Silver-Doped Cadmium Selenide/Graphene Oxide-Filled Cellulose Acetate Nanocomposites for Photocatalytic Degradation of Malachite Green toward Wastewater Treatment
Authors: Mohamed Afifi
Ahmed Esmail Shalan
Mohamed M El-Desoky
Senentxu Lanceros-Méndez
Mohamed K Ahmed
Journal: ACS Omega (2021)
Discipline: CHEMISTRY
Keywords: Silver-doped cadmium selenide; graphene oxide; nanocomposites; cellulose acetate; photocatalytic properties
Affiliations: Department of Physics, Faculty of Science, Suez University, Suez 43518, Egypt, Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan, Cairo 11421, Egypt, Faculty of Nanotechnology for Postgraduate Studies, Cairo University, El-Sheikh Zayed 12588, Egypt, BCMaterials, Basque Center for Materials, Applications and Nanostructures, Martina Casiano, UPV/EHU Science Park, Barrio Sarriena s/n, Leioa 48940, Spain

Abstract:  Silver-doped cadmium selenide/graphene oxide (GO) (Ag-CdSe/GO) nanocomposites have been synthesized, loaded in cellulose acetate (CA) to form Ag-CdSe/GO@CA heterostructure nanofibers, and characterized in terms of structural, morphological, photocatalytic properties, among others. The photocatalytic degradation of malachite green (MG) was estimated using cadmium selenide-filled CA (CdSe@CA), silver-doped cadmium selenide-filled CA (Ag-CdSe@CA), cadmium selenide/GO-filled CA (CdSe/GO@CA), and silver-doped cadmium selenide/GO-filled CA (Ag-CdSe/GO@CA) nanocomposite materials. The Ag-CdSe/GO@CA nanocomposites exhibit and retain an enhanced photocatalytic activity for the degradation of MG dye. This amended performance is associated with the multifunctional supporting impacts of GO, Ag, and CA on the composite structure and properties. The superior photocatalytic activity is related to the fact that both Ag and GO can act as electron acceptors that boost the separation efficiency of photogenerated carriers and the loading of the combined nanocomposite (Ag-CdSe@GO) on CA nanofibers, which can augment the adsorption of electrons and holes and facilitate the movement of carriers. The stability of Ag-CdSe/GO@CA nanocomposite photocatalysts demonstrates suitable results even after five recycles. This study establishes an advanced semiconductor-based hybrid nanocomposite material for efficient photocatalytic degradation of organic dyes. 

Retracted: No

PubPeer comments:
 Fig. 1: is it expected that the XRD spectra of CdSe and Ag-CdSe mostly differ by a vertical scaling factor? Even the noise seems the same. (click to animate) ![file] , 
 Fig. 5. The XRD patterns of Ag-CdSe@CA and Ag-CdSE GO@CA are identical, including noise. Same is true for the CdSe GO@CA, but that curve is vertically scaled. Can the authors please check their data? (click to animate: Ag-CdSe@CA versus Ag-CdSE GO@CA) ![file] (click to animate: CdSe GO@CA versus Ag-CdSe@CA) ![file] , 
 Fig. S1: the stress-strain curve of CdSe GO@CA is, after vertical scaling by 65%, in every detail identical to that of CdSe@CA This is rather unexpected. (click to animate) ![file] , 
 Correction 18-5-2022 .  Here, we report editing errors in Figures 1, 5, and S1 in the published article and provide the corrected figures. These corrections do not affect any discussion or conclusions of the work. We sincerely apologize for any inconvenience caused by these editing errors. I appreciate the authors correcting, And presumably for reading the above pubpeer comments. It would still be nice to have some more explanation about the errors that occured. The correction only gives an explanation for Fig. 1 (see #1):  Duplication occurred while plotting the XRD data of CdSe and Ag-CdSe. . Did the same thing happen for Fig. S1, correction shown below? I am somewhat surprised that many of the editing errors involved duplicating scaled versions of the same curve. This is especially bothersome since [papers from a common author] often show these type of errors, [see here] for a single example. ![file] , 
 Coming back to my concerns about Fig. S1. Upon closer inspection it seems that the original editing errors were more extensive than a single (scaled) duplication. All four curves in the corrected graph are different from their originals: it seems that some non-linear scaling was applied to the horizontal axis. Can the authors please comment? [ transparent overlay, best match to black curve ] ![file] [ click to animate, axis aligned ] ![file] , 
 I have a concerns about Fig. 2 and Fig. 3 reproduced below: ![file] Fig. 2 (left) shows representative SEM images of differently prepared nanocomposites, whilst Fig. 3 (right) shows representative AFM images. Looking at the images it can be seen that one of the panels (a) and (b) must have been inadvertently swapped during figure assembly: the needle-like structures in Fig. 2(a) are clearly visible in Fig. 3(b), but not Fig. 3(a). On closer inspection it becomes apparent that the AFM images in fact show the exact same field-of-view as the corresponding SEM images, see animated overlays below. This leads to two concerns: 1. The SEM images show an ~8x5 um$2$ field, supported by the original SEM info bar. The AFM images show a 94x62 um$2$ field, and thus have a more than 10x lower magnification. 2. It is an immensely impressive feat to locate the exact same 8x5 um$2$ region on a sample with AFM. Like, nearly impossible difficult. This four times, without rotational errors. And it brings no advantage at all. Did the authors maybe make an inadvertent error when determining the AFM scale? Did the authors really do AFM on the exact same location? Or are the images in Fig. 3 possibly more directly related to the SEM images by e.g. plotting in a perspective view using the grayscale information as height? [ Click to animate. Fig. 2a versus Fig. 3b ] ![file] [ Click to animate. Fig. 2c versus Fig. 3c ] ![file] [ Click to animate. Fig. 2d versus Fig. 3d ] ![file] , 
 there is no comments , 
 #7 I am not sure how to interpret this response. With respect to #6: below a comparison of the AFM image in Fig. 3(b) and a 3D rendering of Fig. 2(a). The Matlab surf command was used on the grayscale SEM data to obtain the 3D image. The feature in the left corner is the (a) label from the original SEM image. ![file] (original SEM image) ![file] , 
 there is no comments , 
 #8 A similar issue affects another paper from a shared author: ![file] , 
 The papers [Silver-Doped Cadmium Selenide Graphene Oxide-Filled Cellulose Acetate Nanocomposites for Photocatalytic Degradation of Malachite Green toward Wastewater Treatment] and [Cellulose acetate nanofibers embedded with Ag nanoparticles CdSe graphene oxide composite for degradation of methylene blue] share two authors and use in large part the same materials and experimental data. They do not reference each other. Comparing the two papers shows a number of apparent errors and some surprising discrepancies. The prepared materials are the same. The synthesis sections show some differences, e.g. using 0.1 versus 0.2 M solutions or a 120 oC verus 150 oC autoclave temperature. To show some similarities: the XRD data for the powders is near-identical for the two papers (after the correction of the Silver-doped... paper). The data in the Cellulose... paper has been smoothed and its low-angle data has been corrected (?). [ click to animate ] ![file] Also the XRD data for the nanofibers looks near-identical. However, the CdSe@CA and Ag-CdSe@CA curves have been inadvertently swapped in one of the papers. [ Click to animate. Inset is Fig. 5 of Silver... , large image Fig. 2b of Cellulose... ] ![file] Continuing to the SEM data, it can be seem in the annotation bar that the image in the two papers have been taken on the same day using the same SEM. The timestamps in the images show that the bookkeeping of the authors is insufficient. Compare for example Fig. 5 Fig. 2 of Cellulose... Silver... : ![file] The panels in both papers have identical ordering (a:CdSe, b:Ag-CdSe, c:CdSe GO, d:Ag-CdSe GO). The timestamps for the Cellulose... paper show the images there have been taking in the order a-b-c-d. In contrast, for the Silver... paper the order is b-a-c-d. And there is only 1.5 minute between Cellulose... Fig. 5a and Silver... Fig. 2b. In fact, an area of overlap can be seen between 5a and 2b [click to animate, inset is Fig. 2b]: ![file] The labeling of at least one panel in one paper thus is wrong. With respect to timestamps it is also of interest to look at another paper, https: pubpeer.com publications D9A91FFD9C2009DF2F6421D40AC8B7. That paper studies a very different HAP-V system and its SEM images were taken on the same day as that of this paper. In fact, the timestamps of its Fig. 3(b) and (c) show that these images were taken in between those of Fig. 2c (silver) and Fig. 5d (cellulose): ![file] The pubpeer entry of that paper shows some surprising mix-ups of those very same Fig. 3b and 3c panels with yet two other papers. In this respect it may also be useful to look at https: pubpeer.com publications 58D6CA4DECA8CFB666C880151286E7, showing a list of similar SEM image mix-ups found in other papers of a shared author. To prevent an excessively long comment: a similar issue affects the SEM images shown Fig. 7 Fig. 6 of Cellulose... Silver... . Fig. 3 and 7 of Silver show AFM images and Fig. 6 and 8 of Cellulose show surface roughness of the materials. The roughness is derived from the SEM images in a [non-sensical manner] that has nothing to do with AFM, roughness, or height. The numerical roughness in the paper s tables, a pair of which is reproduced below, thus is meaningless. Suffice it to say that they differ significantly between the paper and that, despite the errors in panel ordering, the average roughness Ra monotonically increases. This is deemed important in the papers. ![file] Both papers show that the four materials can photo-catalytically degrade dyes, with one paper using methylene blue and the other using Malachite green. Finally, both papers show the tensile strength of the four types of nanofibrous membranes. The figures and tables clearly show that the authors made the effort to do separate measurements for both papers, see below: ![file] In fact, there seems to be no relation whatsoever between the results in the two papers. This is somewhat disconcerting, as Fig. S1 of the Silver... paper already needed a correction for a duplication after scaling by 1.5 times editing error. The correction in itself was noteworthy as it did not affect any of the tabulated parameters; despite its different look the maximum strain remained 81.2% and the tensile strength and toughness also were still 1.5x higher than the non-GO CdSe@CA membrane. Can the authors please comment on the differences between the papers? Specifically, the tensile strength measurements, mix-ups in SEM images and XRD data, and the different preparation methods for evidently the same materials? Can the authors also make sure that the SEM images in https: pubpeer.com publications D9A91FFD9C2009DF2F6421D40AC8B7 are not mixed with those of this paper? ,