Deposition of TiO₂ Thin Films on Wood Substrate by an Air Atmospheric Pressure Plasma Jet

Round  1

Reviewer 1 Report

Although the paper has some merit, it is not ready for publication yet. I am especially concerned about the colour measurement method.

Detailed remarks:

Abstract:

- Could the authors include more results in the abstract?

Introduction:

- In their first sentence, the authors claim that wood consists of mainly three components, but list four components afterwards. Please choose either/or.

- The photo-induced colour change of wood depends strongly on the wood species and can have a variety of final colours (as described by e.g. Hon and Shiraishi, 2000).

- the term "mildew" is less common. I adivse to use "mould" instead.

- I am missing the influence of the different TiO2 modifications (anatase, rutile,...) and their differnt band gaps/properties. Especially the difference in photocatalytic activity seems important to me.

Material and Methods:

- at what wavelength was the intensity of 950 µW/cm² measured? Why did you choose this specific intensity? Are your referring to any standard?

- Since the moisture content is crucial for the rate of photooxidation: What was the humidity within the chamber? How was the humidity controllod? What about the (black panel) temperature?

- colour measurments: I am very sceptical about your colour measurment method. Did you use a calibration target (IT8-Target)? What about the light source? Did you have comparable lighting conditions? What about the detector? How can you compare your results to those of a spectrophotometer?

- Contact angle measurments: At what time point was the contact angle measured? After 10 seconds?

Results:

- Could the authors include some images of the samples?

- Where the authors able to determine the crystal morphology (rutile, anatas)?

Discussion:

- The discussion is very short and should be considerably extended.

- Was the contact angle really "0°" or was the water soaked up by the porous substrate?

- The authors claim that TiO2 was chemically bonded to the wood surface through hydrogen-groups. How can they be sure about that?

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Good research and nicely presented. This article can attract many readers.

An important point is related to the "plasma polymerization". Some discusssions are required about the TiO2 polymerization in the presence of  APPJ.

The optical image of the TiO2 coated wood can be presented to see the overall appearance.

A control sample should be made using normal spraying of TiO2 in order to distinguish the effect of plasma or advantage of plasma coating. (Or if any previous studies are made, it can be quoted).

Author Response

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Author Response File: Author Response.pdf

Round  2

Reviewer 1 Report

The authors improved the quality of their paper according to the reviewers comments.

- add response 3:

My original comment on discolouration of wood was aimed at the sentence: "The colour of wood changes to yellow and brown". This statement is certanily not true for all wood species. As is it was pointed out by Hon (2001), the a* and/or b*  and lighness can be increased/decreased during weathering, depending on thw wood species. I recommend therefore to either delete this sentence or make a more precise description/citatation

- Could the authors explain why they measured the contact angle after 10 seconds (and not after e.g. 20 seconds?)

- The discussion still needs considerable improvment. Could the authors compare their results to other papers dealing with stabilization of wood surfaces against photooxidation/photodegradation? Photostabilization of wood using TiO2? Many key-papers and -authors are still missing.

Author Response

Please see the attachment

Author Response File: Author Response.pdf