The Cl Functionalized Aluminum Nitride ( AlN ) and Aluminum Phosphide ( AlP ) Nanocone Sheets as Hydrogen Selenide ( H 2 Se ) Sensor : a Density Functional Investigation

The adsorption of H2Se molecule on AlN-NCS and AlP-NCS surfaces were investigated by using of DFT calculations. The potentials of Cl-functionalized AlN-NCS and AlP-NCS for H2Se adsorption were examined. All processes of H2Se-adsorption on considered nanocone sheets were exothermic reactions. The calculated |Ead| amount of complex H2Se with AlP-NCS was higher than AlN-NCS. The functionalization of considered nanocone sheets with Cl atom increase |Ead| amount of H2Se. Results reveal that, obtained Ead amounts of considered nanocone sheets have linear relationships with corresponding orbital energy amounts. Finally, the novel nanocone sheets with higher efficiency to adsorption of H2Se can be proposed.


Introduction
Hydrogen selenide (H 2 Se) as main toxic gas can be produced via reaction of selenium and hydrogen gas and it can be formed by reaction of acids with selenide.Some paths to H 2 Se preparation in large and small scales have been investigated.][3] H 2 Se is the most toxic gases with a contact boundary of 0.05 ppm over an 8 hour cycle and H 2 Se at really low concentrations is very infuriating smell resembling that of leaking gases. 1,2[6] Aluminum nitride nanocone sheet (AlN-NCS) have been synthesized and it has wide band gap and so it has various applications in optics, electronics and photoelectronics. 7The previous studies shown that AlN-NCS and AlP-NCS were uniform and Al, P and N atoms on surface of AlN-NCS and AlP-NCS have 3-fold coordinate.[10][11][12] The adsorptions of toxic gases with various compounds to identify the suitable sensor are important works to solve the environmental problems.9][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Zaboli and et al. 35 the adsorptions of the H 2 S, H 2 Se and SO 2 molecules on the surface of fullerene by the density functional theory investigated.Obtained results shown that, the adsorption energy amounts of gas molecule were short, so, the sensor were possess at short recovery times. 35Also results shown that H 2 Se molecule with adsorption energy of about -11.28 kJ/mol has the strongest adsorption on surface of fullerene. 35n previous study theoretical methods have been used to investigation influence of metal oxides on various polymers such as polyvinyl alcohol and polyaniline.Results show that, addition of metal oxides increase the total dipole moments of polymers and decrease the band gap energies of polymers.][37] Ibrahim and et al. used theoretical methods to study the dipole moment and geometrical structures of COOH.Their results show that increase of dipole moments are suitable pointer to ability of considered structures.Also they used DFT to study composite of divalent zinc and results show that obtained dipole moment was 23.4 Debye and band gap energy was 0.49 eV.][40] In present work, the adsorptions of H 2 Se molecule on surfaces of AlN-NCS and AlP-NCS were examined theoretically.The Cl-functionalized effects on ability of AlN -NCS and AlP-NCS to adsorption of H 2 Se were calculated via theoretical method.The orbital energy amounts of considered nanocone sheets were calculated and relationships between orbital energy and E ad amounts of considered nanocone sheets were examined.The initial points of this work are: (1) to find the ability of AlN-NCS and AlP -NCS to H 2 Se-adsorption; (2) to categorize the influences of Cl functionalization of NCS on capability of AlN-NCS and AlP-NCS; (3) to discovery the linear relationships between adsorption and orbital energy NCS; (5) To propose the novel NCSs with the highest capacity to H 2 Se-adsorption.

Computational Details
The geometry of AlN-NCS, AlP-NCS and their Cl functionalized derivatives were optimized via DFT method, B3LYP functional and 6-311G (d,p) basis set in GAMESS software. 41,42The geometry of complexes of H 2 Se molecule and considered AlN-NCSs and AlP-NCSs were optimized (obtained structures of considered complexes were reported in figure 1).In order to remove the border effects, termination atoms of considered AlN-NCSs and AlP-NCSs were sodden via hydrogen atoms.][45][46] In this work, adsorption energy (E ad ) and free energy (G ad ) amounts of H 2 Se molecule on considered AlN-NCSs and AlP-NCSs were obtained via equations 1 and 2, respectively: where

1. E ad and G ad Amounts of H 2 Se-nanocone Sheet
In this section E ad and G ad amounts of H 2 Se adsorption on surface of AlN-NCS, AlP-NCS, Cl-AlN-NCS and Cl-AlP-NCS in table 1 were presented.In table 1 48 Abrishamifar: The Cl Functionalized Aluminum Nitride (AlN) ...

2. Orbital Energies of Considered Nanocone Sheets
In this section orbital energy amounts of AlN-NCS, AlP-NCS, AlN-NCS, AlP-NCS were calculated and obtained amounts were represented in table 2  In this section, relationships between E ad and orbital energy amounts of considered nanocone sheets were examined.The E ad amounts of complexes of H 2 Se-NCS in table 1 were modified against the orbital energy amounts of complexes of H 2 Se-NCS in table 2. The equations 3-5 were calculated from these modifications as follow: E ad = 1.43 × (E HOMO ) + 152 E ad = 0.63 × (E HLG ) -523 The relationship constants of equations 3-5 were ca 0.994, 0.997 and 0.994, respectively and so there are linear relationship between E ad and orbital energy amounts of complexes H 2 Se-NCS.
In tables 1 and 2 the E ad and orbital energy amounts of H 2 Se-NCS complexes have similar trends and it can be established that ability of considered nanocone sheets to H 2 Se-adsoprtion were decreased as follow: AlN-NCS < Cl -AlN-NCS < AlP-NCS < Cl-AlP-NCS.Finally, Cl-AlP-N-CS and AlN-NCS have the highest and the lowest capacity to H 2 Se-adsorption and also E ad and orbital energy mounts were main factors to predicate of ability of NCS to H 2 Se -adsorption.

Conclusion
The potentials of AlN-NCS, AlP-NCS, Cl-AlN-NCS and Cl-AlP-NCS to adsorption of H 2 Se molecule via DFT method and B3LYP functional were examined.The interactions of H 2 Se with considered nanocone sheets were exothermic processes and these interactions were possible theoretically.The |E ad | amount of H 2 Se-AlP-NCS were higher than those of H 2 Se-AlN-NCS.The considered Cl -AlP-NCS and Cl-AlN-NCS have higher |E ad | amounts than AlP-NCS and AlN-NCS, respectively.There were linear relationships between of E ad and orbital energy amounts of considered NCSs.The E ad and orbital energy amounts can be considers as main scale to predicate the ability of nanocone sheets to H 2 Se-adsorption.
47(nanocone sheet/H 2 Se) is energy of complexes of H 2 Se and considered nanostructures.The E (H 2 Se) and E (nanocone sheet) are energies of H 2 Se molecule and considered nanostructures, respectively.The negative amounts of E ad and G ad indicated that H 2 Se molecule and AlN-NCSs and AlP-NCSs have exothermic interactions.In this work also the Basis set superposition error (BSSE) amounts of interactions of H 2 Se-nanostructures were calculated.47 the E ad and G ad amounts of H 2 Se-NCS and H 2 Se-Cl-NCS were negative and so the interactions of H 2 Se and considered nanocone sheets were exothermic reactions.The |E ad | and |G ad | amounts of H 2 Se-AlP-NCS were higher than corresponding values of H 2 Se-AlN-NCS ca 41.5 and 43.4 kJ/ mol, respectively.The |E ad | and |G ad | amounts of H 2 Se-Cl-AlP-NCS were higher than corresponding values of H 2 Se-Cl-AlN -NCS ca 18.3 and 18.2 kJ/mol, respectively.Also |E ad | and |G ad | amounts of H 2 Se-Cl-AlP-NCS were higher than corresponding values of H 2 Se-AlP-NCS ca 21.2 kJ/mol and 20.3 kJ/mol, respectively.In table 1 the |E ad | and |G ad | amounts of H 2 Se-NCS and H 2 Se-Cl-NCS were decreased as follow: AlN-NCS < Cl-AlN-NCS < AlP-NCS < Cl-AlP-NCS.Data in table 1 consummated that Cl-AlP-NCS and AlN-NCS have the highest and the lowest performances to H 2 Se-adsorption, respectively.Results in table 1 can be expounded that phosphor and chlorine atoms can stable the AlP-NCS, AlP -Cl-NCS and their H 2 Se complexes; therefore the |E ad | and |G ad | amounts of AlP-NCS AlP-Cl-NCS were higher than corresponding values of AlN-NCS.
and relationships of orbital energy amounts in table 2 and E ad amounts in table 1 were examined.In table 2, AlN-NCS and Cl-AlP -NCS have the highest and the lowest amounts of |E HOMO |, respectively.Therefore in table 2 the Cl-AlP-NCS and AlN-NCS have the highest and the lowest inclination to lose an electron, respectively.In table 2, the |E LUMO | amounts of studied nanostructures were decrease as follow: AlN-NCS < Cl-AlN-NCS < AlP-NCS < Cl-AlP-NCS.In table 2, Cl -AlP-NCS and AlN-NCS have the highest and the lowest amounts of |E LUMO |, respectively.Therefore in table 2 the Cl-AlP-NCS and AlN-NCS have the highest and the lowest capability to receive an electron, respectively.In table 2, E HLG amounts of considered nanocone sheets were decrease as follow: AlN-NCS > Cl-AlN-NCS > AlP-NCS > Cl-AlP-NCS.In table 2, Cl-AlP-NCS and AlN -NCS have the lowest and the highest amounts of E HLG , respectively.So, in table 2 the Cl-AlP-NCS and AlN-NCS have the highest and the lowest reactivity.In table 2, AlP -NCS has higher |E LUMO | and lower |E HOMO | amounts than AlN-NCS.In table 2, Cl-AlN-NCS and Cl-AlP-NCS have higher |E LUMO | and lower |E LUMO | amounts than AlN-NCS and AlP-NCS.So, Cl functionalization increase the capability of AlN-NCS and AlP-NCS to H 2 Se adsorption.