Luminescence आधारित आर्द्रता सेंसर के रूप में Nanostructured एजी-जिओलाइट कंपोजिट
Summary
A protocol for the synthesis of moisture-responsive luminescent Ag-zeolite composites is described in this report.
Abstract
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.
Introduction
छोटे उप नैनोमीटर oligoatomic चांदी समूहों तक ही सीमित जिओलाइट matrices में आत्म विधानसभा द्वारा गठित अद्वितीय ऑप्टिकल गुण प्रदर्शित करते हैं। इस तरह के 1-5 चांदी जिओलाइट कंपोजिट उच्च रासायनिक और फोटो स्थिरता है। हालांकि, उनके photoluminescence गुण चांदी समूहों के स्थानीय पर्यावरण पर अत्यधिक निर्भर हैं। पर्यावरण की स्थिति यह है कि चांदी जिओलाइट कंपोजिट में ऑप्टिकल सुविधाओं को प्रभावित आंतरिक और बाह्य गुण में विभाजित किया जा सकता है। आंतरिक गुणों जिओलाइट टोपोलॉजी, काउंटर संतुलन आयनों के प्रकार, और चांदी लोडिंग से संबंधित हैं। 1 दूसरी ओर, बाह्य गुण ऐसे में adsorbates या पानी के अणुओं की मौजूदगी के रूप में पद-सिंथेटिक परिवर्तन, से जुड़े हुए हैं जिओलाइट गुहाओं। 3,4 बाद के गुण-चांदी जिओलाइट के लिए प्रदान ऑप्टिकली ऐसे जिओलाइट पाड़ 6-8 भीतर नमी के रूपांतरों के रूप में बाहरी उत्तेजनाओं, पर प्रतिक्रिया करने की क्षमता कंपोजिट </sup> या निर्धारित गैसों की उपस्थिति; इसलिए जल वाष्प और गैस सेंसर के रूप में उनके इस्तेमाल का सुझाव दिया गया है। 9,10
हाल ही में एक अध्ययन में हम दिखा दिया है कि नमी के लिए एजी-zeolites के ऑप्टिकल प्रतिक्रिया केवल अवशोषण या उनके उत्सर्जन के शमन में बदलाव के लिए बल्कि उनके पानी की मात्रा के संबंध में अलग-अलग रंगों के उत्सर्जन की उपस्थिति के लिए सहसंबद्ध नहीं है। 5 स्थिरीकरण में आंशिक रूप से ली विमर्श एलटीए zeolites एक नमी संवेदनशील सामग्री जिसमें रिश्तेदार कम नमी पैमाने में परिवर्तन एक गतिशील रंग निर्जलित और हाइड्रेटेड नमूनों में हरी / पीला उत्सर्जन करने के लिए एक नीले रंग से परिवर्तन में परिलक्षित किया गया के गठन के लिए नेतृत्व में क्रमश: रजत समूहों की । इसलिए luminescence आधारित आर्द्रता सेंसर के रूप में इन सामग्रियों के उपयोग का प्रस्ताव रखा था। तिथि करने के लिए, इस तरह के इलेक्ट्रोलाइट्स, चीनी मिट्टी की चीज़ें, पॉलिमर, और nanostructured कंपोजिट के रूप में सामग्री के विभिन्न प्रकार आर्द्रता बी में निगरानी परिवर्तन के लिए प्रस्तावित किया गया हैased बिजली और ऑप्टिकल प्रतिक्रियाओं पर। 11,12 इस विस्तृत प्रोटोकॉल में हम आर्द्रता सेंसर के रूप में एलटीए (ली) -ag zeolites के आवेदन के लिए और आगे प्रोटोटाइप के विकास के लिए एक सबूत की अवधारणा को प्रदर्शित करने का लक्ष्य है। एलटीए (ली) -ag zeolites की चंचलता के कारण विभिन्न substrates में शामिल होने के लिए, अपनी क्षमता scalability और लागत प्रभावी निर्माण, प्रोटोटाइप डिजाइन की जा सकती है। 13 इस तरह के सेंसर इस तरह के रूप में विभिन्न औद्योगिक क्षेत्रों में संभावित प्रयोज्यता हो सकता था कृषि, साथ ही ऑटोमोबाइल और कागज उद्योग। 14
Protocol
Representative Results
Discussion
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 °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 °C. The use of heat-resistant polymers, such as polyvinyl alcohol, could expand the temperature range up to 200 °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.
Disclosures
The authors have nothing to disclose.
Acknowledgements
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.
Materials
| LTA(Na) zeolite | UOP | Molsiv adsorbent 4A | |
| Silver nitrate | Sigma Aldrich | 209139 | ≥99,0% |
| Lithium nitrate | Sigma Aldrich | 62574 | ≥99,0%, calc. on dry substances |
| Polyethyleneimine solution | Sigma Aldrich | 3880 | ~50% H2O |
| Scanning electron microscope (SEM) | JEOL | JSM-6010LV | |
| Thermogravimetric analyzer | TA instruments | Q500 | |
| Spectrofluorimeter | Edinburgh instruments | FLS980-s | |
| Integrating sphere | Labsphere | 4P-GPS-033-SL |
References
- De Cremer, G., et al. Characterization of Fluorescence in Heat-Treated Silver-Exchanged Zeolites. J. Am. Chem. Soc. 131, 3049-3056 (2009).
- De Cremer, G., et al. Optical Encoding of Silver Zeolite Microcarriers. Adv. Mater. 22, 957-960 (2010).
- Coutino-Gonzalez, E., et al. X-ray Irradiation-Induced Formation of Luminescent Silver Clusters in Nanoporous Matrices. Chem. Commun. 50, 1350-1352 (2014).
- De Cremer, G., et al. In Situ Observation of the Emission Characteristics of Zeolite-Hosted Silver Species During Heat Treatment. ChemPhysChem. 11, 1627-1631 (2010).
- Coutino-Gonzalez, E., et al. Thermally Activated LTA(Li)-Ag Zeolites with Water-Responsive Photoluminescence Properties. J. Mater. Chem. C. 3, 11857-11867 (2015).
- Seifert, R., Kunzmann, A., Calzaferri, G. The Yellow Color of Silver-Containing Zeolite. A. Angew. Chem. Int. Ed. 37, 1522-1524 (1998).
- Seifert, R., Calzaferri, G. Colors of Ag+-Exchanged Zeolite A. J. Phys. Chem. A. 104, 7473-7483 (2000).
- Sazama, P., Jirglova, H., Dedecek, J. Ag-ZSM-5 Zeolite as High-Temperature Water-Vapor Sensor Material. Mat. Lett. 62, 4239-4241 (2008).
- Zheng, Y., Li, X., Dutta, P. K. Exploitation of Unique Properties of Zeolites in the Development of Gas Sensors. Sensors. 12, 5170-5194 (2012).
- Sun, T., Seff, K. Silver Clusters and Chemistry in Zeolites. Chem. Rev. 94, 857-870 (1994).
- Yu, Y., Ma, J. P., Dong, Y. B. Luminescent Humidity Sensors Based on Porous Ln3+-MOFs. Cryst. Eng. Comm. 14, 7157-7160 (2012).
- Qi, H., Mader, E., Liu, J. Unique Water Sensors Based on . Sensor. Actuat. B-Chem. 185, 225-230 (2013).
- Basabe-Desmonts, L., Reinhoudt, D. N., Crego-Calama, M. Design of Fluorescent Materials for Chemical Sensing. Chem. Soc. Rev. 36, 993-1017 (2007).
- Yamazoe, N., Shimzu, Y. Humidity Sensors – Principles and Applications. Sensor. Actuator. 10, 379-398 (1986).
- International Organization of Legal Metrology. . The Scale of Relative Humidity of Air Certified Against Saturated Salt Solutions. , (1996).
- Coutino-Gonzalez, E., et al. Determination and Optimization of the Luminescent External Quantum Efficiency of Silver-Clusters Zeolite Composites. J. Phys. Chem. C. 117, 6998-7004 (2013).
- Yahiro, H., et al. EPR Study on NO Introduced into Lithium Ion-Exchanged LTA Zeolites. Phys. Chem. Chem. Phys. 4, 4255-4259 (2002).
- Shelyakina, M. K., et al. Study of Zeolite Influence on Analytical Characteristics of Urea Biosensor Based on Ion-Selective Field-Effect Transistors. Nanoscale Res. Lett. 9, 124 (2014).
