Visible-Light-Enhanced Antibacterial Activity of Silver and Copper Co-Doped Titania Formed on Titanium via Chemical and Thermal Treatments

Round 1

Reviewer 1 Report

The paper entitled “Visible-Light-Enhanced Antibacterial Activity of Silver and Copper Co-Doped Titania Formed on Titanium via Chemical and Thermal Treatments’’ “ is an interesting approach with nice perspective for practical applications in the field of antibacterial surfaces.

This article can thus be accepted in this journal for publication, although after a minor revision. The followings are my suggestions/questions, which the authors may choose to address:

1. As you know anatase TiO2 has band gap (3.2 ev) and it works under UV radiation, the authors said that Ag, Cu doped TiO2 work under visible light, I suggest that authors add absorption and optical band gap.

2. authors said that TiO2 doped with Ag and Cu, is it doping or gust aggregation on the surface, can you give evidence such as is there any unit cell explanation, which is usually calculated from XRD or any shift in the peaks, can you add Raman spectra to see if there is any shift.

3. In line 201 and 202, authors said ‘’ The intensity of the TF-XRD peak attributed to metallic silver around the 2θ angle of 44° was much higher for AG-CU than for AG’’. Is it correct? Can you see Figure 1b.

4. The ratio between rutile and anatase is different. Can you calculate the ratio between rutile and anatase in AG-CU and AG, because this difference plays a vital role in bacterial activity?  

5. I strongly suggest that the authors measure the proportion of silver and copper in TiO2 by using EDX.

6. I suggest that the authors do a study on the toxicity of copper and silver.

7. Is there any change in the oxidation state of copper after antimicrobial activity?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors introduced a titania composite doped with silver and copper with the enhanced antibacterial behavior promoted by visible light. This is a good research paper in this field and worth publishing after some revision. 

Comments 1. Introducing doping elements into TiO2 is critical for modifying the photocatalytic properties of TiO2 and is important for this manuscript. The mechanism of this process should be elucidated in the introduction part.

Comments 2. To elucidate the enhanced antibacterial behavior of the composite, I suggest the authors provide the comparative test images of petri dish.

Comments 3. The authors concluded that the enhanced antibacterial behavior was resulted from the synergy between Ag and Cu. More detailed discussion should be provided, for example, how does Ag interact with Cu in the composite and how could Ag and Cu contribute to the enhanced antibacterial behavior synergistically?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This work is about doping Ag and Cu on the surface of Ti implant materials to improve their properties. The authors executed two doping conditions and compared their surface morphology, apatite formation ability, surface ion-releasing speed, and antibacterial properties. The topic is not very novel, but the characterization methods were sufficient and scientific. All results were emphasized but could be discussed in more detail. I recommend this paper be published after minor revisions. Please refer to my questions and suggestions below.

In the paper, authors sometimes call original materials “Ti chip”, and sometimes call it TiO2. Please clarify if the original material is TiO2 or Ti with an oxide layer on the surface and use one general name to call your original material.

Line 79-84, AG-CU was incubated in AgNO3 and Cu(NO3)2 for 2 days, but only heat-treated with one solution, Cu(NO3)2. Why this method is not consistent with AG preparation?

Figure 4b, what is the purpose of changing the x-axis to the square root of the time? Are you using any kinetic equation to model the releasing process? If so, please include this in your discussion.

In line 269, the authors didn’t explain why Ag+ was released from ion exchange. Which ions were exchanged? What is the mechanism? Also, in line 274, how is Cu2+ released from ion exchange? Please explain it in detail.

In line 287, does AG or AG-CU show strong antibacterial activity under visible-light irradiation?

In Table 3, the concentration of H2O2 and OH* were listed separately, which is not scientific. OH* can be generated from H2O2 decomposition easily. In the methods part (Line 182), the authors mentioned that H2O2 was measured from colorimetric, but OH* can also quench the UV absorption of the indicator. Surprisingly, colorimetric results are much lower than ESR results. Please think about this question carefully.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf