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

1. Preparazione di Pr-drogato SrTiO 3 Polvere <ol><li> Al fine di preparare 10 g di Sr 0,95 Pr 0.05 TiO 3 in polvere, pesare le quantità stechiometriche di SrCO3 polvere (7,53407 g), TiO2 nanopolveri (4,28983 g), e Pr 2 O 3 grumo sinterizzato (0,44299 g) a seguito della reazione per x = 0.05: </li></ol><img alt="Equazione 1" fo:content-width="5in" src="/files/ftp_upload/52869/52869eq1.JPG" width="550" /><ol start="2"><li> Macinare le pesati Pr 2 O 3 grumi sinterizzate a particelle fini che utilizzano un mortaio di agata e pestello. </li><li> Aggiungere il pesato SrCO3 in polvere e TiO 2 nanopolveri al Pr 2 O 3 e continuare a macinare e mescolare con un mortaio di agata e pestello finché una polvere visivamente omogeneo è raggiunto. </li><li> Caricare la polvere del suolo in un vaso di vetro e mescolare con un turbolatore per 30 minuti per omogeneizzare the miscela. </li><li> Caricare la polvere mista risultante in uno stampo in acciaio inox accuratamente pulita e lucidata (1 pollice di diametro) e panino tra due stantuffi in acciaio inox. </li><li> Stampa a freddo la polvere utilizzando una pressa sotto un carico di circa 1 tonnellata. </li><li> Estrarre il pellet pressato a freddo posizionando il dado su un cilindro scavato in acciaio inox e spingendo gli stantuffi e il pellet dalla sommità utilizzando un&#39;asta di spinta. Dopo estrazione del pellet pressato a freddo (corpo verde) dallo stampo, pulire qualsiasi contaminazione sulla superficie circonferenziale del pellet coprendo delicatamente il pellet con un piccolo pezzo di scotch e rimozione di un sottile strato strappa il nastro. </li><li> Posizionare il pellet verticalmente in una barca piena di allumina acquistabile SrTiO 3 polvere come la barriera tra la barca di allumina e la stampa pellet freddo. </li><li> Posizionare la barca in un forno tubolare, riscaldare fino a 1300 ° C in 3 ore e mantenerlo a tale temperatura per 15h. Lasciare che il pellet raffreddare a RT all&#39;interno del forno quando la calcinazione è finita. Questo passo viene definito come &quot;processo di calcinazione&quot; successivamente. </li><li> Macinare il pellet con il mortaio e pestello agata e caricare la polvere risultante in un barattolo di vetro per un ulteriore miscelazione con il turbolatore. </li><li> Caricare la polvere nello stampo in acciaio inox e spremute a freddo sotto un circa 3 tonnellate di carico. </li><li> Ripetere la fase 1.9 ancora una volta a 1400 ° C in 3 ore e mantenerlo a tale temperatura per 20 ore. </li><li> Macinare il pellet con il mortaio e pestello agata. </li><li> Ripetere i punti 1.11, 1.12, 1.13 e ancora una volta per la reazione allo stato solido per raggiungere il completamento. </li></ol> 2. Preparazione di Bulk policristallino Pr-drogato SrTiO 3 Ceramic <ol><li> Pesare 1,6 g della polvere come preparato (per un disco di spessore di 2 mm e 12,7 mm di diametro). </li><li> Preparare pezzi Graphoil circolari per coprire il inte superiore e inferiorerfaccia della polvere di grafite e pistoni a sandwich della filiera grafite. Inoltre, preparare un altro pezzo Graphoil rettangolare per coprire la parete interna dello stampo di grafite. </li><li> Caricare la polvere come preparato in uno stampo di grafite (12.7 mm di diametro interno) e panino la polvere tra due stantuffi grafite delle stesse dimensioni. Praticare un foro di 2 mm al centro della lunghezza della matrice grafite e dalla superficie esterna del dado per circa 2 mm dalla superficie interna per la lettura della temperatura. Nota: regolare la lunghezza degli stantuffi grafite rimanenti esternamente allo stampo e posizionare il centro del cilindro di polvere sandwich in cui il foro è posizionato per ottenere una lettura precisa della temperatura. Le facce dei pistoni grafite devono essere accuratamente livellata durante la lavorazione dei pezzi. Qualsiasi disallineamento può provocare la rottura della pastiglia sinterizzata durante la sinterizzazione scintilla plasma. </li><li> Freddo premere la polvere delicatamente (carico &lt;200 kg) utilizzando una pressa prima del montaggio sulla scintillaplasma piatto sinterizzazione all&#39;interno della camera. Usare piatti piani di supporto in acciaio inox lucidato tra la parte superiore e inferiore stantuffi e la fase stampa per evitare di danneggiare i pistoni di grafite. </li><li> Avvolgere un pezzo di grafite sentiva attorno allo stampo per l&#39;isolamento e fissarlo con filato di grafite. Elaborare una finestra sulla grafite sentita tagliando un pezzo rettangolare di feltro dove il buco lettura di temperatura è posizionato sullo stampo. </li><li> Posizionare il dado caricato grafite e stantuffi nella camera di sinterizzazione scintilla plasma. Spostare il palco per la posizione finale. </li><li> Fuoco e allineare il cerchio di destinazione Pirometro sul foro lettura della temperatura dello stampo. Assicurarsi che l&#39;impostazione di emissività del pirometro è impostato per la grafite. </li><li> Chiudere la camera ed applicare un carico 7,7 kN (circa 60 MPa) sul campione. Vuoto e spurgare la camera con Ar tre volte e lasciare la camera sotto vuoto dinamico di 6 Pa. </li><li> Aumentare la temperatura aumentando la corrente (manualmente o mediante unprogramma). Utilizzare 250 A min -1 (corrispondente a circa 300-400 ° C min -1) per i campioni ottimizzati. Questo è il passo più importante del processo di sinterizzazione scintilla plasma. </li><li> Mantenere la temperatura a 1500 ° C per 5 min regolando manualmente la corrente o utilizzando il programma. Alla fine del periodo di detenzione 5 min, interrompere la corrente off e rilasciare rapidamente il carico 7,7 kN per evitare fessurazioni campione durante il raffreddamento. Lasciar raffreddare il campione RT all&#39;interno della camera. </li><li> Rilasciare il pellet sfuso dalla grafite die delicatamente con la spremitura a freddo. Questo viene fatto mettendo il dado grafite su un cilindro di acciaio scavato e l&#39;espulsione del pellet e gli stantuffi grafite utilizzando un acciaio spingendo un&#39;asta dall&#39;alto. </li><li> Rimuovere il Graphoil sulle facce superiore e inferiore del pellet e la superficie circonferenziale con una lama di rasoio affilata. </li><li> Polacco campione utilizzando una carta vetrata ruvida (400 griglia) giù per 0,3-0,5 mm da ogni lato per assicurarela completa rimozione del Graphoil. Pulire il campione con acetone. </li></ol> 3. Caratterizzazione di Elettronica e Trasporti termica Proprietà della Ceramica Bulk <ol><li> Determinare la densità del disco ceramico, ρ, utilizzando il metodo di Archimede. </li><li> Misurare il peso del campione, W secca, e quindi il peso del campione immerso in acqua, W bagnato, su un sistema di misurazione della densità stabilizzato e calcolare la densità di Archimede da </li></ol><img alt="Equazione 2" fo:content-width="2.1in" src="/files/ftp_upload/52869/52869eq2.JPG" width="260" /> dove l&#39;acqua ρ è la densità dell&#39;acqua alla temperatura di misurazione (per esempio, pari a 1 g cm -3 a 300 K). 14 <ol start="2"><li> Misurare la diffusività termica del campione, d, utilizzando la tecnica laser-flash transitoria sotto un min -1 flusso di Ar 75 ml. Misurare lo spessoredel campione, L, accuratamente prima utilizzando un micrometro digitale. Nota: campioni paralleli facce con diverse dimensioni e forme (ad esempio, dischi rotondi 12,7 millimetri di diametro o quadrata 10 x 10 mm 2 dischi) e spessori tra 0,5 e 5 mm può essere facilmente misurata. <ol><li> Nella laser-flash tecnica diffusività termica, irradiare una faccia del campione con un breve (~ 1 msec) impulso laser e registrare l&#39;aumento di temperatura sulla faccia opposta da un rivelatore a infrarossi. Quindi calcolare diffusività termica dal software di interfaccia laser-flash dallo spessore del campione e il profilo di temperatura tempo di salita usando l&#39;equazione Parker 15 </li></ol></li></ol><img alt="Equazione 3" fo:content-width="1.9in" src="/files/ftp_upload/52869/52869eq3.JPG" width="220" /> dove L è lo spessore del disco e t 1/2 è il primo tempo di sovratemperatura massima dell&#39;altro side del campione. Nota: Il modello di Parker 15 assume le condizioni ideali di campione adiabatico e istantaneo riscaldamento impulso, altri modelli sono stati proposti nel corso degli anni, che rappresentano diverse perdite nella misurazione, come le perdite di calore, durata dell&#39;impulso finita, non uniforme riscaldamento impulsi e non omogenea strutture. Abbiamo utilizzato il modello Cowan 16 con correzione di impulsi che è uno dei metodi più avanzati. Va notato che, al fine di massimizzare la quantità di energia termica trasmessa dalla superficie frontale e massimizzare il segnale osservato dal rivelatore IR, le superfici campione devono essere altamente emissivo. Solitamente questo richiede l&#39;applicazione di un sottile strato di grafite alle superfici campione. Un&#39;incertezza del 2% -5% nella misurazione di diffusività termica esiste, derivanti dalla determinazione di quota. 17 <ol start="3"><li> Tagliare il pellet disco utilizzando una sega diamantata in barre rettangolari, 2 x 2 x 103 mm, conduttività elettrica e Seebeck misurazioni coefficiente così come disco quadrata, 4 x 4 x 1,5 mm 3 per alta temperatura calore specifico e un pezzo rettangolare sottile, 8 x 5 x 1 mm 3 per misure di Hall. </li><li> Misurare il calore specifico, C p, del campione sul pezzo quadrato piatta e lucidata a specchio (4 x 4 x 1,5 mm 3) utilizzando una calorimetria differenziale a scansione (DSC) sotto flusso di argon. 18 <ol><li> Utilizzare una velocità di riscaldamento di 5 K min -1 fino a 40 ° C per una tenuta isotermico per 10 min per permettere il campione raggiungimento dell&#39;equilibrio termico seguito da 20 K tasso min -1 riscaldamento fino a 500 ° C, con una velocità di raffreddamento esatta che ha seguito. Eseguire la misura sotto il flusso di argon (50 ml min -1 è suggerito). </li></ol></li></ol> Nota: A causa della sensibilità del metodo di analisi, condurre tre misurazioni per determinare la capacità termica<html> compreso (1) una misura di base per sottrarre lo sfondo, (2) misurazione del calore specifico di un materiale standard (come zaffiro) con un noto C P, e (3) la misura del calore specifico del campione. Assicurarsi che i campioni sono piatte e lucidata a specchio per fare un contatto ideale con il fondo del crogiolo misura (pentole Pt / Rh con Al 2 O 3 crogioli utilizzati in questo lavoro). Maggiori dettagli sulla struttura esatta del palcoscenico DSC, un confronto delle tecniche DSC ad altri, e le istruzioni esatte per misurare un campione possono essere trovati in varie fonti. 19 <ol start="5"><li> Calcolare la conducibilità termica ad alta temperatura, κ, del campione dai valori misurati di diffusività termica, d, il calore specifico, C P, e la densità, ρ utilizzando 20 </li></ol>/52869/52869eq4.JPG &quot;Width =&quot; 200 &quot;/&gt; <ol start="6"><li> Targa d&#39;oro i punti di contatto sonde (4 contatti) sul 2 x 2 x 10 mm 3 pezzo tagliato dal campione per alleviare i problemi di resistenza di contatto. <ol><li> Per sputter oro solo sulle zone di contatto desiderati, avvolgere un scotch attorno al campione 2 x 2 x 10 mm 3 da utilizzare come stencil. Lasciare il 2 x 2 mm 2 facce un-coperti. Utilizzando una lama di rasoio, tagliare 2 fori molto piccoli (circa 1 mm di diametro) in mezzo alla faccia 2 x 10 mm 2 lungo una linea separata dalla distanza sonde. </li><li> Polverizzazione catodica una pellicola d&#39;oro ~ 200 nm di spessore con un banco unità oro sputtering. 21 </li></ol></li><li> Misurare le proprietà di trasporto elettriche, cioè la conducibilità elettrica e coefficiente Seebeck) del campione in funzione della temperatura 22,23. <ol><li> Misurare la conducibilità elettrica utilizzando il metodo a quattro morsetti. Misurare il coefficiente di Seebeck sul same configurazione utilizzando le misurazioni di temperatura e tensione tramite le due termocoppie middle &quot;sonde&quot;. Misurare la distanza tra queste due sonde utilizzando un microscopio digitale. Maggiori dettagli sulle misure elettriche di trasporto può essere trovato altrove. 22,23 </li></ol></li><li> Misurare la concentrazione di portatori Hall come funzione della temperatura sulla mm 3 campione 8 x 5 x 1 usando un sistema di misurazione delle proprietà fisiche. 24 </li></ol>

<ol>
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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 questo protocollo, abbiamo presentato i passi della strategia di sintesi al fine di prepararsi con successo policristalline massa Pr-drogato SrTiO 3 ceramica espone migliorate proprietà elettroniche e termoelettriche. Le principali fasi del protocollo comprendono (i) la sintesi a stato solido del drogato SrTiO 3 polvere in aria sotto pressione atmosferica e (ii) sfruttando le capacità della tecnica di sinterizzazione spark plasma per addensare la polvere come preparato in alto Densità ceramic...

Termoelettrico ossido hanno dimostrato di essere candidati promettenti per applicazioni termoelettriche ad alta temperatura, di stabilità e di costo prospettive alla proprietà di trasporto elettronico. Tra i termoelettrico ossido di tipo n, titanato di stronzio fortemente drogata (STO) ha attirato molta attenzione per le sue interessanti proprietà elettroniche. Tuttavia, una grande conduttività termica totale (κ ~ 12 W m -1 K -1 a 300 K per monocristalli) 1 e mobilità portante bassa (μ ~ 6 cm 2 V -1 sec -1 a 300 K per cristalli singoli) 1, compromette il rendimento termoelettrico che viene valutato da una figura adimensionale di merito, ZT = α 2 σT / κ, dove α è il coefficiente di Seebeck, σ la conducibilità elettrica, T la temperatura assoluta in gradi Kelvin, e κ la conducibilità termica totale. Siamo qui definiamo il numeratore come il fattore di potenza, PF = α 263; T. Affinché questo materiale termoelettrico ossido di competere con altri termoelettrico ad alta temperatura (come leghe SiGe), un aumento più pronunciato nel fattore di potenza e / o diminuzione in lattice conducibilità termica sono richiesti. La maggior parte degli studi sperimentali, per migliorare le proprietà termoelettriche di STO sono concentrati principalmente sulla riduzione della conducibilità termica mediante strain-campo e la fluttuazione massa dispersione dei fononi. Questi tentativi sono: (i) Scegliere o doppio-doping della Sr 2+ e / o Ti 4+ siti, come i principali sforzi rispetto a questa direzione, 2,3 (ii) Sintesi di superlattice naturale strutture Ruddlesden-Popper 5 Tuttavia, al fine di ridurre ulteriormente la conduttività termica attraverso strati isolanti SRO, 4 e (iii) Tecnica composito mediante aggiunta di una seconda fase nanometriche., fino a poco tempo fa, nessuna strategia enhancement è stato segnalato substantbuona resa aumentare il fattore termoelettrica di questi ossidi. I valori del fattore di potenza massima riportata (PF) in massa mono e poli-cristallino STO sono stati confinati a un limite massimo di PF &lt;1,0 W m -1 K -1. Una varietà di approcci di sintesi e tecniche di lavorazione sono stati impiegati per realizzare le idee tentati sopra. Le vie di sintesi in polvere includono reazione allo stato solido convenzionale, 6 sol-gel, 7 idrotermale, 8 e la combustione di sintesi, 9 considerando sinterizzazione convenzionale, 6 a caldo 10 e recentemente scintilla sinterizzazione plasma 12 sono tra le comuni tecniche utilizzate per addensare le polveri in ceramiche di massa. Tuttavia, per un drogante simile (per esempio, La) e concentrazione di drogaggio, le ceramiche bulk risultanti presentano una gamma di proprietà elettroniche di trasporto e termiche. Ciò è grande a causa del difetto chimica fortemente processo dipendente SrTiO &lt;sub&gt; 3 che si traduce in proprietà di sintesi-dipendente. C&#39;è solo una manciata di rapporti ottimizzando i parametri di sintesi e di elaborazione a beneficio del trasporto termoelettrico. Vale la pena ricordare che a causa della piccola fonone libero cammino medio in SrTiO 3 (l ph ~ 2 nm a 300 K), 11 nanostrutturazione non è un&#39;opzione praticabile per il miglioramento delle prestazioni TE della ceramica bulk STO principalmente attraverso la riduzione della conducibilità termica reticolo. Recentemente, abbiamo riportato più del 30% di miglioramento nella figura termoelettrica di merito in modo non uniforme Pr-drogate SrTiO 3 ceramiche provenienti da un fattore di potenza termoelettrica maggiore simultaneamente e ridotto conducibilità termica. 12,13 In questo protocollo video dettagliato, presentiamo e discutere i passi della nostra strategia di sintesi per la preparazione di questi Pr-drogato ceramiche STO espongono migliorate proprietà elettroniche e termoelettriche.

<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.

Diffrazioni radiografiche modelli sono stati raccolti per le polveri come preparate e le corrispondenti ceramiche bulk in funzione del Pr-contenuti (Figura 1) al fine di studiare l&#39;effetto di Pr-doping sulla SrTiO 3 reticolare, solubilità in Pr SrTiO 3 e la formazione di fase secondaria (s). I modelli confermano la formazione di SrTiO 3 fase tutte le polveri come preparate dove i riflessi possono essere indicizzati al reticolo cubico con gruppo spaziale (Fig...

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.

Sintesi di non-uniforme Pr-drogato SrTiO<sub&gt; 3</sub&gt; Ceramica e le loro proprietà termoelettriche

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

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Research

JoVE Journal

Chemistry

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

9.7K Views.  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.

Ammide Accoppiamento di reazione per la sintesi di leganti a base di Bispyridine e il loro Complessazione di platino come diciclici agenti antitumorali

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

Ricerca

Chimica

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.

Sintesi e caratterizzazione di supramolecolari colloidi

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.

Sintesi di ciclici polimeri e caratterizzazione di loro moto diffusivo allo stato fuso alla molecola Piano unico

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.

Sintesi e caratterizzazione di Fe-drogato Alluminosilicato nanotubi con una maggiore Electron proprietà conduttive

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.

Faccetta--sfaccettatura che collega di cadmio colloidale forma-anisotropo Chalcogenide nanostrutture

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.

Preparazione di stabile biciclico Aziridinium ioni e loro anello-apertura per la sintesi di Azaheterocycles

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.

Sintesi di nanofili Au associato a substrato tramite un meccanismo di crescita superficiale attiva

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.

Districante fibre di aramide copolimero ad alta resistenza per consentire la determinazione delle loro proprietà meccaniche

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.

Sintesi di in37P20(O2CR)51 cluster e la loro conversione in 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 ...

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.