p-Nitroanisole/Pyridine and p-Nitroacetophenone/Pyridine Actinometers Revisited: Quantum Yield in Comparison to Ferrioxalate

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• 作者：Juliana R. Laszakovits ; Stephanie M. Berg ; Brady G. Anderson ; Jessie E. O’Brien ; Kristine H. Wammer ; Charles M. Sharpless
• 刊名：Environmental Science & Technology Letters
• 出版年：2017
• 出版时间：January 10, 2017
• 年：2017
• 卷：4
• 期：1
• 页码：11-14
• 全文大小：277K

文摘

Chemical actinometry is often used to measure irradiance in environmental photochemistry. Two widely adopted actinometers are p-nitroanisole/pyridine (PNA-pyr) and the related but less popular p-nitroacetophenone/pyridine (PNAP-pyr). We report that PNA-pyr predicts systematically lower (−29%) photon irradiance than the well-characterized ferrioxalate actinometer. Thus, quantum yields previously determined using PNA-pyr should be correspondingly lower. Experiments at various pyridine concentrations produced an updated equation for the pyridine (pyr) dependence of the PNA-pyr quantum yield: Φ = 0.29[pyr] + 0.00029. Additionally, we present a standard molar absorption spectrum of PNA for future use. A comparison between PNA-pyr and PNAP-pyr suggests the previously reported PNAP-pyr quantum yield is also too high. Preliminary results suggest a suitable equation for the PNAP-pyr system: Φ = 7.4 × 10p>–3p>[pyr] + 1.1 × 10p>–5p>.