Quantum Rods into Micelles

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Clustering of CdSe/CdS Quantum Dot/Quantum Rods into Micelles Can Form Bright, Non-blinking, Stable, and Biocompatible Probes Mona Rafipoor,*,†,‡,§ Christian Schmidtke,*,† Christopher Wolter,‡ Christian Strelow,‡ Horst Weller,‡,§,⊥ and Holger Lange‡,§ ‡

Institut für Physikalische Chemie, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany The Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, 22761 Hamburg, Germany ⊥ Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia §

S Supporting Information *

ABSTRACT: We investigate clustered CdSe/CdS quantum dots/quantum rods, ranging from single to multiple encapsulated rods within amphiphilic diblock copolymer micelles, by time-resolved optical spectroscopy. The effect of the clustering and the cluster size on the optical properties is addressed. The clusters are bright and stable and show no blinking while retaining the fundamental optical properties of the individual quantum dots/quantum rods. Cell studies show neither unspecific uptake nor morphological changes of the cells, despite the increased sizes of the clusters.

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INTRODUCTION Block copolymers allow for the encapsulation of hydrophobic nanoparticles (NPs) via self-assembly processes in aqueous media.1−3 Multiple4,5 and different6 NPs can be assembled into ordered clusters within the polymeric container.4,5,7 Their morphology can be controlled in a versatile way to form, for example, spherical micelles with NPs in the hydrophobic core, networks, and vesicular structures.8−10 Colloidal semiconductor quantum dots (QDs) exhibit a high extinction coefficient and photostability, long luminescence lifetimes, and narrow emission spectra.11−14 In particular, core−shell quantum dot/ quantum rods (QDQRs) demonstrate high quantum yields and stability.15 However, individual QDs and QDQRs are typically subject to fluorescence intermittency and/or fluorescence lifetime blinking.16,17 A blinking sample limits the use of QDQRs in tracking applications.18 In ensembles, such as clusters, the blinking is reduced for statistical reasons. Rhyner et al. observed a significantly reduced blinking for clustered fluorescent QDs,7 consequently making QD clusters a promising material for bioimaging applications. To further advance this system, the influence of the clustering on the optical properties of the QDQRs has to be studied. To systematically address this, we developed a microfluidic mixing route for CdSe/CdS QDQRs, ranging from single to multiple encapsulated QDQRs in poly(isoprene)-block-poly(ethylene glycol) (PI-b-PEG) diblock copolymer micelles. A subsequent separation according to their density (QDQR payload) by sucrose-gradient centrifugation makes homogeneous aggregates accessible. Because the synthetic conditions are the same for all structures, a direct comparison and investigation of the influence of the clustering on the properties of QDQRs is possible. We compared different polymer weights to different © XXXX American Chemical Society

QDQR payloads and observed negligible changes of the fundamental optical properties after clustering. All resulting clusters are bright, very stable, and show no blinking. Despite the increased size of the clusters compared to individual QDQRs, neither cellular damage nor unspecific cellular uptake is observed in cell studies on human alveolar epithelial cells A549. In combination with the flexibility of the clustering, this makes them promising for biomedical imaging applications.

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RESULTS CdSe/CdS QDQRs were synthesized from CdSe QD seeds in high boiling organic solvents using trioctylphosphine (TOP), trioctylphosphine oxide (TOPO), hexylphosphonic acid (HPA), and octadecylphosphonic acid (ODPA), following a slightly modified version of the well-adapted protocol of Carbone et al.19 For the ligand exchange, the native ligands on the QDQRs were replaced by polyisoprene−diethylenetriamine (PI−DETA). The PI−DETA-coated QDQRs act as a seed for the following micelle formation. To address the influence of the cluster morphology on the optical properties, three different weighted PI-b-PEGs [Mw of 4600 Da (small), 8100 Da (medium), and 14 300 Da (large)] were synthesized by living anionic polymerization with a block length ratio of 1:2, which induced the formation of spherical micelles. For the phase transfer, the PI−DETA-coated QDQRs, PI-b-PEG diblock copolymer, and the radical initiator [2,2′-azobis(2-methylpropionitrile) (AIBN)] were dissolved in tetrahydrofuran (THF) and then mixed with water in a computer-controlled microReceived: April 29, 2015 Revised: August 11, 2015

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DOI: 10.1021/acs.langmuir.5b01570 Langmuir XXXX, XXX, XXX−XXX

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Langmuir fluidic device, where spontaneous self-assembly of PI-b-PEG around the hydrophobic QDQRs occurred under micelle formation. Cross-linking of the PI moieties yielded stable PI-b-PEG micelles containing the QDQRs. The controlled clustering of QDQRs is challenging, as a result of multifactorial parameters influencing the self-assembly process. In general, controlled clustering of NPs can be cumbersomely achieved by varying the NP/polymer ratio and/or the injection speed (shearing forces).20 Using a high polymer excess, predominantly singly encapsulated NPs were obtained. This indicates that the polymer concentration is sufficient to saturate the hydrophobic surface of the particles. Adjusting the amphiphilic polymer/ QDQR ratio below this point resulted in the formation of polydisperse micelles containing single and multiple NPs as well as empty micelles. This polydisperse overall output can be fractionated into monodisperse micelles of different QDQR clusterization by a sucrose-gradient centrifugation. The purification via sucrose gradient centrifugation from 0 to 60% resulted in three main fractions (see Figure S1 and Table 1):

Figure 1. TEM micrographs of QDQR clusters encapsulated with three different PI-b-PEGs: (a) 14 300 Da (large), (b) 8100 Da (medium), and (c) 4600 Da (small). The scale bars correspond to 50 nm (Figure S3).

Figure 2a displays PL intensity maps of the different sample areas. Within the diffraction-limited resolution of the setup [≈300 nm full width at half maximum (fwhm) of the laser spot], the clustered QDQRs are point emitters that are much brighter than single encapsulated QDQRs, which supports their potential as individual biolabels. Note that the intensity in the case of the clustered QDQRs is scaled by a factor of 10 with respect to the single encapsulated QDQRs. The comparison of different clusters across the sample surface shows no differences in the shape and central wavelength of their spectra (Figure 2b). The normalized spectra do not differ significantly from the as-synthesized QDQRs (initial). The same is valid for the PL decays (see the Supporting Information). The ligand exchange/ addition, the variation of the polymer, and the clustering seem to have negligible impact on the fundamental optical properties of the QDQRs. The interesting and tunable optical properties of the QDQRs are retained, and no negative influence on the emission properties is observed. Further on, the QDQR clusters show no blinking. Figure 3 displays time traces of the integrated PL intensities of PI-b-PEG (large) single encapsulated QDQRs and their clustered counterpart. Because the excitation conditions were similar and the intensities are not normalized, they can be compared directly. First, the clusters are at least 1 order of magnitude brighter than the corresponding single encapsulated QDQRs. Second, the PL time traces of the clustered QDQRs show no blinking behavior. All clusters contain enough bright QDQRs (see Figure S8) to constantly luminesce under continuous excitation. If one QDQR within the cluster is dark, the probability of another being still bright is very high, resulting in intensity fluctuations with time but in the absence of clear off states. In contrast, PL intensities of the single encapsulated QDQRs show a distinct blinking behavior. Defined on and off periods of the PL can be observed. This is further confirmed by spatial imaging the emission of an enlarged region of the sample (videos 1 and 2 of the Supporting Information). To test the stability of the clustered encapsulated QDQRs and to simulate long-time luminescence tracking measurements, power-dependent investigations were conducted. Individual micelles were excited with different intensities, and time traces of the PL decay were measured simultaneously with the PL intensity. Figure 4 summarizes the studies for an exemplary polymer weight. As apparent from Figure 4a, the clusters show a constant, non-blinking PL for all excitation powers. After increasing and decreasing the excitation power,

Table 1. Hydrodynamic Diameter via DLS (Volume Distribution) of Sucrose Gradient Fractions of QDQRLoaded PI-b-PEG Diblock Copolymer Micelles diameter by volume (nm) PI-b-PEG diblock copolymer

fraction 1

fraction 2

fraction 3

abbreviation

Mw

empty micelles

≈1 QDDR/micelle

clustered QDQRs

small medium large

4600 8100 14300

18 22 30

31 51 52

73 81 108

the first centimeter of the colorless supernatant contains the empty micelles, and the first intense colored fraction contains the mainly single encapsulated QDQRs per micelle, whereas the pellet consists of the clustered QDQRs. The sucrose gradient fractionation has the benefit that single encapsulated QDQRs and clustered encapsulated QDQRs were exposed to very similar conditions, allowing for a detailed study of the impact of the clustering. The overall molecular weight of the three block copolymers used for the encapsulation determines the hydrodynamic diameter of the resulting micelles (Figure S2). Figure 1 displays exemplary transmission electron microscopy (TEM) micrographs. The micelles appear homogeneous in shape and size and are densely packed with QDQRs. Higher molecular weights of the polymer lead to not only larger clusters but also higher QDQR payloads within the micelle. TEM analysis also suggests a more dense spacing between the QDQRs. The QDQR samples with different polymer weights and different aggregation numbers (single and multiple QDQRs per micelle) were investigated by time-resolved photoluminescence (PL) spectroscopy. To account for the potential as a fluorescent label, individual micelles were immobilized on glass cover slides and investigated by confocal laser scanning microscopy. For each sample, statistical relevant amounts of micelles with different PL intensities were studied. Because each spot on the sample surface was illuminated for the same duration and the focal conditions remained constant, a direct intensity comparison between the structures on the sample surfaces is possible. At each point, the PL spectrum and the PL decay were recorded. B


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Figure 2. (a) PL scans of the investigated QDQR samples. The scale bars correspond to 2.0 μm. The brightness scale bars conform to counts/ms. (b) Exemplary PL spectra of different clusters of the same batch, corresponding to the structures highlighted in panel a by white circles. (c) Comparison of the PL spectra of the initial, single encapsulated, and clustered QDQRs to different polymer weights.

In our experiment, exciton populations above one per QDQR are rarely reached (see Figure S9). However, for the clustered QDQRs, a very distinct additional decay channel can be observed at 450 nW excitation power. In comparison, this behavior is not very prominent in the case of the single encapsulated QDQR. This is tentatively assigned to an interaction between excitons or charges across the QDQRs. The non-monotonic increase of the PL intensity with excitation power in this regime supports the idea of a new, non-radiative multiexciton decay appearing at higher exciton populations. For general imaging applications, especially because the QDQR clusters are bright emitters, this power regime and, thereby, this effect are not relevant. The clusters with large polymer weights prove to be robust, bright, and non-blinking probes. However, their increased sizes might typically affect their interaction with living cells. Biological Applications. As demonstrated previously, the PI-b-PEG diblock copolymer encapsulation of various NPs independent of their composition resulted in micelles that showed neither cell toxicity (no influence on the viability of the cells) nor unspecific adhesion or internalization under biologically relevant conditions.22,23 The hydrophobic part shields the NP, whereas the PEG block provides a layer against serum protein opsonization, hence minimizing unspecific interactions and cellular uptake.24,25 This allows for the use of PI-b-PEG encapsulated NPs as contrast agents in a biological environment and, after coupling to an affinity molecule, for targeted imaging/drug delivery. For biological applications, size control is important to route excretion pathways (e.g., renal clearance versus hepatobiliary accumulation) and the cellular response.26 To address the biocompatibility, cell studies of all QDQR micelles were performed (single encapsulated and clustered). All samples showed no cytotoxicity in vitro tests on human alveolar epithelial cells A549 (see the Supporting Information for a standardized cellomic toxicity assay). After the encapsulated

Figure 3. Time evolution of the spectrally integrated PL of clustered and single encapsulated QDQRs with a large polymer.

the same PL intensity is obtained, indicating no physical changes after enduring high-power excitation. This is confirmed by a comparison of the PL decays (Figure 4c). PL decays with the same excitation power after a stepwise power increase and subsequent decrease are compared. Potential created defects would result in a faster PL decay as a result of new relaxation channels. However, no differences after high power excitation are observed. The optical experiments on the QDQR clusters show them as bright, non-blinking, and stable fluorescent NPs. Increasing the excitation power generally increases the average exciton population per QDQR. This can lead to exciton−exciton interactions and much shorter PL decays.21 For the single encapsulated QDQRs, this is however only slightly observed for the highest employed excitation powers. The decay of samples excited with 450 nW has a biexponential shape with a fast component. C


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Figure 4. (a) PL intensity traces of large polymer clustered QDQRs for different excitation powers and (b) corresponding PL decays. (c and d) Excitation power-dependent PL intensity traces and decays of the corresponding single encapsulated QDQRs. The decay curves after exciting with maximum power are labeled “back”.

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QDQRs were incubated for 16 h on the cells, none of the cells showed morphological changes or influence on the viability. Even in serum-free medium, no non-specific cell interaction/ adhesion or uptake was detected as exemplary displayed for the QDQRs encapsulated with the small-sized polymer in Figure 5. In confocal studies of the human hepatocellular carcinoma cell line (HepG2), we also did not observe cell interactions or uptake, as exemplarily shown in Figure S13 with the mediumsized polymer encapsulated QDQRs. For the single encapsulated NPs, these results are in good agreement with our previous studies.22,23 The clustered QDQRs showed also no uptake, which can be explained with size limitations of endocytic pathways (>80 nm)27 and the properties of the PEG moieties.24,25 For example, Immordino et al. describe the effect of PEG for larger structures, in agreement with our findings.28

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MATERIALS AND METHODS

Materials. Air- or water-sensitive chemical compounds were handled under inert conditions with N2/Ar using the Schlenk technique or glove boxes. All chemicals were used as received. Unless indicated otherwise, all solvents used were of analytical grade (pro analysis). Tri-n-octylphosphine (TOP, 97%) and tri-n-octylphoshine oxide (TOPO, 99%) were purchased from ABCR. Octadecylphosphonic acid (ODPA, 100%) and hexylphosphonic acid (HPA, 100%) were purchased from PCI. Cadmium oxide (CdO, 99.998%, Puratronic) was purchased from Alfa Aesar. Selenium (Se, 99.99%) and sulfur (S, 99.998%) were purchased from Sigma-Aldrich. AIBN was purchased from Aldrich. Water was purified using a Milli-Q system (18.2 MΩ cm). Synthesis. Synthesis of the Block Copolymers. The block copolymers PI-b-PEG (PI−DETA) (see Table 1) are the same, as described previously.23 Synthesis of the CdSe Cores. The synthesis of the CdSe cores was performed via a hot injection synthesis following a slightly modified procedure published by Carbone et al.,19 with applying an extra drying step after forming the Cd complex. In a three-neck quartz flask equipped with a thermocouple, a condenser, and a direct connection to the Schlenk line, a mixture of CdO (60 mg), TOPO (3 g), and ODPA (0.29 g) was dried at 130−150 °C under vacuum of at least 1 × 10−2 bar for 1 h. Under N2, the reaction mixture was heated to 300 °C to decompose CdO and form a Cd(ODPA)2 complex. The formation of the complex leads to a colorless solution. Particular attention was paid to dissolve all CdO attached to higher parts of the flask by shaking the flask and the condenser to rinse off CdO. After a clear and colorless solution was obtained, it was cooled again to 150 °C to evaporate the water formed during the decomposition of CdO via the direct connection to the Schlenk line for about 1 h. After the vacuum of at least 1 × 10−2 bar was reached, the direct connection to the Schlenk line was exchanged with a septum cap. Subsequently, the solution was heated to 300 °C and TOP (1.5 g) was injected. After the temperature was allowed to recover again, the reaction mixture was heated to 380 °C and the TOP/Se (0.36 g/0.058 g) precursor was swiftly injected under vigorous stirring. The reaction was quenched after 8 min by removing the heating mantle and cooling the reaction mixture with a water bath. At 100 °C, toluene (10 mL) was injected.

CONCLUSION

Using a straightforward approach, we synthesized single and clustered encapsulated CdSe/CdS QDQRs within amphiphilic diblock copolymer micelles. A comparison of the optical properties of QDQRs before and after encapsulation/clustering shows that the clusters as bright, stable, and non-blinking probes while retaining the fundamental optical properties of the individual QDQRs. This allows for a huge flexibility in the probe design because QDQRs can be designed independently of the desired cluster structure. We demonstrated that micellar encapsulated QDQR clusters are not toxic for A549 cells and show no unspecific cell uptake or adhesion during incubation. The sum of these properties make clustered QDQRs an ideal candidate for labeling and targeting experiments as individual markers in biological and medical applications. D


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Figure 5. Confocal microscope images of A549 cells incubated with 0.5 μM (a) small polymer, single encapsulated. (b) Small polymer, cluster encapsulated after an incubation time of 16 h in serum-free medium. Red areas would arise in the presence of QDQRs as a result of their fluorescence. The cell nuclei were counterstained with Hoechst 33342 (blue). (c) Control, with no particles applied. (d) Small polymer, single encapsulated, with cells not washed. method published by Carbone et al.,19 with slight modifications. The anisotropic shell growth occurs through the co-injection of the preformed spherical CdSe cores together with a sulfur precursor into a mixture of the Cd precursor together with surfactants directing anisotropic growth at high temperatures. A typical synthesis of CdSe/ CdS QDQRs with an aspect ratio (AR) of around 5 was conducted as follows: To a three-neck quartz flask equipped with a thermocouple, a condenser, and a direct connection to the Schlenk line, a mixture of

The CdSe QDs (cores) were washed by precipitating with methanol and dispersing in chloroform 2 times. After washing the QDs, the concentration was determined via ultraviolet−visible (UV−vis) spectroscopy. Afterward, the chloroform was evaporated, and the cores were transferred to a nitrogen-filled glovebox, where the cores were dispersed in TOP. Synthesis of the QDQRs. The preparation of QDQRs was performed via a hot injection synthesis following a seeded growth E


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Langmuir CdO (57 mg), TOPO (3 g), ODPA (0.28 g), and HPA (80 mg) was dried at 130−150 °C under vacuum of at least 1 × 10−2 bar for 1 h. After the drying procedure, the reaction mixture was heated to around 300 °C under N2 to decompose CdO and form a Cd(ODPA)2 complex. The formation of the complex leads to a colorless solution. Particular attention was paid to dissolve all CdO attached to higher parts of the glass by shaking the flask and the condenser to rinse off CdO. After a clear and colorless solution was obtained, the solution was cooled to 150 °C to evaporate the water formed during the decomposition of CdO via the direct connection to the Schlenk line for about 1 h. After the vacuum of at least 1 × 10−2 bar was reached, the connection to the Schlenk line was exchanged with a septum cap. Afterward, the solution was heated to 300 °C and TOP (1.5 g) was injected. After the temperature was allowed to recover again, the reaction mixture was heated to 350 °C when the preformed CdSe cores in TOP together with the TOP/S (1.5 g/0.12 g) precursor were swiftly injected, using a syringe needle of at least 2 mm diameter under vigorous stirring. For example, to obtain QDQRs with an AR of about 5, 80 nmol of CdSe cores were used for the anisotropic shell growth. The reaction was quenched after 8 min by removing the heating mantle and cooling the reaction mixture with a water bath. At 100 °C, toluene (10 mL) was injected. The QDQRs were washed by precipitation with methanol and redispersing them in n-hexane 2 times. After washing, the QDQRs were stored at ambient conditions under protection from light in n-hexane. Methods. Determination of QDQR Concentrations. Determination of QDQR concentrations and molar extinction coefficients of QDQR concentrations were determined using a protocol described by Dimitrijevic et al.29 Phase Transfer. QDQRs were incubated with a 2000−3000 molar excess of PI−DETA (average Mn ∼ 1.4 kDa). After 3−5 h, QDQRs were precipitated with ethanol from the n-hexane solution and centrifuged. The PI−DETA-coated QDQRs were solved in n-hexane. An aliquot of these NPs (10 nmol) were dried under N2 flow and resuspended by adding a 400-fold excess of PI-b-PEG (average Mw ∼ 4.6, 8.1, and 14.3 kDa) ligand in THF (2 mL). AIBN was added in one-third mass ratio as the used diblock copolymer, and the phase transfer was realized using a computer-controlled flow system via microfluidics (neMESYS pumps from cetoni, Gera, Germany), which is equipped with a microfluidic reactor chip as described by Thiermann et al.30 The THF−QDQR−polymer solution was mixed via a microfluidic chamber (lamellar microstructure with spacing of 45 μm between each lamella) with water. Because of fluctuations in the flow rate at the start and end of the microfluidic process, in a routine process, the before and after run has to be discarded, to obtain monodisperse micelles in the middle fraction. However, fractionation is dispensable, because we demonstrated that the overall output can be gained by fractionation into well-defined monodisperse QDQR micelles of different cluster sizes by sucrose-gradient centrifugation (see below). Afterward, the solution was incubated for 30 min at room temperature. Instrumentation. UV−vis absorption spectra were collected on Cary 50. Hydrodynamic light scattering (DLS) was performed on a Zetasizer Nano ZS system (Malvern) equipped with a single-angle 173 °C backscatter system using He−Ne laser illumination at 633 nm. TEM images were recorded with a Jeol JEM-1011 microscope. Cross-Linking and Purification. After phase transfer, the resulting solution was subsequently heated to 80 °C for 2 h to initiate crosslinking. The resulting NP solution was filtered through a syringe filter (CE, hydrophilic, 0.45 μm) and washed twice with 8 mL of water in centrifugal filter units (Amicon Ultra-15, 100 kDa membrane). Purification, e.g., removal of empty micelles (without NPs), and separating the different QDQR micelle fractions by density, was accomplished via sucrose gradient centrifugation.23 The fractions were washed with water in centrifugal filter units again to remove the sucrose. Single-Particle Spectra and Lifetimes. For photoluminescence spectroscopy, the QDQR solution or the hybrid micelles were diluted and drop-casted on glass substrates, which were first cleaned in a plasma cleaner. A collimated 446 nm laser beam of a pulsed diode laser

(PDL800-D, PiL044X, A.L.S. GmbH) was used for the excitation. The laser beam with an approximate pulse length of 100 ps at a repetition rate of 10 MHz was focused onto single particles in a confocal geometry (100× objective lens Zeiss Achroplan, 0.75 NA). The emitted light was spectrally separated from backscattered laser light with a long-pass filter (edge wavelength of 532 nm, Semrock) and guided to either a spectrograph (Acton SP2500) combined with a charge-coupled device (CCD) camera (ProEM 512B, Princeton Instruments) or to an avalanche photodiode (PDM Series, Micro Photon Devices) attached to a time-correlated single-photon counting (TCSPC) control unit for scan images, PL decay measurements, and blinking time traces (time-tagged time-resolved measurements with PicoHarp 300, PicoQuant GmbH). For the PL scans and blinking experiments, the samples were excited with an average laser power of 200 nW at the sample spot. The power-dependent measurements were recorded over a time span of 10 min with a time bin of 500 ms. The laser power at the sample spot was varied stepwise using neutral density filters from 4 to 450 nW. Confocal Microscope Imaging and Cell Preparation. HepG2 cells (10 000 cells per well) were grown for 2 days in 8-well Nunc-Lab-Teks thin bottom chambers in 200 μL medium [RPMI 1640 + 10% fetal calf serum (FCS) with phenol red] for 48 h. Then, the medium was replaced with serum-free Dulbecco/Vogt modified Eagle’s minimal essential medium (DMEM). Subsequently, the cells were incubated with 0.5 μM PI-b-PEG encapsulated QDQRs (with and without FCS) for 16 h at a temperature of 37 °C in a humidified atmosphere containing 5% CO2. The cells were washed with DMEM twice, and the cells were fixated with 3.7% formaldehyde, counterstained with Hoechst 33342. After repeated rinsing with phosphate-buffered saline (PBS) buffer, the cells were monitored by confocal laser scanning microscopy (Olympus FluoView FV1000 with an IX81 inverted microscope).

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.langmuir.5b01570.

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DLS spectra, additional TEM images and PL data, estimation of the exciton population per QDQR, and additional cell studies (PDF) Video 1 (MOV) Video 2 (MOV)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: mona.rafi[email protected]. *E-mail: [email protected]. Author Contributions †

Mona Rafipoor and Christian Schmidtke contributed equally to this work. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge financial support from the German Research Foundation (DFG) via the Cluster of Excellence “Center of Ultrafast Imaging (CUI)”. The authors acknowledge Johannes Ostermann for support with block copolymers, Artur Feld for TEM support, Jan-Philip Merkel for support and helpful discussion, Alf Mews for spectroscopy lab access, and Charis Schlundt for support with the cell experiments. F


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Quantum Rods into Micelles

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