Hybrid Nanostructures for Enhanced Light-Harvesting: Plasmon ...
Hybrid Nanostructures for Enhanced Light-Harvesting: Plasmon Induced Increase in Fluorescence from Individual Photosynthetic Pigment-Protein-Complexes Sebastian R. Beyer†, Simon Ullrich‡, Stefan Kudera‡, Alastair T. Gardiner¶, Richard J. Cogdell¶ and Jürgen Köhler*,†
†
Experimental Physics IV and Bayreuther Institut für Makromolekülforschung (BIMF), University of Bayreuth, 95440 Bayreuth, Germany ‡
Max-Planck-Institute for Intelligent Systems, Department of New Materials and Biosystems, 70569 Stuttgart, Germany ¶
Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, Biomedical Research Building, Glasgow G12 8QQ, Scotland, UK
S1
Diblock copolymer micelle nanolithography (BCML) Materials The diblock copolymer used was polystyrene (PS) (110000)-b-P2VP (52000), sample P5922S2VP
from
Polymer
Source.
For
further
details
see
data
sheet
at
http://www.polymersource.com/dataSheet/P5922-S2VP.pdf. Gold(III) chloride trihydrate and anhydrous Toluene (99.8%) were obtained from Sigma-Aldrich and used as received. Nanolithography As described by R. Glass et al. [20] the PS (110000)-b-P2VP (52000) polymer was dissolved in Toluene ( 5 mg/ml) and stirred for at least 12 h. After the polymer was completely dissolved the HAuCl4 (loading L= 0.3) was added and the solution was stirred for another 48 h. All substrates were cleaned by RCA treatment, rinsed with water and dried under nitrogen. The substrate was spin-coated with the loaded micelle solution at 6000 rpm for 60 sec to get a highly regular monomicellar film and remove all solvent. After the spin-coating process the substrates were treated by H2 plasma for 45 min at 0.4 mbar and an engine power of 150W in a PVA TePla AG plasma engine to remove all polymer and reduce the gold precursor to spherical nanoparticles. The solution for BCML was prepared with a concentration of 5 mg/ml P5922-S2VP and a HAuCl4 loading of L= 0.3. The amount of the gold precursor used was calculated according to
m
[ HAuCl 4 ⋅3 H 2 O ]
=
m
Polymer
⋅ L⋅M M
[ HAuCl 4 ⋅3 H 2 O ]
Polymer
m(HAuCl4 x 3 H20) = mass HAuCl4 mPolymer = mass polymers
S2
⋅X
PS
L = loading M(HAuCl4 .x3 H20) = molar mass HAuCl4 (393,83 g / mol) XPS = number of polystyren units of the used diblock copolymer MPolymer = molar mass of diblock copolymer
S3
Characterization of the thickness of the PVA films Thin films of polyvinyl alcohol (PVA) were produced by spincoating solutions with varying concentrations of PVA onto fused silica (SiO2) substrates. For the film of 20 nm thickness, we used the same buffer solution as for dilution of the LH2 stock solution (20 mM TRIS/HCl, pH 8, 0.2% LDAO) and added 0.2% PVA. We covered the subtrate completely with the solution and spun it for 16 s at 500 rpm (including a ramp of 6 s) followed by 70 s at 2500 rpm (including a ramp of 10 s) with a Spincoater Model P6700 (Specialty Coating Systems Inc.) resulting in dry PVA films that were homogeneous over the whole substrate surface. In order to characterize the film thickness we scratched a thin line into the polymer with the back of a scalpel. Care was taken not to scratch the substrate itself. Subsequently, the scratch was investigated with an atomic force microscope (AFM, Nanosurf EasyScan 2) in noncontact tapping mode (AppNano Si cantilever, n-type; nominal specifications: rtip < 10nm, f = 145 – 230 kHZ, k = 20 – 95 N/m). Figure S1 shows such a measurement.
Figure S1: a) AFM height image of a PVA film on a fused silica substrate. The image was taken at a resolution of 128 x 128 pixels and a speed of 5 s/line, the length of one edge is 57 µm. b) Height profile along the dotted line. For this example the film thickness amounts to (19.9 ± 1.2) nm, which has been extracted from the two fits (red lines). The steep increase of the height profile is attributed to material that has been dislocated by the scalpel.
S4
This procedure was repeated for several samples and we found similar results as shown in fig.S1. In order to account for the slight differences in the preparation conditions we conservatively quote the film thickness as (20 ± 5) nm.
S5
Control experiment with PVA layer as spacer
Figure S2: Comparison of the distributions of the fluorescence response from individual LH2 complexes from Rb. Sphaeroides on bare SiO2 substrates (grey bars, 745 complexes) and on AuNP-covered SiO2 substrates with a (20±5) nm PVA spacer layer between LH2 and the AuNPs (green bars, 777 complexes). Intensities are given in units of , which corresponds to the mean of the intensity distribution obtained from LH2 on bare SiO2 (grey bars). The mean (standard deviation) of the histograms are 1.0 (0.5) (grey) and 0.9 (0.5) (green), respectively. The negative values on the abscissa are an artifact that occurs for low intensity complexes that undergo blinking. This is not relevant for the conclusions.
S6
†
Experimental Physics IV and Bayreuther Institut für Makromolekülforschung (BIMF), University of Bayreuth, 95440 Bayreuth, Germany ‡
Max-Planck-Institute for Intelligent Systems, Department of New Materials and Biosystems, 70569 Stuttgart, Germany ¶
Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, Biomedical Research Building, Glasgow G12 8QQ, Scotland, UK
S1
Diblock copolymer micelle nanolithography (BCML) Materials The diblock copolymer used was polystyrene (PS) (110000)-b-P2VP (52000), sample P5922S2VP
from
Polymer
Source.
For
further
details
see
data
sheet
at
http://www.polymersource.com/dataSheet/P5922-S2VP.pdf. Gold(III) chloride trihydrate and anhydrous Toluene (99.8%) were obtained from Sigma-Aldrich and used as received. Nanolithography As described by R. Glass et al. [20] the PS (110000)-b-P2VP (52000) polymer was dissolved in Toluene ( 5 mg/ml) and stirred for at least 12 h. After the polymer was completely dissolved the HAuCl4 (loading L= 0.3) was added and the solution was stirred for another 48 h. All substrates were cleaned by RCA treatment, rinsed with water and dried under nitrogen. The substrate was spin-coated with the loaded micelle solution at 6000 rpm for 60 sec to get a highly regular monomicellar film and remove all solvent. After the spin-coating process the substrates were treated by H2 plasma for 45 min at 0.4 mbar and an engine power of 150W in a PVA TePla AG plasma engine to remove all polymer and reduce the gold precursor to spherical nanoparticles. The solution for BCML was prepared with a concentration of 5 mg/ml P5922-S2VP and a HAuCl4 loading of L= 0.3. The amount of the gold precursor used was calculated according to
m
[ HAuCl 4 ⋅3 H 2 O ]
=
m
Polymer
⋅ L⋅M M
[ HAuCl 4 ⋅3 H 2 O ]
Polymer
m(HAuCl4 x 3 H20) = mass HAuCl4 mPolymer = mass polymers
S2
⋅X
PS
L = loading M(HAuCl4 .x3 H20) = molar mass HAuCl4 (393,83 g / mol) XPS = number of polystyren units of the used diblock copolymer MPolymer = molar mass of diblock copolymer
S3
Characterization of the thickness of the PVA films Thin films of polyvinyl alcohol (PVA) were produced by spincoating solutions with varying concentrations of PVA onto fused silica (SiO2) substrates. For the film of 20 nm thickness, we used the same buffer solution as for dilution of the LH2 stock solution (20 mM TRIS/HCl, pH 8, 0.2% LDAO) and added 0.2% PVA. We covered the subtrate completely with the solution and spun it for 16 s at 500 rpm (including a ramp of 6 s) followed by 70 s at 2500 rpm (including a ramp of 10 s) with a Spincoater Model P6700 (Specialty Coating Systems Inc.) resulting in dry PVA films that were homogeneous over the whole substrate surface. In order to characterize the film thickness we scratched a thin line into the polymer with the back of a scalpel. Care was taken not to scratch the substrate itself. Subsequently, the scratch was investigated with an atomic force microscope (AFM, Nanosurf EasyScan 2) in noncontact tapping mode (AppNano Si cantilever, n-type; nominal specifications: rtip < 10nm, f = 145 – 230 kHZ, k = 20 – 95 N/m). Figure S1 shows such a measurement.
Figure S1: a) AFM height image of a PVA film on a fused silica substrate. The image was taken at a resolution of 128 x 128 pixels and a speed of 5 s/line, the length of one edge is 57 µm. b) Height profile along the dotted line. For this example the film thickness amounts to (19.9 ± 1.2) nm, which has been extracted from the two fits (red lines). The steep increase of the height profile is attributed to material that has been dislocated by the scalpel.
S4
This procedure was repeated for several samples and we found similar results as shown in fig.S1. In order to account for the slight differences in the preparation conditions we conservatively quote the film thickness as (20 ± 5) nm.
S5
Control experiment with PVA layer as spacer
Figure S2: Comparison of the distributions of the fluorescence response from individual LH2 complexes from Rb. Sphaeroides on bare SiO2 substrates (grey bars, 745 complexes) and on AuNP-covered SiO2 substrates with a (20±5) nm PVA spacer layer between LH2 and the AuNPs (green bars, 777 complexes). Intensities are given in units of , which corresponds to the mean of the intensity distribution obtained from LH2 on bare SiO2 (grey bars). The mean (standard deviation) of the histograms are 1.0 (0.5) (grey) and 0.9 (0.5) (green), respectively. The negative values on the abscissa are an artifact that occurs for low intensity complexes that undergo blinking. This is not relevant for the conclusions.
S6
