The prominent enhancing effect and mechanism of the methyl group in the X···Y (X=O, S, H₃CO, H₃CS, (H₃C)₂O, (H₃C)₂S; Y=HCN, HNC) hydrogen-bonded complex

Highly Porous Fe2o3-Sio2 Layer for Acoustic Wave Based H2s Sensing: Mass Loading or Elastic Loading Effects?

“…Electronic copy available at: https://ssrn.com/abstract=4080801 ST-cut quartz SAW resonators with the center frequency of ~201 MHz had the same structure as reported in our previous publication [9] (Fig. 1(a)).…”

“…For examples, Wang et al proposed a SnO 2 -CuO composite layer, which improved gas sensitivity of SAW H 2 S sensors due to both mass loading and electrical loading effects [16]. While our previous work based on a porous ZnO-Al 2 O 3 nanocomposite layer showed that the elastic loading effect can also play an important role in the sensing performance of SAW H 2 S sensors [9]. Thus, it is reasonable to conclude that all the three effects may have the contribution toward the response of the SAW H 2 S gas sensor, just as the results revealed by Raj et al when studying ammonia sensors [17].…”

“…Previous studies revealed that the larger volume of pores is beneficial for the diffusion of gas into the sensing layer, which helps the interactions between the layer and gas molecules [32]. While the changes of micropore volumes accounts for the change of the elastic modulus the sensing layer [9].…”

“…Surface acoustic wave (SAW) sensor has been used for H 2 S sensing due to its high sensitivity, fast response, high accuracy, low cost, real-time measurement and wireless sensing capabilities [7][8][9]. The core part of the SAW sensor is a sensitive layer deposited on a conventional SAW resonator [10,11].…”

Non-additivity between substitution and cooperative effects in enhancing hydrogen bonds

“…30 The halogenation of H 2 CS weakens the stability of hydrogen-bonded complex H 2 CS···HCN, while the substituents CH 3 and NH 2 strengthen it. 31 The methyl enhancing role was also found for HBs in H 3 N···HF 32 and X···HCN (X = O and S), 33 and when more than one methyl group is adjoined to the N and X atoms, the average contribution of each methyl group is smaller than that from one methyl group, indicating negative non-additivity of methyl groups. The electron-donating substituent Li in the electron donor is responsible for the strengthening of OH···O HB in phenol-water complex with water as the proton donor.…”