Correction: Liang et al. Highly Sensitive Hydrogen Sensing Based on Tunable Diode Laser Absorption Spectroscopy with a 2.1 μm Diode Laser. Chemosensors 2022, 10, 321

Missing Citation and Citation Revision

In the original publication [1], Avetisov, V.; Bjoroey, O.; Wang, J.; Geiser, P.; Paulsen, K.G. Hydrogen sensor based on tunable diode laser absorption spectroscopy. Sensors 2019, 19, 5313. was not cited. The citation has now been inserted in the third paragraph of 1. Introduction as Ref. [41] and a sentence is added for this new citation In the year of 2019, a TDLAS based H₂ sensing was performed, and a precision of 0.02 %v was achieved with 1 m of absorption pathlength and 1 s of integration time. Therefore, the third paragraph is modified as: …… The TDLAS technique is widely applied in the detection of various kinds of gases [38,39,40] because of the advantages of non-contact measurement, in situ detection, high selectivity, quick response, low cost, and multi-component, multi-parameter measurement. In the year of 2019, a TDLAS based H₂ sensing was performed, and a precision of 0.02 %v was achieved with 1 m of absorption pathlength and 1 s of integration time [41].

Furthermore, some revisions for the reference in this third paragraph have also been made for a more precise citation. The original Refs. [23,24,28,30,35,36] are replaced by the new one. The original Ref. [41] is deleted.

In the Section 2.4. the first paragraph of 2.4 The Selection of Multipass Gas Cell, the citation is modified due to the above revisions. The original is The line strength of the strongest absorption line of H₂ (10⁻²⁶) is still much weaker than other gases (~10⁻²¹) [38–41]. The revised is The line strength of the strongest absorption line of H₂ (10⁻²⁶) is still much weaker than other gases (~10⁻²¹) [38–40].

Equation Correction

The original Equations (1) and (3) are

$$I=I_{0}exp\left[\alpha \left(\nu \right)L\right]$$

(1)

$$\alpha \left(\nu \right)=-PS\left(T\right)\phi \left(\nu \right)C$$

(3)

The negative sign in Equation (1) was missed, and this sign in Equation (3) was redundant. Therefore, the corrected are

$$I=I_{0}exp\left[-\alpha \left(\nu \right)L\right]$$

(1)

$$\alpha \left(\nu \right)=PS\left(T\right)\phi \left(\nu \right)C$$

(3)

Figure Legend

In the original publication, there was a mistake in the legend for Figures 5 and 8. The value for the x-axis should start from 4712.79 cm⁻¹ and end in 4712.98 cm⁻¹. The corrected Figure 5 and Figure 8 appears below. The authors state that the scientific conclusions are unaffected (The correct value for the line peak has already been mentioned in the text many times).

References Correction

• 23. Zifarelli, A.; De Palo, R.; Patimisco, P.; Giglio, M.; Sampaolo, A.; Blaser, S.; Butet, J.; Landry, O.; Müller, A.; Spagnolo, V. Multi-gas quartz-enhanced photoacoustic sensor for environmental monitoring exploiting a Vernier effect-based quantum cascade laser. Photoacoustics 2022, 28, 100401.
• 24. Dello Russo, S.; Zifarelli, A.; Patimisco, P.; Sampaolo, A.; Wei, T.T.; Wu, H.P.; Dong, L.; Spagnolo, V. Light-induced thermo-elastic effect in quartz tuning forks exploited as a photodetector in gas absorption spectroscopy. Opt. Express 2020, 28, 19074–19084.
• 28. Wang, Z.; Wang, Q.; Zhang, H.; Borri, S.; Galli, I.; Sampaolo, A.; Patimisco, P.; Spagnolo, V.L.; De Natale, P.; Ren, W. Doubly resonant sub-ppt photoacoustic gas detection with eight decades dynamic range. Photoacoustics 2022, 27, 100387.
• 30. Sgobba, F.; Sampaolo, A.; Patimisco, P.; Giglio, M.; Menduni, G.; Ranieri, A.C.; Hoelzl, C.; Rossmadl, H.; Brehm, C.; Mackowiak, V.; et al. Compact and portable quartz-enhanced photoacoustic spectroscopy sensor for carbon monoxide environmental monitoring in urban areas. Photoacoustics 2022, 25, 100318.
• 35. Hu, L.E.; Zheng, C.T.; Zhang, M.H.; Zheng, K.Y.; Zheng, J.; Song, Z.W.; Li, X.Y.; Zhang, Y.; Wang, Y.D.; Tittel, F.K. Long-distance in-situ methane detection using near-infrared light-induced thermo-elastic spectroscopy. Photoacoustics 2021, 21, 100230.
• 36. Zhang, Q.D.; Chang, J.; Cong, Z.H.; Wang, Z.L. Application of quartz tuning fork in photodetector based on photothermal effect. IEEE Photonics Technol. Lett. 2019, 31, 1592–1595.
• 38. Craig, I.M.; Taubman, M.S.; Bernacki, B.E.; Stahl, R.D.; Schiffern, J.T.; Myers, T.L.; Cannon, B.D.; Phillips, M.C. Tunable Diode Laser Absorption Spectrometer for detection of hydrogen fluoride gas at ambient pressure. In Proceedings of the Conference on Lasers and Electro-Optics (CLEO), CA, USA, 8–13 June 2014.
• 39. Dong, L.; Tittel, F.K.; Li, C.G.; Sanchez, N.P.; Wu, H.P.; Zheng, C.T.; Yu, Y.J.; Sampaolo, A.; Griffin, R.J. Compact TDLAS based sensor design using interband cascade lasers for mid-IR trace gas sensing. Opt. Express 2016, 24, A528–A535.
• 40. Zhou, X.; Yu, J.; Wang, L.; Gao, Q.; Zhang, Z.G. Sensitive detection of oxygen using a diffused integrating cavity as a gas absorption cell. Sens. Actuator B-Chem. 2017, 241, 1076–1081.
• 41. Avetisov, V.; Bjoroey, O.; Wang, J.; Geiser, P.; Paulsen, K.G. Hydrogen sensor based on tunable diode laser absorption spectroscopy. Sensors 2019, 19, 5313.

The authors apologize for any inconvenience caused and state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated.