This research has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sk&#322;odowska-Curie grant agreement H2020-MSCA-ITN-2015/674990 project "EXCILIGHT". PJS thanks the Royal Society for a Wolfson Research Merit Award.

Caution: Please review all relevant material safety data sheets (MSDS) prior to use. Several of the chemicals used in the synthesis are highly toxic and carcinogenic. When working with silica gel, a protective respiratory mask must be worn to prevent particle inhalation. Please observe all appropriate safety rules when performing a chemical reaction including the use of engineering controls (fume cupboard) and personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes).
All reagents and solvents were purchased commercially and were used without any further purification. 1H and 13C NMR spectra were recorded on a 400 MHz NMR spectrometer using CDCl3 as the solvent. Proton NMR chemical shifts are reported as &#948; values in ppm relative to deuterated solvents: CDCl3 (7.26). Data are presented as follows: chemical shift, multiplicity and coupling constant(s) (J) are in Hz. Multiplets are reported over the range (in ppm) they appeared. Carbon NMR data were collected relative to the corresponding solvent signals CDCl3 (77.16). Melting points were measured using a melting point apparatus. Matrix assisted laser desorption ionisation-time-of-flight (MALDI-TOF) mass spectrometry were run on a Shimadzu Axima-CFR spectrometer (mass range 1-150 000 Da).
1. Synthesis of the reported compounds
<ol>
	<li>Synthesis of compound 1 (3,6-di-tert-butyl-9H-carbazole)19
	<ol>
		<li>Using 500 mL three-neck round-bottom flask, dissolve 9-H-carbazole (10.0 g, 60 mmol) in nitromethane (300 mL) under a nitrogen atmosphere. Then, add zinc (II) chloride (24.3 g, 180 mmol) to this solution.</li>
		<li>Pour 2-chloro-2-methylpropane (19.5 mL, 180 mmol) into the 100 mL addition funnel and add dropwise under vigorous stirring.</li>
		<li>Stir the resulting mixture at room temperature for 6 h.</li>
		<li>Monitor the completion of the reaction by thin layer chromatography (TLC), using dichloromethane: hexane 1:1 v/v as an eluent mixture. After the consumption of 9-H-carbazole, add 100 mL of water to neutralize the solution.</li>
		<li>Extract the product three times with 150 mL of dichloromethane each time. Separate the organic layer from the aqueous layer and additionally wash twice with 150 mL of water.
		<ol>
			<li>Dry the resulting organic layer with 15 g of magnesium sulfate, and evaporate the solvent under reduced pressure to obtain a grey powder.</li>
		</ol>
		</li>
		<li>Purify the residue by column chromatography using dichloromethane: hexane 1:1 v/v solvent mixture as an eluent provided 13.1 g (79 %) of compound 1 as a white powder. 
		Compound 1 Characterization: 
		1H NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 8.12 (d, J = 1.9 Hz, 2H), 7.78 (s b, 1H), 7.5 (dd, J = 8.5, 1.9 Hz, 2H), 7.33 (dd, J = 5.6, 0.5 Hz, 2H), 1.49 (s, 18H). 
		13C NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 142.4, 138.2, 123.7, 123.4, 116.3, 110.2, 34.9, 32.2. 
		MS: m/z 279.4 (M+). 
		Melting point: 233-235 &#176;C.</li>
	</ol>
	</li>
	<li>Synthesis of compound 2 (2,8-dibromodibenzothiophene)20
	<ol>
		<li>Using a 500 mL three-neck round-bottom flask, dissolve dibenzothiophene (15.0 g, 81.3 mmol) in chloroform (100 mL) under nitrogen atmosphere. Next, add dropwise bromine (9.3 mL, 180 mmol) at 0 &#176;C under vigorous stirring.</li>
		<li>After complete addition of bromine, raise the temperature to room temperature and stir the reaction mixture for 18 h.</li>
		<li>Filter off the resulting white precipitate and repeatedly wash with 50 mL water and then with 15 mL of methanol to isolate 2,8-dibromodibenzothiophene in a yield of 23 g (83%) as a white powder. 
		Compound 2 Characterization: 
		1H NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 8.24 (d, J = 2.0 Hz, 2H), 7.71 (d, J = 8.0 Hz, 2H), 7.58 (d, J = 2.0 Hz, 2H). 
		13C NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 138.8, 136.3, 130.5, 124.9, 124.3, 118.8. 
		MS: m/z 342.1 (M+). 
		Melting point: 227-229 &#176;C.</li>
	</ol>
	</li>
	<li>Synthesis of compound 3 (2,8-dibromodibenzothiophene-5-dioxide)21
	<ol>
		<li>Load a 500 mL one-neck round bottom flask with a suspension of 2,8-dibromodibenzothiophene (21.3 g, 60 mmol) and hydrogen peroxide solution (30 mL of 30% (w/w) in H2O) in glacial acetic acid (250 mL) and reflux for 2 h under a nitrogen atmosphere.</li>
		<li>Cool the resulting mixture to room temperature, and filter off a white precipitate.</li>
		<li>Wash three times with 15 mL of water and then 10 mL of methanol, to obtain 19.3 g (85%) of the white powder. 
		Compound 3 Characterization: 
		1H NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 8.22 (d, J = 1.6 Hz, 2H), 7.70 (d, J = 8.0 Hz, 2H), 7.57 (d, J = 2 Hz, 2H). 
		13C NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 133.3, 130.4, 129.1, 125.6, 124.8, 124.3. 
		MS: m/z 374.1 (M+). 
		Melting point: 360-362 &#176;C.</li>
	</ol>
	</li>
	<li>Synthesis of compound 4 (2,8-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)dibenzothiophene-S,S-dioxide)22
	<ol>
		<li>Using 500 mL three-neck round-bottom flask, dissolve 2,8-dibromodibenzothiophene-S,S-dioxide (0.45 g, 1.2 mmol) and 3,6-di-tert-butyl-9H-carbazole (0.80 g, 2.86 mmol) in anhydrous toluene (250 mL) and degas by bubbling through nitrogen for 15 min under vigorous stirring.</li>
		<li>After this, add tris(dibenzylideneacetone)dipalladium(0) (0.025 g, 0.03 mmol) and 2-dicyclohexylphosphino-2&#8242;,4&#8242;,6&#8242;-triisopropylbiphenyl (XPhos, 0.06 g, 0.12 mmol) to the reaction mixture and degas the solution for another 15 min.</li>
		<li>Add sodium tert-butoxide (0.32 g, 0.834 mmol) and tert-butanol (6 mL) and degas the resulting mixture for 15 min.</li>
		<li>Heat the reaction solution at 110 &#176;C under nitrogen atmosphere for 18 h.</li>
		<li>Cool down to room temperature, add water (150 mL) and extract the organic products into dichloromethane (250 mL) and wash the organic layer twice with 150 mL of water.</li>
		<li>Dry the resulting organic layer with 15 g of magnesium sulfate and remove the solvent under reduced pressure to obtain the crude product.</li>
		<li>Purify the crude material by column chromatography (using a mixture of solvents as an eluent: dichloromethane: petroleum ether 1:1 v/v) to yield compound 4 as a white solid (0.58 g, 63%). 
		Compound 4 Characterization: 
		1H NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 8.13 (d, J = 1.6 Hz, 4H), 8.11 (d, J = 8.2 Hz, 2H), 7.99 (d, J = 1.7 Hz, 2H), 7.82 (dd, J = 8.2, 1.8 Hz, 2H), 7.48 (dd, J = 8.7, 1.9 Hz, 4H), 7.40 (d, J = 8.6 Hz, 4H), 1.45 (s, 36H). 
		13C NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 144.4, 144.2, 138.5, 135.8, 133.4, 128.4, 124.4, 124.3, 119.5, 116.8, 109.2, 35.0, 32.2. 
		MS: m/z 769.97 (M+). 
		Melting point: 351-353 &#176;C.</li>
	</ol>
	</li>
	<li>Synthesis of compound 5 (2,8-bis(10H-phenothiazin-10-yl)dibenzothiophene-S,S-dioxide)23
	<ol>
		<li>Using 250 mL three-neck round-bottom flask, dissolve 2,8-dibromodibenzothiophene-S,S-dioxide (0.67 g, 1.8 mmol) and phenothiazine (0.75 g, 3.77 mmol) in anhydrous toluene (60 mL) and degas by bubbling through nitrogen for 15 min under vigorous stirring.</li>
		<li>After this, add tris(dibenzylideneacetone)dipalladium(0) (0.11 g, 0.12 mmol) and 2-dicyclohexylphosphino-2&#8242;,4&#8242;,6&#8242;-triisopropylbiphenyl (XPhos, 0.12 g, 0.23 mmol) to the reaction mixture and degas the solution for another 15 min.</li>
		<li>Add sodium tert-butoxide (0.38 g, 3.94 mmol) and degas the resulting mixture for additional 15 min.</li>
		<li>Heat the reaction solution to 110 &#176;C under a nitrogen atmosphere for 18 h.</li>
		<li>Cool down the reaction mixture to room temperature, add water (150 mL) and extract organic products into dichloromethane (250 mL) and additionally wash twice with 150 mL of water.</li>
		<li>Dry the resulting organic layer was with 15 g of magnesium sulfate and remove the solvent under reduced pressure to give the crude product.</li>
		<li>Purify the crude product by column chromatography (using solvent mixture as an eluent: dichloromethane: hexane 2:1 v/v) to obtain compound 5 as a white solid (0.9 g, 55%). 
		Compound 5 Characterization: 
		1H NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 7.71 (d, J = 8.2 Hz, 2H), 7.36 (dd, J = 7.7, 1.5 Hz, 4H), 7.28-7.19 (m, 8H), 7.16 (dd, J = 7.7, 1.3 Hz, 4H), 7.02 (dd, J = 8.1, 1.3 Hz, 4H). 
		13C NMR (400 MHz, CDCl3, 25 &#176;C, ppm): 148.8, 141.1, 133.2, 131.8, 129.7, 128.1, 126.9, 125.1, 125.3, 123.1, 121.2, 111.7. 
		MS: m/z 610.08 (M+). 
		Melting point: 353-355 &#176;C.</li>
	</ol>
	</li>
</ol>

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We have nothing to disclose.

The purpose of this paper is to show the large-scale synthesis of highly efficient organic materials (Figure 1) for OLED applications from commercially available starting materials. Due to the fact that previous reports only describe the final cross-coupling reaction step and refer to some of the outdated publications, we report the detailed step-by-step synthesis of all the materials together with their full NMR and mass-spectrometry characterization for improved reproducibility of the experiments.
Both emitters bear the same dibenzothiophene-5-dioxide electron acceptor core. The first step in the preparation of compound 3 (Figure 2) is the bromination of the commercially available dibenzothiophene molecule.20 The larger scale reaction occurs overnight with a yield of 83%. The resulting dibrominated compound 2 can be further oxidized with a solution of hydrogen peroxide in glacial acetic acid, yielding 19.3 g of a white powder after filtration and washing.21 Compound 3 was used in the cross-coupling reaction without any further purification.
The difference in photophysical characteristics between the compound 4 and 5 lies in the electron-donating properties of the amine units. One of the compounds has peripheral alkylated carbazole units while the other has phenothiazine groups. The phenothiazine molecule can be purchased from chemical vendors and used without any modifications. However, in the case of compound 4 tert-butyl groups need to be introduced onto the aromatic ring of the carbazole unit in order to increase solubility in organic solvents. It was reported that in the absence of suitable alkyl groups, the solubility of the product drops, which results in a significantly lower reaction yield.24 Alkyl groups can be introduced into each phenyl ring using a Friedel-Crafts reaction between tert-butyl chloride and 9-H-carbazole in the presence of zinc (II) chloride in nitromethane based on the electrophilic aromatic substitution mechanism.19 It was found that the purity of the resulting product is not high enough and several by-products are present in the mixture; therefore the crude grey powder must be additionally purified by column chromatography resulting in isolation of 13.1 g of compound 1 recovered as a white powder.
The desired TADF emitters 4 and 5 were synthesized via palladium-catalyzed carbon-nitrogen cross-coupling reactions using previously described literature procedures.22,23 We found that increasing the amounts of the starting materials does not negatively influence the yield of the desired product, suggesting that further increases to the reaction scale are possible. Compounds 4 and 5 can be obtained in 63% and 55% yield, respectively.
In conclusion, a detailed guideline on how to prepare highly efficient organic molecules for light emitting applications, starting from readily available materials, with the possibility to scale up the whole synthetic procedure has been demonstrated. Through this work, the intention is that large-scale synthesis of many other TADF emitters will ensure a fast transition of the technology from the laboratory bench to industrial applications.

Over the past few decades, researchers have investigated the utilization of organic molecules and their derivatives in organic light-emitting diodes (OLEDs) since their first introduction in 1987.1 The discovery of electroluminescence (EL) has led to organic materials finding a wide range of applications in displays and lighting.2 Enormous interest in producing new organic compounds and studying their photophysical properties are driven by the advantages of OLEDs over the existing technologies; most notably as they are more energy-efficient and can offer superior device performance whilst maintaining high flexibility, small thickness, and low weight. Nevertheless, in comparison to inorganic light-emitting diodes (LEDs), OLEDs still suffer disadvantages that prevent this technology from large scale commercial production, including shorter lifetimes, and low efficiencies. Until recently, most research was based on first generation OLEDs and emission relied on the fluorescence of the organic materials. Due to the fact that fluorescence can occur only from the singlet state, the maximum theoretical internal quantum efficiency (IQE) of the device is only 25%.3,4,5 By utilizing heavy-metal containing organic complexes (such as Ir, Pt), researchers could overcome the 25% efficiency barrier by harvesting the electrons from both the singlet and triplet states by a radiative transition process.6,7,8 Thus, the maximum theoretical efficiency of second generation phosphorescent OLEDs (PHOLEDs) can be as high as 100%.9,10 Nowadays, many commercial OLED devices utilize green and red phosphorescent emitting organometallic complexes based on iridium.11 Although these materials have gained widespread use in mobile displays and other electronic applications, the cost of the heavy-metal precursor salts and their short lifetimes have pushed researchers to look for alternatives.
There are several objectives that must be achieved for widespread commercialization of OLED technology, such as high stability, efficient power consumption and low production cost of the device. In recent years, it has been shown that thermally activated delayed fluorescence (TADF) emitters can be an effective substitute to PHOLED materials to reach the same IQE value, with these materials now considered as third generation OLED materials.12,13,14 Purely organic TADF emitters can be prepared in a few steps from readily available starting materials making the overall device fabrication commercially attractive to the market. To date, there are several comprehensive literature reviews covering all the aspects from material synthesis to the device fabrication.15,16,17,18 The main issue with TADF material preparation is the use of Pd-containing catalysts for the cross-coupling reactions. In order to show the potential for TADF material preparation on an increased scale. we scaled-up the synthesis of TADF emitters from starting materials to the desired products 4 and 5 (Figure 1).22,23 This detailed protocol is intended to help new practitioners in the field to understand the information associated with the synthesis of TADF materials.

<table border="0" cellpadding="0" cellspacing="0" width="973">
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">2-Chloro-2-methylpropane, 99+%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">19780</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">2-Dicyclohexylphosphino-2&#8242;,4&#8242;,6&#8242;-triisopropylbiphenyl (XPhos), 97%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">638064</td>
			<td style="width:167px;">Air sensitive</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">9-H-carbazole, 95%</td>
			<td style="width:163px;">Alfa Aesar</td>
			<td style="width:164px;">A11448</td>
			<td style="width:167px;">Air sensitive</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Bromine, 99.5%</td>
			<td style="width:163px;">Fisher</td>
			<td style="width:164px;">10452553</td>
			<td style="width:167px;">Highly toxic</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Chloroform, anhydrous, 99%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">288306</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Dibenzothiophene, 98%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">D32202</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Dichloromethane, anhydrous, 99.8%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">270997</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Glacial acetic acid, 99.7+%</td>
			<td style="width:163px;">Alfa Aesar</td>
			<td style="width:164px;">36289</td>
			<td style="width:167px;">Corrosive to skin</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Hexane, anhydrous, 95%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">296090</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:480px;">Hydrogen peroxide solution (30 % (w/w) in H2O)</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">H1009</td>
			<td style="width:167px;">Corrosive to skin</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Magnesium sulfate, 99.5%</td>
			<td style="width:163px;">Alfa Aesar</td>
			<td style="width:164px;">33337</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Nitromethane, 98+%</td>
			<td style="width:163px;">Alfa Aesar</td>
			<td style="width:164px;">A11806</td>
			<td style="width:167px;">Highly explosive</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Phenothiazine, 98+%</td>
			<td style="width:163px;">Alfa Aesar</td>
			<td style="width:164px;">A12517</td>
			<td style="width:167px;">Air sensitive</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Sodium tert-butoxide, 97%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">359270</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Tert-butanol, anhydrous, 99.5%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">471712</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Toluene, anhydrous, 99.8%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:164px;">244511</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Tris(dibenzylideneacetone) dipalladium(0), Pd 21.5% min</td>
			<td style="width:163px;">Alfa Aesar</td>
			<td style="width:164px;">12760-03</td>
			<td style="width:167px;">Air sensitive</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:480px;">Zinc (II) chloride, anhydrous, 98+%</td>
			<td style="width:163px;">Alfa Aesar</td>
			<td style="width:164px;">A16281</td>
			<td style="width:167px;"></td>
		</tr>
	</tbody>
</table>

scale-up chemical synthesis of thermally-activated delayed fluorescence emitters based on the dibenzothiophene-s,s-dioxide core

We report a procedure to linearly scale-up the synthesis of 2,8-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)dibenzothiophene-S,S-dioxide (compound 4) and 2,8-bis(10H-phenothiazin-10-yl)dibenzothiophene-S,S-dioxide (compound 5) using Buchwald-Hartwig cross-coupling reaction conditions. In addition, we demonstrate a scaled-up synthesis of all non-commercially available starting materials that are required for the amination cross-coupling reaction. In the present article, we provide the detailed synthetic procedures for all of the described compounds, alongside their spectral characterization. This work shows the possibility to produce organic molecules for optoelectronic applications on a large scale, which facilitates their implementation into real world devices.

The chemical structures of the final TADF emitters (Figure 1) are marked blue for the electron-donating groups and red for the electron-withdrawing core. An alkylated carbazole derivative and a dibrominated dibenzothiopene-S,S-dioxide acceptor molecule can be prepared from inexpensive starting materials (Figure 2). The final products can be prepared by a large-scale version of the Pd-catalyzed amination cross-coupling reaction (Figure 3).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56501/56501fig1.jpg" /> 
Figure 1. Chemical structures of thermally activated delayed fluorescence emitters based on the 2,8-dibenzothiophene-5-dioxide electron acceptor core (shown in red) bearing 3,6-di-tert-butyl-9H-carbazol-9-yl and 10H-phenothiazin-10-yl donor moieties of compound 4 and compound 5 respectively. Electron-donating groups are shown in blue. <a href="https://cloudflare.jove.com/files/ftp_upload/56501/56501fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56501/56501fig2.jpg" /> 
Figure 2. Chemical reaction pathways to prepare 3,6-di-tert-butyl-9H-carbazole (compound 1) by alkylation of 9-H-carbazole and 2,8-dibromodibenzothiophene-5-dioxide (compound 3) in two steps starting from commercially available dibenzothiophene. <a href="https://cloudflare.jove.com/files/ftp_upload/56501/56501fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56501/56501fig3.jpg" /> 
Figure 3. Buchwald-Hartwig cross coupling reactions between 2,8-dibromodibenzothiophene-5-dioxide (compound 3) and a corresponding secondary amine to produce compounds 4 and 5. <a href="https://cloudflare.jove.com/files/ftp_upload/56501/56501fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core at JoVE.com

Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core

Scale-up synthesis of highly efficient thermally activated delayed fluorescence emitters is described in the presented article.

We report a procedure to linearly scale-up the synthesis of 2,8-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)dibenzothiophene-S,S-dioxide (compound 4) and ...

scale-up-chemical-synthesis-thermally-activated-delayed-fluorescence

Research

JoVE Journal

Chemistry

9.5K Views.  University of Strathclyde. Scale-up synthesis of highly efficient thermally activated delayed fluorescence emitters is described in the presented article.

Video: Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core

Determining the Ice-binding Planes of Antifreeze Proteins by Fluorescence-based Ice Plane Affinity

Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal ice growth. AFPs bind to specific planes of ice through their ice-binding surfaces. Fluorescence-based ice plane affinity (FIPA) analysis is a modified technique used to determine the ice planes to which the AFPs bind. FIPA is based on the original ice-etching method for determining AFP-bound ice-planes. It produces clearer images in a shortened experimental time. In FIPA analysis, AFPs are fluorescently labeled with a chimeric tag or a covalent dye then slowly incorporated into a macroscopic single ice crystal, which has been preformed into a hemisphere and oriented to determine the a- and c-axes. The AFP-bound ice hemisphere is imaged under UV light to visualize AFP-bound planes using filters to block out nonspecific light. Fluorescent labeling of the AFPs allows real-time monitoring of AFP adsorption into ice. The labels have been found not to influence the planes to which AFPs bind. FIPA analysis also introduces the option to bind more than one differently tagged AFP on the same single ice crystal to help differentiate their binding planes. These applications of FIPA are helping to advance our understanding of how AFPs bind to ice to halt its growth and why many AFP-producing organisms express multiple AFP isoforms.

Antifreeze proteins (AFPs) bind to specific planes of ice to prevent or slow ice growth. Fluorescence-based ice plane affinity (FIPA) analysis is a modification of the original ice-etching method for determination of AFP-bound ice planes. AFPs are fluorescently labeled, incorporated into macroscopic single ice crystals, and visualized under UV light.

Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal ice growth. AFPs bind to specific planes of ice ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of trifluoromethoxylated aromatic compounds remains a formidable challenge in organic synthesis. Conventional approaches often suffer from poor substrate scope, or require use of highly toxic, difficult-to-handle, and/or thermally labile reagents. Herein, we report a user-friendly protocol for the synthesis of methyl 4-acetamido-3-(trifluoromethoxy)benzoate using 1-trifluoromethyl-1,2-benziodoxol-3(1H)-one (Togni reagent II). Treating methyl 4-(N-hydroxyacetamido)benzoate (1a) with Togni reagent II in the presence of a catalytic amount of cesium carbonate (Cs2CO3) in chloroform at RT afforded methyl 4-(N-(trifluoromethoxy)acetamido)benzoate (2a). This intermediate was then converted to the final product methyl 4-acetamido-3-(trifluoromethoxy)benzoate (3a) in nitromethane at 120 &#176;C. This procedure is general and can be applied to the synthesis of a broad spectrum of ortho-trifluoromethoxylated aniline derivatives, which could serve as useful synthetic building blocks for the discovery and development of new pharmaceuticals, agrochemicals, and functional materials.

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

An operationally simple procedure for the synthesis of ortho-trifluoromethoxylated aniline derivatives via a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxyacetamide followed by thermally induced intramolecular OCF3-migration is reported.

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Hydroquinone Based Synthesis of Gold Nanorods

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag+) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

This paper describes a protocol for the synthesis of gold nanorods, based on the use of hydroquinone as reducing agent, plus the different mechanisms for controlling their size and aspect ratio.

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the ...

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The first COF was reported in 2005 with much effort centered on the establishment of new synthetic routes for its preparation. To date, most available synthetic methods for COF synthesis are based on bulk mixing under solvothermal conditions. Therefore, there is increasing interest in developing systematic protocols for COF synthesis that provide for fine control over reaction conditions and improve COF processability on surfaces, which is essential for their use in practical applications. Herein, we present a novel microfluidic-based method for COF synthesis where the reaction between two constituent building blocks, 1,3,5-benzenetricarbaldehyde (BTCA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB), takes place under controlled diffusion conditions and at room temperature. Using such an approach yields sponge-like, crystalline fibers of a COF material, hereafter called MF-COF. The mechanical properties of MF-COF and the dynamic nature of the approach allow the continuous production of MF-COF fibers and their direct printing onto surfaces. The general method opens new potential applications requiring advanced printing of 2D or 3D COF structures on flexible or rigid surfaces.

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

We present a novel microfluidic-based method for synthesis of covalent organic frameworks (COFs). We demonstrate how this approach can be used to produce continuous COF fibers, and also 2D or 3D COF structures on surfaces.

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The ...

Preparation of Chitosan-based Injectable Hydrogels and Its Application in 3D Cell Culture

The protocol presents a facile, efficient, and versatile method to prepare chitosan-based hydrogels using dynamic imine chemistry. The hydrogel is prepared by mixing solutions of glycol chitosan with a synthesized benzaldehyde terminated polymer gelator, and hydrogels are efficiently obtained in several minutes at room temperature. By varying ratios between glycol chitosan, polymer gelator, and water contents, versatile hydrogels with different gelation times and stiffness are obtained. When damaged, the hydrogel can recover its appearances and modulus, due to the reversibility of the dynamic imine bonds as crosslinkages. This self-healable property enables the hydrogel to be injectable since it can be self-healed from squeezed pieces to an integral bulk hydrogel after the injection process. The hydrogel is also multi-responsive to many bio-active stimuli due to different equilibration statuses of the dynamic imine bonds. This hydrogel was confirmed as bio-compatible, and L929 mouse fibroblast cells were embedded following standard procedures and the cell proliferation was easily assessed by a 3D cell cultivation process. The hydrogel can offer an adjustable platform for different research where a physiological mimic of a 3D environment for cells is profited. Along with its multi-responsive, self-healable, and injectable properties, the hydrogels can potentially be applied as multiple carriers for drugs and cells in future bio-medical applications.

Here we describe a facile preparation of chitosan-based injectable hydrogels using dynamic imine chemistry. Methods to adjust the hydrogel&#8217;s mechanical strength and its application in 3D cell culture are presented.

The protocol presents a facile, efficient, and versatile method to prepare chitosan-based hydrogels using dynamic imine chemistry. The hydrogel is ...

Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical properties, which allow for the absorption of near-infrared (NIR) light and can subsequently convert it into multiplexed emissions that span over a broad range of regions from the UV to the visible to the NIR. This article presents detailed experimental procedures for high-temperature co-precipitation synthesis of core-shell UCNs that incorporate different lanthanide ions into nanocrystals for efficiently converting deep-tissue penetrable NIR excitation (808 nm) into a strong blue emission at 480 nm. By controlling the surface modification with biocompatible polymer (polyacrylic acid, PAA), the as-prepared UCNs acquires great solubility in buffer solutions. The hydrophilic nanocrystals are further functionalized with specific ligands (dibenzyl cyclooctyne, DBCO) for localization on the cell membrane. Upon NIR light (808 nm) irradiation, the upconverted blue emission can effectively activate the light-gated channel protein on the cell membrane and specifically regulate the cation (e.g., Ca2+) influx in the cytoplasm. This protocol provides a feasible methodology for the synthesis of core-shell lanthanide-doped UCNs and subsequent biocompatible surface modification for further cellular applications.

A protocol is presented for the synthesis of core-shell lanthanide-doped upconversion nanocrystals (UCNs) and their cellular applications for channel protein regulation upon near-infrared (NIR) light illumination.

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical ...

Synthesis and Evaluation of a Ruthenium-based Mitochondrial Calcium Uptake Inhibitor

We detail the synthesis and purification of a mitochondrial calcium uptake inhibitor, [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]5+. The optimized synthesis of this compound commences from [Ru(NH3)5Cl]Cl2 in 1 M NH4OH in a closed container, yielding a green solution. Purification is accomplished with cation-exchange chromatography. This compound is characterized and verified to be pure by UV-vis and IR spectroscopy. The mitochondrial calcium uptake inhibitory properties are assessed in permeabilized HeLa cells by fluorescence spectroscopy.

A protocol for the synthesis, purification, and characterization of a ruthenium-based inhibitor of mitochondrial calcium uptake is presented. A procedure to evaluate its efficacy in permeabilized mammalian cells is demonstrated.

We detail the synthesis and purification of a mitochondrial calcium uptake inhibitor, [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]5+. The optimized synthesis of ...