Nanopapers toward Green Photonic and Optical Applications

Abstract

Nanopapers are known as thin sheets chiefly made of firmly crammed renewable nanomaterials including nanocellulose, nanochitin, and nanochitosan that endow much superior physicochemical merits in comparison to ordinary paper. The ever-augmenting popularity of employing nanopapers in copious applications is related to alluring and unrivalled characteristics comprising their innate renewability, biodegradability, nontoxicity, flexibility, and printability as easy-to-functionalize/administrate bioplatforms. Nanopapers have witnessed tremendous growth over the last decades in advanced optical applications ranging from (bio)sensors, optoelectronic devices, photovoltaic (PV) devices, electrochromic devices, organic light-emitting diodes (OLEDs), light diffusers, ultraviolet (UV)-blocking devices, phototransistors, photocatalysis, and anticounterfeiting substrates on account of their inherent natural features together with other optoelectronic properties, particularly their optical transparency, high flexibility, and mechanical properties. In the current review, while introducing different types of nanopapers, we intend to provide novel insights on how they have been tailored and employed in combination with other optical (nano)materials to fabricate nanopaper-based platforms for a wide variety of green photonic and optical applications. Building upon the extraordinarily features unveiled by nanopapers as promising bionanomaterials and significant progress in this area, we envisage that nanopaper-based platforms will provide ground-breaking prospects to develop efficient, affordable, and disposable optical devices in the near future.

Smart Wearable Nanopaper Patch for Continuous Multiplexed Optical Monitoring of Sweat Parameters

“…A micrometer-thick sheet of ChNFs was high-densified in the form of nanopaper. ChNP possesses several distinct features compared to ordinary paper including higher optical transparency and lower surface roughness, which make it a more suitable substrate/platform, particularly for optical (bio)­sensing applications. − Besides, ChNP has a higher reactive surface because of the presence of amide groups, which helps to overcome one of the foremost bottlenecks in fabricating optical sensors, that, is the bleeding of the reagents from the substrate surface. This situation is underscored predominantly in wearable sweat biosensors since there is a constant flow of biofluid (perspiration) with no control over the excreted volume.…”

A smart nanopaper sensor for optical diagnosis ofHelicobacter pyloriinfection

“…What's more, the high optical transparency of ChNF is another paramount feature that can affect the performance of optical (bio)sensors, where the use of non-transparent substrates such as paper encounters practical hurdles, especially for in vivo monitoring. 40,41…”

Research progress in wearable optical sweat sensors

“…Sekine 等 [70] 将设计的微流控装置与手机成像模块相结合实现对汗液中氯离子、 钠离子和锌离 子的原位荧光分析。Tao 等 [71] 制备出具有高透明度、pH 响应性、机械柔韧性和荧光性能的 碳量子点@聚乙烯醇复合膜，其可对运动过程中人体汗液 pH 值进行实时荧光监测。该薄膜 的开发为高稳定性的强荧光材料的制备开辟了新途径。Sharif 等 [72] 提出一种可对汗液 pH 及 汗液量进行荧光监测的智能可穿戴光学传感平台(图 4c)。其中，pH 传感器是通过将荧光 素固定在纳米甲壳素衬底中制成的(Flu-ChNP)；汗液量传感器是一个两层系统，底层同 样为 Flu-ChNP 层，而顶层是通过将氯化铜嵌入纳米甲壳素衬底中制成的(CuCl2-ChNP)。…”

“…除了常用的比色法、荧光法和 SERS 技术之外，还有一些其他的光学检测方法也被用于 汗液检测。化学发光法检测速度快、灵敏度高且线性检测范围广，通常是利用化学反应释放 的能量激发分子到激发态，然后通过分子从激发态返回基态时产生发光现象，从而来检测待 测物。该方法在可穿戴传感及微量汗液分析领域也展现出良好的应用潜力。Roda 等 [81] 采用 3D 打印技术制备出一种基于智能手机的化学发光生物传感器，可用于无创监测汗液中的乳 酸水平，检测限为 0.1 mM。Gao 等 [82] 提出一种具有双重催化活性的新型纳米芯片，其不仅 可以氧化葡萄糖生成过氧化氢，还可以使过氧化氢介导的鲁米诺化学发光，从而实现对汗液 中葡萄糖的灵敏检测，检测限为 10 -4 mM。Rink 等 [83] 开发出一种可用于汗液中 L-乳酸化学 发光检测的通用微流控纸基分析装置(μPAD)。该装置中沉积的乳酸氧化酶会将 L-乳酸氧 化为丙酮酸，并产生过氧化氢。然后，过氧化氢会与基底中的发光探针反应并出现发光现象 (图 4g)。 此外，早期科研人员还使用自制的光学传感系统对人体汗液 pH 进行检测。Caldara 等 [84] 设计出一种用于监测汗液 pH 的小型化光学传感系统， 其中包括高亮度的白色 LED 灯、 RGB 光电二极管、控制驱动器以及数据读取电路。通过测定 RGB 光电二极管输出的频率信号即 可获得织物样品对应的颜色信息以进一步估计汗液 pH 值。Morris 等 [85] 开发出一种基于纺织 物的可穿戴 pH 光学传感系统。利用纺织物收集汗液并将其运输到 pH 传感区域产生颜色变 化，然后通过光学传感系统测量颜色变化可以得到对应的 pH 值。另外，Wang 等 [86] 通过在 商用血氧传感器表面的 PDMS 层上覆盖 pH 敏感的有机改性硅酸盐膜， 制备出能够同时监测 心率、脉搏血氧饱和度以及汗液 pH 值的可拉伸光学传感贴片，实时测量所得的数据可以通 过蓝牙传输到智能手机上。 图 4 汗液光学检测方法：a)用于汗液中营养物比色分析的柔性微流控界面 [63] ；b)用于汗 液中葡萄糖、乳酸、尿素及 pH 比色检测的可穿戴汗液传感器 [65] ；c)用于汗液 pH 及汗液量 荧光检测的智能可穿戴光学传感平台 [72] ；d)集汗液收集、输送、储存和葡萄糖 SERS 检测 为一体的微流控贴片 [32] ；e)用于汗液中多巴胺检测的可穿戴 SERS 传感器 [75] ；f)具有纳 米多孔结构的 SERS 衬底 [78] ；g)通用微流控纸基分析装置(μPAD)及化学发光法检测 L-乳酸的示意图 [83] 。 Figure 4 Sweat optical detection methods. a) A flexible microfluidic interface for colorimetric analysis of nutrients in sweat [63] ; b) a wearable sweat sensor for color detection of glucose, lactate, urea and pH in sweat [65] ; c) an intelligent wearable optical sensing platform for fluorescence detection of sweat pH and sweat volume [72] ; d) a microfluidic patch integrating sweat collection, delivery, storage, and glucose SERS detection [32] ; e) a wearable SERS sensor for dopamine detection in sweat [75] ; f) a SERS substrate with nanoporous structure [78] ; g) a universal microfluidic paper-based analytical device (μPAD) and the schematic of L-lactate detection by chemiluminescence [83] .…”

“…Fluorometry paper wettable interface [20] polymer (PDMS) microfluidic device [70] textile hygroscopic material [69] flexible micro-nano material hygroscopic material [72] SERS polymer (PDMS) microfluidic device [32] textile hygroscopic material [38] flexible micro-nano material hygroscopic material [43] Others Chemiluminescence paper wettable interface [83] Optical sensing system textile hygroscopic material [84,85]…”