Enhanced photocatalytic degradation of Acid Blue dye using CdS/TiO2 nanocomposite

Photocatalytic degradation is essential for the successful removal of organic contaminants from wastewater, which is important for ecological and environmental safety. The advanced oxidation process of photocatalysis has become a hot topic in recent years for the remediation of water. Cadmium sulphide (CdS) nanostructures doped with Titanium oxide (CdS/TiO2) nanocomposites has manufactured under ambient conditions using a simple and modified Chemical Precipitation technique. The nanocomposites crystal structure, thermal stability, recombination of photo-generated charge carriers, bandgap, surface morphology, particle size, molar ratio, and charge transfer properties are determined. The production of nanocomposites (CdS-TiO2) and their efficient photocatalytic capabilities are observed. The goal of the experiment is to improve the photocatalytic efficiency of TiO2 in the visible region by doping CdS nanocomposites. The results showed that as-prepared CdS-TiO2 nanocomposites has exhibited the highest photocatalytic activity in the process of photocatalytic degradation of AB-29 dye, and its degradation efficiency is 84%. After 1 h 30 min of visible light irradiation, while CdS and TiO2 showed only 68% and 09%, respectively. The observed decolorization rate of AB-29 is also higher in the case of CdS-TiO2 photocatalyst ~ 5.8 × 10−4mol L−1 min−1) as compared to the reported decolorization rate of CdS ~ 4.5 × 10−4mol L−1 min−1 and TiO2 ~ 0.67 × 10−4mol L−1 min−1. This increased photocatalytic effectiveness of CdS-TiO2 has been accomplished by reduced charge carrier recombination as a result of improved charge separation and extension of TiO2 in response to visible light.

www.nature.com/scientificreports/ to adjust the potential of conduction and valence bands by making successive composition changes 59 . Due to the suitable band gap (2.4 eV) of CdS 60 , lower CB than TiO 2 , great optical property, and possible application of CdS in photo-electrochemistry, photocatalysis, and water splitting systems, coupling of TiO 2 with cadmium sulphite (CdS) has been widely researched 61 . Due to its low bandgap (2.4 eV), which enables its visible light response, CdS is the most important chalcogenides semiconductor as a hydrogen production catalyst 62,63 . The restricted separation efficiency of photogenerated charge carriers can overcome either by employing CdS in the form of QDs due to a shorter transit path or by integrating CdS onto support materials, such as TiO 2 64,65 . CdS doped TiO 2 nanotube composites were previously synthesized by chemical bath deposition, and their light-harvesting performance was 2.9 times than that of pure TiO 2 nanotubes. Under UV light irradiation, the CdS doped TiO 2 nanotube composite had better photocatalytic activity and photodegradation efficiency than pure TiO 2 nanotube and the degradation efficiency of methyl orange was about 42 percent at a UV intensity of 32 W 66 . Rao et al. 67 created CdS/TiO 2 core/shell nanorods with variable shell thickness to reduce charge carrier recombination and photo corrosion when exposed to UV-Vis light. Du et al. created the same type of composite, but with different morphology, by fabricating pyramid-like CdS nanoparticles and growing them on porous TiO 2 . The H 2 generation rate of 5 mol% CdS-TiO 2 was 1048.7 mol h −1 g −1 under UV-Vis irradiation and without noble-metal co-catalysts, which is about six times and 1.5 times greater than pure TiO 2 and CdS, respectively 68 .
In the present study, a series of TiO 2 NPs were synthesized in this study to investigate the effect of reactant concentration on size, shape, crystal structure, thermal, optical, and photocatalytic activities. According to prior research, a number of manufactured CdS NPs were used in the photocatalytic experiment, and it was discovered that the CdS NPs, has an excellent photo-response, but not suitable for photocatalytic water purification. TiO 2 is not photoactive under the visible region of the solar spectrum. Thus, in order to make CdS potentially applicable for water purification and utilization of TiO 2 in the visible region a nanocomposite of cadmium sulphide and titanium dioxide (CdS-TiO 2 ) was also synthesized and the effect of CdS on TiO 2 and vice versa was studied.

Materials and methods
Synthesis of titanium oxide nanoparticle (TiO 2 NP) by precipitation technique. Controlled precipitation of nanoparticles from precursors dissolved in a solution was used to make TiO 2 NP. The reductive hydrolysis of Titanium Tetra Isopropoxide (TTIP) in methanol at ambient temperature and pressure without calcinations was proposed for the manufacture of TiO 2 nanoparticles 69  The reactions were carried out as follows: 100 mL methanol (24.44 M) was placed in a conical flask, and TTIP was added dropwise (20 drops per minute) while vigorous stirring continued for another 5 h. White precipitates observed were washed with water and acetone several times and then air-dried. The crystal structure of the produced TiO 2 was expected to be a mix of anatase, brookite, and rutile.
Chemical route for the synthesis of cadmium sulphite doped titanium oxide (CdS-TiO 2 ). In a reaction vessel, 100 mL aqueous Cd (NO 3 ) 2 (0.085 M) was added dropwise with continuous stirring, followed by 50 mL methanol (24.44 M). The reaction was then carried out for 1 min in the H 2 S environment with vigorous stirring and then continued for another 2 h. The colour of the solution changed from clear to yellow. 3.53 mL TTIP (0.1 M) was added drop-by-drop to this solution (20 drops per minute). The stirring was extended for another 5 h. The hue of the solution had changed to a faint yellow.
Characterization techniques. The synthesized TiO 2 NP and CdS-TiO 2 NC were characterized by elemental, structural, optical and thermal techniques. Elemental analysis and chemical compositions were examined by energy-dispersive X-ray spectroscopy (EDS, JEOL, JSM6510LV) and Fourier Transform Infrared Spectroscopy. The structural properties were analysed by employing powder X-ray diffraction (Miniflex-TM II Benchtop, Rigaku Co-operation, Tokyo, Japan). Surface morphology and size was characterized by Scanning Electron Microscopy (JEOL, JSM6510LV) and Transmission Electron Microscopy (JEOL, JEM2100). Thermal properties were determined by Thermal Gravimetric Analysis (TGA). The optical properties were determined by employing UV-Visible Spectroscopy (Shimadzu UV-1601).
Photocatalytic experiment. The decolorization of a dye derivative Acid Blue-29 (AB-29) in the presence of UV light was used to investigate the photocatalytic activity of TiO 2 nanoparticles. The photocatalytic studies were carried out in an immersion well Pyrex glass photoreactor (inner and outer jacket) with a magnetic bar, water circulating jacket, and a molecular oxygen opening. A 125 W medium pressure mercury lamp was used to irradiate the area (Philips). The optimal catalyst dosage was established by irradiating the dye (AB-29) aqueous solution with various strengths of TiO 2 nanoparticles. 180 mL dye (AB-29) solution (0.06 mM) containing manufactured nanocatalysts (1 g L −1 ) were magnetically swirled in the dark for at least 20 min in the presence of ambient oxygen to achieve dye (AB-29) and nanocatalyst surface adsorption-desorption equilibrium. After reaching equilibrium, the first aliquot (5 mL, 0 min) was removed and the irradiation process began. During the irradiation, other aliquots of 5 mL were taken at regular intervals and examined following centrifugation. Changes in absorption were used to track the decolorization of AB-29 using a UV-Visible spectroscopic analysis approach (Shimadzu UV-Vis 1601). The dye concentration was determined using a standard calibration curve based on the dye's absorbance at various known values. The photocatalytic activity of the CdS-TiO 2 nanocomposite was tested by examining the decolorization of AB-29 in the presence of visible light using a halogen linear lamp (500 W, 9500Lumens) as a light source and comparable experimental conditions as described before. Photocatalytic studies were conducted for five cycles using the same batch of nanomaterial photocatalysts to www.nature.com/scientificreports/ determine the reusability and recyclability of the nanomaterials as catalysts. Before each photocatalytic run, the nanocomposite catalyst was rinsed with double distilled water after each cycle and a fresh solution of AB-29 was added.

Results and discussion
Spectroscopy analysis. The purity and composition of the samples were validated by FTIR spectra as shown in Fig. 1, which revealed multiple peaks related to TiO 2 in all samples without any other elemental contamination. In the 800-400 cm −1 area, bands for Ti-O and Ti-O-Ti bands were detected. The FTIR spectra of TiO 2 could be in the form of a broad band centred at 400-800 cm −1 due to the Ti-O bond vibration in the TiO 2 lattice 70 or peaks centred at 760 cm −1 , 680 cm −1 , 600 cm −1 , 560 cm −1 , 500 cm −1 , 468 cm −1 , 410 cm −1 , 385 cm −1 and 350 cm −1 attributable to 71,72 . The FTIR spectra of TiO 2 nanoparticles (Tma, Tmb, Tmc, Tmd, and Tme) and their nanocomposites with CdS are shown (CdS-TiO 2 ) in Fig. 1. The varied peaks generated by TiO 2 nanoparticles and their nanocomposites with CdS nanoparticles are explained in Table 1 73,74 . The FTIR spectra of TiO 2 NPs (Tma, Tmb, Tmc, Tmd, and Tme) and CdS-TiO 2 NC in this study were in the shape of a large peak in the 400-800 cm −1 region with multiple tiny peaks. Stretching Vibrations of hydroxyl (OH) groups of water adsorbed by the samples were ascribed to the broad peak showing at 3100-3600 cm −1 . Such TiO 2 -OH groups are formed as a result of the hydrolysis reaction in the process. The bending modes of -OH groups of water molecules adsorbed on the surface of the catalyst are responsible for the peak at 1628 cm −175 . CO 2 deposited on the surface of the particles showed a weak absorption band at 1620-1630 cm −1 . Adsorption of water and CO 2 was ubiquitous for all powder samples exposed to the atmosphere, and significantly more evident for nanosized particles with large surface areas, as well known 75 . In the case of CdS-TiO 2 , the existence of a broad band centred at 400-800 cm −1 with numerous little peaks in it proved the creation of CdS, and the presence of broadband centred at 400-800 cm −1 with several small peaks in it indicated the presence of TiO 2 in the nanocomposite. The creation of a sandwich structure with CdS at the centre (core) and TiO 2 NPs surrounding CdS as a shell result in CdS stretching at 605 cm −1 . The FTIR spectra of the reaction product, obtained  Energy dispersive X-ray spectroscopy (EDAX) analysis. Figure 2 shows the EDAX spectra of the prepared samples. For the samples Tma, Tmb, Tmc, Tmd, and Tme, the spectra revealed the existence of Ti and O peaks, confirming the synthesis of pure TiO 2 with no other elemental impurity. The other peaks in this graph, related to oxygen, carbon, and silicate, were caused by the sputter coating of the glass substrate on the EDS stage and not taken into account. The presence of peaks corresponding to Cd and S, as well as peaks for Ti and O, in the EDS spectra of CdS-TiO 2 confirmed the creation of the CdS-TiO 2 nanocomposite.

Structural analyses.
Diffraction and microscopic examinations were used to conduct structural evaluations. X-Ray Diffraction (XRD) Spectroscopy was used to conduct diffraction research. Due to the physical nature of the materials, the diffraction patterns for TiO 2 NPs (Tma, Tmb, Tmc, Tmd, and Tme) were of poor quality. The XRD pattern of the produced TiO 2 NPs (Tma, Tmb, Tmc, Tmd, and Tme) confirmed the existence of anatase, brookite, and rutile mixes (Fig. 3 82,83 verified the production of cubic CdS. The existence of mixed peaks of cubic CdS and anatase TiO 2 made it impossible to estimate crystallite size for CdS-TiO 2 using the X-ray diffraction peak. Scanning electron microscopy (SEM) analysis. SEM images of the synthesized TiO 2 NP are depicted in Fig. 5a-e. The creation of well-defined spherical mesoporous TiO 2 nanoclusters observed using SEM micro- www.nature.com/scientificreports/ graphs was attributed to the high surface energy of nanosized TiO 2 particles 84 . By agglomerating tiny particles, pure TiO 2 generates a layer-like structure. An amorphous mass with a very small particle structure was visible in the SEM picture of CdS-TiO 2 . Due to the thin amorphous powder, no other distinct particle shape was discernible as CdS particles uniformly covered by the TiO 2 nanoparticles formed a sandwich-type structure. in which CdS is acting as a core surrounded by smaller TiO 2 NPs. SEM pictures of the synthesized CdS-TiO 2 NC are shown in Fig. 5f 85 . (1-2 nm) can be seen in the images. The nanocluster size has shrunk from > 500 nm (Tma) to 50 nm (Tme). In all cases, however, the individual TiO 2 nanoparticles were smaller than 2 nm. The TEM picture of CdS-TiO 2 (Fig. 7) verifies the presence of two different-sized nanoparticles CdS and TiO 2 nanoparticles with close proximity to each other. TEM images of CdS-TiO 2 (Fig. 7a) show two different-sized nanoparticles with smaller ones surrounding the larger ones in a core-shell type fashion. Further, the presence of both CdS and TiO 2 were also confirmed by EDS and XRD test results individually. The observed two distinctly different sized particles with close proximity to each other is the direct prove of the sandwich-type model of nanoparticles with smaller particles (TiO 2 ) surrounding the larger particle (CdS) like a core. Figure 7b shows a TEM image of the CdS-TiO 2 composite. Table 2 shows the particle sizes acquired using TEM.

Transmission electron microscopy (TEM) analysis.
Thermal analyses. The Thermal Gravimetric Analysis (TGA) graphs were used to conduct thermal experiments. TGA findings of the synthesised TiO 2 nanoparticles (Tma, Tmb, Tmc, Tmd, and Tme) and CdS-TiO 2 nanocomposite are shown in Fig. 8. The TGA curve demonstrated great thermal stability, the lack of any impurity or intermediate complex, and a high melting point for the produced nanoparticles. The TiO 2 NPs (Tma,   86,87 . The absorption edges of produced TiO 2 nanoparticles (Tma, Tmb, Tmc, Tmd, and Tme) were found to be in the wavelength range 382-403 nm, implying the presence of mixed phases or a blue shift from the bulk rutile phase. This blue shift was detected with the decrease of TiO 2 NP particle sizes from Tma to Tme, and was in good agreement with previous findings. This change was linked to QSE or the presence of TiO 2 mixed-phase 88 . XRD results given in the study indicated the presence of mixed-phase TiO 2 . The values of the absorption edges of the different TiO 2 NPs are listed in Table 3. Figure 9b shows the bandgap energy of TiO 2 NP. The bandgap curve was plotted (αhν) 1/2 vs hν based on Tauc relation revealed an indirect bandgap 89 . As the size of TiO 2 NP reduced from Tma to Tme, a greater band gap was observed. Table 3 lists the corresponding band gaps of the various TiO 2 NPs. The bandgap of TiO 2 can also be calculated using the Eq. (1): where E g denotes the bandgap energy, and onset denotes the absorption edge as determined by the absorption spectra 90 . The results of the above formula were in good agreement with the Tauc relation curves (Table 3).
(1) E g = 1240/ onset www.nature.com/scientificreports/ In Fig. 9c, the absorption spectra of CdS-TiO 2 are compared to those of bulk CdS and TiO 2 (anatase). Bulk CdS exhibited a sharp edge at 515 nm, while anatase TiO 2 exhibited one at 388 nm. The spectrum of CdS-TiO 2 NC displayed a mixture of these two spectra, with an absorption edge at 487 nm that was blue-shifted from that of pure CdS NP (515 nm) and at 388 nm corresponded to that of pure anatase TiO 2 NP. The synthesis of anatase TiO 2 in CdS-TiO 2 was shown to be good in accordance the XRD results. The creation of a solid solution at the interfaces as a result of close contact between CdS and TiO 2 caused this shift, and this behaviour determined the optical properties of the final nanostructure 91 . Which attributes to electronic semiconductor-support interaction (SEMSI) by several researchers 92,93 . The UV area is used to excite (bulk) TiO 2 (bandgap = 3.2 eV), whereas the visible region is used to excite CdS (bandgap 2.42 eV). As a result of visible light absorption, electrons in CdS nanoparticles can be stimulated from the valence band to the conduction band, forming electron-hole pairs that are then trapped by the surface state 94 . These electrons can transfer from the CdS to the TiO 2 conduction band. They can then migrate across the TiO 2 conduction band and contribute to the reduction of species like oxygen molecules or adsorbed pollutants 95    where k represents the reaction rate constant (mMmin −1 ), K represents the reactant's adsorption coefficient (mM −1 ), and C represents the reactant concentration (mM). When C is very low, KC is minimal in comparison to unity, allowing Eq. (2) to be simplified to apparent pseudo-first-order kinetics 99 .
The decolorization curve (Fig. 10a), emerged as an exponential decay curve which represents pseudo-firstorder kinetics reasonably well. The rate constant was obtained for each experiment by plotting the natural logarithm of dye concentration as a function of irradiation time 100 . The following is a representation of the equation:  www.nature.com/scientificreports/ C 0 represents the starting reactant concentration (mM), C represents the reactant concentration (mM) at time "t", and k app represents the apparent pseudo-first-order rate constant (min −1 ).
The data in Fig. 10a were in good agreement with the pseudo-first-order reaction for our experimental conditions, as shown in Fig. 10b by plotting ln (C 0 /C) versus irradiation time. For all of the experiments, the correlation constant (R 2 ) for the fitted lines was calculated to be 0.99.
In addition, when particle size decreases, band gap energy rises, reducing charge carrier recombination. It is widely assumed that a bigger band gap equates to greater redox capacity 103 . As a result of its large surface area, enhanced bandgap, and strong redox capability with low photo corrosion, Tme had the highest photocatalytic activity. A photocatalytic reaction using TiO 2 is essentially a redox reaction including photogeneration, migration, trapping, and recombination of reactants adsorbed on its surface 104 . The process of photocatalysis over titanium dioxide (TiO 2 ) can be explained as follows: photocatalysis was initiated by the absorption of a photon with energy equal to or greater than the bandgap of TiO 2 (3.2 eV), leading to photo-excitation, producing electron-hole (e/ h + ) pairs (Eq. 6) 105 . As a result, the TiO 2 particle operated as an electron donor or acceptor for molecules in the surrounding medium after irradiation. The photoexcited electron and hole took part in redox reactions with adsorbed species like water, hydroxide ions (OH), organic compounds, and oxygen. The photoexcitation of TiO 2 under UV light irradiation is depicted in Fig. 11 as an example scheme.
The holes (h + ) oxidized water (H 2 O) Eq. (7) or hydroxyl anion (OH) Eq. (8) in the valence band to form the hydroxyl radical (·OH), a highly potent and indiscriminate oxidant. Similarly, the electron (e − ) reduced the  10), which interacted to produce the ·OH radical Eq. (11). ·OH radicals quickly attacked contaminants on the surface, as well as in solution Eq. (12). This prevented the electron from recombining with the hole and resulted in a concentration of oxygen radical species, which aided in the attack on pollutants 106,107 .
The reactions can be expressed as follows: After 90 min of reaction time, the decolorization rates employing TiO 2 nanocatalysts (Tma, Tmb, Tmc, Tmd, and Tme) for the 5-cycling reuse are shown in Fig. 10d. Table 4 shows the results of five successive cycles of decolorization rates for all TiO 2 nanocatalysts (Tma, Tmb, Tmc, Tmd, and Tme). The catalytic activity of TiO 2 nanocatalysts (Tma, Tmb, Tmc, Tmd, and Tme) dropped marginally after the first cycles, according to the findings. Tme showed the most stability among them when compared to other TiO 2 nanocatalysts, which could be owing to Tme's small size.
Because the differences in relative stability among the TiO 2 NPs were not significant, it can be concluded that all of the produced TiO 2 NPs have good photocatalytic activity and UV light irradiation stability. However, because UV radiation accounts for just 4-6% of the total solar spectrum, it is vital to investigate TiO 2 's applicability in the visible zone.  www.nature.com/scientificreports/ As a result, TiO 2 NPs were combined with CdS NPs (CdS-TiO 2 ) and their photoactivity was investigated. A photo-degradation experiment using a dye derivative AB-29 in the presence of visible light was used to investigate the photocatalytic activity of CdS-TiO 2 nanoparticles. The photocatalytic experiment was conducted in the same manner as the TiO 2 NP experiment. The absorption edge of CdS-TiO 2 falls well inside visible radiation, resulting in enhanced photodegradation when exposed to visible light. In the presence of CdS-TiO 2 nanocomposite and ambient oxygen, irradiation of the dye under examination resulted in the decrease in absorption intensity as a function of irradiation time. In the presence and absence of CdS-TiO 2 photocatalysts, the relative change in the concentration of AB-29 (C/C 0 ) as a function of time is shown in Fig. 12a. The results were compared to nanoparticles of TiO 2 (Degussa P-25) and CdS 55 . CdS-TiO 2 demonstrated 84% decolorization of AB-29 after 90 min of visible light irradiation, whereas CdS and TiO 2 showed only 68% and 09%, respectively, as shown in Fig. 12a. In the absence of photocatalyst, however, there was no discernible decrease in dye concentration. In the visible area, it was confirmed that CdS-TiO 2 NC had better photocatalytic activity than individual CdS and TiO 2 NP. The observations were consistent with a pseudo-first-order response, as illustrated in Fig. 12b by plotting ln (C 0 /C) with irradiation time. A visualization of the natural logarithm of dye concentration as a function of irradiation duration Eq. (4) yielded the rate constant. The fitted lines' correlation constant (R 2 ) was calculated to be 0.99.
Using the Eq. (5), the dye degradation rate was estimated. The decolorization rate of AB-29 in the presence of CdS-TiO 2 photocatalyst as shown in Fig. 12c demonstrated that CdS-TiO 2 decolorized AB-29 was faster (5.8 × 10 −4 mol L −1 min −1 ) than CdS (4.5 × 10 −4 mol L −1 min −1 ) or TiO 2 (0.67 × 10 −4 mol L −1 min −1 ). The increased photocatalytic effectiveness of CdS-TiO 2 in the visible area was owing to reduced charge carrier recombination as a result of better charge separation and TiO 2 extension in response to visible light. Figure 12d depicts the photodegradation of AB-29 by CdS-TiO 2 NC and CdS NP over a five-cycle period. After 90 min of response time, the relative decolorization utilising CdS-TiO 2 for the 5-cycling reuse was 83.3%, 79.6%, 75.4%, 72.4%, and 70.1%, respectively.
The catalytic activity of CdS-TiO 2 was declined after the first cycles but at a lower rate than that of pure CdS NP, which reduced at a faster rate (68.4%, 64.3%, 60.1%, 56.1% and 52.3% respectively for 5 consecutive cycles). As a result, CdS-TiO 2 appears to be a superior photocatalyst to pure CdS NP, with increased activity and stability. However, photo corrosion of CdS, which forms cadmium cations, may be the cause of the decrease in CdS-TiO 2 stability during photocatalytic degradation events.
Under the instance of CdS/TiO 2 , the narrow band-gap allowed CdS/TiO 2 to absorb more photons, increasing TiO 2 's photocatalytic efficiency in the sun. The absorption of a photon by CdS with energy equal to or greater   (14). Because holes flow in the opposite direction as electrons, they became trapped in the CdS. As a result, charge separation has improved, and recombination has decreased. A proposed mechanism for the degradation of contaminants on CdS coupled TiO 2 catalyst under visible light irradiation is given in Fig. 13 based on literature findings 13,19,79,89,91,92 and our experiment results.
In oxygen-equilibrated environments, the photoexcited and transmitted electrons in TiO 2 's CB were scavenged by molecular oxygen O 2 , yielding the superoxide radical anion O 2 · Eq. (15) and hydrogen peroxide H 2 O 2 Eq. (16). The interaction of these intermediates resulted in the formation of the hydroxyl radical ·OH Eq. (17). The oxidative breakdown of AB-29 eq was then triggered by the ·OH radical Eq. (18) 91 . The photo-generated and transmitted hole in the VB of CdS cannot form hydroxyl radicals by oxidizing hydroxyl groups and H 2 O molecules, but it can oxidize dye molecules to reactive intermediates and then to final products Eq. (19).
The reactions can be expressed as follows: Because photo-generated holes in CdS nanocrystals are unable to convert hydroxyl groups to hydroxyl radicals due to their valence band potential, photo corrosion of CdS occurs, resulting in the formation of cadmium cations [108][109][110][111] . The decrease in photo-stability of CdS-TiO 2 in the recycle experiment (Fig. 12d) also indicated leaching of cadmium cations. Table 5 provides additional examples of reports for the degradation performance of CdS and other nanocomposites for AB-29 azo dye as organic pollutants at the indicated experimental conditions.

Conclusion
Under ambient conditions, Titanium Dioxide nanoparticles (Tma, Tmb, Tmc, Tmd, and Tme) were effectively produced using a single pot chemical precipitation approach. The size of the TiO 2 nanocluster was reduced as the concentration of the Ti precursor dropped, as seen by the prepared TiO 2 NP. In all TiO 2 samples, a mixed crystalline phase was detected. The micrographic analysis demonstrated the production of spherical clusters   www.nature.com/scientificreports/ whose diameters shrank drastically as the Ti precursor concentration dropped. With the decrease in Ti precursor concentration, the absorption spectra indicated a minor blue shift and, as a result, a slight rise in bandgap energies of TiO 2 NP was observed. Finally, under UV light, the photocatalytic response for the breakdown of the organic dye AB-29 was improved as TiO 2 had photoactive under UV light and CdS found as photocorroded during photocatalytic processes, an effort was made to combine the beneficial qualities of both CdS and TiO 2 while minimizing their disadvantages. A sandwich-type nanocomposite (CdS-TiO 2 ) of CdS with TiO 2 was also successfully synthesized. The CdS-TiO 2 showed good elemental purity and thermal stability. Cubic CdS and anatase TiO 2 were discovered in the XRD spectrum. Because of the presence of TiO 2 , the absorption edge of CdS in CdS-TiO 2 shifted slightly blue, but the absorption edge of TiO 2 was identical to that of pure anatase TiO 2 , indicating an improvement in the crystal structure. TiO 2 's optical sensitivity was moved towards the visible range in CdS-TiO 2 , allowing it to be photocatalytically active in visible light as well. With the decrease in Ti precursor concentration, the absorption spectra indicated a minor blue shift and, as a result, a slight rise in bandgap energies of TiO 2 NP.