Name: a 'plug and play' method to create water-dispersible nanoassemblies containing an amphiphilic polymer, organic dyes and upconverting nanoparticles
Uploaded: 2015-11-14T13:00:00
Description: Watch this Scientific Journal Video about A 'Plug and Play' Method to Create Water-dispersible Nanoassemblies Containing an Amphiphilic Polymer, Organic Dyes and Upconverting Nanoparticles at JoVE.com

This research was supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canada Research Chairs Program, and Simon Fraser University. This work made use of 4D LABS shared facilities supported by the Canada Foundation for Innovation (CFI), British Columbia Knowledge Development Fund (BCKDF) and Simon Fraser University.

1. Synthesis of the NaYF4/Yb3+/Er3+ Upconverting Nanoparticles (UCNP)
<ol>
	<li>Set up the apparatus as followed:
	<ol>
		<li>Place a 250 ml heating mantle on a regular stirring plate and plug the mantle onto the thermal couple.</li>
		<li>Place a 250 ml round bottom flask equipped with a magnetic stir bar onto the heating mantle with proper clamping.</li>
		<li>Attach an air adapter to the left neck of the round bottom flask and connect this air adapter to the Schlenk line with plastic...

<ol>
	<li>Fery-Forgues, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+organic+nanocrystals+and+non-doped+nanoparticles+for+biological+applications.">Fluorescent organic nanocrystals and non-doped nanoparticles for biological applications.</a> Nanoscale. 5 (18), 8428-8442 (2013).</li><li>Vollrath, A., Schubert, S., Schubert, U. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence+imaging+of+cancer+tissue+based+on+metal-free+polymeric+nanoparticles.">Fluorescence imaging of cancer tissue based on metal-free polymeric nanoparticles.</a> J. Mater. Chem. B. 1, 1994-2007 (2013).</li><li>Cheng, X., Lowe, S. B., Reecec, P. J., Gooding, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloidal+silicon+quantum+dots:+from+preparation+to+the+modification+of+self-assembled+monolayers+(SAMs)+for+bio-applications.">Colloidal silicon quantum dots: from preparation to the modification of self-assembled monolayers (SAMs) for bio-applications.</a> Chem. Soc. Rev. 43, 2680-2700 (2014).</li><li>Luo, P. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbon-based+quantum+dots+for+fluorescence+imaging+of+cells+and+tissues.">Carbon-based quantum dots for fluorescence imaging of cells and tissues.</a> RSC Adv. 4, 10791-10807 (2014).</li><li>Wang, Y., Hu, R., Lin, G., Roy, I., Yong, K. -. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functionalized+Quantum+Dots+for+Biosensing+and+Bioimaging+and+Concerns+on+Toxicity.">Functionalized Quantum Dots for Biosensing and Bioimaging and Concerns on Toxicity.</a> ACS Appl. Mater. Interfaces. 5 (8), 2786-2799 (2013).</li><li>Kairdolf, B. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Semiconductor+Quantum+Dots+for+Bioimaging+and+Biodiagnostic+Applications.">Semiconductor Quantum Dots for Bioimaging and Biodiagnostic Applications.</a> Annu. Rev. Anal. 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Chem. 13, 2031-2045 (2009).</li><li>Raymo, F. M., Tomasulo, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electron+and+energy+transfer+modulation+with+photochromic+switches.">Electron and energy transfer modulation with photochromic switches.</a> Chem. Soc. Rev. 34, 327-336 (2005).</li><li>Feringa, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular Switches. , (2010).</li><li>Tian, H., Yang, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+progresses+on+diarylethene+based+photochromic+switches.">Recent progresses on diarylethene based photochromic switches.</a> Chem. Soc. Rev. 33, 85-97 (2004).</li><li>Ubaghs, L., Sud, D., Branda, N. R., Perepichka, I. D., Perepichka, D., Branda, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Handbook in Thiophene-Based Materials: Applications in Organic Electronics and Photonics. 2, (2009).</li><li>Norsten, T. B., Branda, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoregulation+of+Fluorescence+in+a+Porphyrinic+Dithienylethene+Photochrome.">Photoregulation of Fluorescence in a Porphyrinic Dithienylethene Photochrome.</a> J. Am. Chem. Soc. 123 (8), 1784-1785 (2001).</li><li>Giordano, L., Jovin, T. M., Irie, M., Jares-Erijman, E. 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The nanoparticles synthesized according to this protocol have a size distribution from 20 to 25 nm centered at around 22.5 nm.26,27 They can be classified as spherical particles with a &#945;-NaYF4 host lattice structure. There are two critical steps in this protocol. In the UCNP synthesis, it is crucial to maintain the heating temperature and time as precise as possible to assure a narrow distribution of particle size. Simultaneous addition of NaOH and NH4F along with the addition of lan...

Today there is still an urgent need to develop new types of bio-imaging agents. Many novel fluorescent probes have been well documented.1-6 However, substantial improvements in the image resolution remains a challenge.7 One practical method is to directly modulate the fluorescence probes between a &#8216;light&#8217; emissive state and a &#8216;dark&#8217; quenched state.8-12 This particular method has been applied to develop technologies such as stimulated emission depletion (STED) microscopy13 and stochastic optical reconstruction microscopy (STORM).14
Another approach to modulate fluorescence is to couple photoresponsive chromophores together with fluorescent probes.15,16 Toggling the photoresponsive chromophore between two isomers where only one of the isomers can act as an efficient energy-transfer acceptor, allows control over quenching of the fluorescence from the probe through F&#246;rster Resonance Energy Transfer (FRET) and other mechanisms. The result is the creation of an emissive state and a quenched state that can be alternated by exposure of the photoresponsive chromophore to different wavelengths of light.
Photoresponsive diarylethene chromophores can be reversibly toggled between a colorless ring-open isomer and a colored ring-closed isomer upon irradiation with UV and visible light.17-19 The thermal stability of the two isomers and tunable absorption spectra of the ring-closed isomer make diarylethenes very good candidates as controllable FRET acceptors.20-23 Lanthanide-doped NaYF4 upconverting nanoparticles are useful for bio-imaging.24 These nanoparticles absorb near-infrared light and emit light in several regions of the visible spectrum. Examples of fluorescence modulation by combining photoresponsive diarylethene chromophores and nanoparticles have been previously reported by our group.25-27 However, the systems described in each example required an additional synthetic modification to attach the diarylethenes to the surface of the nanoparticles, which complicates the development of more diverse systems.
Herein we demonstrate a simple &#8216;plug-and-play&#8217; method to prepare water-dispersible organic dye molecules and photoresponsive upconverting nanoparticles using a self-assembly strategy. The choice of polymers; poly(styrene-alt-maleic anhydride) and polyether amine 2070 provide both a hydrophobic and hydrophilic environment. The hydrophobic sections of the polymer help to hold the normally water insoluble organic molecules and upconverting nanoparticles together, whereas the hydrophilic region of the polymer is critical for maintaining the water-solubility. We will first demonstrate synthesis of the upconverting nanoparticles by the thermal nucleation method. Then, we will prove how the organic molecules and upconverting nanoparticles are encapsulated within hydrophobic regions of the polymer shell and remain stable in aqueous media by simply co-stirring a solution of the upconverting nanoparticles, polymer and different organic dye molecules, followed by a convenient work-up procedure. We also demonstrate how to modulate fluorescence emission of the assemblies using external light irradiation. We anticipate the scope of using this &#8216;plug-and-play&#8217; method to make water-dispersible nanoassemblies will continue to expand.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>yttrium acetate</td>
			<td>sigma</td>
			<td>326046</td>
			<td>Yttrium(III) acetate hydrate</td>
		</tr>
		<tr>
			<td>ytterbium acetate</td>
			<td>sigma</td>
			<td>544973</td>
			<td>&#160;Ytterbium(III) acetate hydrate&#160;</td>
		</tr>
		<tr>
			<td>erbium acetate</td>
			<td>sigma</td>
			<td>325570</td>
			<td>Erbium(III) acetate hydrate</td>
		</tr>
		<tr>
			<td>oleic acid</td>
			<td>sigma</td>
			<td>75096</td>
			<td>analytical standard</td>
		</tr>
		<tr>
			<td>octadecene</td>
			<td>sigma</td>
			<td>O806&#160;</td>
			<td>Technical grade&#160;</td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td></td>
			<td>S5881&#160;</td>
			<td>reagent grade</td>
		</tr>
		<tr>
			<td>NH4F</td>
			<td></td>
			<td>216011</td>
			<td>ACS reagent</td>
		</tr>
		<tr>
			<td>poly(styrene-alt-maleic anhydride)</td>
			<td>sigma</td>
			<td>4422699</td>
			<td>Average Mn= 1700</td>
		</tr>
		<tr>
			<td>JeffAmine 2070</td>
			<td>Huntsman</td>
			<td>M-2070</td>
			<td></td>
		</tr>
		<tr>
			<td>Varian Carry 300</td>
			<td>Agilent</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>JDSU NIR laser</td>
			<td>JSDU</td>
			<td>L4-9897510-100M</td>
			<td>980 nm diode laser</td>
		</tr>
	</tbody>
</table>

a 'plug and play' method to create water-dispersible nanoassemblies containing an amphiphilic polymer, organic dyes and upconverting nanoparticles

In this protocol, we first describe a procedure to synthesize lanthanide doped upconverting nanoparticles (UCNPs). We then demonstrate how to generate amphiphilic polymers in situ, and describe a protocol to encapsulate the prepared UCNPs and different organic dye molecules (porphyrins and diarylethenes) using polymer shells to form stable water-dispersible nanoassemblies. The nanoassembly samples containing both the UCNPs and the diarylethene organic dyes have interesting photochemical and photophysical properties. Upon 365 nm UV irradiation, the diarylethene group undergoes a visual color change. When the samples are irradiated with visible light of another specific wavelength, the color fades and the samples return to the initial colorless state. The samples also emit visible light from the UCNPs upon irradiation with 980 nm near-infrared light. The emission intensity of the samples can be tuned through alternate irradiation with UV and visible light. Modulation of fluorescence can be performed for many cycles without observable degradation of the samples. This versatile encapsulation procedure allows for the transfer of hydrophobic molecules and nanoparticles from an organic solvent to an aqueous medium. The polymer helps to maintain a lipid-like microenvironment for the organic molecules to aid in preservation of their photochemical behavior in water. Thus this method is ideal to prepare water-dispersible photoresponsive systems. The use of near-infrared light to activate upconverting nanoparticles allows for lower energy light to be used to activate photoreactions instead of more harmful ultraviolet light.

Absorption spectra and photoluminescence spectra were collected for sample DAE-UCNP. The absorption spectra are used for comparing the spectral overlap between the closed diarylethene chromophores and the upconverting nanoparticles. Photographs of the samples (both TPP-UCNP and DAE-UCNP) were also included to demonstrate successful encapsulation of organic dye molecules and upconverting nanoparticles, which are located within the amphiphilic polymer shells in the aqueous phase. The modulation of photochemistry and fluore...

Watch this Scientific Journal Video about A 'Plug and Play' Method to Create Water-dispersible Nanoassemblies Containing an Amphiphilic Polymer, Organic Dyes and Upconverting Nanoparticles at JoVE.com

A 'Plug and Play' Method to Create Water-dispersible Nanoassemblies Containing an Amphiphilic Polymer, Organic Dyes and Upconverting Nanoparticles

Organic dye molecules and oleic acid coated upconverting nanoparticles are not water-soluble. This protocol describes a &#8216;plug and play&#8217; method that enables the transfer of organic dye molecules and upconverting particles from their initial hydrophobic solvent to water.

In this protocol, we first describe a procedure to synthesize lanthanide doped upconverting nanoparticles (UCNPs). We then demonstrate how to generate ...

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Chemistry

Analysis of Volatile and Oxidation Sensitive Compounds Using a Cold Inlet System and Electron Impact Mass Spectrometry

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The analysis of volatile and oxidation sensitive compounds by mass spectrometry is not easily achieved, as all state-of-the-art mass spectrometric methods require at least one sample preparation step, e.g., dissolution and dilution of the analyte (electrospray ionization), co-crystallization of the analyte with a matrix compound (matrix-assisted laser desorption/ionization), or transfer of the prepared samples into the ionization source of the mass spectrometer, to be conducted under atmospheric conditions. Here, the use of a sample inlet system is described which enables the analysis of volatile metal organyls, silanes, and phosphanes using a sector field mass spectrometer equipped with an electron impact ionization source. All sample preparation steps and the sample introduction into the ion source of the mass spectrometer take place either under air-free conditions or under vacuum, enabling the analysis of compounds highly susceptible to oxidation. The presented technique is especially of interest for inorganic chemists, working with metal organyls, silanes, or phosphanes, which have to be handled using inert conditions, such as the Schlenk technique. The principle of operation is presented in this video.

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The presented technique is especially of interest for inorganic chemists, working with metal organyls, silanes, or phosphanes which have to be handled using inert conditions, such as the Schlenk technique.

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

An ELISA Based Binding and Competition Method to Rapidly Determine Ligand-receptor Interactions

A comprehensive understanding of signaling pathways requires detailed knowledge regarding ligand-receptor interaction. This article describes two fast and reliable point-by-point protocols of enzyme-linked immunosorbent assays (ELISAs) for the investigation of ligand-receptor interactions: the direct ligand-receptor interaction assay (LRA) and the competition LRA. As a case study, the ELISA based analysis of the interaction between different lambda interferons (IFNLs) and the alpha subunit of their receptor (IL28RA) is presented: the direct LRA is used for the determination of dissociation constants (KD values) between receptor and IFN ligands, and the competition LRA for the determination of the inhibitory capacity of an oligopeptide, which was designed to compete with the IFNLs at their receptor binding site. Analytical steps to estimate KD and half maximal inhibitory concentration (IC50) values are described. Finally, the discussion highlights advantages and disadvantages of the presented method and how the results enable a better molecular understanding of ligand-receptor interactions.

The presented protocols describe two enzyme-linked immunosorbent assay (ELISA) based techniques for the rapid investigation of ligand-receptor interactions: The first assay allows the determination of dissociation constant between ligand and receptor. The second assay enables a rapid screening of blocking peptides for ligand-receptor interactions.

A comprehensive understanding of signaling pathways requires detailed knowledge regarding ligand-receptor interaction. This article describes two fast and ...

The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ethylene-propylene rubber, grafted with maleic anhydride, is thermo-reversibly cross-linked in two steps. The pending anhydride moieties are first modified with furfurylamine to graft furan groups to the rubber backbone. These pendant furan groups are then cross-linked with a bis-maleimide via a Diels-Alder coupling reaction. Both reactions can be performed under a broad range of experimental conditions and can easily be applied on a large scale. The material properties of the resulting Diels-Alder cross-linked rubbers are similar to a peroxide-cured ethylene/propylene/diene rubber (EPDM) reference. The cross-links break at elevated temperatures (&#62; 150 &#176;C) via the retro-Diels-Alder reaction and can be reformed by thermal annealing at lower temperatures (50-70 &#176;C). Reversibility of the system was proven with infrared spectroscopy, solubility tests and mechanical properties. Recyclability of the material was also shown in a practical way, i.e., by cutting a cross-linked sample into small parts and compression molding them into new samples displaying comparable mechanical properties, which is not possible for conventionally cross-linked rubbers.

A simple two-step approach involving rubber modification and cross-linking yields fully reworkable, elastic rubber products.

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ...

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient radiolabeling of DBCO-group-functionalized gold nanoparticles using a copper-free click reaction. Radioiodination of the stannylated precursor (2) was carried out by using [125I]NaI and chloramine T as an oxidant at room temperature for 15 min. After HPLC purification of the crude product, the purified 125I-labeled azide (1) was obtained with high radiochemical yield (75 &plusmn; 10%, n = 8) and excellent radiochemical purity (&gt;99%). For the synthesis of radiolabeled 13-nm-sized gold nanoparticles, the DBCO-functionalized gold nanoparticles (3) were prepared by using a thiolated polyethylene glycol polymer. A copper-free click reaction between 1 and 3 gave the 125I-labeled gold nanoparticles (4) with more than 95% of radiochemical yield as determined by radio-thin-layer chromatography (radio-TLC). These results clearly indicate that the present radiolabeling method using a strain-promoted copper-free click reaction will be useful for the efficient and convenient radiolabeling of DBCO-group-containing nanomaterials.

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group

A detailed procedure for the synthesis of a 125I-labeled azide and the radiolabeling of dibenzocyclooctyne (DBCO)-group-conjugated, 13-nm-sized gold nanoparticles using a copper-free click reaction is described.

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables the acquisition of photoluminescence spectra covering the time regime from nanoseconds up to 0.1 s. This enables us to follow the changes in the intensity (decay) and emission of the spectra over time. Using this method, it is possible to study diverse photophysical phenomena, such as the emission of phosphorescence, and the contributions of prompt and delayed fluorescence in molecules showing thermally activated delayed fluorescence (TADF). Remarkably, all spectra and decays are obtained in a single experiment. This can be done for solids (thin film, powder, crystal) and liquid samples, where the only limitations are the spectral sensitivity of the camera and the excitation wavelength (532 nm, 355 nm, 337 nm, and 266 nm). This technique is, thus, very important when investigating the excited state dynamics in organic emitters for their application in organic light-emitting diodes and other areas where triplet harvesting is of paramount importance. Since triplet states are strongly quenched by oxygen, emitters with efficient TADF luminescence, or those showing room temperature phosphorescence (RTP), must be correctly prepared in order to remove any dissolved oxygen from solutions and films. Otherwise, no long-lived emission will be observed. The method of degassing solid samples as presented in this work is basic and simple, but the degassing of liquid samples creates additional difficulties and is particularly interesting. A method of minimizing solvent loss and changing the sample concentration, while still enabling to remove oxygen in a very efficient and a repeatable manner, is presented in this work.

Here, we present a method of the spectroscopic characterization of organic molecules by means of time-resolved photoluminescence spectroscopy on the nanosecond-to-millisecond timescale in oxygen-free conditions. Methods to efficiently remove oxygen from the samples and, thus, limit luminescence quenching are also described.

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables ...

Raman and IR Spectroelectrochemical Methods as Tools to Analyze Conjugated Organic Compounds

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule on the vibrational level of energy. Raman and IR spectroelectrochemistry can be used for advanced characterization of the structural changes in the organic electroactive compounds. Here, the step-by-step analysis by means of Raman and IR spectroelectrochemistry is shown. Raman and IR spectroelectrochemical techniques provide complementary information about structural changes occurring during an electrochemical process, i.e. allows for the investigation of redox processes and their products. The examples of IR and Raman spectroelectrochemical analysis are presented, in which the products of the redox reactions, both in solution and solid state, are identified.

A protocol of step-by-step Raman and IR spectroelectrochemical analysis is presented.

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule ...

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, allowing for the synthesis of isotactic poly(&#945;-hydroxy acids) with expected molecular weights (&#62;140 kDa) and narrow molecular weight distributions (Mw/Mn &#60; 1.1). This ring-opening polymerization is mediated by Ni and Zn complexes in the presence of an alcohol initiator and a photoredox Ir catalyst, irradiated by a blue LED (400 - 500 nm). The polymerization is performed at a low temperature (-15 &#176;C) to avoid undesired side reactions. The complete monomer consumption can be achieved within 4 - 8 hours, providing a polymer close to the expected molecular weight with narrow molecular weight distribution. The resulted number-average molecular weight shows a linear correlation with the degree of polymerization up to 1000. The homodecoupling 1H NMR study confirms that the obtained polymer is isotactic without epimerization. This polymerization reported herein offers a strategy for achieving rapid, controlled O-carboxyanhydrides polymerization to prepare stereoregular poly(&#945;-hydroxy acids) and its copolymers bearing various functional side-chain groups.

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

A protocol for the controlled photoredox ring-opening polymerization of O-carboxyanhydrides mediated by Ni/Zn complexes is presented.

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...