Fabrication of ZnO/CdMoO?/T-GCN Ternary Nanocomposite using Neem Extract for Photocatalytic Degradation of Rhodamine Dye

Abstract

This study successfully prepared a green-synthesized ZnO/CdMoO?/T-GCN (ZCMG) nanocomposite using neem (Azadirachta indica) leaf extract through a microwave-assisted co-precipitation method. The neem extract functioned as a natural reducing, stabilizing, and capping agent, facilitating an environmentally sustainable and economical synthesis pathway. The rapid microwave irradiation facilitated uniform nucleation, enhanced crystallinity, and diminished particle agglomeration. The structural and morphological characteristics of the synthesized nanocomposite were validated through XRD, FTIR, SEM, and UV–Vis. The establishment of a heterojunction among ZnO, CdMoO?, and T-GCN improved light absorption and inhibited electron-hole recombination. The photocatalytic efficacy of the ZCMG nanocomposite was assessed by the degradation of Rhodamine dye under ultraviolet (UV) exposure. The composite demonstrated considerably better degradation efficiency relative to the individual components, due to enhanced charge separation and synergistic interfacial interactions. The improved photocatalytic activity is assigned to the establishment of an efficient Z-scheme/heterojunction system, enhanced reactive oxygen species production, and a broadened light absorption spectrum. The study presents a sustainable methodology for the design of effective ternary nanocomposites designed for wastewater treatment applications.

Introduction

Rapid industrialization has led to the discharge of synthetic dyes into water bodies, creating serious environmental and health hazards. Rhodamine dye, widely used in textile, paper, and printing industries, is highly stable, toxic, and resistant to conventional wastewater treatment. Its presence in aquatic systems reduces light penetration, disrupts photosynthesis, and harms living organisms. Therefore, sustainable and efficient dye degradation methods are urgently needed.

Photocatalysis as a Solution

Photocatalysis is an eco-friendly advanced oxidation process capable of degrading organic pollutants under light irradiation. Semiconductor materials such as zinc oxide (ZnO) are attractive photocatalysts due to:

• High photosensitivity

• Strong oxidizing ability

• Chemical stability

• Non-toxicity

However, ZnO has limitations:

• Wide band gap (~3.2 eV), restricting activity mainly to UV light

• Rapid electron–hole recombination

Similarly, cadmium molybdate (CdMoO?) shows good chemical stability and optical properties but suffers from insufficient visible-light absorption and fast charge recombination.

Thiourea-derived graphitic carbon nitride (T-GCN) is a metal-free semiconductor with a narrower band gap (~2.7 eV), good visible-light response, and high stability. Combining ZnO and CdMoO? with T-GCN into a ternary heterojunction system enhances:

• Light absorption

• Charge carrier separation

• Interfacial electron transfer

• Overall photocatalytic efficiency

Green and Microwave-Assisted Synthesis

The study reports the green synthesis of a ZnO/CdMoO?/T-GCN ternary nanocomposite using neem (Azadirachta indica) leaf extract via microwave-assisted co-precipitation.

Role of Neem Extract:

Neem leaves contain flavonoids, terpenoids, phenolics, and reducing sugars that act as:

• Natural reducing agents

• Capping agents

• Stabilizers

This eliminates toxic chemicals and enhances particle stability.

Microwave Assistance Benefits:

• Rapid and uniform heating

• Faster nucleation

• Reduced reaction time

• Improved crystallinity

The combination of green chemistry and microwave irradiation produces an efficient and eco-friendly photocatalyst.

Structural and Optical Characterization

XRD Analysis:

• Confirmed successful formation of ZnO (hexagonal phase), CdMoO? (tetragonal phase), and T-GCN.

• No impurity peaks detected.

• Strong interfacial interaction among components.

• Average crystallite size: ~12.4 nm (Debye–Scherrer equation).

UV–DRS Analysis:

• Absorption edge shifted, indicating enhanced light harvesting.

• Band gap reduced to ~3.1 eV (slightly lower than pure ZnO).

• Band gap narrowing attributed to heterojunction formation and sulfur-related electronic effects.

These findings confirm nanoscale crystallinity and effective heterostructure formation.

Photocatalytic Performance

The nanocomposite was tested for degradation of Rhodamine dye under UV light:

• Initial dye concentration: 10 mg/L

• Catalyst dosage: 50 mg

• Dark adsorption equilibrium: 30 min

• UV irradiation with periodic sampling

Degradation efficiency was calculated using:

(C0−Ct)/C0×100(C_0 - C_t)/C_0 \times 100(C0?−Ct?)/C0?×100

Results showed significant dye degradation, following pseudo-first-order kinetics. The enhanced performance is attributed to:

• Efficient heterojunction formation

• Improved charge separation

• Suppressed electron–hole recombination

• Strong interfacial charge transfer

Recyclability and Stability

The nanocomposite was tested over multiple degradation cycles:

• Minimal loss in photocatalytic efficiency

• Structural integrity maintained (confirmed by XRD)

• Slight activity reduction due to minor material loss or surface contamination

Strong interfacial interactions between ZnO, CdMoO?, and T-GCN improved durability and resistance to photocorrosion.

Conclusion

This study successfully synthesized and investigated a ZnO/CdMoO?/T-GCN nanocomposite via a green synthesis method using neem (Azadirachta indica) leaf extract for the photocatalytic degradation of Rhodamine dye under ultraviolet (UV) exposure. Neem extract served as a natural reducing, stabilizing, and capping agent, providing the synthesis process environmentally friendly, economical, and sustainable. UV–DRS analysis demonstrated an optical band gap of 3.1 eV, indicating improved light absorption relative to the individual components. The establishment of a heterojunction between ZnO, CdMoO?, and T-GCN markedly enhanced charge separation efficiency and reduced electron-hole recombination. Scavenger studies revealed that superoxide radicals (•O??) and photogenerated holes (h?) were the primary reactive species in the degradation process, whereas hydroxyl radicals (•OH) assumed a secondary role. The proposed Z-scheme mechanism elucidated the improved redox capacity and effective charge transfer within the composite system. Moreover, the photocatalyst demonstrated significant degradation efficiency, coupled with outstanding recyclability and structural stability across numerous cycles, thereby affirming its durability and practical utility in wastewater treatment. The green-synthesized ZnO/CdMoO?/T-GCN nanocomposite exhibits considerable promise as an effective, stable, and eco-friendly photocatalyst for sustainable environmental remediation applications.

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Copyright © 2026 Swati ., Dr. Heena Dahiya. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.