Journal of Molecular Structure 1225 (2021) 129176 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstr Costus speciosus koen leaf extract assisted cs-znx (X = O or S) nanomaterials: Synthesis, characterization and photocatalytic degradation of rr 120 dye under uv and direct sunlight S. Ravikumar a , V. Pandiyan a,∗ , Manawwer Alam c , Naushad Ahmad c , V. Nithya d , Balu Krishnakumar b,∗ , Abilio J.F.N. Sobral b a Department of Physics, Nehru Memorial College (Autonomous), Puthanampatti- 621 007, Tamil Nadu, India b Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal c Department of Chemistry, College of Science, Riyadh-11451, King Saud University, Riyadh, Kingdom of Saudi Arabia d Department of Animal Health and Management, Pharmacognosy Lab, Alagappa University, Karaikudi-630 003, Tamil Nadu, India a r t i c l e i n f o Article history: Received 21 June 2020 Revised 28 August 2020 Accepted 29 August 2020 Keywords: Reactive red 120 CS-ZnO CS-ZnS costus speciosus koen Photocatalytic activity a b s t r a c t The distinct nanocrystalline CS-ZnX (X = O or S) were achieved through Costus speciosus Koen leaf extract assisted precipitation cum hydrothermal method. The formation of the materials was confirmed by differ- ent characterization techniques such as XRD, FT-IR, Raman, FE-SEM, EDS, HR-TEM, DRS, and PL measure- ments. The photocatalytic activity of the prepared materials was tested on the decolourization of Reactive Red 120 dye (RR 120) aqueous solution. The photocatalytic activity was further confirmed by Acid Black 1 (AB 1) dye degradation. The dye photocatalytic process was investigated by considering the influence of test parameters such as catalyst concentration and initial dye pH. Moreover, complete decolourization of 50 ppm of RR 120 solution was achieved within 180 min at pH 5. Both catalysts were found to be reusable. The photocatalytic degradation of RR 120 by CS-ZnX (X = O or S) were confirmed GC–MS anal- ysis, and suitable degradation pathways were proposed based on molecular ion and fragmentation peak values. The probable degradation mechanism was proposed and discussed. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Organic dyes are used in industry, such as textiles, paper, paint, and bio-medical are non-biodegradable because of its complex chemical structure. These dyes have produced adverse effects and several uncurable problems for the environment and human health [1]. Many researchers in these fields are hardly working to find a suitable solution for this problem using nanotechnology but no suitable results have been obtained so far. Recently, zinc oxide and zinc sulfide (ZnS) are proved to be a favourable nanomaterial for different applications such as nano-sized sensors [2], photodiode, and photocatalyst [3-5] for the degradation of organic dyes [6,7]. It has been acting as a semiconductor material with a high bandgap energy of ZnO (3.37 eV) and ZnS (3.72 eV) [8,9]. Moreover, these photocatalysts produce hydroxyl radicals via charged holes (h + ) and excited electrons (e − ) which are the main reactive species for oxidative/reductive degradation of a wide range of organic pollu- ∗ Corresponding authors. E-mail addresses: pandiyanphy@gmail.com (V. Pandiyan), chemkrishna2006@yahoo.co.in (B. Krishnakumar). tants. Generally, it has been found that these materials are more active in the UV region than solar for the degradation of various harmful organic dyes [10]. Nowadays the well-known biological strategy for the synthesis of NPs using microorganisms is a ver- satile method to solve the environmental-related problems in var- ious streams [11-13]. Enzymes and plants or plant leaf extracts are recommended as chemical and eco-friendly alternatives to chemi- cal and physical methods. The efficiency of NP for degradation of dyes obtained from this rout has proved to be the best due to its performance against pollutants. There are numerous works found in the literature stating that it has been a new simple and en- vironmental benefit of green synthesis processes. Those are used for toxic chemicals and high energy input avoided. Recently, differ- ent types of research work have been undertaken to determine the bio-reduction of various metal ions and metal NPs [14-16]. Costus speciosus is one of a medicinal plant belonging to the family of Costaceae. Its common names are crepe ginger, cane- reed, malay ginger, spiral flag, and wild ginger. Costus speciosus has been traditionally used in Ayurveda to treat fever, rash, asthma, rancidity, and intestinal worms. In our earlier work, Costus specio- sus leaf extract was used for the preparation of silver (CS-Ag) and https://doi.org/10.1016/j.molstruc.2020.129176 0022-2860/© 2020 Elsevier B.V. All rights reserved.