在紙基材表面上碳奈米量子點的原位合成

Abstract

碳基奈米結構，常見的有像是碳奈米管和石墨烯，而與這些碳奈米結構相比，碳量子點 (Carbon dots, CDs) 是一種零維的碳奈米材料，近年來，碳點已被證明具有許多獨特的特性，如可調節的PL、低毒性、生物相容性等優點近年來受到許多領域的關注。其中碳量子點的紙基分析設備日益增加，而到目前為止，紙基設備中使用的量子點多是在紙基外部預合成，再透過多步驟過程嵌入到紙中，這通常需要較高的合成溫度與時間，且容易造成碳點與紙張之間作用力不穩定，使液體任意流動，造成螢光量測誤差。 因此，在本研究中，我開發了一種具成本效益、簡單易行的方法，透過將紙張浸泡在前驅物溶液中後進行加熱，運用原位合成方式，直接在紙上產生碳量子點。我首先找到合成最佳溫度與時間條件，得知相較於傳統方法，本研究在相對低溫的環境，且在9分鐘便可以完成。後續接著探討調節碳前驅物pH值，可以得到與pH依賴性的螢光強度結果，尋找紙上最合適、螢光強度最強的pH條件。並且運用檸檬酸、不同胺基酸的碳前驅體進行原位合成，進一步去討論在不同成分之纖維紙基材的原位合成，對螢光結果的影響。以此方法製備的碳點紙張，也和傳統熱解檸檬酸製備碳點的方法做比較，本研究方法有螢光效率高、與紙張附著力強的優點，對於螢光檢測應用方面帶來有用的優勢。因此除了合成之外，本研究所製備的碳點紙張也帶來一些感測的能力，我發現在pH 2.2以下的溶液能改變碳點紙的螢光發射波長，顏色由綠轉藍，展現優異的可視化檢測。最後，運用前驅物溶液均勻、延展性良好的優勢，將其製備成墨水，嘗試將碳點圖樣化，運用噴墨印表機在紙上印製圖樣，透過這樣原位合成的方法，將碳量子點定點印製在紙上，使其更均勻地在紙上生成，並且能夠同時並行產出不同的碳點。

Carbon-based nanostructures, the common ones are carbon nanotubes and graphene, etc. Compared with these carbon nanostructures, carbon quantum dots (CDs) is a kind of zero-dimensional carbon nanomaterials. In recent years, carbon dots have been shown to have many unique properties, such as tunable PL, low toxicity, biocompatibility, etc., which have attracted attention from many fields. Among them, the paper-based analysis devices (PADs) of CDs is increasing day by day. However, the CDs used in PADs are mostly pre-synthesized without the paper, and then embedded into the paper through a multi-step process. This usually required high temperature and took long time to be synthesized. And it is easy to cause unstable binding between the CDs and the paper, resulting in the movement between the paper and the liquid, and causing fluorescence measurement errors. Therefore, in this study, we developed a cost-effective and simple method to directly generate CDs on paper. We soaked the paper in the precursor solution and then heating it. By using in-situ synthesis method, CDs were produced directly on paper. We first found the optimal temperature and time conditions for synthesis. Compared with traditional methods, our methods can be completed in 9 minutes at a relatively low temperature environment. Then, we discussed the adjustment of the pH value of the carbon precursor to obtain the pH-dependent fluorescence intensity results, and found the most suitable pH condition with the highest fluorescence intensity on paper. And we used citric acid and amino acid as carbon precursors for in-situ synthesis to discuss the influence on different fiber paper substrates and the fluorescence results. The CDs paper prepared by this method is also compared with the traditional method of pyrolyzing citric acid. We found that our method has higher fluorescence efficiency and stronger adhesion to paper. This is a great advantage in the application of fluorescence detection. Therefore, in addition to synthesis, the CDs paper prepared in this study also has the ability of pH sensing. We found that the solution below pH 2.2 can change the fluorescent emission wavelength of the CDs paper, and the color changes from green to blue, which demonstrated excellent visual detection. Finally, we patterned the CDs and used an inkjet printer to print the pattern on the paper. Through this in-situ synthesis method, the CDs are fixed-point printed on the paper. So that it can be generated more uniformly on the paper, and different kinds of CDs can be produced at the same time.