×10-18m2/W)

(×10-13esu)

(×10-13esu)

(×10-11m/W)

(×10-13esu)

(×10-13esu)

(×10-13esu ml mg-1)

0.51

-0.27±0.01

-9.2±0.3

-0.36±0.01

0.42±0.13

0.22±0.06

0.42±0.06

0.82±0.1

0.24

-0.14±0.01

-4.8±0.3

-0.18±0.01

0.23±0.06

0.12±0.03

0.22±0.03

0.89±0.1

0.14

-0.09±0.01

-3.1±0.3

-0.11±0.01

0.13±0.05

0.07±0.03

0.13±0.03

0.97±0.2

-0.19±0.03

-6±1

-0.25±0.01

0.11±0.01

0.18±0.05

0.31±0.05

0.63±0.1

-0.14±0.03

-5±1

-0.18±0.01

0.09±0.01

0.05±0.01

0.18±0.01

0.27±0.01

0.69

-0.14±0.01

-4.8±0.3

-0.18±0.01

-

-

0.18±0.01

0.25±0.01

0.43

-0.10±0.02

-3.4±0.6

-0.13±0.03

-

-

0.13±0.03

0.29±0.07

1.20

-0.09±0.01

-2.9±0.3

-0.10±0.01

-3.11±0.30

-1.43±0.10

1.43±0.10

1.18±0.08

0.62

-0.09±0.01

-2.9±0.3

-0.10±0.01

-2.88±0.70

-1.32±0.30

1.32±0.30

2.2±0.5

0.43

-0.07±0.01

-2.2±0.3

-0.07±0.01

-1.94±0.50

-0.89±0.20

0.89±0.20

2.1±0.5

DMF

0.46±0.02

15.7±0.7

0.59±0.03

-

-

0.59±0.03

H 2O

0.19±0.01

6.0±0.03

0.22±0.01

-

-

0.22±0.01

ND/Au 10%

ND/Au 5% 0.49 ND/Au 1% 0.69 NDs

Au

1064 nm, 35 ps Au 1.149

0.05±0.01

1.6±0.3

0.05±0.01

-

0.05±0.01

0.05±0.01

DMF

0.17±0.01

5.4±0.3

0.22±0.01

-

-

0.17±0.01

H 2O

0.06±0.01

2.1±0.3

0.06±0.01

-

-

0.07±0.01



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Graphical Abstract


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Nonlinear Optical Response of Gold-Decorated Nanodiamond

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