The authors gratefully acknowledge financial support from the Belgian Federal government (Belspo through the IAP VI/27 and IAP-7/05 programs), the European Union's Seventh Framework Programme (FP7/2007-2013 under grant agreement no. 310651 SACS), the Flemish government in the form of long-term structural funding "Methusalem" grant METH/08/04 CASAS, the "Strategisch Initiatief Materialen" SoPPoM program, and the Fund for Scientific Research Flanders (FWO) grant G.0349.12. W.B. gratefully acknowledge the chemistry department of the KU Leuven for a FLOF-scholarship. The authors thank UOP Antwerp for the kind donation of zeolite samples and the mechanical workshop of the KU Leuven for helping with the design and construction of the heating/vacuum cell used in this study.

Attenzione: I prodotti chimici e reagenti utilizzati nella presente relazione sono stati maneggiati con cura utilizzando le adeguate protezioni di sicurezza (camici, guanti, occhiali di sicurezza, cappe). Questo studio si occupa della manipolazione di materiali inorganici microporosi (zeoliti con dimensioni che vanno da 1 a 5 micron), quindi una particolare attenzione era rivolta al uso di un&#39;adeguata protezione antipolvere (maschere antipolvere). Si consiglia la consultazione dei dati di sicurezza materiale pertinente (MSDS) dei prodotti chimici e reagenti impiegati in questo lavoro prima dell&#39;uso per una corretta manipolazione e / o lo smaltimento dei rifiuti. 1. Zeolite pre-trattamento <ol><li> Calore pretrattamento NOTA: Pre-trattare i materiali zeolite prima dell&#39;uso per rimuovere le impurità, come impurità organiche, che potrebbero ostacolare la formazione di cluster argento e luminescenza. <ol><li> Pesare 10 g di (Na) zeoliti commerciali LTA (zeoliti commerciali LTA contengono sodio come ioni contro-bilanciamento nei loro quadri) e deposedersi omogeneamente su un vassoio di porcellana. </li><li> Riscaldare la polvere di zeolite notte in un forno a muffola a 450 ° C con una rampa di temperatura di 5 ° C / min con intervalli di 1 ora a 80 ° C e 110 ° C per evitare danni zeolite struttura. </li><li> Rimuovere il materiale di zeolite dal forno e lasciate raffreddare fino a temperatura ambiente in condizioni ambientali. </li></ol></li><li> la selezione delle dimensioni delle particelle di zeolite NOTA: Questo genererà una granulometria più uniforme dei materiali di partenza zeolite, necessario per la creazione di un film omogeneo. Questo passaggio rimuove anche grandi particelle amorfe, che sono spesso presenti nelle zeoliti di produzione industriale. <ol><li> Pesare 10 g di LTA commerciale (Na) e sospende in 1 L di acqua deionizzata. </li><li> Sonicare la sospensione per 1 ora, scuotendo vigorosamente la sospensione da parte ogni 10 min. </li><li> Versare la sospensione in un cilindro Atterberg (1 L) per 30 min. Particelle inferiori a 10 micron di dimensionerimangono in sospensione, ma le particelle più grandi precipitano. </li><li> Decantare la sospensione e recuperare la polvere per filtrazione usando un imbuto Buchner. Lavare la polvere recuperata tre volte con acqua deionizzata. </li><li> Il calore trattare la polvere come descritto al punto 1.1.2. </li></ol></li></ol> 2. Preparazione di luminescenti LTA (Na) -AG Zeolite Compositi <ol><li> Sintesi di argento luminescenti scambiata LTA zeolite [LTA (Na) -AG] come materiale di riferimento <ol><li> Disciogliere 74,8 mg di nitrato d&#39;argento in 200 ml di acqua deionizzata in un 250 ml polipropilene ad alta densità (HDPE). </li><li> Pesare 1 g del campione pretrattato LTA (Na) e sospensione nella soluzione di nitrato d&#39;argento. </li><li> Lasciare la muffola HDPE agitazione durante la notte in un end-over-end forno agitatore a temperatura ambiente. </li><li> Filtrare la sospensione con un imbuto Büchner e lavare la polvere di zeolite 3 volte con acqua deionizzata. </li><li> Riscaldare la polvere recuperata in una muffola a 450 ° C, utilizzando la stessa procedura descritta al punto 1.1.2. </li><li> Raffreddare il campione e collocarlo in un essiccatore con umidità controllata (98% di umidità relativa). Controllo dell&#39;umidità relativa ponendo una soluzione satura di solfato di potassio dentro l&#39;essiccatore. 15 </li><li> Misurare la eccitazione ed emissione spettri dei campioni (a diverse lunghezze d&#39;onda) utilizzando uno spettrofluorometro nonché la loro efficienza quantica esterna. <ol><li> Misurare due piazzole di eccitazione-emissione dimensionali ponendo il campione in una cuvetta di quarzo percorso 1 mm. Raccogliere spettri di emissione a partire dal 30 nm di lunghezza d&#39;onda di eccitazione di sopra del fino a 800 nm con 5 passi nm e un tempo di permanenza di 0,1 sec. </li><li> Applicare correzioni utilizzando il software dello strumento per l&#39;intensità della lampada e la lunghezza d&#39;onda di rilevamento carico del percorso di emissione dei dati grezzi. Inoltre, utilizzare un filtro passa lungo per evitare il secondo picco di ordine nelle due lotti dimensionali. </li><li> Eseguire effici quantisticamisure renza utilizzando una sfera di integrazione attaccato al spettrofluorimetro. 16 Registrare la scansione di emissione da 240 nm a 600 nm sia per il campione di zeolite e BaSO 4 riferimento utilizzando 260 nm come lunghezza d&#39;onda di eccitazione, e quindi calcolare l&#39;efficienza quantica utilizzando il software dello strumento. </li></ol></li></ol></li></ol> 3. Preparazione di luminescenti [LTA (Li) -AG] Zeolite Composites <ol><li> Sintesi di zeolite scambiata parzialmente litio LTA [LTA (Li)] Nota: La procedura seguita per la fabbricazione di LTA (LI) zeoliti scambiate in parte è stato adattato dal rapporto Yahiro e collaboratori 17. <ol><li> Sciogliere 17,2 g di nitrato di litio a 2,5 L di acqua deionizzata. </li><li> Versare 0,5 L della soluzione di nitrato di litio in un pallone da 1 L HDPE. </li><li> Pesare 3 g di LTA (Na) zeolite pre-trattata e sospende nel pallone HDPE contenente la soluzione di nitrato di litio. </li><li> Agitare la beuta con un fine-over-end shaker forno a temperatura ambiente per una notte. </li><li> Filtrare la sospensione con un imbuto Büchner e lavare la polvere recuperata 3 volte con acqua deionizzata. </li><li> Eseguire lo scambio di litio <ol><li> Aggiungere 0,5 L di soluzione di nitrato di litio fresco (3.1.1) in un matraccio HDPE 1 L contenente la polvere recuperata dalla fase di filtrazione (3.1.5). </li><li> Ripetere i punti 3.1.4 e 3.1.5. </li><li> Ripetere i punti 3.1.6.1 e 3.1.6.2 altre 4 volte. </li></ol></li><li> Recuperare la polvere di zeolite e riscaldare in un forno a muffola a 450 ° C per una notte con una rampa di temperatura di 5 ° C / min con intervalli di 1 ora a 80 ° C e 110 ° C. </li></ol></li><li> Sintesi di luminescenti [LTA (LI) -AG] zeoliti <ol><li> Disciogliere 74,8 mg di nitrato d&#39;argento in 200 ml di acqua deionizzata utilizzando un flacone HDPE 250 ml. </li><li> Pesare 1 g del parzialmente scambiate litio LTA zeolite [LTA (Li)] e sospenderlo nella soluzione di nitrato d&#39;argento (3.2.1). </li><li> Agitare il fl HDPEchiedere utilizzando un forno agitatore end-over-end a temperatura ambiente per una notte. </li><li> Filtrare la sospensione con un imbuto Büchner e lavare la zeolite polvere recuperata 3 volte con acqua deionizzata. </li><li> Calore-trattare la polvere in un forno a muffola a 450 ° C per una notte con una rampa di temperatura di 5 ° C / min con intervalli di 1 ora a 80 ° C e 110 ° C. </li><li> Raffreddare il campione in condizioni di umidità controllata utilizzando un essiccatore contenente una soluzione satura di solfato di potassio all&#39;interno (umidità relativa 98%). 15 </li><li> Misurare la eccitazione ed emissione spettri dei campioni e la loro efficienza quantica esterna seguendo la procedura descritta nel passaggio 2.1.7. </li><li> Effettuare analisi termogravimetrica (TGA) per determinare il contenuto di acqua nel campione a diverse temperature. 1 Brevemente, posizionare 30 a 50 mg del campione preparato su un portacampioni platino e caricarlo nel dispositivo TGA. Misurare la perdita di peso da 50° C fino a 600 ° C con un tasso di calore di 5 ° C / min, sotto flusso di azoto (90 ml / min). </li></ol></li></ol> 4. Realizzazione di un LTA (Li) -AG / polietilenimmina (PEI) Composito depositato Film per umidità Sensing Applications Nota: La procedura di deposizione utilizzata in questo rapporto è stato modificato e adattato da riferimento 18. <ol><li> LTA (Li) -AG preparazione sospensione colloidale. <ol><li> Diluire 1 ml di 50% in peso soluzione commerciale PEI a 100 ml con acqua deionizzata. </li><li> Pesare 250 mg del luminescenti LTA (Li) materiale -AG. </li><li> Mescolare la zeolite e soluzione PEI insieme in un flacone in HDPE da 125 ml e agitare vigorosamente la sospensione. </li><li> Posizionare il flacone in un bagno sonicatore 40 kHz a temperatura ambiente per una notte, per ottenere una sospensione omogenea. </li><li> Versare la sospensione LTA (Li) -AG / PEI in un flacone spray. </li></ol></li><li> Deposizione di un film LTA (Li) -ag / PEI su una lastra di quarzo per il sensore protla produzione oType. <ol><li> Pulire una lastra di quarzo da risciacquo con acqua deionizzata e acetone consecutivamente, prima della deposizione di film. Essiccare le piastre pulite in un forno a 80 ° C per 1 ora. </li><li> Spruzzare ricoprire la piastra di quarzo da un lato, posizionando la piastra di quarzo orizzontalmente su un foglio di alluminio e spruzzare tre volte (3 sec ogni volta) da una distanza di circa 20 cm. Posizionare la piastra rivestita all&#39;interno di un forno di essiccazione a 50 ° C per 30 min. </li><li> Ripetere il punto 4.2.2 altre 4 volte fino a quando il film è uniforme. </li></ol></li><li> Idratazione / disidratazione del prototipo di sensore. <ol><li> Posizionare la piastra di quarzo rivestito nel vano campione di una cella di riscaldamento / vuoto in-house. 5 </li><li> Chiudere la camera del campione della cella inserendo una lastra di quarzo pulito in combinazione con un anello di gomma sulla parte superiore della piastra rivestita e sigillare la cella utilizzando un tappo di Teflon e viti come illustrato nella figura 2. </li><li> Applicare alto vuoto, noiing una pressione inferiore a 10 -3 mbar, alla notte cellula per disidratare il campione. </li><li> monitorare visivamente i cambiamenti di colore di emissione (nella regione visibile) del film depositato utilizzando una lampada UV. </li><li> Aprire la camera del campione di monitorare i cambiamenti di colore di emissione, nella regione del visibile, sulla reidratazione del film utilizzando una lampada UV. </li><li> Ripetere il ciclo più volte a partire dal punto 4.3.2 a 4.3.5 per testare la reversibilità del film LTA (Li) -AG / PEI. </li></ol></li></ol>

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The authors have nothing to disclose.

A simple device to demonstrate the proof of concept of using LTA(Li)-Ag as a luminescence based humidity sensor was produced by spray coating the LTA(Li)-Ag powder suspended in a PEI solution onto a quartz plate. The PEI solution produces a polymer layer with homogenous thickness when the water is evaporated. The polymer-zeolite composite layer displays similar luminescent properties as that of the zeolite in powder form. The PEI/LTA(Li)-Ag zeolite composite displays the expected water-responsive luminescent properties, whose emission color changes upon variations in the water content present in the composite at relatively low humidity scale. 
Replacing Na with Li ions in LTA zeolites (calculated exchange rate 33%) has a notable impact on the self-assembly and stabilization of luminescent silver clusters in the LTA(Li) scaffolds leading to unique optical properties. The EQE of LTA(Li)-Ag as compared to LTA(Na)-Ag samples is enhanced by more than one order of magnitude. Moreover, the emission colors displayed by the LTA(Li)-Ag samples have a water-dependence, providing a potential application of the samples as luminescence based humidity sensors. 
We have thus demonstrated an easy method to fabricate a luminescent film-like humidity sensor through which changes in hydration levels can be visually monitored simply by using a UV lamp. The availability of the raw materials, the direct visualization of the color changes correlated with humidity content, the photo-stability of the films, and the relative ease of fabricating cost-effective devices make these luminescent materials potential candidates to compete with state-of-the-art humidity sensors based upon electrical responses. The procedure described in this report could also be applied and extended to different substrates, at different micro and macro scales, to make the sensor more flexible. Additionally, several critical steps during the fabrication of Ag-zeolites, which play an important role in determining the final optical properties of such materials, were discussed in this protocol. For instance, the pre-cleaning of the raw zeolite material leads to the removal of optical and chemical impurities, as well as to homogenous zeolite crystal size distribution. This is crucial for the incorporation of zeolites into functional devices. One limitation of the present methodology is the restriction on the use of thin film sensors beyond 75 &#176;C. This is mainly due to the decomposition of the PEI polymer, rather than to the degradation of the LTA(Li)-Ag zeolites, which can withstand up to 500 &#176;C. The use of heat-resistant polymers, such as polyvinyl alcohol, could expand the temperature range up to 200 &#176;C. We expect that further investigations will be directed to the development of methodologies for the synthesis of nanostructured Ag-zeolite composites with (multi)functional properties and finally to the design of advanced sensor prototypes.

Piccolo sub-nanometrica grappoli d&#39;argento oligoatomic formati da auto-assemblaggio in matrici zeolite ristretti visualizzare le proprietà ottiche uniche. 1-5 Tali composti d&#39;argento-zeolite hanno alta chimica e la foto-stabilità. Tuttavia, le proprietà di fotoluminescenza sono fortemente dipendenti l&#39;ambiente locale dei cluster argento. Le condizioni ambientali che influenzano le caratteristiche ottiche in compositi argento zeolite possono essere suddivisi in proprietà intrinseche ed estrinseche. Proprietà intrinseche sono legati alla topologia zeolite, il tipo di ioni di controbilanciamento, e il carico di argento. 1 D&#39;altra parte, proprietà estrinseche sono associate ai cambiamenti post-sintetici, quali la presenza di adsorbati o molecole di acqua nella zeolite cavità. 3,4 quest&#39;ultima proprietà conferiscono ad argento-zeolite Panelli la capacità di rispondere otticamente a stimoli esterni, quali variazioni di umidità all&#39;interno della zeolite scaffold 6-8 </sup&gt; o la presenza di gas determinati; pertanto il loro uso come sensori vapore acqueo e gas è stato suggerito. 9,10 In un recente studio abbiamo dimostrato che la risposta ottica di Ag-zeoliti di umidità non solo è correlato ai cambiamenti nell&#39;assorbimento o tempra della loro emissione, ma anche alla comparsa di diversi colori di emissione rispetto al loro contenuto di acqua. 5 La stabilizzazione dei cluster d&#39;argento in parte Li scambiati zeoliti LTA portato alla formazione di un materiale di umidità-sensibile in cui le variazioni di scala relativa bassa umidità sono riflesse in un cambio dinamico del colore da blu a emissione verde / giallo in campioni disidratati e idrati, rispettivamente, . Pertanto è stato proposto l&#39;uso di questi materiali come sensori di umidità luminescenza-based. Fino ad oggi, i diversi tipi di materiali come elettroliti, ceramiche, polimeri e compositi nanostrutturati sono stati proposti per il monitoraggio dei cambiamenti di umidità based sulle risposte elettriche e ottiche. 11,12 In questo protocollo dettagliato ci proponiamo di dare prova di una proof-of-concept per l&#39;applicazione delle zeoliti LTA (Li) -AG come sensori di umidità e per ulteriori sviluppi prototipo. Grazie alla versatilità di LTA zeoliti (Li) -ag essere incorporati in diversi substrati, il loro potenziale scalabilità e fabbricazione economica, la progettazione del prototipo potrebbe essere facilitato. 13 Tali sensori potrebbero avere potenziale applicabilità in diversi settori industriali, come ad esempio in agricoltura, così come l&#39;industria automobilistica e della carta. 14

<table border="0" cellpadding="0" cellspacing="0" width="833">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:268px;">LTA(Na) zeolite</td>
			<td style="width:169px;">UOP</td>
			<td style="width:167px;">Molsiv adsorbent 4A</td>
			<td style="width:229px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Silver nitrate</td>
			<td>Sigma Aldrich</td>
			<td>209139</td>
			<td>&#8805;99,0%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Lithium nitrate</td>
			<td>Sigma Aldrich</td>
			<td>62574</td>
			<td>&#8805;99,0%, calc. on dry substances</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Polyethyleneimine solution</td>
			<td>Sigma Aldrich</td>
			<td>3880</td>
			<td>~50% H2O</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Scanning electron microscope (SEM)</td>
			<td>JEOL</td>
			<td>JSM-6010LV</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Thermogravimetric analyzer</td>
			<td>TA instruments</td>
			<td>Q500</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Spectrofluorimeter</td>
			<td>Edinburgh instruments</td>
			<td>FLS980-s</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Integrating sphere</td>
			<td>Labsphere</td>
			<td>4P-GPS-033-SL</td>
			<td></td>
		</tr>
	</tbody>
</table>

nanostructured ag-zeolite composites as luminescence-based humidity sensors

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high external quantum efficiencies (EQE) and spans the whole visible spectrum. It has been recently reported that the UV excited luminescence of partially Li-exchanged sodium Linde type A zeolites [LTA(Na)] containing luminescent silver clusters can be controlled by adjusting the water content of the zeolite. These samples showed a dynamic change in their emission color from blue to green and yellow upon an increase of the hydration level of the zeolite, showing the great potential that these materials can have as luminescence-based humidity sensors at the macro and micro scale. Here, we describe the detailed procedure to fabricate a humidity sensor prototype using silver-exchanged zeolite composites. The sensor is produced by suspending the luminescent Ag-zeolites in an aqueous solution of polyethylenimine (PEI) to subsequently deposit a film of the material onto a quartz plate. The coated plate is subjected to several hydration/dehydration cycles to show the functionality of the sensing film.

SEM micrografie della zeolite LTA-Ag sono stati registrati dopo la fase di scambio cationico e trattamento termico. Successivamente la fotoluminescenza bidimensionali (2D) di eccitazione / trame di emissione sono stati misurati sia per il idratata LTA (Na) -AG e LTA (Li) zeoliti -AG (Figura 1). Analisi elementare è stata eseguita sul XPS Ag scambiate zeoliti per determinare la loro composizione chimica. L&#39;analisi mostra che lo scambio d&#39;argento su LTA (Na) e LTA zeoliti (Li) è molto stretto con una percentuale in peso di argento del 19,6% in peso e 21,5% in peso, rispettivamente. La differenza in percentuale in peso potrebbe essere ascritta al peso atomico inferiore atomi Li. Inoltre l&#39;analisi elementare ha anche mostrato che, dopo lo scambio Li 33% di Na è sostituito. Lo scambio cationico e la successiva fase di trattamento termico eseguito sui campioni non sembrano influenzare la struttura dei cristalli LTA, come dimostrato da SEM. Inoltre, la formazione di argento ingrandisci nanoparticles sulla superficie dei cristalli di zeolite non era visualizzate. Le proprietà luminescenti in gran parte differiscono sia la LTA (Li) -AG e campioni LTA (Na) -AG nel loro stato idratato. Incorporando litio nell&#39;ambito zeolite come catione controbilanciamento, uno spostamento blu in eccitazione massima si verifica da 370 nm a 260 nm, per LTA (Na) -ag e LTA (Li) -ag rispettivamente. In contrasto massimo di emissione subisce un piccolo spostamento rossa da 550 al 565 nm aggiungendo Li nel sistema. La più grande differenza tra questi campioni si osserva nelle loro efficienza quantica esterna (EQE). LTA (Na) zeoliti -ag possiedono un EQE di circa 4% al massimo di eccitazione (370 nm), mentre la EQE per LTA (Li) zeoliti -ag raggiunge 62% (quando eccitato a 260 nm). Questo si traduce in un giallo brillante Emitting polvere sotto 254 nm UV illuminazione. Le proprietà luminescenti del campione LTA (Li) -ag dipendono anche il contenuto di acqua delsistema. Questo è stato dimostrato da una combinazione di TGA e temperatura dipendente esperimenti luminescenza, TGA correla la temperatura al livello di idratazione della zeolite. Inoltre, la temperatura sia indirettamente correlata al colore di emissione mostrata dal campione LTA (Li) -ag utilizzando una cella di riscaldamento interno (figura 2). Le variazioni di colore dal giallo delle emissioni oltre verde al blu, quando si rimuove l&#39;acqua dal sistema di LTA (Li) -AG. Il EQE scende costantemente dal 62% (stato idratato) al 21% (stato di disidratazione). A causa del comportamento reattivo in acqua di LTA (Li) -ag, questo materiale è stato usato per fabbricare un prototipo di sensore di umidità luminescenza basato sospendendo la polvere in una soluzione PEI e successivamente spruzzare rivestimento composito su una piastra di quarzo. Immagini (sotto la luce del giorno e UV illuminazione) e SEM micrografie del film LTA (Li) -AG / PEI spruzzo rivestite vengono visualizzati in figura 3. Abbiamo osservato che da USI<html> ng questa procedura di rivestimento, uno strato relativamente omogenea del composito polimero zeolite in termini di luminescenza è stata ottenuta. La micrografia SEM mostra che i cristalli di zeolite non sono alterati dalla procedura di rivestimento. Utilizzando un riscaldamento / cella a vuoto in casa è stato anche dimostrato che il film polimerico-zeolite mantiene le proprietà reattivo in acqua che sono stati osservati nella zeolite in forma di polvere. <img alt="Figura 1" src="/files/ftp_upload/54674/54674fig1.jpg" /> Figura 1: foto SEM e proprietà luminescenti dell&#39;argento scambiati zeoliti LTA micrografie SEM e 2D trame eccitazione-emissione di LTA (Na) -ag (a, b) e LTA (Li) -ag (c, d).. Gli inserti nelle trame di eccitazione-emissione 2D lo schermo a colori di emissione simulati dei campioni in diverse lunghezze d&#39;onda di eccitazione (254, 300, 366 e 450 nm).<html> OAD / 54674 / 54674fig1large.jpg &quot;target =&quot; _ blank &quot;&gt; Clicca qui per vedere una versione più grande di questa figura. <img alt="figura 2" src="/files/ftp_upload/54674/54674fig2.jpg" /> Figura 2: Effetto del livello di idratazione sulle proprietà luminescenti di LTA (Li) -AG. a) Rappresentazione schematica della cella di riscaldamento / vuoto internamente impiegato in questo studio b) terreno TGA per la LTA (Li) -ag campione c) spettri di emissione normalizzato (su 260 nm eccitazione) della LTA (Li).. - campione Ag misurata a diverse temperature. d) Schema di visualizzazione del cambiamento di colore emissione di campioni reali rispetto al contenuto di acqua. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54674/54674fig2large.jpg" target="_blank">Si prega di cliccare qui per vedere una versione più grande di questa figura.</a> ftp_upload / 54674 / 54674fig3.jpg &quot;/&gt; Figura 3: sensore di umidità luminescente sulla base di un composito LTA (Li) -AG / PEI. a) Le fotografie della piastra rivestita sotto illuminazione diurna. (B, c) Immagini di piastra disidratata e idratata rivestito sotto 254 nm UV-irradiazione di luce rispettivamente. D) Micrografia SEM del film depositato mostra la distribuzione dei LTA (Li) cristalli -ag sulla superficie del quarzo. L&#39;inserto mostra un ingrandimento di un&#39;area selezionata della microfotografia SEM originale. E) Emissione Maxima dei idratata e disidratato PEI / LTA (Li) -AG zeolite composito, durante 10 idratazione / disidratazione cicli utilizzando 260 nm come eccitazione lunghezza d&#39;onda. F) trama visualizzare l&#39;emissione profili Maxima comportamento del PEI / LTA (Li) -AG zeolite composito dopo cicli di 10 idratazione / disidratazione. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54674/54674fig3large.jpg" target="_blank">clicca qui a vi</a>ew una versione più grande di questa figura.

Watch this Scientific Journal Video about Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors at JoVE.com

Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors

A protocol for the synthesis of moisture-responsive luminescent Ag-zeolite composites is described in this report.

Compositi nanostrutturati Ag-zeolite come Sensori di umidità a base di luminescenza

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high ...

nanostructured-ag-zeolite-composites-as-luminescence-based-humidity

Nanyang Technological University

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10.1K Views.  KU Leuven. A protocol for the synthesis of moisture-responsive luminescent Ag-zeolite composites is described in this report.

Video: Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors

Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The optical modes are frequently referred to as "whispering gallery modes" (WGM) or "morphology dependent resonances" (MDR) and exhibit high optical quality factors. Some proposed applications of micro-cavity optical resonators are in spectroscopy1, micro-cavity laser technology2, optical communications3-6 as well as sensor technology. The WGM-based sensor applications include those in biology7, trace gas detection8, and impurity detection in liquids9. Mechanical sensors based on microsphere resonators have also been proposed, including those for force10,11, pressure12, acceleration13 and wall shear stress14. In the present, we demonstrate a WGM-based electric field sensor, which builds on our previous studies15,16. A candidate application of this sensor is in the detection of neuronal action potential.
The electric field sensor is based on polymeric multi-layered dielectric microspheres. The external electric field induces surface and body forces on the spheres (electrostriction effect) leading to elastic deformation. This change in the morphology of the spheres, leads to shifts in the WGM. The electric field-induced WGM shifts are interrogated by exciting the optical modes of the spheres by laser light. Light from a distributed feedback (DFB) laser (nominal wavelength of ~ 1.3 &mu;m) is side-coupled into the microspheres using a tapered section of a single mode optical fiber. The base material of the spheres is polydimethylsiloxane (PDMS). Three microsphere geometries are used: (1) PDMS sphere with a 60:1 volumetric ratio of base-to-curing agent mixture, (2) multi layer sphere with 60:1 PDMS core, in order to increase the dielectric constant of the sphere, a middle layer of 60:1 PDMS that is mixed with varying amounts (2% to 10% by volume) of barium titanate and an outer layer of 60:1 PDMS and (3) solid silica sphere coated with a thin layer of uncured PDMS base. In each type of sensor, laser light from the tapered fiber is coupled into the outermost layer that provides high optical quality factor WGM (Q ~ 106). The microspheres are poled for several hours at electric fields of ~ 1 MV/m to increase their sensitivity to electric field.

A high-sensitivity photonic micro sensor was developed for electric field detection. The sensor exploits the optical modes of a dielectric sphere. Changes in the external electric field perturb the sphere morphology leading to shifts in its optical modes. The electric field strength is measured by monitoring these optical shifts.

Sviluppo di Whispering Galleria polimerici modalità micro-ottici sensori di campo elettrico

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The ...

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A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

The durability of polymers and fiber-reinforced polymer composites in service is a critical aspect for their designs and condition-based maintenance. We present a novel low-cost laboratory testing platform for the investigation of the influence of concurrent mechanical and environmental loadings, and may help design more efficient yet safer composite structures.

Una piattaforma di prova per una durata Studi di polimeri e fibra-Reinforced Polymer Composites sotto Stimoli Concurrent Hygrothermo-meccanico

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs ...

Preparation and Reactivity of Gasless Nanostructured Energetic Materials

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the balls. Among other applications, it is a versatile technique that allows for effective preparation of gasless reactive nanostructured materials with high energy density per volume (Ni+Al, Ta+C, Ti+C). The structural transformations of reactive media, which take place during HEBM, define the reaction mechanism in the produced energetic&#160;composites. Varying the processing conditions permits fine tuning of the milling-induced microstructures of the fabricated composite particles. In turn, the reactivity, i.e., self-ignition temperature, ignition delay time, as well as reaction kinetics, of high energy density materials depends on its microstructure. Analysis of the milling-induced microstructures suggests that the formation of fresh oxygen-free intimate high surface area contacts between the reagents is responsible for the enhancement of their reactivity. This manifests itself in a reduction of ignition temperature and delay time, an increased rate of chemical reaction, and an overall decrease of the effective activation energy of the reaction. The protocol provides a detailed description for the preparation of reactive nanocomposites with tailored microstructure using short-term HEBM method. It also describes a high-speed thermal imaging technique to determine the ignition/combustion characteristics of the energetic materials. The protocol can be adapted to preparation and characterization of a variety of nanostructured energetic composites.

This protocol describes the preparation of gasless nanostructured energetic materials (Ni+Al, Ta+C, Ti+C) using the short-term high-energy ball milling (HEBM) technique. It also describes a high-speed thermal imaging method to study the reactivity of mechanically fabricated nanocomposites. These protocols can be extended to other reactive nanostructured energetic materials.

Preparazione e reattività di gasless Nanostrutturati materiali energetici

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the ...

Surface Enhanced Raman Spectroscopy Detection of Biomolecules Using EBL Fabricated Nanostructured Substrates

Fabrication and characterization of conjugate nano-biological systems interfacing metallic nanostructures on solid supports with immobilized biomolecules is reported. The entire sequence of relevant experimental steps is described, involving the fabrication of nanostructured substrates using electron beam lithography, immobilization of biomolecules on the substrates, and their characterization utilizing surface-enhanced Raman spectroscopy (SERS). Three different designs of nano-biological systems are employed, including protein A, glucose binding protein, and a dopamine binding DNA aptamer. In the latter two cases, the binding of respective ligands, D-glucose and dopamine, is also included. The three kinds of biomolecules are immobilized on nanostructured substrates by different methods, and the results of SERS imaging are reported. The capabilities of SERS to detect vibrational modes from surface-immobilized proteins, as well as to capture the protein-ligand and aptamer-ligand binding are demonstrated. The results also illustrate the influence of the surface nanostructure geometry, biomolecules immobilization strategy, Raman activity of the molecules and presence or absence of the ligand binding on the SERS spectra acquired.

We describe the fabrication and characterization of nano-biological systems interfacing nanostructured substrates with immobilized proteins and aptamers. The relevant experimental steps involving lithographic fabrication of nanostructured substrates, bio-functionalization, and surface-enhanced Raman spectroscopy (SERS) characterization, are reported. SERS detection of surface-immobilized proteins, and probing of protein-ligand and aptamer-ligand binding is demonstrated.

Surface Enhanced Raman Spectroscopy Rilevamento di Biomolecole Utilizzando EBL manufatti nanostrutturati Substrati

Fabrication and characterization of conjugate nano-biological systems interfacing metallic nanostructures on solid supports with immobilized biomolecules ...

Preparation and Evaluation of Hybrid Composites of Chemical Fuel and Multi-walled Carbon Nanotubes in the Study of Thermopower Waves

When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs along the interface between the fuel and core materials. Simultaneously, dynamic changes in thermal and chemical potentials across the micro/nanostructured materials result in concomitant electrical energy generation induced by charge transfer in the form of a high-output voltage pulse. We demonstrate the entire procedure of a thermopower wave experiment, from synthesis to evaluation. Thermal chemical vapor deposition and the wet impregnation process are respectively employed for the synthesis of a multi-walled carbon nanotube array and a hybrid composite of picric acid/sodium azide/multi-walled carbon nanotubes. The prepared hybrid composites are used to fabricate a thermopower wave generator with connecting electrodes. The combustion of the hybrid composite is initiated by laser heating or Joule-heating, and the corresponding combustion propagation, direct electrical energy generation, and real-time temperature changes are measured using a high-speed microscopy system, an oscilloscope, and an optical pyrometer, respectively. Furthermore, the crucial strategies to be adopted in the synthesis of hybrid composite and initiation of their combustion that enhance the overall thermopower wave energy transfer are proposed.

A protocol for conducting thermopower wave experiments is presented. The synthesis of hybrid composites of a chemical fuel and micro/nanostructured material, manufacturing of a thermopower wave generator, and methods for measuring the corresponding physical phenomena are described.

Preparazione e valutazione dei compositi ibridi di combustibile chimico e multi-walled nanotubi di carbonio nello studio di termoelettrico Waves

When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs ...

Iridium Oxide-reduced Graphene Oxide Nanohybrid Thin Film Modified Screen-printed Electrodes as Disposable Electrochemical Paper Microfluidic pH Sensors

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use integrated paper microfluidic electrochemical pH sensor for resource-limited settings. Taking advantages from both pH meters and strips, the pH sensing platform is composed of hydrophobic barrier-patterned paper micropad (&#181;PAD) using polydimethylsiloxane (PDMS), screen-printed electrode (SPE) modified with IrO2-graphene films and molded acrylonitrile butadiene styrene (ABS) plastic holder. Repetitive cathodic potential cycling was employed for graphene oxide (GO) reduction which can completely remove electrochemically unstable oxygenated groups and generate a 2D defect-free homogeneous graphene thin film with excellent stability and electronic properties. A uniform and smooth IrO2 film in nanoscale grain size is anodically electrodeposited onto the graphene film, without any observable cracks. The resulting IrO2-RGO electrode showed slightly super-Nernstian responses from pH 2-12 in Britton-Robinson (B-R) buffers with good linearity, small hysteresis, low response time and reproducibility in different buffers, as well as low sensitivities to different interfering ionic species and dissolved oxygen. A simple portable digital pH meter is fabricated, whose signal is measured with a multimeter, using high input-impedance operational amplifier and consumer batteries. The pH values measured with the portable electrochemical paper-microfluidic pH sensors were consistent with those measured using a commercial laboratory pH meter with a glass electrode.

The study demonstrates the growth of iridium oxide-reduced graphene oxide (IrO2-RGO) nanohybrid thin films on irregular and rough screen-printed carbon substrate through a green electrochemical synthesis, and their implementation as a pH sensor with a patterned paper-fluidic platform.

Grafene ossido nanoibrido film sottile elettrodi serigrafati Iridium ossido-riduzione modificato come usa e getta di carta elettrochimica microfluidici pH Sensori

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use ...

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints.

A straightforward procedure for ultrasonic welding of thermoplastic composite coupons for basic mechanical testing is described. Key characteristics of this ultrasonic welding process are the use of flat energy directors for simplified process preparation and the use of process data for the fast definition of optimum processing conditions.

Saldatura ad ultrasuoni di tagliandi termoplastico composito per la caratterizzazione meccanica dei giunti saldati attraverso singolo giro Shear Test

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ...

Fiber Optic Distributed Sensors for High-resolution Temperature Field Mapping

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists chiefly of velocity and temperature readings, both ideally having high spatial and temporal resolution to facilitate rigorous code validation. While high resolution velocity data is readily obtained through optical measurement techniques such as particle image velocimetry, it has proven difficult to obtain temperature data with similar resolution. Traditional sensors such as thermocouples cannot fill this role, but the recent development of distributed sensing based on Rayleigh scattering and swept-wave interferometry offers resolution suitable for CFD code validation work. Thousands of temperature measurements can be generated along a single thin optical fiber at hundreds of Hertz. Sensors function over large temperature ranges and within opaque fluids where optical techniques are unsuitable. But this type of sensor is sensitive to strain and humidity as well as temperature and so accuracy is affected by handling, vibration, and shifts in relative humidity. Such behavior is quite unlike traditional sensors and so unconventional installation and operating procedures are necessary to ensure accurate measurements. This paper demonstrates implementation of a Rayleigh scattering-type distributed temperature sensor in a thermal mixing experiment involving two air jets at 25 and 45 &#176;C. We present criteria to guide selection of optical fiber for the sensor and describe installation setup for a jet mixing experiment. We illustrate sensor baselining, which links readings to an absolute temperature standard, and discuss practical issues such as errors due to flow-induced vibration. This material can aid those interested in temperature measurements having high data density and bandwidth for fluid dynamics experiments and similar applications. We highlight pitfalls specific to these sensors for consideration in experiment design and operation.

We demonstrate use of a fiber optic distributed sensor for mapping the temperature field of mixing air jets. The Rayleigh scattering-based sensor generates thousands of data points along a single fiber to provide exceptional spatial resolution that is unattainable with traditional sensors such as thermocouples.

Fibre ottiche sensori distribuiti per alta risoluzione Mappatura temperatura Campo

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists ...

Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise composition of these materials is essential, especially in the design of surface catalysts, where the surface concentration of the active component determines the activity of the material. Antimicrobial materials which utilize nanoparticles are a particular focus of this technology. Recently swell encapsulation has emerged as a technique for inserting antimicrobial nanoparticles into a host polymer matrix. Swell encapsulation provides the advantage of localizing the incorporation to the external surfaces of materials, which act as the active sites of these materials. However, quantification of this nanoparticle uptake is challenging. Previous studies explore the link between antimicrobial activity and surface concentration of the active component, but this is not directly visualized. Here we show a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of CdSe/ZnS nanoparticles can be accurately visualized through cross-sectional fluorescence imaging. Using this method, we can quantify the uptake of nanoparticles via swell encapsulation and measure the surface concentration of encapsulated particles, which is key in optimizing the activity of functional materials.

Here we present a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of cadmium selenide quantum dots can be accurately visualized through cross-sectional fluorescence imaging.

Avanzate analisi composizionale di Compositi nanoparticelle-polimero Uso diretto imaging di fluorescenza

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

Fabbricazione ad alta temperatura di Nanostrutturati di ossido di ittrio stabilizzato-Zirconia (YSZ) Ponteggi da<em&gt; In Situ</em&gt; Carbon Templating xerogel

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...