Tunable emission from H-type supramolecular polymers in optical nanocavities

H-type supramolecular polymers with preferred helicity and highly efficient emission have been prepared from the self-assembly of chiral tetraphenylene-based monomers. Implementation of the one-dimensional fibers into dielectric nanoparticle arrays allows for a significant reshaping of fluorescence due to weak light–matter coupling.

For all spectroscopic measurements, sealed Hellma Quartz Suprasil cuvettes with an optical path length of 1 cm or 0.1 cm were used.TCE solutions for spectroscopic measurements were prepared by weighing the desired amount of compound in a sealed vial and adding the required volume of solvent using Gilson MICROMAN positivedisplacement pipettes to achieve the desired concentration.The solutions were then sonicated in a 40 °C water bath for 60 seconds and vortexed for 30 seconds.They were then transferred to sealed cuvettes.For the preparation of solutions in decalin/TCE mixtures, a stock solution in TCE was first prepared according to the procedure described above with a concentration 10 times higher than the target one.A volume of this solution was then transferred to another vial and the required volume of decalin was added to achieve the desired concentration.The resulting solutions were then vortexed for 30 seconds and stirred at 110 °C for 30 minutes.Subsequently, the samples were transferred while still hot into sealed cuvettes.All spectroscopic measurements were performed on freshly prepared solutions.
Steady-state absorption, circular dichroism (CD) and fluorescence spectroscopy were performed on a JASCO J-815 CD spectrometer equipped with a JASCO MPTC-490S temperature controller and a Jasco FMO-427S/15 emission monochromator.Variable temperature (VT) measurements were performed after heating the sample at 100 °C for 20 minutes in the spectrophotometer.A cooling rate of 1 °C/min was used for full spectra measurements at VT.The cooling ramp was stopped during the acquisition of the spectra.Single steady-state measurements at 20 °C were performed after heating the sample at 100 °C for 20 minutes followed by cooling to 20 °C at a rate of 1°C/min.Atomic force microscopy (AFM) images were collected using a Cypher Environmental Scanner (ES) equipped with a closed cell and a normal laser diode.A heating and cooling stage was used to actively control the temperature at 20 °C.Silicon NCSTR probes (Oxford Instruments, spring constant k = 7.4 N/m; f = 160 kHz) with a tip height of 10-15 µm and a radius of 7 nm were used for all measurements.The AFM tip was thermally calibrated using the 'Get Real' function of the Igor Pro software.Subsequent height images were acquired in repulsive tapping mode (phase <90) at a resolution of 1024x1024 pixels using a scan rate of ~2 Hz and an integral gain of 50-150.Image contrast was enhanced using first order planefit and flattening with Gwyddion v2.60.on.Emission microscopy images were acquired with a STED Abberior microscope in the confocal mode using a 405 nm laser (spectral range: 471-611 nm).Microscopy samples were prepared by either spin-coating or drop-casting 20 μM solutions of the compound in decalin/TCE 9:1 (v/v) onto freshly cleaved 1.5x1.5 cm sized mica (AFM) or 22x50 mm sized borosilicate glass (emission microscopy).Solutions for microscopy were prepared following the same procedure used for preparing solutions for spectroscopic measurements.Prior to deposition, the solutions were heated in the spectrophotometer at 100 °C for 20 minutes and then cooled to 20 °C at a rate of 1°C/min.A spin rate of 1000 rpm was used for the preparation of spin-coated samples.
The TiO2 nanoparticle arrays were prepared on a SiO2 glass substrate by electronbeam lithography followed by reactive ion etching.First, a TiO2 thin layer with thickness of 94 nm was deposited on the substrate by RF (radio frequency) magnetron sputtering.Then, a resist (ZEP520A) was spin-coated and the nanohole array pattern was written by electron-beam lithography.After that, a Cr layer (120 nm) was deposited by electronbeam deposition, and the following lift-off process resulted in a Cr dot array pattern on the TiO2 layer.Then, the TiO2 layer was etched away by reactive ion etching with CHF3 gas to make the nanoparticle array.The Cr dot mask was then removed by wet etching.
The energy and momentum resolved extinction of the arrays are measured in a Fourier microscope.The 40x, 0.6NA excitation objective (Nikon Plan Fluor) focuses a 400 nm laser onto the sample.The laser beam is generated by frequency doubling the output of a Ti:sapphire regenerative amplifier (Coherent Astrella), λ= 800 nm with a pulse duration of 150 fs.The fluorescence from the sample is collected by a 60x, 0.7 NA objective (Nikon Plan Fluor).The back focal plane of this objective is imaged on the spectrometer slit (Princeton Instruments SP2300) using 2 lenses in a 4f configuration.The spectrometer slit transmits the light along one of the principal axis of the array and disperses light on the CCD camera (Princeton Instruments ProEM:512) using a 150 lines/mm grating.

Dispersion of the arrays
The angle dependent photoluminescence from the S-TPE fibers on top of the nanocavities is plotted below.With increasing lattice period, a red shift of the emission is visible.The width of the cavity modes differs slightly between the arrays, which is mainly attributed to small differences in the nanoparticle dimensions.On the top right of each panel, the maximum number of counts of each image is given.The overall emission from fibers on top of the array is higher than outside the array, but there is a large variation in intensity due to the uneven coverage of the arrays with the S-TPE fibers.The arrays with a period of 380 and 385 nm were not covered and therefore these dispersions are missing.

Figure
Figure S7.a) CD and b) fluorescence (λex=332 nm, 700 V) spectra of 20 μM S-TPE solutions in decalin/TCE mixtures at 20 °C in the presence of different volume ratios of TCE.Measurements were performed after heating the samples at 100 °C for 20 minutes and then cooling to 20 °C at a rate of 1 °C/min.Optical path length: 10 mm.

Figure S8 .Figure S9 . 2 Figure
Figure S8.a) CD and b) fluorescence (λex=332 nm, 700 V) spectra of 20 μM S-TPE in decalin/TCE 9:1 (v/v) at 20 °C after the addition of different volume ratios of MeOH as an H-bond scavenger.MeOH was added after heating the sample at 100 °C for 20 minutes and then cooling to 20 °C at a rate of 1°C/min.Optical path length: 10 mm.

Figure S14 .
Figure S14.Angle dependent fluorescence maps of the TiO2 nanoparticle arrays covered with S-TPE.