We present experimental results of fluctuation-enhanced gas sensing by low-cost resistive sensors made of a mixture of graphene flakes and TiO₂ nanoparticles. Both components are photocatalytic and activated by UV light. Two UV LEDs of different wavelengths (362 and 394 nm) were applied to modulate the gas sensing of the layers. Resistance noise was recorded at low frequencies, between 8 Hz and 10 kHz. The sensors’ response was observed in an ambient atmosphere of synthetic air and toxic NO₂ at selected concentrations (5, 10, and 15 ppm). We observed that flicker noise changed its frequency dependence at different UV light wavelengths, thereby providing additional information about the ambient atmosphere. The power spectral density changed by a few times as a result of UV light irradiation. The sensors were operated at 60 and 120°C, and the effect of UV light on gas sensing was most apparent at low operating temperature. We conclude that UV light activates the gas-sensing layer and improves gas detection at low concentrations of NO₂. This result is desirable for the detection of the components of gas mixtures, and the modulated sensor can replace an array of independent resistive sensors which would consume much more energy for heating. We also suggest that a more advanced technology for preparing the gas-sensing layer, by use of spin coating, will produce corresponding layers with thickness of about a few μm, which is about ten times less than that for the tested samples. The effects induced by the applied UV light, having a penetration depth of only a few μm, would then be amplified.

中文翻译：

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石墨烯鳞片/ TiO2纳米颗粒层对紫外线调制的波动增强的气体传感

我们介绍了由石墨烯薄片和TiO ₂纳米颗粒的混合物制成的低成本电阻式传感器的气体增强波动的实验结果。两种组分都是光催化的，并被紫外线激活。应用两个不同波长（362和394 nm）的UV LED来调制各层的气体感应。在8 Hz至10 kHz的低频下记录电阻噪声。在合成空气和有毒NO ₂的环境中观察到传感器的响应在选定的浓度（5、10和15 ppm）下。我们观察到，闪烁噪声在不同的紫外线波长下改变了其频率依赖性，从而提供了有关环境大气的其他信息。由于紫外线的照射，功率谱密度变化了几次。传感器在60和120°C的温度下工作，在低工作温度下，紫外线对气体传感的影响最为明显。我们的结论是，紫外线在低浓度的NO _2时会激活气体感应层并改善气体检测。该结果对于检测气体混合物的成分是理想的，并且调制传感器可以代替独立的电阻式传感器阵列，该阵列将消耗更多的能量来加热。我们还建议，通过使用旋涂制备气敏层的更先进技术将产生相应的层，其厚度约为几微米，比被测样品的厚度小十倍。然后，由具有仅几μm的穿透深度的所施加的UV光引起的效果将被放大。