Charge Photogeneration and Transfer in Polyaniline/Titanium Dioxide Heterostructure

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper focuses on the photoinduction process in the p-n heterogeneous structure of PANi (polyaniline) and TiO2 (titanium dioxide). Specifically, the PANi layer in the heterostructure shows two modes of response to excitation light: a negative mode (decrease in conductance) for certain UV wavelengths and a positive mode (increase in conductance) for visible light. In summary, the paper presents significant findings on the charge photogeneration and transfer in PANi/TiO2 heterostructures, but could benefit from more detailed mechanistic studies, a broader range of experimental conditions, thorough stability analysis, and comparative studies with other heterostructures to enhance its applicability and impact. This paper could be accepted by the journal of Catalysts after minor revisions. The detailed issues are listed as follows:

1. The study primarily relies on conductance measurements to infer charge photogeneration and transfer mechanisms. While it provides some explanation for the observed light sensitivity modes, it lacks in-depth analysis and confirmation of the underlying mechanisms through more advanced techniques such as transient absorption spectroscopy, time-resolved photoluminescence, photoelectrochemical test, surface photovoltage test, or in-situ XPS spectra under light irradiation.

2. The research explores the response to only a few specific wavelengths of excitation light. A broader range of wavelengths and light intensities could provide a more comprehensive understanding of the photogeneration and transfer processes in the PANi/TiO2 heterostructure.

3. The paper does not thoroughly investigate the long-term stability and surface interaction dynamics between PANi and TiO2. These factors are crucial for practical applications, as they influence the durability and efficiency of the heterostructure in real-world conditions.

4. The study focuses on the PANi/TiO2 combination but does not provide a comparative analysis with other potential heterostructures. This limits the understanding of the relative advantages and potential improvements that could be achieved with different material combinations.

5. In Figure 1, it involves the formation of reactive oxygen species. Is there any experimental evidence in the article proving the existence of oxygen free radicals?

6. In Figure 9, is there any experimental evidences supporting the types and band structure positions of the two semiconductors discussed in this paper?

Comments on the Quality of English Language

The overall quality of the English in the paper is acceptable but needs improvements for clarity and readability. Numerous grammatical errors, such as missing articles (e.g., "in PANi/TiO2 structure" should be "in the PANi/TiO2 structure") and incorrect verb tenses (e.g., "It has found" should be "It has been found"). Overly complex sentence structures make the argument difficult to follow. Shorter, simpler sentences would help. Some word choices are awkward or incorrect. Ensure consistent terminology (e.g., avoid using "TiO2" and "titanium dioxide" interchangeably).

Author Response

Response to Reviewer 1

 

1. The study primarily relies on conductance measurements to infer charge photogeneration and transfer mechanisms. While it provides some explanation for the observed light sensitivity modes, it lacks in-depth analysis and confirmation of the underlying mechanisms through more advanced techniques such as transient absorption spectroscopy, time-resolved photoluminescence, photoelectrochemical test, surface photovoltage test, or in-situ XPS spectra under light irradiation.

Response:

The study primary relies on conductance measurements of a PANi layer beneath of a TiO₂ layer upon exposure to excitation light. The motivation simply is trying to clarify if there is any correlation between the photoinduction process in a PANi/TiO₂ heterogeneous structure with the electronic properties of its PANi component. From some initial observed light sensitivity mode, we could explain semi-quantitatively the features based on the modification of the PANi/TiO₂ heterojunction by the appearance of excess photogenerated charges. The recommendation is correct that our explanation could be more confirmative if we could go further with more advanced techniques to clarify the nature of any charge traps and defect on the surface, the surface bonding condition, the modification of electronic configurations in both PANi and TiO₂ in the normal and excited state, and the others. However, with our current laboratory facilities and experiment conditions we were not able to proceed further. However, we do hope that our approach and initial results could catch up any attention from anyone who could do further and look insight the phenomenon.

Actually, the conductance of the PANi layer is an electrical microparameter and it is affected by a variety of microprocesses and depends on many parameters inside the materials and outside environment. For a quantitative confirmation, we should identify and classify the possible parameters could affect the measurement such as of the starting materials, the preparation conditions, the testing conditions and instruments, testing techniques, etc.

2. The research explores the response to only a few specific wavelengths of excitation light. A broader range of wavelengths and light intensities could provide a more comprehensive understanding of the photogeneration and transfer processes in the PANi/TiO₂ heterostructure.

Response

As stated in response 1, the study initially is trying to find out a possible correlation between the photoresponse of the PANi/TiO₂ heterostructure to its PANi component conductance. With an assumption that the photoexcitation in TiO₂ is the critical parameter affecting the photogeneration in the PANi/TiO2 structure we have focused on the monochromatic light source could be used in the study. The available information for the band gap of the TiO₂ is in a range from 3.0 to 3.3 eV (anatase 3.0 V, rutile 3.2 eV and brookite 3.3 eV), according to the excitation photon with wavelength of 413, 388 and 375 nm). The excitation light then is chosen from available LEDs sources of 369 and 396 to ensure that we can excite rutile and anatase. The excitation light of wavelength 663 nm is to ensure that is out of photoexcited range of TiO₂, the excitation light of wavelength 447 nm is to confirm if any expanding beyond the photosensitive limitation of TiO₂.

It seems that, most studies made on the photocatalytic activities involving the relative reduction of absorbent during the light exposure using one light source either UV or solar light but not much studies identify and clarify what and how are the wavelength dependence and redox radicals involved.   

3. The paper does not thoroughly investigate the long-term stability and surface interaction dynamics between PANi and TiO₂. These factors are crucial for practical applications, as they influence the durability and efficiency of the heterostructure in real-world conditions.

Response

The recommendation is correct, our study has focused mainly on the light sensitivity and explain the photoresponse of the PANi layer conductance in the PANi/TiO₂. We have also recognized the shift of baseline of the PANi conductance during the experiment. The baseline is considered as a parameter can be used to evaluate the stability of the material and the surface interaction dynamics between PANi and TiO₂. The upward and downward trend of baseline give a hind of influence of inactivated or activated TiO₂ on PANi over the interfacial contact. The interaction between of TiO₂ and PANi can affect the long-term stability and surface interaction dynamics between PANi and TiO₂ and then influence the durability and efficiency of the heterostructure in real-world conditions. Based on the chemical structure of PANi, activated TiO₂ and secondary redox radicals seem not affect the polymer structure but can affect the doping conditions and the surface conditions then modify the electronic configuration. To have a confirmation, we may need extra study to classify the modification in electronic configuration and the influence of O₂ and H₂O content as well as the other substances in the surrounding environment in long term.  

4. The study focuses on the PANi/TiO₂ combination but does not provide a comparative analysis with other potential heterostructures. This limits the understanding of the relative advantages and potential improvements that could be achieved with different material combinations.

Response

In the revised version, we have briefly introduced the recent review articles on the other potential heterostructure based on TiO₂ with inorganic and conducting polymers.

5. In Figure 1, it involves the formation of reactive oxygen species. Is there any experimental evidence in the article proving the existence of oxygen free radicals?

Response:

It seems that not much studies made to identify and classify directly the appearance of oxygen free radicals in photocatalysis. Some studies have indicated the presence of oxygen free radicals using either chemical or physical methods such as chemical probe, near-infrared phosphorescence, laser induced fluorescence, etc such as followings articles.

1. Nosaka Y, Nakamura M, & Hirakawa T (2002) Behavior of Superoxide Radicals Formed on TiO₂ Powder Photocatalysts Studied by a Chemiluminescent Probe Method. Phys Chem Chem Phys 4: 1088-1092. DOI:10.1039/b108441k

A luminol chemiluminescence (CL) probe method was successfully applied to the investigation of the superoxide radical (O₂⁻˙) formed on photoirradiated TiO₂ powders. For several kinds of commercially available TiO₂ photocatalysts and their calcined samples, the amount of O₂⁻˙ produced at the steady state was measured and found to increase with the secondary particle size or the degree of aggregation. The decay of O₂⁻˙ for the non-calcined samples was as long as several hundred seconds and obeyed second order kinetics, indicating that disproportionation is the main deactivation pathway. For some TiO₂ photocatalysts, oxidative species such as OH˙ radicals are suggested to exist for 1 s after irradiation. On the other hand, reductive photoinduced electrons may remain for several seconds after irradiation since the decay of O₂⁻˙ starts after a delay of more than 1 s. On calcination at temperatures up to 1173 K, O₂⁻˙ decays by a mechanism other than disproportionation, suggesting the prolonged lifetime of an oxidative species that can react with O₂⁻˙.

2. Toshihiro D and Yoshio N (2007) Formation and Behavior of Singlet Molecular Oxygen in TiO₂Photocatalysis Studied by Detection of Near-Infrared Phosphorescence. J Phys Chem C 111(11): 4420-4424. https://doi.org/10.1021/jp070028y.

Singlet molecular oxygen (¹O₂), which was produced with a significant yield, was detected from a powder-type TiO₂ photocatalyst irradiated with a 355-nm laser pulse by monitoring its near-infrared phosphorescence at 1270 nm. Lifetime measurements for the ¹O₂ produced at TiO₂ (Degussa P25) in various environments, such as in air and in suspensions of H₂O, D₂O, and ethanol, indicated that quenching takes place mainly at the TiO₂ surface in the absence of reactants. Quantum yields for ¹O₂ generation were measured for ten commercial TiO₂ photocatalysts in air and ranged from 0.12 to 0.38, while the lifetimes ranged from 2.0 to 2.5 μs. Since the quenching by the TiO₂ surface is quite fast, the formation and decay processes of ¹O₂ have not been distinguished from the recombination of the photogenerated electron−hole pairs. The values of quantum yield suggest that ¹O₂ may contribute to the oxidation of some organic molecules at the irradiated TiO2 surface.

3. Demyanenko A. V et al (2019) Singlet Oxygen ¹O₂ in Photocatalysis on TiO₂. Where Does It Come from? J Phys Chem C 123 (4): 2175-2181. https://doi.org/10.1021/ACS.JPCC.8B09381.

Features of the near-infrared phosphorescence of singlet oxygen ¹O₂ photosensitized by TiO₂ in solutions have been investigated. The short-lived phosphorescence of ¹O₂ with spectral maximum at approximately 1300 nm is observed to follow excitation by pulsed laser radiation at 355 nm of TiO₂ suspended in CCl₄ and water H₂O. The shorter lifetime and spectral shift of this phosphorescence, as compared with phosphorescence of ¹O₂ sensitized by phenalenone in these solvents, are attributed to the adsorbed state of emitting singlet oxygen. The observed laser pulse energy dependence indicates the two-photon and three-photon nature of this phosphorescence initiation in CCl₄ and H₂O, respectively. The formation of ¹O₂ in CCl₄ is assumed to be provided by the sequence of one-photon excitation of TiO₂, giving rise to superoxide anion O₂^– and one-photon photodetachment of electron from O₂^–. The photodetachment of electron from O₂^– in water H₂O is a two-photon process because of higher solvation energy of superoxide anion in water. The processes that govern the rise and decay of singlet oxygen phosphorescence sensitized by TiO₂ are discussed. The factors affecting the yield of singlet oxygen provided by electron photodetachment are also considered.

4. Nosaka, Y. (2010). Surface Chemistry of TiO₂Photocatalysis and LIF Detection of OH Radicals. In: Anpo, M., Kamat, P. (eds) Environmentally Benign Photocatalysts. Nanostructure Science and Technology. Springer, New York, NY. https://doi.org/10.1007/978-0-387-48444-0_8.

By means of laser induced fluorescence (LIF) method, OH radicals formed and released from the surface of TiO₂ photocatalysts were detected. The effect of heat treatments of TiO₂ on the OH radical formation shows that the amount of OH radicals is affected by the states of surface hydroxyl groups but not the crystalline phase. The effects of the surface hydroxyl groups were discussed based on the measurements of the trapped holes with low temperature ESR spectroscopy and adsorbed water with proton NMR spectroscopy. Then, the reaction mechanism of OH radical formation on the TiO₂ surface was suggested to be the reduction of adsorbed H₂O₂ which is accumulated on the surface by photo irradiation. Finally, the previously reported reaction mechanism of the acetic-acid decomposition was reconsidered based on the mechanism of OH radical formation.

6. In Figure 9, is there any experimental evidence supporting the types and band structure positions of the two semiconductors discussed in this paper?

Response:

The types and band structure of separate TiO₂ and PANi semiconductor are investigated by many studies and presented in many review articles that can search directly on the Web. In our study the TiO₂ is identified to be the rutile. Rutile has direct bandgap of around 3.0eV while the PANi i is in oxidation state of emerandine salt band gap < 2.7eV). However, the band structure and band bending in the PANi/TiO₂ heterostructure is deduced based on inorganic-inorganic heterojunction that has been set up and proved in solid state and electronics. Some articles involved to the band structure and position of TiO₂ and PANi are shown as bellow.

1- Zhang J., Zhou P, Liu J. and Yu J., New understanding of the difference of photocatalytic activity among anatase, rutile and brookite TiO2, Phys. Chem. Chem. Phys. 2014, 16, 20382–20386. https://doi.org/10.1039/C4CP02201G.

In general, anatase TiO₂ exhibits higher photocatalytic activities than rutile TiO₂. However, the reasons for the differences in photocatalytic activity between anatase and rutile are still being debated. In this work, the band structure, density of states, and effective mass of photogenerated charge carriers for anatase, rutile and brookite TiO₂ are investigated by the first-principle density functional theory calculation. The results indicate that anatase appears to be an indirect band gap semiconductor, while rutile and brookite belong to the direct band gap semiconductor category. Indirect band gap anatase exhibits a longer lifetime of photoexcited electrons and holes than direct band gap rutile and brookite because the direct transitions of photogenerated electrons from the conduction band (CB) to valence band (VB) of anatase TiO₂ is impossible. Furthermore, anatase has the lightest average effective mass of photogenerated electrons and holes as compared to rutile and brookite. The lightest effective mass suggests the fastest migration of photogenerated electrons and holes from the interior to surface of anatase TiO₂ particle, thus resulting in the lowest recombination rate of photogenerated charge carriers within anatase TiO₂. Therefore, it is not surprising that anatase usually shows a higher photocatalytic activity than rutile and brookite. This investigation will provide some new insight into understanding the difference of photocatalytic activity among anatase, rutile and brookite.

2. Ola O, Maroto-Valer MM (2015) Review of material design and reactor engineering on TiO₂ photocatalysis for CO₂ reduction. J Photochem Photobiol C Photochem Rev 24: 16–42. https://doi.org/10.1016/j.jphotochemrev.2015.06.001.

The continuous combustion of non-renewable fossil fuels and depletion of existing resources is intensifying the research and development of alternative future energy options that can directly abate and process ever-increasing carbon dioxide (CO₂) emissions. Since CO₂ is a thermodynamically stable compound, its reduction must not consume additional energy or increase net CO₂ emissions. Renewable sources like solar energy provide readily available and continuous light supply required for driving this conversion process. Therefore, the use of solar energy to drive CO₂ photocatalytic reactions simultaneously addresses the aforementioned challenges, while producing sustainable fuels or chemicals suitable for use in existing energy infrastructure. Recent progress in this area has focused on the development and testing of promising TiO₂ based photocatalysts in different reactor configurations due to their unique physicochemical properties for CO₂ photoreduction. TiO₂ nanostructured materials with different morphological and textural properties modified by using organic and inorganic compounds as photosensitizers (dye sensitization), coupling semiconductors of different energy levels or doping with metals or non-metals have been tested. This review presents contemporary views on state of the art in photocatalytic CO₂ reduction over titanium oxide (TiO₂ ) nanostructured materials, with emphasis on material design and reactor configurations. In this review, we discuss existing and recent TiO₂ based supports, encompassing comparative analysis of existing systems, novel designs being employed to improve selectivity and photoconversion rates as well as emerging opportunities for future development, crucial to the field of CO2 photocatalytic reduction. The influence of different operating and morphological variables on the selectivity and efficiency of CO₂ photoreduction is reviewed. Finally, perspectives on the progress of TiO2 induced photocatalysis for CO₂ photoreduction will be presented.

3. Mailu SM, Ajayi RF, Molapo KM, Njomo N, Masikini M, Baker PG, Ndangili P, Mbambisa G, & Iwuoha EI (2012). Electronics of Conjugated Polymers (I): Polyaniline. Int J Electrochem Sci 7: 11859 – 11875. https://doi.org/10.1016/S1452-3981(23)16509-6.

Conducting polymers have elicited much interest among researchers because of their reasonably good conductivity, stability, ease of preparation, affordability and redox properties compared to other organic compounds. In particular, the electronic and electrochemical properties of conducting polymers have made them find applications in photovoltaic cells, organic light emitting diode and sensors. Among the conducting polymers, polyaniline has received much attention and intensive research work has been performed with the polymer in its native state or functionalized form. This is mainly due to the fact that polyaniline and its derivatives or composites or co-polymers with other materials are easy to synthesise chemically or electrochemically by oxidative polymerisation. The mechanism for the synthesi s of polyaniline and its electronic properties are presented in this short review.

5. Fu Y, Janczarek M (2023) Polyaniline–Titanium Dioxide Heterostructures as Efficient Photocatalysts: A Review. Crystals 13: 1637. https://doi.org/10.3390/cryst13121637. (Ref 32).

This review paper focuses on present issues concerning the use of polyaniline–TiO₂ heterostructures as potentially efficient photocatalysts. Conducting polymers such as polyaniline (PANI) are used in the preparation of heterojunction systems with metal oxides like titania to overcome their inherent limitations, e.g., their sole absorption of UV light and overly fast recombination of charge carriers. This review discusses preparation methods, the properties of resultant products and mechanistic aspects. An important part of this paper is its presentation of the major challenges and future perspectives of such photocatalytic materials.

Comments on the Quality of English Language

The overall quality of the English in the paper is acceptable but needs improvements for clarity and readability. Numerous grammatical errors, such as missing articles (e.g., "in PANi/TiO2 structure" should be "in the PANi/TiO2 structure") and incorrect verb tenses (e.g., "It has found" should be "It has been found"). Overly complex sentence structures make the argument difficult to follow. Shorter, simpler sentences would help. Some word choices are awkward or incorrect. Ensure consistent terminology (e.g., avoid using "TiO2" and "titanium dioxide" interchangeably).

Response

We have revised the manuscript and checked and scanned grammatical errors and typos.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Please see the report

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Please see the report

Author Response

Response for Reviewer 2

 

1. The authors shall provide the complete names for the polymer and nanoparticle used in the title.

Response

We have revised and given full name of TiOw and PANi in the manuscript tittle.

2. The abstract is too long, and the authors should reduce it.

Response:

We have revised and shortened the Abstract as recommendation.

3. The Introduction is lacking some recent literatures about TiO₂ nanoparticles and their applications in different areas. So, more recent articles should be provided like

“ https://doi.org/10.1016/j.ceramint.2024.07.220”,

Response:

The recommendation is right, smart and active packaging polymeric materials with self-destruction and antibacterial or UV shielding are good examples of new applications from TiO₂ photocatalyst in environmental protection. We have added two refs as suggestion.

1. Madbouly, A., Morsy, M., & Moustafa, H. (2024). Utilization of torrefied date stones with synthesized TiO2 nanoparticles for promoting humidity sensing of PVA/PVP nanocomposites for smart food packaging and biomedical applications. Ceramics International. (Ceram Int) https://doi.org/10.1016/j.ceramint.2024.07.220. https://www.sciencedirect.com/science/article/pii/S0272884224031250)

Abstract: Fabricating smart and active packaging films with affordable cost has become the first demand for serving to market needs, particularly after COVID-19 disaster, for ensuring food security. Therefore, the broader goal of this work was to improve intelligent and active packaging films having humidity-sensing and antibacterial properties for biodegradable poly vinyl alcohol (PVA)/Polyvinylidene (PVP) reinforced with torrefied date stones (DS) and lethal amounts of TiO2 nanoparticles by a solvent-casting approach. Various concentrations of TiO2 NPs (i.e. 0.05, 0.15, and 0.30 %) in presence of 10 % torrefied DS (biochar) as a fixed content were used to fabricate PVA/PVP nanocomposite films. FT-IR spectra were utilized to monitor the DS functional groups before and after torrefaction at 270 °C. The crystal structure of synthesized TiO2 NPs as well as its impact on the PVA/PVP nanocomposites were verified by X-ray diffraction (XRD). The XRD micrographs and FT-IR spectra-based biofilms showcased that the degree of crystallinity and dispersibility of filler in the blend matrix were promoted, when the nanoparticles added. This was evidenced by SEM images. Mechanical testing also manifested that a great improvement in the tensile properties were noticed, especially at 0.30 % NPs and found the tensile strength reached ∼33 MPa compared to PVA/PVP blank (∼23.70 MPa) or PVA/PVP-BC (∼18.20 MPa). The humidity sensing properties were performed over a wide span of relative humidity from (11–97 % RH) and frequency (50 Hz-10 kHz). The data manifested that 100 Hz was the optimum testing frequency. Moreover, the gotten findings from humidity-sensing tests at 100 Hz exhibited that the sensor containing 0.15 % TiO2 NPs had higher sensitivity and could be considered as a nano-sensor for smart food packaging. Furthermore, the impact of TiO2 NPs on antibacterial activity was investigated to probably use these films in active packaging with prolonged shelf-life of food products and other promising applications including biological area.

Keywords: PVA/PVP; Torrefaction of date stones; Mechanical properties; Humidity sensor; Active/smart food packaging; Biological area

and “DOI: 10.21608/EJCHEM.2017.1932.1159

2. Hesham Moustafa, Abdallah M. Karmalawi, Ahmed M. Youssef, Development of dapsone-capped TiO2 hybrid nanocomposites and their effects on the UV radiation, mechanical, thermal properties and antibacterial activity of PVA bionanocomposites, Environmental Nanotechnology, Monitoring & Management, Volume 16, 2021,100482,

https://doi.org/10.1016/j.enmm.2021.100482.

(https://www.sciencedirect.com/science/article/pii/S221515322100057X)

Abstract: In the present work, dapsone-capped TiO2 nanoparticles (DAP-TiO2-NPs) were successfully prepared as a decorated bio-agent for enhancing the properties of the biodegradable polyvinyl alcohol (PVA) nanocomposites. The structure of synthesized TiO2-NPs was characterized by X-ray diffraction (XRD). The fabricated biodegradable films were subjected to variable tests like SEM analysis, UV–vis spectroscopy, mechanical properties, thermogravimetric analysis (TGA), as well as antibacterial activity. The SEM images showed that the capping dapsone into the surface of TiO2-NPs improved the dispersion degree and miscibility of DAP inside the PVA matrix, especially at 0.1 % filler content. The obtained results from UV–vis exhibited that all fabricated films based on DAP-TiO2-NPs possessed superb UV-shielding properties even at lower nanofiller ratios, blocking nearly all three bands of UV lights, and up 98 % of visible light as well, irrespective to neat PVA or PVA/DAP blend. Withal, UV–vis reflectance was revealed that the reflectivity of filled films was changed in the visible range with increasing UV exposure time, indicating the color change in the film within a few minutes. These data were confirmed by chromaticity co-ordinates calculations. Also, the tensile properties, thermal stability, and antibacterial activity of nanocomposite films were remarkably improved. This study points out that a new utilization for PVA/DAP-TiO2 nanocomposite films in promising applications such as food-safe packaging and UV-blocking biomedical areas.

Keywords: Biodegradable PVA; Dapsone; TiO2 nanoparticles; UV-radiation; Mechanical properties; Antibacterial activity

4. The resolution of Figure 2 shall be improved.

Response:

We have replaced Figure 2 with higher resolution and revised the thicknesses of PANi and TiO₂ layer relative to SEM picture.

5. The authors should be presented the XRD for synthesized TiO₂ NPs to investigate the rutile/anatase phases, and PANi/TiO₂ nanocomposites as well

(please check this: https://doi.org/10.1016/j.enmm.2021.100482).

We have revised and added XRD patterns of TiO2 and TiO₂/PANi to confirm the structure of TiO2 rutile in the PANi/TiO₂ structure and used the article suggested by reviewer as a reference.

Hesham Moustafa, Abdallah M. Karmalawi, Ahmed M. Youssef, Development of dapsone-capped TiO2 hybrid nanocomposites and their effects on the UV radiation, mechanical, thermal properties and antibacterial activity of PVA bionanocomposites, Environmental Nanotechnology, Monitoring & Management, Volume 16, 2021,100482,

https://doi.org/10.1016/j.enmm.2021.100482.

(https://www.sciencedirect.com/science/article/pii/S221515322100057X)

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have done a systematic scientific work and the manuscript could be accepted for publication in the present form.

Author Response

The manuscript is revised and checked for grammatical errors and typos

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

After authors corrections, the revised manuscript is now suitable for publication without modification.