The present investigation was supported by the Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic (project 2/0112/22).&#160;The present investigation was also supported by ERA-MIN3 POTASSIAL 27 project.

1. Preparation of CuS mixture with the stoichiometry 1.6:1
<ol>
	<li>Tare the weighing paper.</li>
	<li>Weigh 7.6024 g of elemental copper and 2.3974 g of elemental sulfur powder to achieve the stoichiometry ratio of Cu and S at 1.6:1, with a total mass of 10 g.</li>
	<li>Before milling, mix the Cu and S powder. After weighing, introduce both Cu and S powders into a plastic weighing dish and mix intensively with a spatula, until a powder of homogeneous color free from large lumps of sulfur is obtained. 
	NOTE: The purpose of the mixing is to homogenize the powder and ensure a uniform distribution of powders before the milling experiment.</li>
</ol>
2. Preparation of SnSe mixture with the stoichiometry 1:1
<ol>
	<li>Tare the weighing paper.</li>
	<li>Weigh 6.0055 g of Sn and 3.9945 g of Se to make the stoichiometry ratio 1:1, with a total mass of 10 g.</li>
	<li>Before milling, mix the Sn and Se powder by using a spatula to ensure homogeneity (the rules from 1.3 also apply here).</li>
</ol>
3. Sensor setup
<ol>
	<li>Place the sensor board on the top of the jar lid and insert the sensor transistor into the small hole that passes through the lid.</li>
	<li>Switch on the sensor device and connect it to the software on the laptop via Bluetooth.</li>
</ol>
4. Performing milling with in situ temperature monitoring
NOTE: The necessary equipment, including the scheme of the temperature monitoring device, is shown in Figure 1.
<ol>
	<li>Insert tungsten carbide balls, as specified in Table 1, into the milling jar using the tweezers or just &#34;pour&#34; them inside using gravitational force.</li>
	<li>Transfer the prepared sample either from section 1 or section 2 to the tungsten carbide milling jar for the synthesis of Cu1.8S or SnSe.</li>
	<li>Close the milling jar with the lid that has been set up with the sensor from section 3.</li>
	<li>Load the jar into the mill by placing the jar and the counterweight into the P7 planetary mill and setting the parameters on the display as specified in Table 1.</li>
	<li>Type the name of the sample on the active software.</li>
	<li>Press the Start button on the milling display.</li>
	<li>After hearing the milling start, click Start in the active software for the sensor to begin recording the temperature during milling.</li>
	<li>When the MSR occurs, indicated by the sudden increase in temperature, stop the milling and the temperature measurement immediately. 
	NOTE: Repeat the experiment with the same system once again for reproducibility</li>
</ol>
5. Collecting samples
<ol>
	<li>Open the jar over a paper sheet in the fume hood, separate the milling balls by sieving the powder through the strainer. The balls remain on the strainer while the fine powder drops on the paper. In the case of large agglomerates, these are removed from ther strainer using tweezers.&#160;Collect the sample from the paper.</li>
</ol>
6. Transferring the powders
<ol>
	<li>Transfer the powders from the paper to the glass vials using the gravitational force and&#160;spatula, label them, and store them in the desiccator before the measurement.</li>
</ol>
7. Labeling the glass vials
<ol>
	<li>Label the glass vials based on the sample name.</li>
</ol>
8. Cleaning the jar and sensor
<ol>
	<li>Clean the sensor transistor by wiping it with the tissue soaked in etaben.</li>
	<li>In the case of the jar, pour 75 mL of the etaben solution into the milling jars and perform milling at 300 rpm for 5 min.</li>
	<li>Use a steel strainer to collect the balls from the jars, and dispose of the toxic aqueous waste into the container.</li>
	<li>Repeat steps 8.2 and 8.3 until the jar and the balls are free from the solid powder.</li>
</ol>
9. Processing data from in situ temperature monitoring
<ol>
	<li>After finishing the monitoring, the software saves the data automatically as .xlsx files in the download folder on the computer.</li>
	<li>Process the data in the data treatment software to plot the graph temperature vs time. The raw data obtained from the measurement are directly stored as a .csv file and are already segregated into columns.</li>
</ol>
10. Powder X-ray diffraction (XRD) measurement
<ol>
	<li>Crush the obtained samples by using a mortar and pestle. The samples&#39; appearance is depicted in Figure 2.</li>
	<li>Transfer each sample with a spatula to the sample holders and label each sample holder.</li>
	<li>Gently compress the powder with a glass slide, carefully sliding or rotating it to flatten the surface evenly.</li>
	<li>Transfer the sample holder to the XRD diffractometer.</li>
	<li>Set up the XRD measurement in the computer using the XRD commander program programming the given measurement conditions. 
	NOTE: The instrument used in this study is an X-ray diffractometer using CuK&#945; (40 kV, 40 mA) radiation. The parameter for the powder X-ray diffraction (PXRD) experiment: 2-theta range: 10&#176;-80&#176;, step time: 1 s, step size 0.05 s.</li>
	<li>Start the PXRD measurement. The XRD data is saved as a &#34;.raw file &#34;on the computer disk.</li>
	<li>After finishing the measurement, collect the powder back from the sample holder into the glass vial using paper.</li>
	<li>Convert the .raw file into another file type that is suitable for processing in data treatment software (e.g., Origin) 
	NOTE: The PowDLL converter will allow one to convert the file extensions to the desired extension, for example, to .xy format, which is required for Rietveld refinement.</li>
</ol>
11. Rietveld refinement
<ol>
	<li>Do the proper semi-quantitative phase analysis using the XRD software to identify the phases that will be included in the refinement.</li>
	<li>Download corresponding .CIF files from the internet, e.g., from Crystallography Open Database. Download the one for CuS, rhombohedral Cu1.8S, cubic Cu1.8S, SnSe, and SnSe2.</li>
	<li>Run JEdit and powder diffraction data analysis software. 
	NOTE: The powder diffraction data analysis software used here is Topas Academic software. JEdit was formerly modified to be capable of working with the powder diffraction data analysis software.</li>
	<li>Create an input file in JEdit. Ensure that the file contains information about the diffractometer and structural parameters of the phases that are included in the refinement.</li>
	<li>Decide which parameters will be refined.</li>
	<li>Run the refinement in powder diffraction data analysis software. The software saves the result in the .out file, which automatically becomes the new input &#34;.inp&#34; file if another refinement is run.</li>
	<li>Modify the input parameters to get the best refinement possible (determined by the Rwp factor) and run the refinement again.</li>
	<li>Once it is not possible to further improve the refinement, modify the input file in such a way as to save also the results as a .xyd file, which can be read by Origin software.</li>
	<li>Run the refinement for one last time and export the .xyd file.</li>
	<li>Find the information about crystallite size and phase composition in the refinement result (there is an option to run the refinement to provide this information) and note it down.</li>
	<li>Process the data in data analysis software and make the final figures. 
	NOTE: This study used Origin software.</li>
</ol>

Synthesis of High-ZT Thermoelectric Materials via Mechanochemical Methods

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X., Feng, J., Ge, Z. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+thermoelectric+performance+of+Cu1.8S+via+lattice+softening.">Enhanced thermoelectric performance of Cu1.8S via lattice softening.</a> Chem. Eng. J. 428, 131153 (2022).</li><li>Zhao, L. D., 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=Ultralow+thermal+conductivity+and+high+thermoelectric+figure+of+merit+in+SnSe+crystals.">Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals.</a> Nature. 508 (7496), 373-377 (2014).</li><li>Byeon, D., 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=Dynamical+variation+of+carrier+concentration+and+colossal+Seebeck+effect+in+Cu2S+low-temperature+phase.">Dynamical variation of carrier concentration and colossal Seebeck effect in Cu2S low-temperature phase.</a> J Alloys Compd. 826, 154155 (2020).</li><li>Cai, B., Hu, H., Zhuang, H. L., Li, J. 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The authors have no competing financial interests

Mechanically induced self-propagating reactions (MSR) are an immediate transformation of precursors into products via an exothermic combustion-like process activated by mechanical action (similar to self-heat sustaining reactions where similar processes are activated by heat). The occurrence of MSR can often be identified by changes in the physical appearance of the product, a distinct smell at the moment of the reaction, or a scratching sound from the milling&#160;jar. However, empirical evidence suggests that these sen...

Statistically, more than 60% of energy in the world is lost, mostly as waste heat.&#160;Utilizing&#160;the waste heat for thermoelectricity (TE) applications has a great potential. TE offers a suitable method to convert waste heat into electrical energy. Special applications, like electrical energy sources in radioactive thermoelectric generators for space research and/or replacing the old Hg-Zn batteries in cardiac pacemakers, can be mentioned1.
Among various TE materials, chalcogenides belong among the favorites, especially if they are composed of abundant and non-toxic elements. Chalcogenides with tellurium, lead, and germanium content were reported as perspective TE materials in the past, with Bi2Te3 and (Bi,Sb)2Te3 being among the most prominent examples. However, both Bi and Te are rare and/or toxic, making the mass production of TE materials with this composition challenging2. Looking forward to selection among chalcogenides, the new alternatives that bear in mind non-toxicity, earth-abundancy, and TE efficiency are considered. Two systems that fulfill these criteria are copper sulfides Cu2-xS and tin selenide SnSe.
Copper sulfides are present frequently in nature as minerals in several compositions, with chalcocite Cu2S and covellite CuS as border members. In between, several&#160;non-stoichiometric&#160;compounds exist3. Among them, Cu1.97S and Cu1.98S, with interesting properties, were already synthesized by directly melting the elements Cu and S4,5.&#160;&#160;Also, digenite Cu1.8S is particularly interesting for thermoelectrics.
Tin selenide SnSe represents a high TE figure among chalcogenides. The synthesis at&#160;1223 K for over 9.5 h led to its ultralow thermal conductivity and subsequent high thermoelectric efficiency6. Accompanying phenomena were not studied.
Synthesis routes of copper sulfides and tin selenides encompass mostly high-temperature treatment of reaction precursors4,7,8,9,10. However, there are also alternative, more environmentally sound synthesis routes such as mechanochemical synthesis3,11,12,13. The&#160;mechanochemical synthesis of chalcogenides&#160;from elements can, under some circumstances, occur as a mechanically induced self-propagating reaction (MSR), which is a combustion-like process instantly yielding the products in a very short timeframe14,15,16. For both systems reported in this study, the MSR was reported- for Cu1.8S, it was done instantly, albeit the Cu:S ratio 1.6 needed to be used due to the volatility of sulfur16,17, and for SnSe, it occurred in about 15 s16.
The ignition of an MSR is accompanied by a sudden increase in temperature and pressure. Upon monitoring these characteristics via specifically engineered milling jars, it is possible to determine the MSR onset. However, the commercially available devices for planetary ball milling monitoring offer only the data collection every 2 s, and due to the location of the sensors, MSR can be detected only via pressure monitoring, neither by temperature one16,18. Moreover, the mentioned system is not transferrable and can only be both purchased and used together with the specifically engineered milling jar, which is both limiting and costly. We have recently developed a transferrable device capable of collecting temperature data every 80 ms19. This advanced measuring system developed for in situ temperature monitoring during mechanochemical synthesis significantly enhances the capabilities over existing commercial solutions. This system employs an NRBG104F3435B2F NTC thermistor, featuring a resistance tolerance of &#177;1% at 25 &#176;C and a beta value tolerance of &#177;1%, ensuring high-precision temperature measurements. With a data capture frequency of every 80 milliseconds, the system provides a high-resolution monitoring crucial for detecting the initiation of MSRs. The thermistor&#39;s high sensitivity to temperature changes, indicated by a steep resistance-temperature relationship, ensures accurate detection of rapid temperature spikes. The temperature sensor is strategically placed within an existing screw mechanism used for pressure release and gas addition, located in the hole of a massive cap. This placement protects the sensor from mechanical collisions and signal noise caused by the milling balls, ensuring stable and reliable temperature readings.&#160;The limitation is that the ball diameter needs to be larger than the hole diameter. With 10 mm balls, there is no problem. The system&#39;s wireless communication capability and robust sealing mechanism prevent material or heat leakage, thereby enhancing the reliability and accuracy of the temperature data collected during the milling process. Designed to be cost-effective and portable, this system represents a significant advancement in the real-time&#160;temperature monitoring of chemical reactions during planetary ball milling, offering critical insights for the optimization of materials synthesis.
This study aims to demonstrate the performance of this newly developed device by monitoring temperature during the mechanochemical synthesis of two selected metal chalcogenides that are interesting for TE applications. Another objective is to show the sustainable, simple, and time-saving character of the mechanochemical synthesis, which is boosted when the reaction occurs as an MSR.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Copper</td>
			<td>Pometon, Germany</td>
			<td>7440-50-8</td>
			<td>Red powder</td>
		</tr>
		<tr>
			<td>D8 Advance diffractometer&#160;</td>
			<td>Bruker, Germany</td>
			<td>M88-E03036</td>
			<td>X-ray instrument</td>
		</tr>
		<tr>
			<td>DiffracPlus Evaluation package release</td>
			<td>Bruker, Germany</td>
			<td>DOC-M85-EXX002</td>
			<td>Diffraction analysis software</td>
		</tr>
		<tr>
			<td>Etaben</td>
			<td>Mikrochem, Slovakia</td>
			<td>64-17-5</td>
			<td>solution</td>
		</tr>
		<tr>
			<td>Jedit</td>
			<td>Open Source software</td>
			<td></td>
			<td>Programmer&#39;s text editor</td>
		</tr>
		<tr>
			<td>Project SAV 1.0</td>
			<td></td>
			<td></td>
			<td>Software developed to record data from in situ temeprature monitoring</td>
		</tr>
		<tr>
			<td>Pulverisette P7 planetary mill</td>
			<td>Fritsch, Germany</td>
			<td>07.5000.00</td>
			<td>The milling device, utilized in the synthesis of Cu1.8S and SnSe</td>
		</tr>
		<tr>
			<td>Selenium</td>
			<td>Acros Organic, Germany</td>
			<td>7782-49-2</td>
			<td>Gray powder</td>
		</tr>
		<tr>
			<td>Sulfur</td>
			<td>Sigma Aldrich, Germany</td>
			<td>7704-34-9</td>
			<td>Yellow powder</td>
		</tr>
		<tr>
			<td>Tin</td>
			<td>Merck, Germany</td>
			<td>7440-31-5</td>
			<td>Gray powder</td>
		</tr>
		<tr>
			<td>Topas Academic</td>
			<td>Coelho Software</td>
			<td></td>
			<td>General non-linear least squares software driven by a scripting language. Its main focus is in crystallography, solid state chemistry and optimization.</td>
		</tr>
	</tbody>
</table>

demonstrating the simplicity and in situ temperature monitoring of the mechanochemical synthesis of metal chalcogenides suitable for thermoelectrics

Mechanochemical synthesis is an extremely useful strategy to reach thermoelectric materials due to its solvent-free one-step character, as the targeted thermoelectricity (TE) materials in a nanocrystalline format can be prepared by mere high-energy milling of elemental precursors. Nevertheless, the subsequent densification method (e.g., spark plasma sintering or hot pressing) is required afterward, similarly to other synthetic methodologies. In this study, the simplicity of mechanochemical synthesis is&#160;presented for two selected metal chalcogenides, namely copper sulfide (Cu1.8S, digenite) and tin selenide (SnSe, svetlanaite), which are known for high ZT values. These compounds can be prepared via a mechanically induced self-propagating reaction (MSR), which is a combustion-like process instantly yielding the products in a very short timeframe (within 1 min). The occurrence of MSR can be well-tracked by in situ temperature monitoring since an abrupt temperature increase occurs at the moment of MSR. We have developed a device which is capable of monitoring the temperature inside the milling jar every 80 ms during planetary ball milling, and it is therefore possible to very precisely track the moment of MSR ignition. The developed device presents an improvement in the monitoring capabilities in comparison with commercially available analogs. This contribution aims to provide a visual insight into all steps, with simple high-energy ball milling of elements to reach TE materials and in situ temperature monitoring being the central points.

The temperature during milling was recorded using Project SAV 1.0 software and plotted accordingly. Figure 3 demonstrates the changes in temperature with milling time. For the Cu1.8S samples (Figure 3A), the ignition times fall within the range of 0-0.6 s. In the sample Cu1.8S-1, the MSR occurred before temperature data collection began. Therefore, when performing the two next experiments (Cu1.8S-2 and 4), data collection was sta...

Demonstrating the Simplicity and In Situ Temperature Monitoring of the Mechanochemical Synthesis of Metal Chalcogenides Suitable for Thermoelectrics

Here, we present a protocol to synthesize two metal chalcogenides (Cu1.8S and SnSe) suitable for thermoelectrics via an ultrafast (second-range), solvent-free, and one-step mechanochemical synthesis using elemental precursors. Simultaneously, we demonstrate the monitoring of the temperature in the jar during planetary ball milling in situ by the newly developed device.

Mechanochemical synthesis is an extremely useful strategy to reach thermoelectric materials due to its solvent-free one-step character, as the targeted ...

demonstrating-simplicity-situ-temperature-monitoring-mechanochemical

Research

JoVE Journal

Chemistry

254 Views.  Slovak Academy of Sciences. Here, we present a protocol to synthesize two metal chalcogenides (Cu1.8S and SnSe) suitable for thermoelectrics via an ultrafast (second-range), solvent-free, and one-step mechanochemical synthesis using elemental precursors. Simultaneously, we demonstrate the monitoring of the temperature in the jar during planetary ball milling in situ by the newly developed device. 

Video: Demonstrating the Simplicity and In Situ Temperature Monitoring of the Mechanochemical Synthesis of Metal Chalcogenides Suitable for Thermoelectrics

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox reactions. The Cu (I) complex of the peptide model of a Cu (I) binding metallochaperone protein, which includes the sequence MTCSGCSRPG (underlined is conserved), was determined in solution under inert conditions by NMR spectroscopy.
NMR is a widely accepted technique for the determination of solution structures of proteins and peptides. Due to difficulty in crystallization to provide single crystals suitable for X-ray crystallography, the NMR technique is extremely valuable, especially as it provides information on the solution state rather than the solid state. Herein we describe all steps that are required for full three-dimensional structure determinations by NMR. The protocol includes sample preparation in an NMR tube, 1D and 2D data collection and processing, peak assignment and integration, molecular mechanics calculations, and structure analysis. Importantly, the analysis was first conducted without any preset metal-ligand bonds, to assure a reliable structure determination in an unbiased manner.

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

The NMR-solution structure of a metallochaperone model peptide with Cu (I) was determined, and a detailed protocol from sample preparation and 1D and 2D data collection to a three-dimensional structure is described.

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox ...

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.
The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC50 values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.
Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC50 values.

A method for synthesis of air-sensitive titanium and vanadium anticancer agents is described, along with the evaluation of their cytotoxic activity towards human cancer cell line by the MTT Assay.

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; ...

Split-and-pool Synthesis and Characterization of Peptide Tertiary Amide Library

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid phase by using combinatorial chemistry. One of the most well studied classes of peptidomimetics is peptoids. Peptoids are easy to synthesize and have been shown to be proteolysis-resistant and cell-permeable. Over the past decade, many useful protein ligands have been identified through screening of peptoid libraries. However, most of the ligands identified from peptoid libraries do not display high affinity, with rare exceptions. This may be due, in part, to the lack of chiral centers and conformational constraints in peptoid molecules. Recently, we described a new synthetic route to access peptide tertiary amides (PTAs). PTAs are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. With side chains on both &#945;-carbon and main chain nitrogen atoms, the conformation of these molecules are greatly constrained by sterical hindrance and allylic 1,3 strain. (Figure 1) Our study suggests that these PTA molecules are highly structured in solution and can be used to identify protein ligands. We believe that these molecules can be a future source of high-affinity protein ligands. Here we describe the synthetic method combining the power of both split-and-pool and sub-monomer strategies to synthesize a sample one-bead one-compound (OBOC) library of PTAs.

Peptide tertiary amides (PTAs) are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. Here we describe a synthetic method which combines&#160;both split-and-pool and sub-monomer strategies to synthesize a one-bead one-compound library of PTAs.

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid ...

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 ...

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, quantum dots should be highly fluorescent and small/monodisperse in size. While commonly used cadmium-based quantum dots possess these qualities, they are potentially toxic due to the possible release of Cd2+ ions through nanoparticle degradation. Indium-based quantum dots, specifically InP/ZnS, have recently been explored as a viable alternative to cadmium-based quantum dots due to their relatively similar fluorescence characteristics and size. The synthesis presented here uses standard hot-injection techniques for effective nanoparticle growth; however, nanoparticle properties such as size, emission wavelength, and emission intensity can drastically change due to small changes in the reaction conditions. Therefore, reaction conditions such temperature, reaction duration, and precursor concentration should be maintained precisely to yield reproducible products. Because quantum dots are not inherently soluble in aqueous solutions, they must also undergo surface modification to impart solubility in water. In this protocol, an amphiphilic polymer is used to interact with both hydrophobic ligands on the quantum dot surface and bulk solvent water molecules. Here, a detailed protocol is provided for the synthesis of highly fluorescent InP/ZnS quantum dots that are suitable for use in biomedical applications.

In this protocol, the synthesis of Cd-free InP/ZnS quantum dots (QDs) is detailed. InP-based QDs are gaining popularity due to the toxicity of Cd2+ ions that may be released through nanoparticle degradation. After synthesis, QDs are solubilized in water using an amphiphilic polymer for use in biomedical applications.

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

Microfluidic Chips for In Situ Crystal X-ray Diffraction and In Situ Dynamic Light Scattering for Serial Crystallography

This protocol describes fabricating microfluidic devices with low X-ray background optimized for goniometer based fixed target serial crystallography. The devices are patterned from epoxy glue using soft lithography and are suitable for in situ X-ray diffraction experiments at room temperature. The sample wells are lidded on both sides with polymeric polyimide foil windows that allow diffraction data collection with low X-ray background. This fabrication method is undemanding and inexpensive. After the sourcing of a SU-8 master wafer, all fabrication can be completed outside of a cleanroom in a typical research lab environment. The chip design and fabrication protocol utilize capillary valving to microfluidically split an aqueous reaction into defined nanoliter sized droplets. This loading mechanism avoids the sample loss from channel dead-volume and can easily be performed manually without using pumps or other equipment for fluid actuation. We describe how isolated nanoliter sized drops of protein solution can be monitored in situ by dynamic light scattering to control protein crystal nucleation and growth. After suitable crystals are grown, complete X-ray diffraction datasets can be collected using goniometer based in situ fixed target serial X-ray crystallography at room temperature. The protocol provides custom scripts to process diffraction datasets using a suite of software tools to solve and refine the protein crystal structure. This approach avoids the artefacts possibly induced during cryo-preservation or manual crystal handling in conventional crystallography experiments. We present and compare three protein structures that were solved using small crystals with dimensions of approximately 10-20 &#181;m grown in chip. By crystallizing and diffracting in situ, handling and hence mechanical disturbances of fragile crystals is minimized. The protocol details how to fabricate a custom X-ray transparent microfluidic chip suitable for in situ serial crystallography. As almost every crystal can be used for diffraction data collection, these microfluidic chips are a very efficient crystal delivery method.

Microfluidic Chips for In Situ Crystal X-ray Diffraction and In Situ Dynamic Light Scattering for Serial Crystallography

This protocol describes in detail how to fabricate and operate microfluidic devices for X-ray diffraction data collection at room temperature. Additionally, it describes how to monitor protein crystallization by dynamic light scattering and how to process and analyze obtained diffraction data.

This protocol describes fabricating microfluidic devices with low X-ray background optimized for goniometer based fixed target serial crystallography. The ...

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good&#39;s buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

In this work, a protocol for signal enhancement of nanoprobe-based biosensing is presented. The protocol is based on the reduction of chloroauric acid onto the surface of existing nanoprobes that consist of gold, silver, silica or iron-oxide nanoparticles.

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...