这项工作是由来自水设备及策略（WEP）NSF工业/大学合作研究中心（I / UCRC）的资助。作者还感谢了亚尔马D.和珍妮特·W·布鲁恩奖学金和路易斯和Elsa汤姆森威斯康辛杰出研究生奖学金在威斯康星大学麦迪逊分校提供给JY

1.μPAD和设备准备<ol><li>刻在底部塑料保持器500微米槽以容纳SPE与由三维（3D）铣床及具有直径为1.6mm铣削位的ABS或兼容塑料片材。与夹持器（ 图1A）在测试过程中保持在适当位置SPE和μPAD牢固。 </li><li>使印模和使用合成树脂片或相容的塑料片材与凹凸花纹，分别真空罩，由3D铣床，以在纸张上焊盘图案疏水PDMS障碍。 <ol><li>制备的PDMS预聚合物和交联剂的混合物中以10:1的比例，或通过制造商的建议，拌入抹刀和应用适当的量到的PDMS印模的凸面。 </li></ol></li><li>放置印章上的滤纸垫预切割成所需要的尺寸，然后在整个纸张印模的相对侧上的真空盖的顶部。应用VACU嗯用于通过手工操作真空泵达30秒。除去从印模和真空罩的纸垫，并在80℃的对流烘箱中烘烤10分钟，以硬化图案化的PDMS（ 图1B）。所得纸垫具有约为0.2 cm 2的感测区和1个厘米×0.4厘米亲水样品芯吸区域。 注:取上施加的PDMS和真空时间的量特别注意事项，以避免在液体样品转移滤纸的内部亲水区的任何可能的PDMS污染。 </li></ol> 2. SPE的修改与2的IrO -RGO纳米杂化薄膜<ol><li>降投3微升所制备的1毫克∙毫升-1 GO SPE上的石墨碳工作电极溶液用微量并让它干燥在培养皿室温。吹扫用N 2的pH 5.0的PBS缓冲液20分钟，浸在SPE中10毫升脱气PBS缓冲液，同时保持Ñ&lt;子&gt; 2流动，并从0.0到-1.5V时重复进行阴极电位循环100次，以减少电化学进入RGO。冲洗用DI水在SPE中一个喷射瓶并在室温下干燥。 注:嗯剥离的GO表，通过静电排斥稳定，从采用改良悍马的方法，其他地方7日报道石墨粉。合成的RGO膜的均匀性是很重要的，因为它充当的IrO 2的薄膜的进一步生长的碳载体。 </li><li>使（IrCl 4）0.15四氯化铱组成100毫升的IrO 2沉积溶液，0.6毫升50％（W / W）过氧化氢（H 2 O 2）和0.5g草酸通过在去离子水中添加它们脱水。逐渐添加无水碳酸钾少量，同时搅拌直到pH达到10.5，通过基于实验室的pH计进行验证。然后，溶液变成淡黄色。老龄化在室温temperatu 48小时解决再次，那么它的颜色是最终关闭的淡蓝色。 </li><li>把RGO-SPE在上述沉积溶液和适用+ 0.6V的恒定电位5分钟。的IrO 2薄膜的厚度可以通过沉积电势和时间被精确地控制。 </li><li>确认通过SEM传感区域的结构。获得SEM照片下面的材料科学中心在威斯康星大学麦迪逊分校的指令，因为我们7以前那样。 </li></ol> 3.价格低廉，便携数字pH计建设<ol><li>通过在任何一个系列的两个单LF356N运算放大器（运算放大器）或者一个INA111高速场效应晶体管（FET） -输入仪表放大器的堵塞建造廉价且小型化的pH计用数字显示（高输入阻抗&gt; 10 12Ω）在面包板，以实现稳定的测量足够高的内部阻抗。 注:所有的部件很容易交流从电子商店够到，并且可以容易地组装。 </li><li>使用税务条例2 -RGO-SPE作为pH探头和运算放大器作为单位增益缓冲器。串联连接两个接地9 V碱性电池消费的pH计的电源插上电线插入基于运算放大器的引脚布局线路板。 </li><li>在阴极和阳极连接到销7和4.又一个数字万用表的正面和负面的探针分别连接到销6和运算放大器5来测量输出电压和显示读数。参考和SPE工作电极连接到引脚2和3水涨船高。详细的连接示于图1D。 </li></ol> 4. pH测量<ol><li>制备100ml的BR缓冲液与0.04M的等摩尔磷酸，乙酸和硼酸和用0.2M氢氧化钠（NaOH）的不同体积（5，25，42，60，78和98），混合到由2-实现不同pH 12，用于校准。 </li><li>禄吃图案在传感区域的顶部μPAD。安装60微升液体样品直接通过微量吸入μPAD的芯吸的亲水区。该μPAD可以在使用或不ABS的盖进行，当它被浸湿。 </li><li>测量的IrO 2 -RGO工作电极和随着时间的推移或者是基于实验室的CHI 660D电化学分析仪或便携式数字pH计，当开路电位（OCP）变得稳定的Ag / AgCl参考电极之间的电压信号（电位变型&lt;5％）。 </li><li>保持浸渍液体样品在纸垫湿感测区域进行测试，如果需要的话，以达到更好的电接触，以及稳定和可重现的读数在长期操作。记录稳态OCP值是在各pH值平均，以确定校准曲线。 </li></ol>

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作者有没有竞争经济利益。

设备安装 pH传感器的工作原理，通过测量在工作电极和参考电极之间的OCP，因为它按比例改变到的 H +浓度的负对数。测量可以通过一个基于实验室的电位如CHI 660D和与通过万用表阅读面包板构造简单的pH计来实现两者。两个不同的便携式pH计类似地构建在使用两个9伏碱性电池，一个数字万用表，所合成的IrO 2 -RGO-SPE和不同运算放大器，这是两个串行LF356N或一种INA111面包板。这些pH计的全部费用通常是低于25 $包括围绕每个一次性pH值的IrO $ 1 2 -RGO-SPE的成本计算（不包括成本和时间进行化学制备和电化学沉积）。 图1C示出了电路图和连接用2 LF356N或者一个INA111。整个的概略根据INA111的连接销装置示于图1D。两个9伏电池被用于创建+/- 9 V双电源通过连接到10MΩ输入引脚2和3 1/4-W 4波段增益电阻（R G）的运算放大器供电（5％容限）被连接管脚1和8之间，从而导致所期望的增益（G）接近1，如从等式（1）计算。由于万用表的比较低的内部电阻，足够大的负载电阻接地并连接短路销5和6，其进一步连接万用表的阴性和阳性探针稳定OCP读数之间。其结果，可以从公式来计算输出电压（2）正好等于的IrO 2 -RGO工作电极和Ag / AgCl参比电极之间的电位差，对应于所述溶液的pH值。 <img alt="式（1）" src="/files/ftp_upload/53339/53339eq1.jpg" />其中G是GINA111的AIN，V 输出是传感器输出（V），和在 V +和V - 分别是在非反相运算放大器的反相输入的电压和。 表面形貌 图2A扫描电子显微镜（SEM）图像示出了具有柔性和超薄的石墨烯片通过粗丝网印刷碳电极表面铺展构成的典型皱纹理形成间歇RGO膜的表面形态。该GO降低发生于势比-0.65 V的详细负，并且迅速的，不可逆转的，可控的，而不会降低试剂7。的IrO 2的沉积之后，将黑色RGO膜目视和特别是变成暗紫色，示出阳极电沉积的IrO 2的特性的电致变色功能。的IrO 2 -RGO纳米杂化物薄膜（ 图2C）在微米范围第ickness与在整个表面上均匀地分散的纳米级微晶观察。这部电影似乎是均匀光滑，没有任何明显的裂纹或泥结构。此外，在目前的研究中一个有趣的发现是，的IrO 2膜不能在丝网印刷的石墨碳底物形成没有RGO的相同的条件下（ 图2B）下的援助。也是良好的成膜石墨烯的能力被设想在薄膜沉积过程中的关键部件。在沉积溶液中的草酸盐可以触发复合物的形成，防止在碱性介质中铱沉淀。的沉积是通过oxalated铱（IV）与CO 2的释放和在阳极表面伴随铱（Ⅳ）氧化物形成的化合物的阳极氧化来实现，如由山8,9描述 [IR（COO）2（OH）4] 2-⇔的IrO 2 + 2CO 2 + 2H 2 O + 2e的̵1; pH测量性能 在pH值感测金属氧化物的一般机制已经由雾和巴克与OH基团承载表面10内的离子交换过程相关指示。不同的IrO 2系在自然界由于在它们的合成机制的差异存在电极。一些可能的机制，提出涉及铱氧化物11的两个氧化态之间的pH依赖性的氧化还原嵌入平衡。作为在电化学合成铱氧化物的情况下，主要的状态是水合形式8可提供具有比在59毫伏/ pH值的无水形式优异的灵敏度的超能斯特响应。该机制可以使用下面的公式8,9进行说明: 2 [2的IrO（OH）2·2H 2 O）] 2- + 3H + + 2E - ⇔2 [的IrO2（OH）2·2H 2 O）] 2- + 3H 2 O 如图3A（黑色）中所示，的IrO 2 -RGO电极显示出在宽pH范围内发挥良好定义的线性特性的2至12，与-61.71毫伏/ pH值的轻微超能斯特斜率更靠近阳极电沉积的IrO 2片近乎Nerstian反应11,12，而不是那些超级斯特13,14。可能发生这种情况是由于不同电沉积条件和基板在每种情况下。可能的是在阳极电沉积期间形成在石墨烯的无水和水合的IrO 2膜的混合物。间纹纸微流体装置（ 图3A，红色）和散装液pH测量的微不足道的差异表明纤维状纤维素纸基体不妨碍氢离子扩散到任何明显的程度。溶解ð大气中的氧，由于其氧化还原过程遍在样品有时可以极大地影响潜在读数存在，特别是在生物系统12。当电极被放置在N 2 -或空气饱和的缓冲溶液中，只有轻微的差异（ 图3B）。同时，由于离子强度和组合物视缓冲器是不同的，一些pH缓冲剂进行了测试，包括商业pH校正缓冲器，BR缓冲液，磷酸盐缓冲盐水（PBS）和NaOH / HCl调节DI水（ 图3C）。灵敏度（每单位pH值毫伏）是在所有的缓冲区几乎相同。然而，在具有相对窄的pH范围内的PBS缓冲液中观察到一个明显的电位漂移。这可以归因于在PBS中的IrO 2 -RGO pH电极的不同条件的标准电位（E 0&#39;在能斯特方程的平衡术语）。 响应时间，一个键F在任何遥感应用的演员，通常被定义为需要达到平衡OCP的一定比例的时间。典型的响应时间是所有pH值下，在不到250秒，但可能是强烈的pH依赖型11。滞后，或所谓的记忆效应，是公知的现象，在同一电极的重复使用玻璃和金属氧化物的pH电极。氢离子选择性电极的这种现象被认为是延迟的响应于pH变化的结果。税务条例2 -RGO pH电极在pH缓冲液进行了测试从低到高，依次从高分到低分。 pH值2-12-2和12-2-12的这个循环周期通过在周期（ 图4B）依次测量不同pH缓冲液的OCP评估。滞后宽度计算为大约13毫伏在两个周期，这是在常规pH测量可接受和准确，特别是关于在这里所研究的很宽的pH范围内。 为了进一步VAlidate所述的IrO 2 -RGO纳米杂化物薄膜pH传感器，表现在平行进行试验以用pH / mV的/离子/电导率仪（ 图5A）的标准玻璃电极。结果相关性良好对方，这表明发达的pH传感器的精度高，性能可靠。要真正实现现场pH测量特色的便携式电纸微流体装置，两个简单的数字pH计，用配置稍有不同建造。使用这两种米计算pH值与基于实验室的电化学分析仪高度一致。再现性，用在不同pH的BR缓冲液相同的电极测试多次，并且还与不同的电极。相对标准偏差（RSD）的值是典型的全部&lt;15％。 总之，快速，可控，绿色电化学方法是一致的合成和流畅的IrO 2 -RGO纳米杂化薄膜Ø开发ñ粗糙SPE表面，经RGO的良好的成膜性和配套能力协助。将所得的固态电极表现出与-62毫伏/ pH和以良好的线性在从2至12的电极的宽的pH范围的高灵敏度的略微超能斯特响应也有小的滞后，响应时间快，重现，并与商用玻璃电极配备基于实验室的pH计好协议。小型化的纸垫微被PDMS疏水屏障图案制成。一个简单的pH计使用两种9伏碱性电池，数字万用表，和运算放大器制造。测量的pH的结果，从使用基于实验室的技术获得的那些良好相关的传感器。因此，它结合了pH计和pH条优势传感器是未来在现场或点护理pH测量一个有前途的平台，尤其是在有限的资源情况。

pH值的测定是在食品，生理，药用和环境研究中无处不在。用于pH检测两种最常用的工具是pH值条和pH计。纸条浸渍有变色的pH指示剂分子，但读数在pH范围，主观和半定量的一些偏差，有时受到限制。另一方面，pH计通常配有玻璃电极可以通过数字用户界面准确到0.01的水平，并显示测量的pH值。基于实验室的pH计不仅需要特别注意维护和校准，也不用对小体积样品很好地工作，往往需要一个干净的容器，如执行测量烧杯中。尽管它的灵敏度，选择性和稳定性的，玻璃电极从酸/碱误差，高阻抗，温度不稳定和机械脆性1受损。因此，这是有利的具有embod的pH测量系统IES pH计和pH条的简易性和成本方面的准确性。 总是有许多发展中地区，其中昂贵的实验室设备或商业实验室是负担不起的未满足的需要对有限资源的条件下，这样的工具。此外，新的易于使用，对现场检测平台的作用越来越被用于点护理检测这样的需求推动。电化学检测是简单，容易小型化和令人满意敏感，在市场上商业化的低成本SPE和各种血糖监测系统作为证明。作为光，灵活和一次性的多孔材料，纸也可具有各种可控的特征，如不同的孔尺寸，官能团，和芯吸速率。 作为纸基材几乎影响分析物扩散和电化学检测2-4，纸流体装置和电分析技术的组合具有recentlŸ受到了广泛的利益。这样的组合的表观优点是样品体积的在其中可以潜在防止在测量过程中的振动和对流的干扰测量中使用的微小量。例如，图案化的微流体垫被施加到芯吸和提供液体样品到SPE的传感区域检测重金属离子和葡萄糖2,5。建立使用纸微流体电化学发光类似的设备来完成检测NADH 4。最近，简单的电化学纸微流体装置可在载玻片上建立与铅笔电极6或使用酶纸张与SPE 3。 使用简便，高效的电化学方法制备的IrO 2和RGO组成的纳米杂化薄膜材料。我们发现，不规则和粗SPE石墨碳表面上，阳极电沉积的IrO 2薄膜不能平滑，稳定，没有RGO的帮助。所得的IrO 2 -RGO SPE被整合到已图案化用于pH传感疏水屏障纸微流体装置。该组装的装置显示，pH值传感出色的分析性能有略微超能斯特行为。结果是可比的常规基于实验室的pH计用玻璃电极。最后，高性价比的小型化pH计是建立在面包板与数字万用表测量开路电位输出信号。便携式pH计的测定良好相关与这些商业实验室pH计的。

<table>
	<tbody>
		<tr>
			<td>Screen-printed electrodes</td>
			<td>Zensor</td>
			<td>TE100</td>
			<td>3-electrode integrated</td>
		</tr>
		<tr>
			<td>acrylonitrile butadiene styrene (ABS)&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Polydimethylsiloxane (PDMS) prepolymer and cross linker mixture</td>
			<td>Dow-Corning Co.</td>
			<td>Sylgard 184</td>
			<td>10:1 mixture w/w</td>
		</tr>
		<tr>
			<td>Whatman No. 1 filter paper</td>
			<td>GE Healthcare co.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;3D milling system</td>
			<td>Roland DGA Co.</td>
			<td>iModela IM-01</td>
			<td></td>
		</tr>
		<tr>
			<td>PDMS stamp and vacuum cover</td>
			<td>Roland DGA co.</td>
			<td>Sanmodur</td>
			<td>Synthetic resin tablet</td>
		</tr>
		<tr>
			<td>hand-operated vacuum pump</td>
			<td>Cole-Parmer co.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Electrochemical workstation</td>
			<td>CH Instruments</td>
			<td>CHI 660D</td>
			<td></td>
		</tr>
		<tr>
			<td>LF356N operational amplifiers</td>
			<td>Texas Instruments Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;INA111 high speed field-effect transistor (FET)-input instrumentation amplifier</td>
			<td>Burr-Brown Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DMM914 digital multimeter&#160;</td>
			<td>Tektronix Inc.</td>
			<td>70979101</td>
			<td></td>
		</tr>
		<tr>
			<td>From Fisher or Sigma:</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;iridium tetrachloride (IrCl4)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>50% (w/w) hydrogen peroxide (H2O2)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>oxalic acid dihydrate</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>potassium carbonate (K2CO3)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>phosphoric acid</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>acetic acid&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>boric acid</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>sodium hydroxide (NaOH)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Na2HPO4</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

iridium oxide-reduced graphene oxide nanohybrid thin film modified screen-printed electrodes as disposable electrochemical paper microfluidic ph sensors

2的IrO -graphene纳米杂化薄膜的一种简便，可控，价格低廉，绿色电化学合成开发制造一个易于使用的集成微纸电化学pH值资源有限的环境传感器。以优势来自pH计和试纸，pH值检测平台由使用聚二甲基硅氧烷（PDMS）疏水屏障图案纸micropad（μPAD）中，丝网印刷电极（SPE）改性的IrO 2 -graphene薄膜和模塑丙烯腈-丁二烯-苯乙烯（ABS）的塑料保持器。重复阴极电位自行车被用于氧化石墨烯（GO）减少其可以完全具有优良的稳定性和电子属性中删除电化学不稳定含氧组，并生成一个二维无缺陷的均匀的石墨烯薄膜。在纳米颗粒大小均匀，光滑的IrO 2膜阳极电沉积石墨烯薄膜，没有任何观察的裂缝。所得的IrO 2 -RGO电极中的BR（BR），具有良好的线性，迟滞小，低响应时间和再现在不同的缓冲器，以及低敏感性不同干涉缓冲器表明在pH 2-12略微超能斯特响应离子物质和溶解的氧。一个简单的便携式数字pH计是捏造，是用万用表测量其信号，使用高输入阻抗运算放大器和消费电池。与便携式电化学纸微流体pH传感器测得的pH值下分别为与使用商业实验室pH计用玻璃电极测定一致。

电化学的IrO 2 -RGO-SPE pH传感器结合纸微流控的设置显示在图1A。与PDMS疏水屏障的构图纸垫被放置在其上位于ABS塑料支架的IrO 2 -RGO-SPE的敏感区域的顶部。纸垫的感应区进行了仔细的与电极表面对齐。水性亚甲蓝染料溶液用来测试图案化纸垫和所观察到的，将样品灯芯到亲水性区域（ 图1B）与由疏水屏障调节的流体路径。 SEM图像示出了由电化学还原技术地层2D无缺陷的均一的石墨烯薄膜，并且也均匀光滑的IrO 2膜的无无可观察到的裂纹通过电沉积一个合成（ 图2A和C）。由此产生的IrO 2 -RGO电极呈小幅SUP从pH值2-12的BR（BR），在两者的本体溶液和纸（ 图3A）良好的线性缓冲器ER-能斯特响应，小的滞后宽度（ 图4B）和低敏感性溶解氧（ 图3B）。与便携式电化学纸微流体pH传感器测得的pH值下分别为用玻璃电极（ 图5A）商业实验室pH计一致。 <img alt="图1" src="/files/ftp_upload/53339/53339fig1.jpg" /> 图1:（A）设置为电纸微流体pH值敏感的示意图:（1）2的IrO -RGO-SPE，（2）采样和检测微垫纸，（3）ABS塑料支架框的SPE。 （B）在染料溶液邪恶微流体纸垫的照片:（1）亲水采样区域为芯吸（2）巴氏呃样品交货（3）感测区中的SPE微流体通道（4）由PDMS构图（5）区域的疏水性障碍保持设备。 （C）的具有内置于面包板不同的电路的两个便携式pH值测量装置（详细电路示于补充信息）:一个万用表（1）工作电极（2）的参考电极（3）的正探针（4）阴性探针（5）电池正极（6）阳极（7）蓄电池接地（8）10MΩ增益电阻（9）10MΩ负载电阻（10）接地。 （D）与INA111的IrO和2 -RGO-SPE内置便携式电纸流体pH传感器的连接图。 （ 五 ）使用便携式电纸微流体装置pH值用在不同pH值LF365N集成电路开路电位典型的数字读数。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53339/53339fig1large.jpg" target="_blank">请点击此处查看这个大版本</a>数字。 <img alt="图2" src="/files/ftp_upload/53339/53339fig2.jpg" /> 图2:SEM图像（A）RGO（B）的IrO 2和（C）RGO-2的IrO修饰的SPE。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53339/53339fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/53339/53339fig3.jpg" /> 图3:在BR缓冲的本体溶液或使用与空气或N 2在不同缓冲体系（C）的饱和的BR缓冲液的微流体纸（B）的RGO-的IrO 2的SPE在不同pH的pH值的反应 （A）中<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53339/53339fig3large.jpg" target="_blank">，请这里查看</a>更大的版本这个数字。 <img alt="图4" src="/files/ftp_upload/53339/53339fig4.jpg" /> 图4:（A）在BR缓冲液pH 4,8和10 RGO-2的IrO SPE的潜力-时间曲线。 （B）RGO-税务条例滞后宽度2特殊目的实体在不同pH值的2-12-2和12-2-12循环周期BR缓冲。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53339/53339fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图5" src="/files/ftp_upload/53339/53339fig5.jpg" /> 图5:RGO- 的IrO 2的SPE中在不同pH BR缓冲的pH值的反应 （A）和一个标准商业pH计用玻璃电极（B）的相关性通过不同dev的测量值的比较。冰。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53339/53339fig5large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about Iridium Oxide-reduced Graphene Oxide Nanohybrid Thin Film Modified Screen-printed Electrodes as Disposable Electrochemical Paper Microfluidic pH Sensors at Jo

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

这项研究表明铱-氧化还原的石墨烯氧化物的（的IrO 2 -RGO）生长纳米杂化物通过一个绿色电化学合成不规则和粗丝网印刷碳基板上的薄膜，其作为pH传感器实现具有图案化纸流体平台。

氧化铱还原氧化石墨烯纳米杂化薄膜修饰丝网印刷电极一次性电化学微流控纸pH传感器

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

iridium-oxide-reduced-graphene-oxide-nanohybrid-thin-film-modified

Nanyang Technological University

Research

JoVE Journal

Engineering

10.5K 次观看.  University of Wisconsin-Madison. 这项研究表明铱-氧化还原的石墨烯氧化物的（的IrO 2 -RGO）生长纳米杂化物通过一个绿色电化学合成不规则和粗丝网印刷碳基板上的薄膜，其作为pH传感器实现具有图案化纸流体平台。 

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

Polycrystalline Silicon Thin-film Solar cells with Plasmonic-enhanced Light-trapping

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To compensate for lower light absorption such physically thin devices have to incorporate light-trapping which increases their optical thickness. Light scattering by textured surfaces is a common technique but it cannot be universally applied to all solar cell technologies. Some cells, for example those made of evaporated silicon, are planar as produced and they require an alternative light-trapping means suitable for planar devices. Metal nanoparticles formed on planar silicon cell surface and capable of light scattering due to surface plasmon resonance is an effective approach.
The paper presents a fabrication procedure of evaporated polycrystalline silicon solar cells with plasmonic light-trapping and demonstrates how the cell quantum efficiency improves due to presence of metal nanoparticles.
To fabricate the cells a film consisting of alternative boron and phosphorous doped silicon layers is deposited on glass substrate by electron beam evaporation. An Initially amorphous film is crystallised and electronic defects are mitigated by annealing and hydrogen passivation. Metal grid contacts are applied to the layers of opposite polarity to extract electricity generated by the cell. Typically, such a ~2 &mu;m thick cell has a short-circuit current density (Jsc) of 14-16 mA/cm2, which can be increased up to 17-18 mA/cm2 (~25% higher) after application of a simple diffuse back reflector made of a white paint.
To implement plasmonic light-trapping a silver nanoparticle array is formed on the metallised cell silicon surface. A precursor silver film is deposited on the cell by thermal evaporation and annealed at 23&deg;C to form silver nanoparticles. Nanoparticle size and coverage, which affect plasmonic light-scattering, can be tuned for enhanced cell performance by varying the precursor film thickness and its annealing conditions. An optimised nanoparticle array alone results in cell Jsc enhancement of about 28%, similar to the effect of the diffuse reflector. The photocurrent can be further increased by coating the nanoparticles by a low refractive index dielectric, like MgF2, and applying the diffused reflector. The complete plasmonic cell structure comprises the polycrystalline silicon film, a silver nanoparticle array, a layer of MgF2, and a diffuse reflector. The Jsc for such cell is 21-23 mA/cm2, up to 45% higher than Jsc of the original cell without light-trapping or ~25% higher than Jsc for the cell with the diffuse reflector only.
Introduction
Light-trapping in silicon solar cells is commonly achieved via light scattering at textured interfaces. Scattered light travels through a cell at oblique angles for a longer distance and when such angles exceed the critical angle at the cell interfaces the light is permanently trapped in the cell by total internal reflection (Animation 1: Light-trapping). Although this scheme works well for most solar cells, there are developing technologies where ultra-thin Si layers are produced planar (e.g. layer-transfer technologies and epitaxial c-Si layers) 1 and or when such layers are not compatible with textures substrates (e.g. evaporated silicon) 2. For such originally planar Si layer alternative light trapping approaches, such as diffuse white paint reflector 3, silicon plasma texturing 4 or high refractive index nanoparticle reflector 5 have been suggested.
Metal nanoparticles can effectively scatter incident light into a higher refractive index material, like silicon, due to the surface plasmon resonance effect 6. They also can be easily formed on the planar silicon cell surface thus offering a light-trapping approach alternative to texturing. For a nanoparticle located at the air-silicon interface the scattered light fraction coupled into silicon exceeds 95% and a large faction of that light is scattered at angles above critical providing nearly ideal light-trapping condition (Animation 2: Plasmons on NP). The resonance can be tuned to the wavelength region, which is most important for a particular cell material and design, by varying the nanoparticle average size, surface coverage and local dielectric environment 6,7. Theoretical design principles of plasmonic nanoparticle solar cells have been suggested 8. In practice, Ag nanoparticle array is an ideal light-trapping partner for poly-Si thin-film solar cells because most of these design principle are naturally met. The simplest way of forming nanoparticles by thermal annealing of a thin precursor Ag film results in a random array with a relatively wide size and shape distribution, which is particularly suitable for light-trapping because such an array has a wide resonance peak, covering the wavelength range of 700-900 nm, important for poly-Si solar cell performance. The nanoparticle array can only be located on the rear poly-Si cell surface thus avoiding destructive interference between incident and scattered light which occurs for front-located nanoparticles 9. Moreover, poly-Si thin-film cells do not requires a passivating layer and the flat base-shaped nanoparticles (that naturally result from thermal annealing of a metal film) can be directly placed on silicon further increases plasmonic scattering efficiency due to surface plasmon-polariton resonance 10.
The cell with the plasmonic nanoparticle array as described above can have a photocurrent about 28% higher than the original cell. However, the array still transmits a significant amount of light which escapes through the rear of the cell and does not contribute into the current. This loss can be mitigated by adding a rear reflector to allow catching transmitted light and re-directing it back to the cell. Providing sufficient distance between the reflector and the nanoparticles (a few hundred nanometers) the reflected light will then experience one more plasmonic scattering event while passing through the nanoparticle array on re-entering the cell and the reflector itself can be made diffuse - both effects further facilitating light scattering and hence light-trapping. Importantly, the Ag nanoparticles have to be encapsulated with an inert and low refractive index dielectric, like MgF2 or SiO2, from the rear reflector to avoid mechanical and chemical damage 7. Low refractive index for this cladding layer is required to maintain a high coupling fraction into silicon and larger scattering angles, which are ensured by the high optical contrast between the media on both sides of the nanoparticle, silicon and dielectric 6. The photocurrent of the plasmonic cell with the diffuse rear reflector can be up to 45% higher than the current of the original cell or up to 25% higher than the current of an equivalent cell with the diffuse reflector only.

Polycrystalline silicon thin-film solar cells on glass are fabricated by deposition of boron and phosphorous doped silicon layers followed by crystallisation, defect passivation and metallisation. Plasmonic light-trapping is introduced by forming Ag nanoparticles on the silicon cell surface capped with a diffused reflector resulting in ~45% photocurrent enhancement.

多晶硅薄膜太阳能电池电浆增强光捕获

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To ...

科研

工程学

Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding combined with layer transfer enables the replication of arbitrary surface patterns from a master structure onto the functional material. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes. In particular we demonstrate the fabrication of patterned transparent zinc oxide electrodes for light trapping applications in solar cells.

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes.

Nanomoulding功能材料，灵活的互补模式的复制方法，以奈米

We describe a nanomoulding technique which  allows low-cost nanoscale patterning of functional materials, materials stacks  and full devices. Nanomoulding ...

Picoinjection of Microfluidic Drops Without Metal Electrodes

Existing methods for picoinjecting reagents into microfluidic drops require metal electrodes integrated into the microfluidic chip. The integration of these electrodes adds cumbersome and error-prone steps to the device fabrication process. We have developed a technique that obviates the needs for metal electrodes during picoinjection. Instead, it uses the injection fluid itself as an electrode, since most biological reagents contain dissolved electrolytes and are conductive. By eliminating the electrodes, we reduce device fabrication time and complexity, and make the devices more robust. In addition, with our approach, the injection volume depends on the voltage applied to the picoinjection solution; this allows us to rapidly adjust the volume injected by modulating the applied voltage. We demonstrate that our technique is compatible with reagents incorporating common biological compounds, including buffers, enzymes, and nucleic acids.

We have developed a technique for picoinjecting microfluidic drops that does not require metal electrodes. As such, devices incorporating our technique are simpler to fabricate and to use.

微流控的Picoinjection滴无金属电极

Existing methods for picoinjecting reagents into microfluidic drops require metal electrodes integrated into the microfluidic chip. The integration of ...

Visible-light Induced Reduction of Graphene Oxide Using Plasmonic Nanoparticle

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using visible light irradiation with plasmonic nanoparticles. The plasmonic nanoparticle is used to improve the reduction efficiency of GO. It only takes 30 min&#160;at RT by illuminating the solutions with Xe-lamp, the r-GO solutions can be obtained by completely removing gold nanoparticles through simple centrifugation step. The spherical gold nanoparticles (AuNPs) as compared to the other nanostructures is the most suitable plasmonic nanostructure for r-GO preparation. The reduced graphene oxide prepared using visible light and AuNPs was equally qualitative as chemically reduced graphene oxide, which was supported by various analytical techniques such as UV-Vis spectroscopy, Raman spectroscopy, powder XRD and XPS. The reduced graphene oxide prepared with visible light shows excellent quenching properties over the fluorescent molecules modified on ssDNA and excellent fluorescence recovery for target DNA detection. The r-GO prepared by recycled AuNPs is found to be of same quality with that of chemically reduced r-GO. The use of visible light with plasmonic nanoparticle demonstrates the good alternative method for r-GO synthesis.

A simple protocol for the preparation of reduced graphene oxide using visible light and plasmonic nanoparticle is described.

可见光诱导的还原氧化石墨烯的使用电浆纳米粒子

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using ...

Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

合成和3D纳米石墨烯材料的功能化:石墨烯气凝胶和石墨烯宏组件

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. ...

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.

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

纳米银沸石复合材料作为基于发光的湿度传感器

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

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

通过时间分辨微波电导率重组动力学薄膜光伏材料

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for Cu(In,Ga)Se2 Solar Cells

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction of degradation mechanisms and prevention of module field failure can consequently decrease investment risks as well as increase the electricity yield. An improved knowledge level can for these reasons significantly decrease the total costs of PV electricity. 
In order to better understand and minimize the degradation of PV modules, the occurring degradation mechanisms and conditions should be identified. This should preferably happen under combined stresses, since modules in the field are also simultaneously exposed to multiple stress factors. Therefore, two 'Combined Stress test with in situ measurement' setups have been designed and constructed. These setups allow the simultaneous use of humidity, temperature, illumination, and electrical biases as independently controlled stress factors on solar cells and minimodules. The setups also allow real-time monitoring of the electrical properties of these samples. This protocol presents these setups and describes the experimental possibilities. Moreover, results obtained with these setups are also presented: various examples about the influence of both deposition and degradation conditions on the stability of thin film Cu(In,Ga)Se2 (CIGS) as well as Cu2ZnSnSe4 (CZTS) solar cells are described. Results on the temperature dependency of CIGS solar cells are also presented.

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for CuIn,GaSe2 Solar Cells

Two &#39;Combined Stress test with in situ measurement&#39; setups, which allow real-time monitoring of accelerated degradation of solar cells and modules, were designed and constructed. These setups allow the simultaneous use of humidity, temperature, electrical biases, and illumination as independently controlled stress factors. The setups and various experiments executed are presented.

就地太阳能电池和模块加速性能退化的监测: 铜 (in, Ga) Se2太阳能电池的实例研究

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction ...

Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.

The synthesis of high quality bulk and thin film (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O entropy-stabilized oxides is presented.

组分变熵稳定氧化物的体积和薄膜合成

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and ...

Film Control to Study Contributions of Waves to Droplet Impact Dynamics on Thin Flowing Liquid Films

Droplet impact is a very common phenomenon in nature and attracts attention due to its aesthetic fascination and wide-ranging applications. Previous studies on flowing liquid films have neglected the contributions of spatial structures of waves to the impact outcome, while this has recently been shown to have a significant influence on the drop impact dynamics. In this report, we outline a step-by-step procedure to investigate the effect of periodic inlet forcing of a flowing liquid film leading to the production of spatiotemporally regular wave structures on drop impact dynamics. A function generator in connection with a solenoid valve is used to excite these spatiotemporally regular wave structures on the film surface while the impact dynamics of uniform-sized droplets are captured using a high-speed camera. Three distinct regions are then studied; viz. the capillary wave region preceding the large wave peak, the flat film region, and the wave hump region. The effects of important dimensionless quantities such as film Reynolds, drop Weber and Ohnesorge numbers parameterized by the film flow rate, drop speed, and drop size are also examined. Our results show interesting, hitherto undiscovered dynamics brought about by this application of film inlet forcing of the flowing film for both low and high inertia drops.

A protocol to study the contributions of waves to droplet impact dynamics on flowing liquid films is presented.

薄膜控制研究波浪对液滴冲击动力学的影响薄流动液体薄膜

Droplet impact is a very common phenomenon in nature and attracts attention due to its aesthetic fascination and wide-ranging applications. Previous ...