The authors wish to acknowledge the competitive faculty-initiated collaboration (FIC) grant from KAUST.

1. Preparation of Pr-doped SrTiO3 Powder
<ol>
	<li>In order to prepare 10 g of Sr0.95Pr0.05TiO3 powder, weigh the stoichiometric amounts of SrCO3 powder (7.53407 g), TiO2 nanopowder (4.28983 g), and Pr2O3 sintered lump (0.44299 g) following the reaction for x = 0.05:</li>
</ol>
<img alt="Equation 1" fo:content-width="5in" src="/files/ftp_upload/52869/52869eq1.JPG" width="550" />
<ol start="2">
	<li>Grind the weighed Pr2O3 sintered lumps to fine particles using an agate mortar and pestle.</li>
	<li>Add the weighed SrCO3 powder and TiO2 nanopowder to the Pr2O3 and continue grinding and mixing using an agate mortar and pestle until a visually homogenous powder is achieved.</li>
	<li>Load the ground powder into a glass jar and mix using a turbulator for 30 min to homogenize the mixture.</li>
	<li>Load the resulting mixed powder into a meticulously cleaned and polished stainless steel die (1 inch in diameter) and sandwich it between two stainless steel plungers.</li>
	<li>Cold press the powder using a press under an approximately 1 metric ton load.</li>
	<li>Eject the cold-pressed pellet by placing the die on a hollowed stainless steel cylinder and pushing the plungers and the pellet out from the top using a pushing rod. Upon ejection of the cold pressed pellet (green body) from the die, clean any contamination on the circumferential surface of the pellet by gently covering the pellet with a small piece of scotch-tape and removing a thin layer by ripping the tape.</li>
	<li>Place the pellet vertically in an alumina boat filled with commercially purchased SrTiO3 powder as the barrier between the alumina boat and the cold press pellet.</li>
	<li>Place the boat in a tube furnace, heat up to 1,300 &#176;C in 3 hr and keep it at this temperature for 15 hr. Allow the pellet to cool down to RT inside the furnace when the calcination is over. This step is referred to as the &#8220;calcination process&#8221; thereafter.</li>
	<li>Grind the pellet using the agate mortar and pestle and load the resulting powder into a glass jar for further mixing using the turbulator.</li>
	<li>Load the powder into the stainless steel die and cold pressed under an approximately 3 metric tons of load.</li>
	<li>Repeat the step 1.9 one more time at 1,400 &#176;C in 3 hr and keep it at this temperature for 20 hr.</li>
	<li>Grind the pellet using the agate mortar and pestle.</li>
	<li>Repeat steps 1.11, 1.12, and 1.13 one more time for the solid state reaction to reach completion.</li>
</ol>
2. Preparation of Bulk Polycrystalline Pr-doped SrTiO3 Ceramic
<ol>
	<li>Weigh 1.6 g of the as-prepared powder (for a disk 2 mm thick and 12.7 mm in diameter).</li>
	<li>Prepare circular graphoil pieces to cover the top and bottom interface of the sandwiched powder and graphite plungers in the graphite die. Also, prepare another rectangular graphoil piece to cover the inner wall of the graphite die.</li>
	<li>Load the as-prepared powder into a graphite die (12.7 mm in inner diameter) and sandwich the powder between two graphite plungers of the same size. Drill a 2-mm hole in the middle of the length of the graphite die and from the outer surface of the die to about 2 mm of the inner surface for temperature reading. 
	Note: Adjust the length of the graphite plungers remaining outside the die and position the center of the sandwiched powder cylinder where the hole is placed to get an accurate temperature reading. The faces of the graphite plungers need to be meticulously leveled during the machining of the pieces. Any misalignment can result in the cracking of the sintered pellet during spark plasma sintering.</li>
	<li>Cold-press the powder gently (load &#60; 200 kg) using a press prior to mounting on the spark plasma sintering plate inside the chamber. Use flat polished stainless steel support plates between the top and bottom plungers and the press stage to avoid damaging the graphite plungers.</li>
	<li>Wrap a piece of graphite felt around the die for insulation and secure it with graphite yarn. Devise a window on the graphite felt by cutting a rectangular piece of the felt where the temperature reading hole is placed on the die.</li>
	<li>Place the loaded graphite die and plungers in the spark plasma sintering chamber. Move the stage to the final position.</li>
	<li>Focus and align the Pyrometer target circle on the temperature reading hole of the die. Make sure the emissivity setting of the pyrometer is set for graphite.</li>
	<li>Close the chamber and put a 7.7 kN load (approximately 60 MPa) on the sample. Vacuum and purge the chamber with Ar three times and leave the chamber under dynamic vacuum of 6 Pa.</li>
	<li>Increase the temperature by increasing the current (manually or using a program). Use 250 A min-1 (corresponding to approximately 300-400 &#176;C min-1) for the optimized samples. This is the most important step of the spark plasma sintering process.</li>
	<li>Keep the temperature at 1,500 &#176;C for 5 min by manually adjusting the current or using the program. At the end of the 5 min holding period, shut the current off and quickly release the 7.7 kN load to avoid cracking the sample during the cooling down. Let the sample cool to RT inside the chamber.</li>
	<li>Release the bulk pellet from the graphite die gently using the cold press. This is done by placing the graphite die on a hollowed steel cylinder and ejecting the pellet and the graphite plungers using a steel pushing rod from the top.</li>
	<li>Remove the graphoil on top and bottom faces of the pellet as well as the circumferential surface using a sharp razor blade.</li>
	<li>Polish the sample using a rough sand paper (400 grid) down for 0.3-0.5 mm from each side to assure the complete removal of the graphoil. Clean the sample with acetone.</li>
</ol>
3. Characterization of Electronic and Thermal Transport Properties of Bulk Ceramics
<ol>
	<li>Determine the density of the ceramic disk, &#961;, using the Archimedes method.</li>
	<li>Measure the weight of the sample, Wdry, and then the weight of the sample submerged in water, Wwet, on a stabilized density measurement system and calculate the Archimedes density from</li>
</ol>
<img alt="Equation 2" fo:content-width="2.1in" src="/files/ftp_upload/52869/52869eq2.JPG" width="260" />
where &#961;water is the density of the water at the measurement temperature (e.g., equals 1 g cm-3 at 300 K).14
<ol start="2">
	<li>Measure the thermal diffusivity of the sample, d, using the transient laser-flash technique under a 75 ml min-1 flow of Ar. Measure the thickness of the sample, L, accurately first using a digital micrometer. 
	Note: Parallel-faced samples with different sizes and shapes (e.g., round discs 12.7 mm in diameter or square 10 x 10 mm2 disks) and thicknesses between 0.5 and 5 mm can be easily measured.
	<ol>
		<li>In the laser-flash thermal diffusivity technique, irradiate one face of the sample by a short (~1 msec) laser pulse and record the temperature rise on the opposite face by an infra-red detector. Then calculate thermal diffusivity by the laser-flash interface software from the thickness of the sample and the temperature rise-time profile using the Parker equation15</li>
	</ol>
	</li>
</ol>
<img alt="Equation 3" fo:content-width="1.9in" src="/files/ftp_upload/52869/52869eq3.JPG" width="220" />
where L is the thickness of the disk and t1/2 is the half-time of the maximum temperature rise of the other side of the sample.
Note: The Parker model15 assumes ideal conditions of adiabatic sample and instantaneous pulse heating, other models have been proposed over the years, which account for various losses in the measurement such as heat losses, finite pulse duration, non-uniform pulse heating and nonhomogeneous structures. We have used the Cowan model16 with pulse correction which is one of the most advanced methods. It should be noted that in order to maximize the amount of thermal energy transmitted from the front surface and to maximize the signal observed by the IR detector, the sample surfaces must be highly emissive. Usually this requires the application of a thin coating of graphite to the sample surfaces. An uncertainty of 2%-5% in the measurement of thermal diffusivity exists, arising from the determination of dimension.17
<ol start="3">
	<li>Cut the disk pellet using a diamond saw into rectangular bars, 2 x 2 x 10 mm3, electrical conductivity and Seebeck coefficient measurements as well as a square disk, 4 x 4 x 1.5 mm3 for high-temperature specific heat and a thin rectangular piece, 8 x 5 x 1 mm3 for Hall measurements.</li>
	<li>Measure the specific heat, Cp, of the sample on the flat and mirror-polished square piece (4 x 4 x 1.5 mm3) using a differential scanning calorimetry (DSC) under argon flow.18
	<ol>
		<li>Use a heating rate of 5 K min-1 up to 40 &#176;C for an isothermal hold for 10 min to allow the sample to reach thermal equilibrium followed by 20 K min-1 heating rate up to 500 &#176;C, with an exact cooling rate which followed. Perform the measurement under the flow of argon (50 ml min-1 is suggested).</li>
	</ol>
	</li>
</ol>
Note: Due to the sensitivity of the method used for analysis, conduct three measurements to determine the heat capacity including (1) a baseline measurement to subtract the background, (2) measurement of the specific heat of a standard material (such as sapphire) with a known CP, and (3) measurement of the specific heat of the sample. Ensure that samples are flat and mirror-polished in order to make an ideal contact with the bottom of the measurement crucible (Pt/Rh pans with Al2O3 crucibles used in this work). More details on the exact structure of the DSC stage, a comparison of the DSC techniques to others, and exact instructions for measuring a sample can be found in various sources.19
<ol start="5">
	<li>Calculate the high-temperature thermal conductivity, &#954;, of the sample from the measured values of thermal diffusivity, d, the specific heat, CP, and the density, &#961; using20</li>
</ol>
<img alt="Equation 4" fo:content-width="1.4in" src="/files/ftp_upload/52869/52869eq4.JPG" width="200" />
<ol start="6">
	<li>Gold plate the probes contact points (4 contacts) on the 2 x 2 x 10 mm3 piece cut from the sample to alleviate the contact resistance issues.
	<ol>
		<li>In order to sputter gold only on the desired contact areas, wrap a scotch-tape around the 2 x 2 x 10 mm3 sample to use as a stencil. Leave the 2 x 2 mm2 faces un-covered. Using a razor blade, cut out 2 very small holes (approximately 1 mm in diameter) in the middle of the 2 x 10 mm2 face along a line separated by the probes distance.</li>
		<li>Sputter a ~ 200 nm-thick gold film using a bench-top gold sputtering unit.21</li>
	</ol>
	</li>
	<li>Measure the electrical transport properties, namely the electrical conductivity and Seebeck coefficient) of the sample as a function of temperature22,23.
	<ol>
		<li>Measure electrical conductivity using the four-terminal method. Measure the Seebeck coefficient on the same setup using the measurements of temperature and voltage via the two middle thermocouple &#8220;probes&#8221;. Measure the distance between these two probes using a digital microscope. More details on the electrical transport measurements can be found elsewhere.22,23</li>
	</ol>
	</li>
	<li>Measure the Hall carrier concentration as a function of temperature on the 8 x 5 x 1 mm3 sample using a Physical Properties Measurement System.24</li>
</ol>

<ol>
	<li>Ohta, S., Nomura, T., Ohta, H., Koumoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-temperature+Carrier+Transport+and+Thermoelectric+Properties+of+Heavily+La-or+Nb-doped+SrTiO3+Single+Crystals.">High-temperature Carrier Transport and Thermoelectric Properties of Heavily La-or Nb-doped SrTiO3 Single Crystals.</a> J. Appl. Phys. 97, (2005).</li><li>Wang, H. C., 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=Enhancement+of+Thermoelectric+Figure+of+Merit+by+Doping+Dy+in+La0.1Sr0.9TiO3+Ceramic.">Enhancement of Thermoelectric Figure of Merit by Doping Dy in La0.1Sr0.9TiO3 Ceramic.</a> Mater. Res. Bull. 45, 809-812 (2010).</li><li>Bhattacharya, S., Mehdizadeh Dehkordi, A., Alshareef, H. N., Tritt, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis&#8211;Property+Relationship+in+Thermoelectric+Sr1&#8722;xYbxTiO3&#8722;&#948;+Ceramics.">Synthesis&#8211;Property Relationship in Thermoelectric Sr1&#8722;xYbxTiO3&#8722;&#948; Ceramics.</a> J. Phys. D: Appl. Phys. 47, 385302 (2014).</li><li>Wang, Y., Lee, K. H., Ohta, H., Koumoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+Properties+of+Electron+Doped+SrO(SrTiO3)n+(n=1,2)+Ceramics.">Thermoelectric Properties of Electron Doped SrO(SrTiO3)n (n=1,2) Ceramics.</a> J. Appl. Phys. 105, 1037011-1037016 (2009).</li><li>Wang, N., 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=Effects+of+YSZ+Additions+on+Thermoelectric+Properties+of+Nb-Doped+Strontium+Titanate.">Effects of YSZ Additions on Thermoelectric Properties of Nb-Doped Strontium Titanate.</a> J. Electron. Mater. 39, 1777-1781 (2010).</li><li>Muta, H., Kurosaki, K., Yamanaka, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+Properties+of+Rare+Earth+Doped+SrTiO3.">Thermoelectric Properties of Rare Earth Doped SrTiO3.</a> J. Alloys Compd. 350, 292-295 (2003).</li><li>Shang, P. -. P., Zhang, B. -. P., Li, J. -. F., Ma, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Sintering+Temperature+on+Thermoelectric+Properties+of+La-doped+SrTiO3+Ceramics+Prepared+by+Sol-gel+Process+and+Spark+Plasma+Sintering.">Effect of Sintering Temperature on Thermoelectric Properties of La-doped SrTiO3 Ceramics Prepared by Sol-gel Process and Spark Plasma Sintering.</a> Solid State Sciences. 12, 1341-1346 (2010).</li><li>Wang, Y., Fan, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sr1-xLaxTiO3+Nanoparticles:+Synthesis,+Characterization+and+Enhanced+Thermoelectric+Response.">Sr1-xLaxTiO3 Nanoparticles: Synthesis, Characterization and Enhanced Thermoelectric Response.</a> Scripta Materialia. 65, 190-193 (2011).</li><li>Kikuchi, A., Okinakab, N., Akiyama, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Large+Thermoelectric+Figure+of+Merit+of+La-doped+SrTiO3+Prepared+by+Combustion+Synthesis+with+Post-Spark+Plasma+Sintering.">A Large Thermoelectric Figure of Merit of La-doped SrTiO3 Prepared by Combustion Synthesis with Post-Spark Plasma Sintering.</a> Scripta Materialia. 63, 407-410 (2010).</li><li>Obara, H., 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=Thermoelectric+Properties+of+Y-Doped+Polycrystalline+SrTiO3.Jpn.">Thermoelectric Properties of Y-Doped Polycrystalline SrTiO3.Jpn.</a> J. Appl. Phys. 43, L540-L542 (2004).</li><li>Koumoto, K., Wang, Y., Zhang, R., Kosuga, A., Funahashi, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxide+Thermoelectric+Materials:+A+Nanostructuring+Approach.">Oxide Thermoelectric Materials: A Nanostructuring Approach.</a> Annu. Rev. Mater. Res. 40, 363-394 (2010).</li><li>Mehdizadeh Dehkordi, 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=Large+Thermoelectric+Power+Factor+in+Pr-Doped+SrTiO3&#8722;&#948;+Ceramics+via+Grain-Boundary-Induced+Mobility+Enhancement.">Large Thermoelectric Power Factor in Pr-Doped SrTiO3&#8722;&#948; Ceramics via Grain-Boundary-Induced Mobility Enhancement.</a> Chem. Mater. 26, 2478-2485 (2014).</li><li>Mehdizadeh Dehkordi, A., Bhattacharya, S., He, J., Alshareef, H. N., Tritt, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Significant+Enhancement+in+Thermoelectric+Properties+of+Polycrystalline+Pr-doped+SrTiO3+Ceramics+Originating+from+Nonuniform+distribution+of+Pr+dopants.">Significant Enhancement in Thermoelectric Properties of Polycrystalline Pr-doped SrTiO3 Ceramics Originating from Nonuniform distribution of Pr dopants.</a> Appl. Phys. Lett. 104, 1939021-1939024 (2014).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes&#8217; Principle. , (2015).</li><li>Parker, W. J., Jenkins, R. J., Butler, C. P., Abbott, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flash+Method+of+Determining+Thermal+Diffusivity,+Heat+Capacity+and+Thermal+Conductivity.">Flash Method of Determining Thermal Diffusivity, Heat Capacity and Thermal Conductivity.</a> J. Appl. Phys. 32, 1679-1684 (1961).</li><li>Cowan, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulse+Method+of+Measuring+Thermal+Diffusivity+at+High+Temperatures.">Pulse Method of Measuring Thermal Diffusivity at High Temperatures.</a> J. Appl. Phys. 34, 926-927 (1963).</li><li>Mehdizadeh-Dehkordi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> An Experimental Investigation Towards Improvement of Thermoelectric Properties of Strontium Titanate Ceramics. , (2014).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> DSC Pegasus 404C Operating Manual. , (1999).</li><li>Daw, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+Specific+Heat+Capacity+Using+Differential+Scanning+Calorimeter.">Measurement of Specific Heat Capacity Using Differential Scanning Calorimeter.</a> Report of US Department of Energy. , (2008).</li><li>Tritt, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Thermal Conductivity: Theory, Properties and Applications. , (2004).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> SC7610 Sputter Coater Operating Manual. , (2002).</li><li>Tritt, T. M., Rowe, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+and+Thermal+Transport+Measurement+Techniques+for+Evaluation+of+the+figure-of-Merit+of+Bulk+Thermoelectric+Materials.">Electrical and Thermal Transport Measurement Techniques for Evaluation of the figure-of-Merit of Bulk Thermoelectric Materials.</a> Thermoelectrics Handbook: Macro to Nano. , 23-1-23-17 (2006).</li><li>Burkov, A. T., Rowe, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+of+Resistivity+and+Thermopower:+Principles+and+Practical+Realization.">Measurements of Resistivity and Thermopower: Principles and Practical Realization.</a> Thermoelectrics Handbook: Macro to Nano. , 22-1 (2006).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Physical Property Measurement System: AC Transport Option User&#8217;s Manual. , (2003).</li><li>Ohta, S., Ohta, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grain+Size+Dependence+of+Thermoelectric+Performance+of+Nb-doped+SrTiO3.">Grain Size Dependence of Thermoelectric Performance of Nb-doped SrTiO3.</a> Polycrystals. J. Ceram. Soc. Jpn. 114, 102 (2006).</li><li>Wang, N., He, H., Ba, Y., Wan, C., Koumoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+Properties+of+Nb-doped+SrTiO3+Ceramics+Enhanced+by+Potassium+Titanate+Nanowires+Addition.">Thermoelectric Properties of Nb-doped SrTiO3 Ceramics Enhanced by Potassium Titanate Nanowires Addition.</a> J. Ceram. Soc. Jpn. 118, 1098 (2010).</li><li>Ohta, S., 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=Large+Thermoelectric+Performance+of+Heavily+Nb-doped+SrTiO3+Epitaxial+Film+at+High+Temperature.">Large Thermoelectric Performance of Heavily Nb-doped SrTiO3 Epitaxial Film at High Temperature.</a> Appl. Phys. Lett. 87, 092108 (2005).</li><li>Kovalevsky, A., Yaremchenko, A., Populoh, S., Weidenkaff, A., Frade, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+Thermoelectric+Performance+in+Strontium+Titanate+by+Praseodymium+Substitution.">Enhancement of Thermoelectric Performance in Strontium Titanate by Praseodymium Substitution.</a> J. Appl. Phys. 113, 053704 (2013).</li><li>Kovalevsky, A. V., 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=Towards+a+High+Thermoelectric+Performance+in+Rare-Earth+Substituted+SrTiO3:+Effects+Provided+by+Strongly-Reducing+Sintering+Conditions.">Towards a High Thermoelectric Performance in Rare-Earth Substituted SrTiO3: Effects Provided by Strongly-Reducing Sintering Conditions.</a> Phys. Chem. 16, 26946 (2014).</li><li>Dawson, J. A., Tanaka, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+Structure+and+Energetics+of+Pr-+and+La-Doped+SrTiO3+Grain+Boundaries+and+the+Influence+on+Core–Shell+Structure+Formation.">Local Structure and Energetics of Pr- and La-Doped SrTiO3 Grain Boundaries and the Influence on Core–Shell Structure Formation.</a> J. Phys. Chem. C. 118, 25765-25778 (2014).</li><li>Mehdizadeh Dehkordi, 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=New+Insights+on+the+Synthesis+and+Electronic+Transport+in+Bulk+Polycrystalline+Pr-doped+SrTiO3&#8722;&#948;.">New Insights on the Synthesis and Electronic Transport in Bulk Polycrystalline Pr-doped SrTiO3&#8722;&#948;.</a> Appl. Phys. Lett. 117, 055102 (2015).</li></ol>

The authors have nothing to disclose.

In this protocol, we have presented the steps of the synthesis strategy in order to successfully prepare bulk polycrystalline Pr-doped SrTiO3 ceramics exhibiting improved electronic and thermoelectric properties. The main steps of the protocol include (i) the solid-state synthesis of the doped SrTiO3 powder in air under atmospheric pressure and (ii) taking advantage of the capabilities of spark plasma sintering technique to densify the as-prepared powder into high-density bulk ceramics and at the sa...

Oxide thermoelectrics were shown to be promising candidates for high-temperature thermoelectric applications, from stability and cost perspectives to electronic transport properties. Among the n-type oxide thermoelectrics, highly doped strontium titanate (STO) has attracted much attention due to its intriguing electronic properties. However, a large total thermal conductivity (&#954; ~ 12 W m-1 K-1 at 300 K for single crystals)1 and a low carrier mobility (&#181; ~ 6 cm2 V-1 sec-1 at 300 K for single crystals)1 detrimentally affect the thermoelectric performance which is evaluated by a dimensionless figure of merit, ZT = &#945;2&#963;T/&#954;, where &#945; is the Seebeck coefficient, &#963; the electrical conductivity, T the absolute temperature in Kelvin, and &#954; the total thermal conductivity. We herein define the numerator as the power factor, PF = &#945;2&#963;T. In order for this oxide thermoelectric material to compete with other high-temperature thermoelectrics (such as SiGe alloys), a more pronounced increase in the power factor and/or decrease in lattice thermal conductivity are required.
The majority of the experimental studies in order to improve the thermoelectric properties of STO have mainly focused on the reduction of thermal conductivity through strain-field and mass fluctuation scattering of phonons. These attempts include: (i) Single- or double-doping of the Sr2+ and/or Ti4+ sites, as the main efforts with respect to this direction,2,3 (ii) Synthesis of natural superlattice Ruddlesden&#8211;Popper structures in order to further reduce the thermal conductivity through insulating SrO layers,4 and (iii) Composite engineering by addition of a nanosized second phase.5 However, up until recently, no enhancement strategy has been reported to substantially increase the thermoelectric power factor in these oxides. The reported maximum power factor (PF) values in bulk single- and poly-crystalline STO have been confined to an upper limit of PF &#60; 1.0 W m-1 K-1.
A variety of synthesis approaches and processing techniques have been employed to implement the ideas attempted above. The powder synthesis routes include conventional solid-state reaction,6 sol-gel,7 hydrothermal,8 and combustion synthesis,9 whereas conventional sintering,6 hot pressing10 and recently spark plasma sintering12 are among the common techniques used to densify the powders into bulk ceramics. However, for a similar dopant (e.g., La) and doping concentration, the resulting bulk ceramics exhibit a range of electronic and thermal transport properties. This is in large due to the strongly process-dependent defect chemistry of SrTiO3 which results in synthesis-dependent properties. There is only a handful of reports optimizing the synthesis and processing parameters to benefit thermoelectric transport. It is worth mentioning that due to the very small phonon mean free path in SrTiO3 (lph~2 nm at 300 K),11 nanostructuring is not a viable option for the improvement of the TE performance of bulk STO ceramics primarily through the reduction of the lattice thermal conductivity.
Recently, we reported more than 30% improvement in the thermoelectric figure of merit in non-uniformly Pr-doped SrTiO3 ceramics originating from a simultaneously enhanced thermoelectric power factor and reduced thermal conductivity.12,13 In this detailed video protocol, we present and discuss the steps of our synthesis strategy for the preparation of these Pr-doped STO ceramics exhibiting improved electronic and thermoelectric properties.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>SrCO3 Powder, 99.9%</td>
			<td>Sigma Aldrich</td>
			<td>472018</td>
			<td></td>
		</tr>
		<tr>
			<td>TiO2 Nanopowder, 99.5%</td>
			<td>Sigma Aldrich</td>
			<td>718467</td>
			<td></td>
		</tr>
		<tr>
			<td>Pr2O3 Sintered Lumps, 99.9%</td>
			<td>Alfa Aesar</td>
			<td>35663&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Name of&#160; Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Spark Plasma Sintering&#160;</td>
			<td>Dr. Sinter Lab</td>
			<td>SPS-515S</td>
			<td></td>
		</tr>
		<tr>
			<td>Resistivity/Seebeck Coefficient Measurement System</td>
			<td>Ulvac-Riko</td>
			<td>ZEM-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Flash Thermal Diffusivity Measurement System</td>
			<td>Netzsch</td>
			<td>LFA-457 Microflash</td>
			<td></td>
		</tr>
		<tr>
			<td>Differential Scanning Calorimetry (DSC) System</td>
			<td>Netzsch</td>
			<td>404C Pegasus</td>
			<td></td>
		</tr>
		<tr>
			<td>Physical Property Measurement system (PPMS)</td>
			<td>Quantum Design</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Field Emission Scanning Electron Microscope (FE-SEM)</td>
			<td>Hitachi</td>
			<td>SU-6600</td>
			<td></td>
		</tr>
		<tr>
			<td>Energyy-dispersive X-ray Spectroscopy (EDS)</td>
			<td>Oxford Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray Diffractometer</td>
			<td>Rigaku</td>
			<td>Ultima IV</td>
			<td></td>
		</tr>
		<tr>
			<td>Bench-top Sputter Coater</td>
			<td>Denton Vacuum</td>
			<td>Desk II</td>
			<td></td>
		</tr>
		<tr>
			<td>Diamond&#160; Wheel Saw</td>
			<td>South Bay Technology</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of non-uniformly pr-doped srtio3 ceramics and their thermoelectric properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

X-ray diffractions patterns were collected for the as-prepared powders and the corresponding bulk ceramics as a function of Pr-content (Figure 1) in order to study the effect of Pr-doping on the SrTiO3 lattice, solubility of Pr in SrTiO3 and the formation of secondary phase(s). The patterns confirm the formation of SrTiO3 phase in all the as-prepared powders where the reflections can be indexed to a cubic lattice with space group (Figure 1A). The monotoni...

Watch this Scientific Journal Video about Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties at JoVE.com

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

synthesis-non-uniformly-pr-doped-srtio3-ceramics-their-thermoelectric

Research

JoVE Journal

Chemistry

9.8K vistas.  Clemson University. A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

Video: Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single molecule level. An electrostatic self-assembly and covalent fixation (ESA-CF) process is used for the synthesis of the cyclic poly(tetrahydrofuran) (poly(THF)). The diffusive motion of individual cyclic polymer chains in a melt state is visualized using single molecule fluorescence imaging by incorporating a fluorophore unit in the cyclic chains. The diffusive motion of the chains is quantitatively characterized by means of a combination of mean-squared displacement (MSD) analysis and a cumulative distribution function (CDF) analysis. The cyclic polymer exhibits multiple-mode diffusion which is distinct from its linear counterpart. The results demonstrate that the diffusional heterogeneity of polymers that is often hidden behind ensemble averaging can be revealed by the efficient synthesis of the cyclic polymers using the ESA-CF process and the quantitative analysis of the diffusive motion at the single molecule level using the MSD and CDF analyses.

A protocol for the synthesis and characterization of diffusive motion of cyclic polymers at the single molecule level is presented.

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single ...

Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe aims at lowering the band gap of imogolite, an insulator with the chemical formula (OH)3Al2O3SiOH, and at modifying its adsorption properties towards azo-dyes, an important class of organic pollutants of both wastewater and groundwater.
Fe-doped nanotubes are obtained in two ways: by direct synthesis, where FeCl3 is added to an aqueous mixture of the Si and Al precursors, and by post-synthesis loading, where preformed nanotubes are put in contact with a FeCl3&#8226;6H2O aqueous solution. In both synthesis methods, isomorphic substitution of Al3+ by Fe3+ occurs, preserving the nanotube structure. Isomorphic substitution is indeed limited to a mass fraction of ~1.0% Fe, since at a higher Fe content (i.e., a mass fraction of 1.4% Fe), Fe2O3 clusters form, especially when the loading procedure is adopted. The physicochemical properties of the materials are studied by means of X-ray powder diffraction (XRD), N2 sorption isotherms at -196 &#176;C, high resolution transmission electron microscopy (HRTEM), diffuse reflectance (DR) UV-Vis spectroscopy, and &#950;-potential measurements. The most relevant result is the possibility to replace Al3+ ions (located on the outer surface of the nanotubes) by post-synthesis loading on preformed imogolite without perturbing the delicate hydrolysis equilibria occurring during nanotube formation. During the loading procedure, an anionic exchange occurs, where Al3+ ions on the outer surface of the nanotubes are replaced by Fe3+ ions. In Fe-doped aluminosilicate nanotubes, isomorphic substitution of Al3+ by Fe3+ is found to affect the band gap of doped imogolite. Nonetheless, Fe3+ sites on the outer surface of nanotubes are able to coordinate organic moieties, like the azo-dye Acid Orange 7, through a ligand-displacement mechanism occurring in an aqueous solution.

Here, we present a protocol to synthesize and characterize Fe-doped aluminosilicate nanotubes. The materials are obtained by either sol-gel synthesis upon addition of FeCl3&#8226;6H2O to the mixture containing the Si and Al precursors or by post-synthesis ionic exchange of preformed aluminosilicate nanotubes.

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe ...

Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be covalently and site-specifically linked via their end facets, resulting in polymer-like linear or branched chains. The linking procedure begins with a cation-exchange process in which the end facets of the cadmium chalcogenide NCs are first converted to silver chalcogenide. This is followed by the selective removal of ligands at their surface. This results in cadmium chalcogenide NCs with highly reactive silver chalcogenide end facets that spontaneously fuse upon contact with each other, thereby establishing an interparticle facet-to-facet attachment. Through the judicious choice of precursor concentrations, an extensive network of linked NCs can be produced. Structural characterization of the linked NCs is carried out via low- and high-resolution transmission electron microscopy (TEM), as well as energy-dispersive X-ray spectroscopy, which confirm the presence of silver chalcogenide domains between chains of cadmium chalcogenide NCs.

A protocol detailing how shape-anisotropic colloidal cadmium chalcogenide nanocrystals can be covalently linked via their end facets is presented here.

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be ...

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles

Bicyclic aziridinium ions were generated by the removal of an appropriate leaving group through internal nucleophilic attack by nitrogen atom in the aziridine ring. The utility of bicyclic aziridinium ions, specifically 1-azoniabicyclo[3.1.0]hexane and 1-azoniabicyclo[4.1.0]heptane tosylate highlighted in the aziridine ring openings by the nucleophile with the release of the ring strain to yield the corresponding ring-expanded azaheterocycles such as pyrrolidine, piperidine and azepane with diverse substituents on the ring in regio- and stereospecific manner. Herein, we report a simple and convenient method for the preparation of the stable 1-azabicyclo[4.1.0]heptane tosylate followed by selective ring opening via a nucleophilic attack either at the bridge or at the bridgehead carbon to yield piperidine and azepane rings, respectively. This synthetic strategy allowed us to prepare biologically active natural products containing piperidine and azepane motif including sedamine, allosedamine, fagomine and balanol in highly efficient manner.

Bicyclic aziridinium ions such as 1-azoniabicyclo[4.1.0]heptane tosylate were generated from 2-[4-tolenesulfonyloxybutyl]aziridine, which was utilized for the preparation of substituted piperidines and azepanes via regio- and stereospecific ring-expansion with various nucleophiles. This highly efficient protocol allowed us to prepare diverse azaheterocycles including natural products such as fagomine, febrifugine analogue and balanol.

Bicyclic aziridinium ions were generated by the removal of an appropriate leaving group through internal nucleophilic attack by nitrogen atom in the ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to diversify the fiber choices in the United States body armor market, copolymer fibers based on the combination of 5-amino-2-(p-aminophenyl) benzimidazole (PBIA) and the more conventional PPTA were introduced. Little is known regarding the long-term stability of these fibers, but as condensation polymers, they are expected to have potential sensitivity to moisture and humidity. Therefore, characterizing the strength of the materials and understanding their vulnerability to environmental conditions is important for evaluating their use lifetime in safety applications. Ballistic resistance and other critical structural properties of these fibers are predicated on their strength. To accurately determine the strength of the individual fibers, it is necessary to disentangle them from the yarn without introducing any damage. Three aramid-based copolymer fibers were selected for the study. The fibers were washed with acetone followed by methanol to remove an organic coating that held the individual fibers in each yarn bundle together. This coating makes it difficult to separate single fibers from the yarn bundle for mechanical testing without damaging the fibers and affecting their strength. After washing, fourier transform infrared (FTIR) spectroscopy was performed on both washed and unwashed samples and the results were compared. This experiment has shown that there are no significant variations in the spectra of poly(p-phenylene-benzimidazole-terephthalamide-co-p-phenylene terephthalamide) (PBIA-co-PPTA1) and PBIA-co-PPTA3 after washing, and only a small variation in intensity for PBIA. This indicates that the acetone and methanol rinses are not adversely affecting the fibers and causing chemical degradation. Additionally, single fiber tensile testing was performed on the washed fibers to characterize their initial tensile strength and strain to failure, and compare those to other reported values. Iterative procedural development was necessary to find a successful method for performing tensile testing on these fibers.

The primary goal of the study is to develop a protocol to prepare consistent specimens for accurate mechanical testing of high strength copolymer aramid fibers, by removing a coating and disentangling the individual fiber strands without introducing significant chemical or physical degradation.

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to ...

Synthesis of In37P20(O2CR)51 Clusters and Their Conversion to InP Quantum Dots

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 clusters have been observed as intermediates in the synthesis of InP quantum dots from molecular precursors (In(O2CR)3, HO2CR, and P(SiMe3)3) and may be isolated as a pure reagent for subsequent study and use as a single-source precursor. These clusters readily convert to crystalline and relatively monodisperse samples of quasi-spherical InP quantum dots when subjected to thermolysis conditions in the absence of additional precursors above 200 &#176;C. The optical properties, morphology, and structure of both the clusters and quantum dots are confirmed using UV-Vis spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and powder X-ray diffraction. The molecular symmetry of the clusters is additionally confirmed by solution-phase 31P NMR spectroscopy. This protocol demonstrates the preparation and isolation of atomically-precise InP clusters, and their reliable and scalable conversion to InP QDs.

Synthesis of In37P20O2CR51 Clusters and Their Conversion to InP Quantum Dots

A protocol for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots is presented.

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 ...

Design, Synthesis, and Photochemical Properties of Clickable Caged Compounds

Caged compounds enable the photo-mediated manipulation of the cell physiology with high spatiotemporal resolution. However, the limited structural diversity of currently available caging groups and the difficulties in synthetic modification without sacrificing their photolysis efficiencies are obstacles to expanding the repertoire of caged compounds for live cell applications. As the chemical modification of coumarin-type photo-caging groups is a promising approach for the preparation of caged compounds with diverse physical and chemical properties, we report a method for the synthesis of clickable caged compounds that can be modified easily with various functional units via the copper(I)-catalyzed Huisgen cyclization. The modular platform molecule contains a (6-bromo-7-hydroxycoumarin-4-yl)methyl (Bhc) group as a photo-caging group, which exhibits a high photolysis efficiency compared to those of the conventional 2-nitrobenzyls. General procedures for the preparation of clickable caged compounds containing amines, alcohols, and carboxylates are presented. Additional properties such as the water solubility and cell targeting ability can be readily incorporated into clickable caged compounds. Furthermore, the physical and photochemical properties, including the photolysis quantum yield, were measured and were found to be superior to those of the corresponding Bhc caged compounds. The described protocol could therefore be considered a potential solution for the lack of structural diversity in the available caged compounds.

A protocol for the synthesis and measurement of the photochemical properties of modular caged compounds with clickable moieties is presented.