The conventional synthesis methods for ZnO nanoparticles have limitations

The gap

Evidence profile

Sourced from the future work and synthesized and stated research gap of the source papers, classified as general, drawn from work published between 2024 and 2026, spanning 6 journals. Those papers have been cited 75 times in total.

Supporting evidence — 6 representative gaps

• A comprehensive review on ZnO/layered double hydroxide heterostructure as photocatalysts and photoelectrocatalysts for environmental remediation and clean energy (2026) · Discover Chemistry · cited 1× · doi

  ZnO/LDH heterostructures have emerged as a versatile class of photocatalysts and pho- toelectrocatalysts due to their unique structural flexibility, tunable band structures, and synergistic charge separation properties. The integration of ZnO with LDH layers not only enhances visible light absorption but also improves electron–hole pair separation through effective heterojunction formation. This results in significantly improved pho- tocatalytic and photoelectrocatalytic performance for applications such as organic dye degradation, water purification, CO2 reduction, and photoelectrochemical water split- ting. Numerous studies have confirmed that rational design strategies, such as morphol- ogy control, doping, defect engineering, and the construction of Z-scheme architectures further optimize their catalytic efficiency. Despite these promising advances, several challenges remain. The long-term stabil- ity of ZnO/LDH composites under real sunlight irradiation, possible photocorrosion of ZnO, and performance limitations in treating complex real wastewater are issues that require systematic investigation. In addition, the current synthesis approaches often rely on energy-intensive or chemically harsh methods, which hinder large-scale translation. Mechanistic studies are still limited, with most works relying on indirect radical trap- ping experiments; in-situ spectroscopy, advanced operando characterization, and com- putational modeling are necessary to unravel the charge transfer pathways and reaction kinetics more precisely. Future work will be focus on developing green and scalable synthesis routes, incor- porating earth-abundant and non-toxic elements to replace Cd- or Co-based LDHs for multifunctionality and on the rational engineering of interfacial charge dynamics, par- ticularly by transforming commonly formed Type-II band alignments into S-scheme heterojunctions to preserve strong redox potentials. Key approaches include atomic- scale interface engineering to regulate band bending and suppress interfacial recombina- tion losses, as well as exploiting the compositional flexibility of LDHs through controlled cation and anion exchange. Such methods enable the design and engineering of multi- functional hybrid materials that integrate selective adsorption or operate synergistically with photocatalytic activity. Finally, the translation of these materials into real-world applications will rely on scal- able fabrication directions and the effective immobilisation of photocatalysts within modular, flow-through reactor configurations. Beyond pollutant degradation, ZnO/ LDH composites hold immense potential in energy conversion applications, including hydrogen generation, CO2 reduction, NH3 synthesis, and supercapacitors, bridging the gap between environmental remediation and clean energy technologies. With continu- ous innovations in material design, mechanistic understanding, and application testing, Anitha et al. Discover Chemistry (2026) 3:199 Page 24 of 28 ZnO/LDH heterostructures are well-positioned to become next-generation catalysts for sustainable environmental and energy solutions.

  generalfuture work
  Keywords: engineering energy band charge applications design real synthesis heterostructures photocatalysts flexibility separation effective performance degradation
• Calcination temperature-dependent structural and photocatalytic properties of green-synthesized ZnO nanostructures using Mitragyna speciosa leaf extract (2026) · Creative Science · doi

  towards Dyes Mineralization. Journal of Nanotechnology, 2021, 6629180. https://doi.org/10.1155/2021/6629180 [44] Chimupala, Y., Phromma, C., Yimklan, S., Semakul, N., & Ruankham, P. (2020). Dye wastewater treatment enabled by piezo-enhanced photocatalysis of single-component ZnO nanoparticles. RSC Advances, 10(48), 28567–28575. https://doi.org/10.1039/D0RA04746E [45] Singh, K., Verma, R., Chauhan, A., Jasrotia, R., Saini, S., Thakur, P., Kumar, V., Thakur, P., & Thakur, A. (2024). Waste Water Treatment Using Piezoelectric Materials: A Review on Piezo-photocatalysis. Topics in Catalysis, 67(17), 1101–1128. https://doi.org/10.1007/s11244-024-01966-0 [46] Al-Askar, A. A., Hashem, A. H., Elhussieny, N. I., & Saied, E. (2023). Green Biosynthesis of Zinc Oxide Nanoparticles Using Pluchea indica Leaf Extract: Antimicrobial and Photocatalytic Activities. Molecules, 28(12), 4679. https://doi.org/10.3390/molecules28124679 [47] Ong, C. B., Ng, L. Y., & Mohammad, A. W. (2018). A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications. Renewable and Sustainable Energy Reviews, 81, 536–551. https://doi.org/10.1016/j.rser.2017.08.020 22

  generalfuture work
  Keywords: https nanoparticles thakur treatment piezo photocatalysis using review molecules towards dyes mineralization journal nanotechnology chimupala
• Inorganic-Chemistry Approaches to the Treatment of Dye-Polluted Water: A Comparative Review of Five Methods (2026) · International Journal of Scientific Research and Modern Technology · doi

  Despite five decades of work, several practical issues continue to limit the deployment of inorganic-chemistry methods for dye treatment. Real textile effluents contain salt loads, surfactants, sizing agents and natural organic matter that compete for adsorbent sites and scavenge radicals; performance figures obtained on a single dye in deionised water rarely survive translation to a real effluent matrix without recalibration. Catalyst recovery from small particle sizes, and the prevention of secondary metal leaching from Fe-, Cu- and Co-based catalysts into the treated water, remain demanding outside structured- support formats. Cost is a barrier for MOFs and for BDD- anode electrochemistry at full scale; energy demand limits the deployment of electrocatalytic oxidation in regions with expensive electricity. The toxicity of degradation intermediates particularly the aromatic amines produced by anaerobic or reductive cleavage of azo dyes is well documented but routinely under-monitored in laboratory studies than mineralisation. that report only decolorisation rather Several themes are likely to dominate the next decade. Solar-driven photocatalysts with truly visible-light response and low cost (g-C₃N₄, Bi-based oxides, Fe- MOFs) are an active frontier. Sulfate-radical AOPs are expanding rapidly because they extend the operating pH range of Fenton chemistry. Hybrid systems adsorbents that double as Fenton supports, photocatalysts that double as adsorbents, electrocoagulation followed by photocatalytic polishing are increasingly the norm. And the integration of through in-situ monitoring the nanomaterial-sensing approaches discussed in our companion reviews [29] is, in our view, the most likely route by which laboratory performance will translate into deployed technology. XI. CONCLUSION drive electro-Fenton electrocoagulation, semiconductors and photocatalytic Inorganic chemistry supplies the central toolkit for the treatment of dye-polluted water. Metal oxides, layered double hydroxides, clays and mesoporous silicas drive their adsorption; metal-oxide degradation; heterojunctions transition-metal redox couples drive Fenton and sulfate- radical advanced oxidation processes; metal nodes in coordination polymers drive selective adsorption and multifunctional catalysis; and electrochemical interfaces and drive electrocatalytic oxidation. The five methods are complementary rather than competing: each handles a different combination of dye class, concentration, matrix and budget, and the most effective modern treatment trains combine two or three of them on a single platform. The trajectory is unambiguous. As the cost of MOFs falls, as visible-light photocatalysts mature, as sulfate-radical AOPs replace classical Fe

  generalfuture work
  Keywords: metal drive fenton chemistry treatment water cost mofs oxidation photocatalysts sulfate radical double five several
• Synthesis and characterization of CuO/ZnO nanocomposites for quinoline yellow dye degradation and multifunctional applications (2026) · Journal of the Iranian Chemical Society · doi

  Comparative photocatalytic efficiency of neem-synthesized Ag-ZnO bimetallic nanoparticles against a range of structurally diverse organic dyes under standardized conditions has not been established. Existing studies test individual dyes (methylene blue, rhodamine B, quinoline yellow) with varying light sources and reaction times, preventing direct assessment of the Ag-ZnO system's broad-spectrum dye-degradation capability.

  generalsynthesizedevidence 5/5
  Keywords: comparative photocatalytic efficiency neem-synthesized ag-zno bimetallic nanoparticles against
• Green synthesis of zinc oxide nanoparticles using Padina pavonica extract for efficient photocatalytic removal of methylene blue (2024) · Scientific Reports · cited 74× · doi

  The conventional synthesis methods for ZnO nanoparticles have limitations. The wide bandgap of ZnO limits its photocatalytic activity to UV light. There is a need for sustainable and environmentally friendly approaches for wastewater treatment.

  generalstated research gapevidence 5/5
  Keywords: conventional synthesis methods zno nanoparticles have limitations wide
• Enhanced photocatalytic oxidation activity of supramolecular self-assembled spherical binuclear Zn2Pc2(EP)4/g-C3N4 via π-π stacking interactions for dye-containing wastewater (2026) · Research on Chemical Intermediates · doi

  The paper identifies the limitations of current techniques for treating dye wastewater, such as high costs or strict environmental control. There is a need for efficient and low-cost methods for wastewater treatment. The paper aims to address this gap by exploring the use of supramolecular self-assembled spherical binuclear Zn2Pc2(EP)4/g-C3N4 for photocatalytic oxidation.

  generalstated research gapevidence 5/5
  Keywords: paper identifies limitations current techniques treating dye wastewater

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