Questo lavoro è stato supportato da JCO A * STAR Investigatorship concedere (progetto n. 1437 00135), A * STAR Science & Engineering Consiglio settore pubblico finanziamenti per la ricerca (progetto n. 1421200076) e progetti di ricerca congiunta un JSP-NUS concedere (WBS R143-000-611-133).

<ol>
	<li>Figuerola, 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=End-to-End+Assembly+of+Shape-Controlled+Nanocrystals+via+a+Nanowelding+Approach+Mediated+by+Gold+Domains.">End-to-End Assembly of Shape-Controlled Nanocrystals via a Nanowelding Approach Mediated by Gold Domains.</a> Adv. Mat. 21, 550-554 (2009).</li><li>Tang, Z., Kotov, N. A., Giersig, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spontaneous+Organization+of+Single+CdTe+Nanoparticles+into+Luminescent+Nanowires.">Spontaneous Organization of Single CdTe Nanoparticles into Luminescent Nanowires.</a> Science. 297, 237-240 (2002).</li><li>Kim, D., Kim, W. D., Kang, M. S., Kim, S. -. H., Lee, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-Organization+of+Nanorods+into+Ultra-Long+Range+Two-Dimensional+Monolayer+End-to-End+Network.">Self-Organization of Nanorods into Ultra-Long Range Two-Dimensional Monolayer End-to-End Network.</a> Nano Lett. 15, 714-720 (2015).</li><li>Schliehe, 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=Ultrathin+PbS+Sheets+by+Two-Dimensional+Oriented+Attachment.">Ultrathin PbS Sheets by Two-Dimensional Oriented Attachment.</a> Science. 329, 550-553 (2010).</li><li>Chakrabortty, 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=Facet+to+facet+Linking+of+Shape+Anisotropic+Inorganic+Nanocrystals+with+Site+Specific+and+Stoichiometric+Control.">Facet to facet Linking of Shape Anisotropic Inorganic Nanocrystals with Site Specific and Stoichiometric Control.</a> Nano Lett. 16, 6431-6436 (2016).</li><li>Leatherdale, C. A., Woo, W. K., Mikulec, F. V., Bawendi, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+Absorption+Cross+Section+of+CdSe+Nanocrystal+Quantum+Dots.">On the Absorption Cross Section of CdSe Nanocrystal Quantum Dots.</a> J Phys Chem B. 106, 7619-7622 (2002).</li><li>Dabbousi, B. O., 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=(CdSe)ZnS+Core-Shell+Quantum+Dots:+Synthesis+and+Characterization+of+a+Size+Series+of+Highly+Luminescent+Nanocrystallites.">(CdSe)ZnS Core-Shell Quantum Dots: Synthesis and Characterization of a Size Series of Highly Luminescent Nanocrystallites.</a> J Phys Chem B. 101, 9463-9475 (1997).</li><li>Carbone, L., 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=Synthesis+and+Micrometer-Scale+Assembly+of+Coilloidal+CdSe/CdS+Nanorods+Prepared+by+Seeded+Grwoth+Approach.">Synthesis and Micrometer-Scale Assembly of Coilloidal CdSe/CdS Nanorods Prepared by Seeded Grwoth Approach.</a> Nano Lett. 7, 2942-2950 (2007).</li><li>Shaviv, E., 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=Absorption+properties+of+Metal-Semiconductor+Hybrid+Nanoparticles.">Absorption properties of Metal-Semiconductor Hybrid Nanoparticles.</a> ACS Nano. 5, 4712-4719 (2011).</li><li>Lim, J., 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=Controlled+Synthesis+of+CdSe+Tetrapods+with+High+Morphological+Uniformity+by+the+Persistent+Kinetic+Growth+and+the+Halide-Mediated+Phase+Transformation.">Controlled Synthesis of CdSe Tetrapods with High Morphological Uniformity by the Persistent Kinetic Growth and the Halide-Mediated Phase Transformation.</a> Chem Mat. 25, 1443-1449 (2013).</li></ol>

Non abbiamo nulla da rivelare.

La tecnica di collegamento descritta in questo lavoro permette per cadmio forma-anisotropo calcogenuri nanoparticelle che possono subire scambio cationico con Ag+ da unire, faccetta sfaccettatura, in assembly come catene lineari o ramificate reti. Il mancato formano ben dispersi, vasti assemblee di nanoparticelle collegate faccetta--sfaccettatura è spesso a causa di due motivi: (i) la ODPA non è disperso bene nella soluzione contenente NR, che può essere affrontata di sonicating la miscela per il prescritto quantità di tempo dettagliata nel protocollo; o (ii) la concentrazione di Ag+ utilizzata è non ottimale. Quando la concentrazione di Ag+ utilizzata è troppo bassa, la maggior parte delle nanoparticelle calcogenuri cadmio non subiscono scambio cationico, conseguente poco o nessun collegamento (come descritto nei Risultati rappresentante). Quando la concentrazione di Ag+ utilizzata è troppo alta, più domini di Ag2S modulo su ogni particella, con conseguente grave aggregazione su collegamento.
Il nostro approccio per il collegamento di faccetta--sfaccettatura delle nanoparticelle inorganiche forma-anisotropo è attualmente limitata a nanoparticelle di metallo calcogenuri che possono subire scambio cationico con Ag+ o Cu+ (non illustrato in questo lavoro) sotto reazione delicata condizioni. Gli sforzi sono in corso per ampliare il repertorio di materiali inorganici che possono essere collegati direttamente tramite la nostra strategia sintetica. Precedentemente abbiamo dimostrato che la faccetta sfaccettatura legata nanoparticella assembly possono subire ulteriori processi di scambio cationico e può essere trasformato in altri materiali semiconduttori pur mantenendo la loro architettura collegato5. Questo modificato la procedura di collegamento, anche se più noioso, può ampliare significativamente la diversità dei nanomateriali di semiconduttore che possono essere portati insieme in assembly sfaccettatura-collegata.
Perché le assemblee delle nanoparticelle di semiconduttore collegati sono unite in join faccetta-sfaccettatura, sono accoppiati elettronicamente a vicenda. Questo può essere vantaggioso per le applicazioni come soluzione-elaborati optoelettronica, dove un problema principale è il trasporto di carica poveri attraverso isolanti ligandi che circondano le nanoparticelle di semiconduttori. Ulteriore lavoro è necessario per valutare l'efficacia delle assemblee di nanoparticelle di semiconduttore collegati come materiale attivo in dispositivi optoelettronici.

Il montaggio diretto di semiconduttore colloidali NCs offre una via sintetica per la fabbricazione di nanostrutture cui proprietà fisico-chimiche sono sia la somma collettiva di o radicalmente diversi da loro individuali NC particelle elementari1 , 2 , 3 , 4. tra i vari approcci all'Assemblea di nanoparticelle, il metodo di fissaggio orientato - in quale NCs essenzialmente sono fusi con l'altro - si distingue come uno che consente di accoppiamento elettronico interparticella. Tuttavia, attaccamento orientata convenzionale richiede in genere il delicato bilanciamento della particella dipolo, ligando e interazioni solvente che sono generalmente difficili da eseguire e rendere applicabile a sistemi diversi di NC.
Recentemente abbiamo sviluppato un metodo di bagnato-chimico di unirsi covalentemente cadmio forma-anisotropo calcogenuri NCs introducendo un intermedio reattivo inorganico attraverso un processo di nucleazione sito-selettivo. Le particelle sono successivamente collegate tramite la fusione spontanea dei reattivi inorganici intermedio dei domini5. Anche se la tecnica è ancora basata su un meccanismo orientato allegato, c'è molto meno bisogno di considerare deboli interazioni interparticella, consentendo in tal modo maggiore flessibilità e controllo. Il collegamento di cadmio forma-anisotropo calcogenuri NCs è effettuato convertendo prima loro sfaccettature di punta in argento calcogenuri tramite un processo di scambio cationico parziale (in soluzione); Questo è seguito dalla rimozione selettiva di ligandi passivazione della superficie. NCs quindi si uniscono tramite la fusione delle sfaccettature esposta calcogenuri d'argento, conseguente assemblee del cadmio calcogenuri NCs collegati-to-end.
In questo protocollo, dimostriamo che il collegamento tra tecnica può essere applicata ad una varietà di forma-anisotropo cadmio calcogenuri NCs (cioè, CdSe-seminato CD NRs e seminato CdSe CdSe NRs o TPs), rendimento lineare lunga NR catene o altamente ramificati TP reti. Questi risultati suggeriscono che la tecnica può essere estesa a una vasta gamma di forme di NC e metallo calcogenuri suscettibili di scambio cationico d'argento.

<table width="724">
	<colgroup>
		<col />
		<col span="2" />
		<col />
	</colgroup>
	<tbody>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Cadmium oxide (CdO), 99.5%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Highly toxic</td>
		</tr>
		<tr height="43">
			<td height="43" style="width:288px;height:43px;">Tri-n-octylphosphine oxide (TOPO), 90 % and 99%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Technical and analytical grade</td>
		</tr>
		<tr height="47">
			<td height="47" style="width:288px;height:47px;">Cadmium acetylacetonate (Cd(acac)2), 99.9%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Highly toxic</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Hexadecanediol (HDDO), 90%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Technical grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">1-octadecene (ODE), 90%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Technical grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Dodecylamine (DDA), 98%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Toxic</td>
		</tr>
		<tr height="47">
			<td height="47" style="width:288px;height:47px;">Cadmium nitrate tetrahydrate ((CdNO3)2.4H2O), 98%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Highly toxic</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Myristic acid (MA), 99%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Octyl phosphonic acid (OPA), 97%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Oleylamine (Oly), 70%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Technical grade</td>
		</tr>
		<tr height="43">
			<td height="43" style="width:288px;height:43px;">Hexadecyltrimethylammonium bromide (CTAB), 95%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Toxic</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Selenium pellets (Se, 5 mm), 99.99%</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Hexadecylamine (HDA), 90%</td>
			<td style="width:123px;">Alfa Aesar</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Technical grade, toxic</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">n-tetradecylphosphonic acid (TDPA), 98%&#160;</td>
			<td style="width:123px;">Alfa Aesar</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade</td>
		</tr>
		<tr height="26">
			<td height="26" style="width:288px;height:26px;">Silver nitrate (AgNO3), 99.9%</td>
			<td style="width:123px;">Alfa Aesar</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Oleic acid (OA), 90%</td>
			<td style="width:123px;">Alfa Aesar</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Technical grade</td>
		</tr>
		<tr height="43">
			<td height="43" style="width:288px;height:43px;">Tri-n-octylphosphine (TOP), 97%</td>
			<td style="width:123px;">Strem</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade, toxic, air sensitive</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">n-hexylphosphonic acid (HPA), 97%</td>
			<td style="width:123px;">Strem</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">n-octadecylphosphonic acid (ODPA), 97%</td>
			<td style="width:123px;">Strem</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Tellurium powder (Te), 99.9%</td>
			<td style="width:123px;">Strem</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Air sensitive</td>
		</tr>
		<tr height="43">
			<td height="43" style="width:288px;height:43px;">Tri-n-butylphosphine (TBP), 99%</td>
			<td style="width:123px;">Strem</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Analytical grade, highly toxic, air sensitive</td>
		</tr>
		<tr height="22">
			<td height="22" style="width:288px;height:22px;">Diisooctylphosphonic acid (DIPA), 90%</td>
			<td style="width:123px;">Fluka</td>
			<td style="width:123px;"></td>
			<td style="width:191px;">Technical grade, toxic</td>
		</tr>
	</tbody>
</table>

facet-to-facet linking of shape-anisotropic colloidal cadmium chalcogenide nanostructures

Qui, descriviamo un protocollo che permette di cadmio forma-anisotropo calcogenuri nanocristalli (NCs), ad esempio nanorod (NRs) e tetrapodi (TPs), per essere covalentemente e site-specifically collegati tramite loro sfaccettature fine, conseguente simil-polimero lineare o ramificata catene. La procedura di collegamento inizia con un processo di scambio cationico in cui le sfaccettature di fine del cadmio calcogenuri NCs verrà convertito in calcogenuri d'argento. Questo è seguito dalla rimozione selettiva di ligandi alla loro superficie. In questo modo cadmio calcogenuri NCs con altamente reattivo calcogenuri d'argento fine sfaccettature che si fondono spontaneamente al contatto con l'altro, stabilendo così un allegato di faccetta--sfaccettatura interparticella. Attraverso la scelta giudiziosa delle concentrazioni di precursore, una vasta rete di NCs collegato può essere prodotto. Caratterizzazione strutturale del NCs collegate avviene tramite bassa e alta risoluzione microscopia elettronica a trasmissione (TEM), così come spettroscopia a raggi x energia-dispersiva, che confermano la presenza di domini di calcogenuri d'argento tra le catene di cadmio calcogenuri NCs.

Utilizzando CdSe-seminato CD NRs come sistema modello, come illustrato nella Figura 1(a), abbiamo dimostrato che possiamo utilizzare un parziale processo di scambio di Ag+ per trasformare in modo specifico le sfaccettature sulle punte NR Ag2S. Le sfaccettature di2S Ag sono ricoperti dalle DDA, che reagisce con ODPA tramite una reazione acido-base per formare un sale insolubile5. Questo fa sì che i ligandi DDA essere rimosso dalle sfaccettature2S Ag, causando loro di fondersi con l'altro al contatto e alla forma collegata catene NR, come mostrato in Figura 1(b). Per accertare se l'individuo NRs si fondono all'interno della catena o semplicemente sono tenute insieme da forze di Van der Waals, analisi HRTEM sulle regioni congiunte è stata effettuata. Come illustrato nella Figura 1(c), c'è un dominio distinto nel contatto epitassiale con due NRs. Un'analisi FFT dell'immagine HRTEM (inserto di Figura 1(c)) rivela l'esistenza di due costanti reticolari differenti che possono essere attribuite ad i facet (001) di Ag2S e CD. Inoltre, punto raggi x energia-dispersiva analisi di spettroscopia (EDX) sulla regione sollevatore prominente Mostra la presenza di Ag e l'assenza di Cd (Figura 1(d)), che conferma la nostra nozione di Ag2punta S CdSe-seminato CD NRs colmato tramite la fusione di Ag2 S domini. La resa e la natura statistica del processo di collegamento possono essere visualizzati tramite un istogramma (Figura 1(e)) che indica il numero di barre collegati all'interno di una catena NR.
Il meccanismo per il collegamento precedentemente è stato segnalato da Sabyasachi et al. 5 e non saranno descritti in dettaglio in questo lavoro. Si è osservato che, senza l'aggiunta di ODPA, nessun collegamento viene effettuato come si vede nella Figura 2(a), secondo la visione che l'aggiunta di ODPA provoca i nativi leganti di superficie della punta2S Ag a venire fuori. Questo può essere visto chiaramente in Figura 2(c), come mostra l'istogramma per la reazione di una parte cospicua del singolo, scollegato NRs. La presenza di dimeri potrebbe essere a causa di residui che ODPA rimasto dalla reazione di sintesi NR, permettendo una piccola quantità di collegamento per verificarsi. Oltre a ODPA, la concentrazione di AgNO3 inoltre è stata trovata per essere estremamente importante, come illustrato nella Figura 2(b), dove sono state ottenute solo brevi catene sotto le concentrazioni non ottimale di AgNO3. Dove la concentrazione di Ag+ usata era troppo bassa, l'istogramma mostra che la distribuzione è stata pesantemente verso lunghezze di catena. Infatti, le statistiche di collegamento per le catene illustrate nella Figura 2(b) caratteristica una percentuale sostanziale di dimeri, seguita da monomeri, come si vede nella Figura 2(d).
Oltre alla testa di serie CdSe CD NRs, indichiamo che l'Ag+-processo di collegamento mediato può essere esteso a testa di serie CdSe CdSe NRs e TPs, che sono mostrati in Figura 3(a) e (b), rispettivamente. Sotto le condizioni di reazione riassunte nella tabella 1, mostriamo che possiamo realizzare reti simili concatenate di CdSe-seminato CdSe NRs e TPs, come esemplificato nella Figura 3(c) e (d). Come nel caso di Ag2S-collegato CdSe-seminato CD NRs, le nanoparticelle di CdSe CdSe-teste di serie sono collegate tramite Ag2Se intermedi.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56009/56009fig1.jpg"> Figura 1. Caratterizzazione di collegato CdSe-seminato NRs CD. (a) a bassa risoluzione che mostra di immagine TEM come-sintetizzato CdSe-seminato CD NR. (b) a bassa risoluzione immagine TEM risultati Ag2S-collegato CdSe-seminato CdS NRs. (c) ad alta risoluzione (HRTEM) immagine TEM di un singolo giunto tra due NRs. Inset è un Fast Fourier Transform (FFT) dell'immagine HRTEM, mostrando due punti diversi della grata che sono attribuito a CD e Ag2S. (d) analisi EDX punto su un punto singolo collegamento, confermando la sua composizione come Ag2S. (e) istogramma mostra la distribuzione del numero di NRs per catena in un campione tipico collegato NR. <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56009/56009fig1large.jpg" target="_blank">Clicca qui per visualizzare una versione più grande di questa figura.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56009/56009fig2.jpg"> Figura 2 . Risultati delle condizioni di reazione non ottimale. (a) immagine TEM di CdSe-seminato NRs CD con punte di2S Ag che ha subito la procedura di collegamento, con l'eccezione che nessun ODPA è stato utilizzato. (b) immagine TEM mostrando brevi catene di Ag2S-collegato NRs CD CdSe-seminato quando la concentrazione di Ag+ non è stata ottimizzata. (c) istogramma che mostra che la maggior parte delle specie presenti sono singolo NRs quando ODPA è assente. (d) istogramma che mostra che, quando la concentrazione di Ag+ non è ottimizzata, solo brevi catene sono presenti. <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56009/56009fig2large.jpg" target="_blank">Clicca qui per visualizzare una versione più grande di questa figura.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56009/56009fig3.jpg"> Figura 3 . Estensione del processo di collegamento di nanostrutture CdSe CdSe-seminato. (a) a bassa risoluzione immagine TEM mostrando come sintetizzato CdSe-seminato CdSe NRs. (b) Low-resolution TEM immagine mostrando come sintetizzato CdSe-seminato CdSe TPs. (c) Low-resolution l'immagine mostrando la testa di serie CdSe CdSe NRs dopo il collegamento. (d) a bassa risoluzione immagine TEM mostrando la testa di serie CdSe CdSe TPs dopo il collegamento. <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56009/56009fig3large.jpg" target="_blank">Clicca qui per visualizzare una versione più grande di questa figura.</a>
<table fo:keep-together.within-page="1"><tbody>
<tr>
<td>Nanoparticella</td>
			<td>Concentrazione della soluzione di NC (mM)</td>
			<td>Concentrazione della soluzione di Ag+ (mM)</td>
			<td>Mescolando tempo (ore)</td>
		</tr>
<tr>
<td>CdSe seminato CD NRs</td>
			<td>3</td>
			<td>1</td>
			<td>1</td>
		</tr>
<tr>
<td>CdSe seminato CdSe NRs</td>
			<td>5</td>
			<td>0,8</td>
			<td>1</td>
		</tr>
<tr>
<td>CdSe seminato CdSe TPs</td>
			<td>5</td>
			<td>0.6</td>
			<td>0,5</td>
		</tr>
</tbody></table>Tabella 1. Riepilogo delle concentrazioni approssimative della soluzione NC e l'Ag+ soluzione e del tempo richiesto agitazione.

Watch this Scientific Journal Video about Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures at JoVE.com

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

Un protocollo di dettagliare come forma-anisotropo cadmio colloidale calcogenuri nanocristalli possono essere legata covalentemente tramite loro sfaccettature di fine sono presentato qui.

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 ...

facet-to-facet-linking-shape-anisotropic-colloidal-cadmium

Nanyang Technological University

Research

JoVE Journal

Chemistry

7.6K Views.  National University of Singapore. Un protocollo di dettagliare come forma-anisotropo cadmio colloidale calcogenuri nanocristalli possono essere legata covalentemente tramite loro sfaccettature di fine sono presentato qui.

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

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template&#39;s channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

This article describes the preparation of well-ordered nickel nanofoams via electroless metal deposition onto nanoporous templates obtained from self-assembled diblock copolymer based supramolecules.

Gyroid Nickel Nanostrutture da diblock Copolimero supramolecole

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, ...

Ricerca

Chimica

Quantitative and Qualitative Examination of Particle-particle Interactions Using Colloidal Probe Nanoscopy

Colloidal Probe Nanoscopy (CPN), the study of the nano-scale interactive forces between a specifically prepared colloidal probe and any chosen substrate using the Atomic Force Microscope (AFM), can provide key insights into physical interactions present within colloidal systems. Colloidal systems are widely existent in several applications including, pharmaceuticals, foods, paints, paper, soil and minerals, detergents, printing and much more.1-3 Furthermore, colloids can exist in many states such as emulsions, foams and suspensions. Using colloidal probe nanoscopy one can obtain key information on the adhesive properties, binding energies and even gain insight into the physical stability and coagulation kinetics of the colloids present within. Additionally, colloidal probe nanoscopy can be used with biological cells to aid in drug discovery and formulation development. In this paper we describe a method for conducting colloidal probe nanoscopy, discuss key factors that are important to consider during the measurement, and show that both quantitative and qualitative data that can be obtained from such measurements.

Colloidal probe nanoscopy can be used within a variety of fields to gain insight into the physical stability and coagulation kinetics of colloidal systems and aid in drug discovery and formulation sciences using biological systems. The method described within provides a quantitative and qualitative means to study such systems.

Esame quantitativa e qualitativa delle interazioni particella-particella colloidale Uso Probe Nanoscopia

Colloidal Probe Nanoscopy (CPN), the study of the nano-scale interactive forces between a specifically prepared colloidal probe and any chosen substrate ...

Synthesis of Indoxyl-glycosides for Detection of Glycosidase Activities

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are rapidly oxidized, for example by atmospheric oxygen, to indigo type dyes. This reaction enables fast and easy screening in vivo without isolation or purification of enzymes, as well as rapid tests on agar plates or in solution (e.g., blue-white screening, micro-wells) and is used in biochemistry, histochemistry, bacteriology and molecular biology. Unfortunately the synthesis of such substrates proved to be difficult, due to various side reactions and the low reactivity of the indoxyl hydroxyl function. Especially for glucose type structures low yields were observed. Our novel approach employs indoxylic acid ester as key intermediates. Indoxylic acid esters with varied substitution patterns were prepared on scalable pathways. Phase transfer glycosylations with those acceptors and peracetylated glycosyl halides can be performed under common conditions in high yields. Ester cleavage and subsequent mild silver mediated glycosylation yields the peracetylated indoxyl glycosides in high yields. Finally deprotection is performed according to Zempl&#233;n.

Indoxyl glycosides are well-established and widely used tools for enzyme screening and enzyme activity monitoring. Especially for glucose type structures previous syntheses proved to be challenging and low yielding. Our novel approach employs indoxylic acid esters as precious intermediates to yield a considerable number of indoxyl glycosides in good yields.

Sintesi di indoxyl-glicosidi per il rilevamento di glicosidasi Attività

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are ...

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

A two dimensional model material of discotic zirconium phosphate was developed. The inorganic crystal with lamellar structure was synthesized by hydrothermal, reflux, and microwave-assisted methods. On exfoliation with organic molecules, layered crystals can be converted to monolayers, and nematic liquid crystal phase was formed at sufficient concentration of monolayers.

Sintesi ed esfoliazione della discotici zirconio Fosfati di ottenere cristalli liquidi colloidale

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

Visualization of Ambient Mass Spectrometry with the Use of Schlieren Photography

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass spectrometer, it is necessary to characterize and understand the physical principles of the source. Most commercial ambient ionization sources utilize jets of nitrogen, helium, or atmospheric air to facilitate the ionization of the analyte. As a consequence, schlieren photography can be used to visualize the gas streams by exploiting the differences in refractive index between the streams and ambient air for visualization in real time. The basic setup requires a camera, mirror, flashlight, and razor blade. When properly configured, a real time image of the source is observed by watching its reflection. This allows for insight into the mechanism of action in the source, and pathways to its optimization can be elucidated. Light is shed on an otherwise invisible situation.

This paper presents a protocol for the visualization of gaseous streams of an ambient ionization source using schlieren photography and mass spectrometry.

Visualizzazione di ambiente spettrometria di massa con l&#39;uso della fotografia Schlieren

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Preparazione e caratterizzazione di nanostrutture ibride C60/Graphene

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

The Effect of Ultraviolet Radiation on the Chemical Bath Deposition of Bis(thiourea) Cadmium Chloride Crystals and the Subsequent CdS Obtention

In this work, the effects on the preparation of bis(thiourea) cadmium chloride crystals when illuminated with ultraviolet (UV) light at a wavelength of 367 nm using the chemical bath deposition technique are studied comparatively. Two experiments are performed to make a comparison: one without UV light and the other with the aid of UV light. Both experiments are performed under equal conditions, at a temperature of 343 K and with a pH of 3.2. The precursors used are cadmium chloride (CdCl2) and thiourea [CS(NH2)2], which are dissolved in 50 mL of deionized water with an acidic pH. In this experiment, the interaction of electromagnetic radiation is sought at the moment the chemical reaction is carried out. The results demonstrate the existence of an interaction between the crystals and the UV light; the UV light assistance causes crystal growths in an acicular shape. Also, the final product obtained is cadmium sulfide and shows no evident difference when synthesized with or without the use of UV light.

The Effect of Ultraviolet Radiation on the Chemical Bath Deposition of Bisthiourea Cadmium Chloride Crystals and the Subsequent CdS Obtention

This article presents a protocol for the synthesis of bis(thiourea) cadmium chloride crystals by chemical bath deposition. Two experiments are described: one aided by ultraviolet light compared to one without ultraviolet light.

L'effetto delle radiazioni ultraviolette sulla bagno chimico deposizione di cristalli di cloruro di cadmio Bis(thiourea) e il conseguente ottenimento di CdS

In this work, the effects on the preparation of bis(thiourea) cadmium chloride crystals when illuminated with ultraviolet (UV) light at a wavelength of ...

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F&#8722;

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound electrons with neutral molecules/atoms. State-of-the-art in vacuo anion generation techniques allow application to a broad range of atomic, molecular, and cluster anion systems. These are separated and selected using time-of-flight mass spectrometry. Electrons are removed by linearly polarized photons (photo detachment) using table-top laser sources which provide ready access to excitation energies from the infra-red to the near ultraviolet. Detecting the photoelectrons with a velocity mapped imaging lens and position sensitive detector means that, in principle, every photoelectron reaches the detector and the detection efficiency is uniform for all kinetic energies. Photoelectron spectra extracted from the images via mathematical reconstruction using an inverse Abel transformation reveal details of the anion internal energy state distribution and the resultant neutral energy states. At low electron kinetic energy, typical resolution is sufficient to reveal energy level differences on the order of a few millielectron-volts, i.e., different vibrational levels for molecular species or spin-orbit splitting in atoms. Photoelectron angular distributions extracted from the inverse Abel transformation represent the signatures of the bound electron orbital, allowing more detailed probing of electronic structure. The spectra and angular distributions also encode details of the interactions between the outgoing electron and the residual neutral species subsequent to excitation. The technique is illustrated by the application to an atomic anion (F&#8722;), but it can also be applied to the measurement of molecular anion spectroscopy, the study of low lying anion resonances (as an alternative to scattering experiments) and femtosecond (fs) time resolved studies of the dynamic evolution of anions.

Here, we present a protocol for photoelectron imaging of anionic species. Anions generated in vacuo and separated by mass spectrometry are probed using velocity mapped photoelectron imaging, providing details of anion and neutral energy levels, anion and neutral structure and the nature of the anion electronic state.

Imaging di fotoelettroni di anioni illustrato da 310 Nm distaccamento di F−

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound ...

Stable DNA Motifs, 1D and 2D Nanostructures Constructed from Small Circular DNA Molecules

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D DNA nanostructures. Over decades, the rapid development of DNA nanotechnology is attributed to the use of linear DNAs as the source materials. For example, the DAO (double crossover, antiparallel, odd half-turns) tile is well-known as a building block for construction of 2D DNA lattices; the core structure of DAO is made from two linear single-stranded (ss) oligonucleotides, like two ropes making a right hand granny&#160;knot. Herein, a new type of DNA tiles called cDAO (coupled DAO) are built using a small circular ss-DNA of c64nt or c84nt (circular 64 or 84 nucleotides) as the scaffold strand and several linear ss-DNAs as the staple strands. Perfect 1D and 2D nanostructures are assembled from cDAO tiles: infinite nanowires, nanospirals, nanotubes, nanoribbons; and finite nano-rectangles. Detailed protocols are described: 1) preparation by T4 ligase and purification by denaturing PAGE (polyacrylamide gel electrophoresis) of small circular oligonucleotides, 2) annealing of stable circular tiles, followed by native PAGE analysis, 3) assembling of infinite 1D nanowires, nanorings, nanospirals, infinite 2D lattices of nanotubes and nanoribbons, and finite 2D nano-rectangles, followed by AFM (Atomic Force Microscopy) imaging. The method is simple, robust, and affordable for most labs.

This article presents a detailed protocol for T4 ligation and denaturing PAGE purification of small circular DNA molecules, annealing and native PAGE analysis of circular tiles, assembling and AFM imaging of 1D and 2D DNA nanostructures, as well as agarose gel electrophoresis and centrifugation purification of finite DNA nanostructures.

Motivi di DNA stabile, 1D e 2D nanostrutture costruito da molecole di DNA circolare piccola

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D ...

Gene-therapy Inspired Polycation Coating for Protection of DNA Origami Nanostructures

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in physiological fluids induce denaturation and degradation of self-assembled DNA nanostructures. In non-viral gene delivery, enzymatic degradation of DNA is overcome by the encapsulation of the negatively charged DNA in a cationic shell. Herein, inspired by gene delivery advancements, a simple, one-step and robust methodology is presented for the stabilization of DNA origami nanostructures by coating them with chitosan and linear polyethyleneimine. The polycation coating efficiently protects DNA origami nanostructures in Mg-depleted and nuclease-rich media. This method also preserves the full addressability of enzyme- and aptamer-based functionalization of DNA nanostructures.

Here, a protocol for the protection of DNA origami nanostructures in Mg-depleted and nuclease-rich media using natural cationic polysaccharide chitosan and synthetic linear polyethyleneimine (LPEI) coatings is presented.

Terapia genica ispirato Polycation rivestimento per la protezione di nanostrutture di DNA Origami

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in ...

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

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