In order to extend the photoactivity of titanium dioxide into the visible region, highly porous nitrogen-doped TiO₂ catalysts (NTiO₂) were successfully synthesized by a modified co-precipitation method with ammonium hydroxide as a nitrogen source. Different approaches such as dosing order of the reagents and temperature of the synthesis, calcination period and temperature were tested to examine the optimum outcome regarding photocatalytic OH radical formation under UV and visible light. Coumarin as a traditional probe for this purpose was applied; measuring the luminescence of 7-hydroxycoumarin produced in the reaction with OH radicals, beside the formation of other hydroxylated derivatives. Only a few percentages of the coumarin molecules reacted with OH radicals, while most of them underwent reactions with other photogenerated species such as electrons (anaerobic/aerobic) and superoxide anion radicals (aerobic). Accordingly, our observations suggest that coumarin can also be used as a probe to quantify the formation of other reactive species. The results were obtained from the difference between the amounts of degraded coumarin and hydroxylated coumarin derivatives formed during photocatalytic experiments. These coumarin-based quantifications of photoactivity was applied for the characterization of the prepared nitrogen-doped TiO₂ catalysts (NTiO₂). In addition, material analysis (X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, and Fourier transform infrared spectroscopy) showed that crystallinity and nitrogen content were found to be crucial features in the photocatalytic performance of the catalysts.

为了将二氧化钛的光活性扩展到可见光区域，使用了高度多孔的氮掺杂TiO ₂催化剂（NTiO ₂通过改进的共沉淀法以氢氧化铵为氮源成功合成了）。测试了不同的方法，例如试剂的加药顺序和合成温度，煅烧时间和温度，以检查有关在紫外线和可见光下形成光催化OH自由基的最佳结果。为此使用了香豆素作为传统探针。除了形成其他羟基化衍生物以外，还测量与OH自由基反应生成的7-羟基香豆素的发光。只有少数香豆素分子与OH自由基反应，而大多数香豆素分子则与其他光生物种发生反应，例如电子（厌氧/好氧）和超氧阴离子自由基（好氧）。因此，我们的观察结果表明，香豆素还可以用作定量其他反应性物种形成的探针。从光催化实验过程中降解的香豆素和羟基化香豆素衍生物的数量之间的差异获得了结果。这些基于香豆素的光活度定量用于表征制备的氮掺杂TiO_2种催化剂（NTiO ₂）。此外，材料分析（X射线衍射，扫描电子显微镜，能量色散X射线光谱和傅里叶变换红外光谱）表明，结晶度和氮含量是催化剂光催化性能的关键特征。