Introduction

Over the past few years, nanotechnology studies have made significant progress, not just contributing to material science and electronics but also to biomedicine. Nanomaterials have transformed the healthcare domain by providing superior nanoscale properties along with distinctive optical, chemical, and biological properties that can be employed in various therapeutic and diagnostic purposes.1 To this end, copper chalcogenide compounds of the type Cu2MX4, where M is a transition metal such as Fe, Co, Ni, or Zn and X represents the presence of a chalcogen like S, Se, or Te, have been widely sought after. The Cu2MX4 compounds consist of very versatile structural as well as functional properties, hence emerging as a potent class of nanomaterials, especially intriguing for biomedical research.2 Cu2MX4 compounds were first of interest in applications in energy storage, catalysis, and optoelectronics. The compounds have striking electronic structures, high surface area, and tunable conductivity, which serve as benefits.3 Nevertheless, as scientists delved deeper into the possibility of these compounds, they were able to find areas of application in biomedicine. Advancements in synthetic chemistry and nanofabrication methods have made it possible to have a precise level of control over their properties, and these materials are poised as strong contenders for uses in drug delivery, photothermal therapy, photodynamic therapy, and bioimaging.4 These materials have superior photothermal and photoluminescent properties and can be seen as potential contenders for targeted cancer treatment and imaging applications. Their catalytic ability facilitates the construction of novel strategies for antimicrobial interventions and biosensing technology.5Figure 1 shows the overview of Cu2MX4 (CMX)-based nanocomposites. Such responses are a reflection of the philosophy of nano architectonics, which is defined as a converging methodology combining nanotechnology, supramolecular chemistry, and material science aimed at designing and structuring functional materials at the nanoscale for biomedical and other high-tech applications.

Figure 1 Biomedical applications of Cu2MX4.

The structure of Cu2MX4 compounds is a complex network of crystalline frameworks in which transition metals and chalcogens are accommodated, coordinating with copper ions. Flexibility within the choice of “M” and “X” elements allows fine-tuning of the physical and chemical properties of compounds with adaptability that extends to various biomedical uses. The magnetic or catalytic properties are provided by transition metal atoms like Fe, Co and Zn, whereas optical and electronic properties are provided by chalcogen atoms such as S, Se, and Te.6 This kind of compositional flexibility allows the preparation of Cu2MX4 nanomaterials with a specific electronic bandgap and minimal variation, which is important for applications in which a particular optical response is necessary, such as bioimaging or photothermal therapy. The typical crystalline structure of Cu2MX4 compounds is usually tetragonal or cubic, allowing for efficient electron or phonon transfer across the material, which is beneficial for biomedical applications.7 Copper atoms are generally in a +1 oxidation state, whereas the oxidation state of the transition metal may vary, balancing the compound’s overall charge and enhancing its stability and reactivity. Also, surface properties can be tailored by functionalizing them with organic molecules, polymers, or biomolecules.8 Thus, their application range can be further expanded in biomedicine. Because functionalization results in selective interactions with cell types or molecules present within the body, such materials can be used in specific applications, such as drug delivery and biosensing.9 The structure of the CMX nanomaterial is presented in Figure 2. Figure 2 depicts (A, B) the chemical structure of CMX architectures in side and top views, and (C) the layered structure of ternary Cu2MX4, where the P-phase and I-phase are along the a, b, and c axes. The I-phase (intermediate tetragonal) and P-phase (kesterite/polyhedral) differ in atomic arrangements and stability, influencing optical/electronic properties. The green ball represents the M site atom in the Cu2MX4 lattice.

Figure 2 Schematics showing the (A and B) chemical structure of CMX architectures, with side view and top view. (C) The layered structure of ternary Cu2MX4 with P-phase and I-phase form a, b and c-axis.

Cu2MX4 compounds possess several features that make them excellent candidates for therapeutic and diagnostic applications. One of their most compelling characteristics is their ability to convert photonic energy into heat, which forms the basis for photothermal therapy (PTT) for cancer treatment.10 This photothermal efficiency, particularly at longer wavelengths, can be tuned by adjusting the particle size, morphology, and composition of Cu2MX4 nanomaterials, enabling absorption to extend into the near-infrared (NIR) range. In PTT, nanoparticles made from the Cu2MX4 are administered directly to the cancerous tissue, followed by exposure to specific wavelengths of light. These particles absorb and convert light into localized heat, killing cancer cells without affecting the surrounding healthy tissue. The targeted nature of this treatment has shown promise in experimental cancer models, leading to growing interest in optimizing Cu2MX4 compounds for even more efficient photothermal responses.11 In addition to photothermal therapy, Cu2MX4 compounds are utilized in photodynamic therapy (PDT), which selectively induces oxidative damage to cancer cells through the generation of reactive oxygen species (ROS). PDT can occur through two mechanisms: Type I, electron transfer to produce radical species (superoxide, hydroxyl radicals) regardless of oxygen concentration, and Type II, energy transfer to molecular oxygen to produce singlet oxygen (¹O2). Cu2MX4 primarily occurs through Type II oxygen-dependent pathways; however, methods like co-delivery of oxygen carriers or with oxygen-evolving systems can increase the efficacy of PDT under hypoxia. Notably, in contrast to most organic photosensitizers, Cu2MX4 shows very little aggregation-induced quenching (AIQ) as a result of its stable inorganic lattice structure, which maintains photoluminescence and ROS formation even at high concentration of particles. Some compositions of Cu2MX4 nanomaterials have high photosensitivity and generate ROS upon exposure to light. Targeted ROS generation can cause damage or destruction of cancer cells without damaging adjacent healthy tissue. The advantage of PDT with Cu2MX4 nanomaterials is that, in addition to reducing systemic toxicity, it provides a noninvasive alternative treatment with fewer side effects compared to traditional treatments.12

Cu2MX4 nanostructures also offer significant potential for bioimaging, serving as fluorescent probes or magnetic resonance imaging (MRI) agents. This is because of their exceptional optical qualities, which can guarantee bright image quality and accurate diagnosis of medical diseases.13 Some Cu2MX4 compounds emit near-infrared fluorescence that penetrates deeper into the tissue while producing clearer images for diagnostic purposes. In addition, since Cu2MX4 materials are metallic, they can be used as MRI contrast agents through magnetic interactions. Therefore, these materials can be used in both diagnostic and therapeutic fields. One of the most important biomedical applications of Cu2MX4 compounds is their potential use in antimicrobial treatment.14,15 These nanomaterials are very effective antimicrobial agents; thus, they can be used for the development of novel infection treatments or as a basis for the development of antimicrobial-coated devices for medical purposes. The Cu2MX4-based nanoparticles exhibit strong antibacterial properties, including effectiveness against drug-resistant bacteria, by disrupting cell walls or generating ROS to eliminate pathogens.15 This property is highly relevant to the healthcare field because of global antimicrobial resistance; the Cu2MX4 compounds may represent assets against difficult-to-treat infections. Several distinct properties confer biomedical value to the Cu2MX4 compounds and clearly distinguish them from other nanomaterials. It makes it possible to adjust the composition to fine-tune properties such as the bandgap, magnetic susceptibility and photothermal efficiency for specific biomedical needs. Moreover, Cu2MX4 materials are typically nontoxic and exhibit suitable biocompatibility, especially compared with metallic nanoparticles. Copper is an essential trace element in the human body. Consequently, due to variations in size, surface characteristics and dosage adjustments in the size of nanoparticles, Cu2MX4 nanomaterials are capable of delivering therapeutic benefits without much negative impact. The potential synthesis of nanoforms such as nanoparticles, nanorods and nanosheets of Cu2MX4 compounds, the application of these materials will further increase versatility. Such diversification allows for an extensive range of potential applications, from injectable formulations to local applications and even coatings for medical devices. In addition, surface modification makes Cu2MX4 nanomaterials suitable for specific biomedical applications, such as targeting certain cell types or therapeutic agent delivery in response to changes in the environment, pH and temperature. In drug delivery, nanoparticles of Cu2MX4 may be functionalized to be selectively adsorbed by cancer cells, which allows local release of the drug and thus reduces side effects.16 The multifunctionality of Cu2MX4 nanomaterials, combining photothermal, photodynamic and imaging modalities within one particle, makes them especially promising candidates as theranostics: platforms that integrate therapeutic and diagnostic functions. This property aligns particularly well with the goals of personalized medicine, in which integrated diagnostics and targeted therapies streamline care, reduce costs and improve patient outcomes. In addition, the combined potential of photothermal and photodynamic therapies can be used to treat cancer, which is a complicated disease.

Thus, Nanoarchitectures based on Cu2MX4 show promise for biomedical applications. Their essence is to represent tunable physical properties, multifunctionality and adaptation through surface modification. These features make them highly promising for biomedical applications, such as treating cancer, treating multiresistant microbes and bioimaging. The problems associated with biocompatibility, stability and large-scale clinical practice are not posed by these compounds. In future, continued developments in nanotechnology and materials science may provide potential applications in surgery, where such compounds are expected to play an enormously significant role in future innovations. This review captures the trend of the past year for Cu2MX4 based nanocomposite concerning their synthesis, properties and applications, as well as challenges in current times and directions into the future with biomedical applications.

History of Biomedical Applications of CMX-Based Nanocomposite

Early investigations in the first half of the 2010s investigated the specific optical, electronic and structural characteristics of Cu2MX4 compounds and identified their possible biomedical applications. In the mid-2010s, scientists began to consider PTT and PDT applications while also considering their biocompatibility and antimicrobial potential. The materials soon found application in multifunctional theranostic in which imaging and the therapeutic aspects of treatment converge at a targeted site. In the near past, there has been a vast advancement in the improvement of photothermal efficiency. This allows them to be used in combination therapies and targeted drug delivery. They are now in their best stages of optimizing synthesis for scalability and initiating preclinical trials, thus moving closer to clinical implementation in cancer therapy and antimicrobial applications. Table 1 summarizes the history of biomedical applications of CMX-based nanocomposite. The biomedical applications of CMX-based nanocomposite are presented in Figure 3.

Figure 3 CMX properties and bio functional attributes of various CMX-based nanocomposite.

Table 1 History of Biomedical Applications of CMX-Based Nanocomposite

Properties of Cu2MX4

Nanostructures of Cu2MX4, where M is a variable metal element and X refers to a chalcogen: sulfur, selenium and tellurium. These nanostructures have shown high interest in biomedical applications because of their unique electronic, optical and catalytic properties.14 These nanostructures exhibit excellent electronic, optical and catalytic properties, making them versatile materials for applications in bioimaging, drug delivery and biosensing. Their morphologies are also easily tunable in addition to their high surface area, which enhances their interaction with biological systems; therefore, they can be efficiently functionalized and targeted toward specific tissues or cellular components. Cu2MX4 nanostructures have outstanding photothermal and photodynamic activity, making them suitable candidates for non-invasive therapeutic applications, especially PTT and PDT.

Biocompatibility and degradability also significantly contribute to their biocompatibility, as they can notably reduce long-term risks related to toxicity, an important parameter for ensuring safe integration into biomedical applications. Moreover, the intrinsic conductivity and electron transfer properties of the Cu2MX4 compounds are likely to render them suitable for their controlled drug release and responsive behaviour in therapeutic systems. The stability of the Cu2MX4 compound in biological environments also recommends its use for longer periods and safety.14 In summary, the multifunctional properties of the nanostructures of Cu2MX4 and their amenability to surface modification make them excellent candidates for advanced, personalized medical applications. Table 2 highlights the structural, optical and chemical properties of Cu2MX4 nanostructures, along with their relevance to biomedical applications of Cu2MX4 nanostructures.

Table 2 The Structural, Optical and Chemical Properties of Cu2MX4 Nanostructures

Comparison of Cu2MX4 Nanoarchitectures with Other Nanomaterials

CMX-based nanoarchitectures have proven to be excellent candidates for biomedical applications owing to their high antibacterial, anticancer and photothermal capabilities. In contrast to conventional nanomaterials like gold nanoparticles (AuNPs), MXenes and carbon-based nanomaterials, Cu2MX4 exhibits high therapeutic efficacy mainly because of its copper-ion-mediated reactive oxygen species (ROS) production.15 This property renders it especially potent against bacterial infections and cancer cells, with 80–95% killing of tumour cells and 90–99% inhibition of bacteria in studies. Despite this, biocompatibility issues persist due to cytotoxicity, as Cu ion release can trigger oxidative stress in normal tissues. Biocompatibility-wise, AuNPs are superior to Cu2MX4 because of their established safety record and FDA-approved products with cell viability >90% at therapeutic levels.16 MXenes are moderately biocompatible, with surface terminations and oxidation affecting their toxicity. Carbon nanomaterials, including graphene and CNTs, are variable in biocompatibility, where pristine materials tend to be toxic but functionalized derivatives have 85–95% cell viability.31

One of the primary strengths of Cu2MX4 compared to conventional organic photosensitizers (like porphyrins or phthalocyanines) is that there is minimal aggregation-induced quenching (AIQ) as a result of the stable inorganic lattice, guaranteeing reliable photoluminescence and ROS generation even at concentrated levels.19 Furthermore, Cu2MX4 has higher photothermal conversion efficiency, wider absorption in the near-infrared (NIR) window by bandgap tuning, and higher catalytic activity, while most organic agents have limited absorption windows, poor stability, and decreased effectiveness under hypoxic tumour conditions. Such inherent advantages render Cu2MX4 more dependable and multifunctional for long-term therapeutic use.

Scalability is also an important consideration in nanomaterial development. AuNPs and carbon nanomaterials both have large-scale synthesis routes and are thus very scalable.32 Cu2MX4, however, has moderate scalability issues because of cost-expensive synthesis pathways and reproducibility issues, like MXenes, which are plagued by stability problems in large-scale production. Regulatory issues are also a major challenge for Cu2MX4 nanoarchitectures. AuNPs have moderate regulatory issues, with some FDA-approved products on the market, whereas Cu2MX4, MXenes and carbon-based nanomaterials have greater regulatory issues owing to sparse clinical data and toxicity issues.33 The Cu2MX4 nanoarchitectures hold strong therapeutic promise, anticancer applications, but need to be studied more in terms of biocompatibility, scalability and regulatory acceptance before reaching the clinic. Their biomedical applicability can be further optimized by surface modifications and the mitigation of toxicity through future research studies. Table 3 shows a comparison of Cu2MX4 nanoarchitectures with other nanomaterials for biocompatibility, scalability and therapeutic efficacy, scalability and therapeutic efficacy.

Table 3 A Comparison of Cu2MX4 Nanoarchitectures with Other for Biocompatibility, Scalability and Therapeutic Efficacy. Nanomaterials

Synthesis and Fabrication of Cu2MX4 (CMX)-Based Nanocomposite

CMX-based nanocomposite is known to hold great promise for applications in a wide range of fields, including drug delivery, biosensing and phototherapy and their synthesis and fabrication have attracted considerable interest. The unique structural, electronic and catalytic features can be identified and engineered through specific synthesis and fabrication methods. This would be very challenging because the final nanoarchitectures of CMX materials are highly sensitive to their structures and properties.31 Precise control over morphology, particle size distribution, stability and functionalization are essential for optimizing the performance of these materials in biomedical and environmental applications. Precise control of the structural and functional properties of the CMX nanostructures was achieved by different synthesis techniques, such as the use of a combination of solvothermal/hydrothermal processes, chemical vapour deposition (CVD), electrochemical deposition and the sol-gel methods.19 These materials are particularly useful for template-assisted synthesis, molecular layer deposition (MLD) and atomic layer deposition (ALD), which prove to be advantageous for structures that offer layered or composite structures in developing the material’s performance and its range of applications. Other techniques, such as sonochemical and microwave-assisted synthesis, are very rapid and energy-saving and produce products that may have higher surface areas and active sites.32

Each synthesis technique has its advantages and limitations, and the choice of method depends on the specific application. Cost, scalability, environmental compatibility and facility determine the easy functionalization of the chosen method.33 Ongoing innovations in CMX synthesis methods have focused on improving the uniformity, scalability and stability of these nanoarchitectures. These advances open them to various biomedical and technological fields. Here, the most commonly applied synthesis and fabrication methods for creating CMX nanoarchitectures are discussed, summarizing their mechanisms, advantages and suitability for biological applications.

Solvothermal and Hydrothermal Synthesis

In the last decade, solvothermal and hydrothermal synthesis methods is the common method, and have gained increasing popularity in the synthesis of nanoarchitectures based on CMX, which control the size, morphology and crystallinity of the particles. The reactions used in solvothermal and hydrothermal synthesis occur in sealed high-pressure vessels at very high temperatures, usually with water as a medium (hydrothermal) or with other solvents (solvothermal).25 High pressure and temperature favour fast nucleation and growth, allowing precise control over nanostructure formation. These approaches are advantageous for the preparation of uniform and stable CMX nanostructures, which are critical for biomedical applications. However, these methods often require long reaction times and are not scalable to produce large quantities.

Increased research interest has been paid to the synthesis of CMX-based nanocomposite for the distinctive and versatile applications of copper-based nanomaterials. Early investigations of copper oxide nanomaterials have revealed some promising properties; CuO is a monoclinic p-type semiconductor. The remarkable thermal conductivity, photovoltaic properties and antimicrobial properties of CuO trigger its use in catalysis, gas sensing and conversion of solar energy.17 Other environmentally friendly syntheses have been explored for the synthesis of copper-based chalcogenide nanocrystals, such as Cu2FeSnS4 as a low-cost, non-toxic and mechanochemically synthesized copper-rich sulphide. This demonstrates the structural properties of Cu2FeSnS4 with enhanced thermoelectric performance.39

The further synthesis of two-dimensional copper nanomaterials has been motivated by the potential of copper as a low-cost, conductive alternative material that can replace other materials and has applications in energy storage where surface morphology could enhance light absorption. The synthesis of two-dimensional nanomaterials by both “bottom-up” and “top-down” methods is critically discussed in line with the evolving manufacturing landscape of nanomaterials.18 The size-controlled Cu2SnS3 quantum dots whose scalable growth promises exciting applications in infrared photodetectors, expand the utility of copper-based materials.28 Green synthesis methods for 2D Cu nanosheets focus on replacing toxic chemicals with the need for sustainable nanomaterial production. Further characterization of these nanosheets shows impressive conductivity and catalytic efficiency with significant roles of Cu in advanced nanomaterial designs.40 Another application involves microwave-assisted hydrothermal synthesis, which has produced high-quality copper-substituted spinels, thus giving evidence to this method’s versatility and effectiveness for the production of nanomaterials.

Moreover, green synthesis routes based on plant extracts not only offer an eco-friendly approach because wastes containing toxic products are minimized and synthesis mediated through plants appears to be the panacea for today’s challenges in research.41 Therefore, propagating these methods toward biotechnological applications requires further improvements to enhance green synthesis techniques in terms of their applicability for industrial purposes. Hence, nanoarchitectonics based on CMX can be considered as a new and green frontier in which various methods for synthesis and possibilities for application can be observed regarding copper-based nanomaterials that correspond to the needs of recent research priorities. High-quality Cu2MoS4 single-crystal nanosheets may be easily and sustainably generated utilizing the solvothermal process, which uses Cu2O nanocrystals as the sacrificial template. Other Cu2MX4 compounds, including the Cu2WS4, can also be synthesized using this method. According to experimental findings, our Cu2MoS4 nanosheets have the potential to be both electrocatalysts for the HER and photocatalysts at visible wavelengths.42 The schematic representation of the solvothermal synthesis steps of ternary CMX nanosheets is schematically illustrated in Figure 4.

Figure 4 The schematic representation of solvothermal synthesis steps of ternary CMX nanosheets (Image is created by Biorender.com).

Chemical Vapour Deposition (CVD) Techniques

The Chemical Vapour Deposition technique can be used with great versatility for the synthesis of high-purity and uniform nanoarchitectonics of CMX. In the CVD process, gaseous precursors are allowed to enter a reactor where they decompose thermally or react chemically on the substrate at elevated temperatures, eventually depositing a thin CMX film or nanostructure layer-by-layer. This process proves to be useful for precise control of the nanostructure thickness, composition and morphology, thus being used in applications requiring very uniform coatings. CVD techniques, including thermal and plasma-enhanced CVD, imply better tailoring of CMX properties, but use specialized equipment for many applications and, hence, may have higher operational costs.28

In recent times, critical studies have been followed by a surge of research activities focused on the development of CVD techniques for synthesizing CMX-based nanoarchitectonics. The basis for future studies on the reusability of nanoparticles and particle size adjustment: Both are important parameters for optimizing Cu-based materials in applications. Seeding-nanocrystal synthesis route to β-Cu2V2O7 emphasizes that the size of the seed particles strongly controls the grain size and photoelectrochemical performance of the final material.43 This method not only includes sol-gel and solid-state chemistries but also opens new horizons for synthesizing complex materials with enhanced properties, making the importance of CVD techniques in the development of advanced nanoarchitectures evident. The multi-walled carbon nanotube (CNTs) CVD process shows the utility of the CVD method for obtaining high-purity CNTs on desired substrates, which is necessary for integrating these nanostructures into electronic devices. The discussion of different CVD methods, both at atmospheric pressure and low pressure, illustrates the flexibility of CVD synthesis processes for a wide variety of nanomaterials, such as those based on Cu2MX4.44 Challenges in bilayer graphene synthesis through atmospheric pressure CVD, stressing the understanding of growth mechanisms to improve quality and scalability. The results of this study are crucial for refining the CVD processes, particularly for the synthesis of high-quality graphene that can be integrated with Cu2MX4 materials.45 Here, an innovative water vapor-assisted CVD technique is reported for synthesizing WS2-MoS2 heterostructures and overcoming the reproducibility problems associated with the growth of two-dimensional transition metal dichalcogenides (MX2). The results point out the critical influence of environmental factors on the growth process and could be highly useful in developing similar methods for Cu2MX4-based materials, where control of the growth conditions becomes pivotal for achieving the desired properties.46 The developments in CVD processes for silicon carbide (SiC) films with low-temperature processes and atomic layer deposition (ALD) emphasizes that material properties should be controlled for use in micro- and nanoelectromechanical systems, similar to the demand for proper control over the synthesis of materials when synthesizing the Cu2MX4 materials.47

The growth of single-crystal transition-metal dichalcogenide seeds in S-CVT establishes the possibility of obtaining high-quality optoelectronic materials through this method. The possibility of large-scale crystal growth with S-CVT makes it particularly relevant for the synthesis of Cu2MX4 materials, which opens promising prospects for future research.48 Synthesis and application of CVD-fabricated graphene: significance of substrate choice and growth conditions. The results show that transfer techniques are essential for graphene-based applications, which may be reflected in the preparation of devices with CMX samples.49 Studies on MXene derivatives are summarized to present various synthetic routes and some applications in energy conversion and storage. Insight into the control of the morphology and structural design of MXenes will be useful for synthesizing Cu2MX4 materials, especially for optimizing their performance in electronic applications.24 A systematic study on the solution/ammonolysis synthesis of copper(I) nitride nanostructures, indicating the flexibility of synthetic methods to yield various nanostructures with specific surface areas, emphasizes the potential of methods in the context of Cu2MX4 nanocomposite, where tailored properties are critical for specific applications.50,51

Thus, the CVD of MoS2 flakes, highlighting key parameters determining growth reproducibility and material quality, focusing on growth protocol optimization, aligns with more general objectives for enhancing synthesis methods for Cu2MX4 materials, which are both likely to produce high-quality reproducible output.52 Several studies on the importance of wafer-scale production of two-dimensional transition metal chalcogenides and their assessment of various growth methods, including CVD, support their applicability in achieving a uniform thickness and large crystal domains, features crucial for the industrial application of Cu2MX4 materials are still interesting.53 The schematic representation of the CVD method of preparation for CMX is presented in Figure 5.

Figure 5 Schematic representation of CVD method of preparation for CMX (Image is created by Biorender.com).

Electrochemical Deposition Methods

Electrochemical deposition is an efficient and controlled means of fabricating nanoarchitectures based on CMX with a specified thickness, composition and morphology. Electrodeposition involves the use of an electric current that passes through a solution containing metal precursors to deposit CMX layers onto a conductive substrate. This method allows for the layer-by-layer construction of nanostructures necessary for any application that requires specific surface features and active sites. Electrochemical deposition is particularly useful for forming uniform, adhesive coatings, especially on complex geometries. Although it is an inexpensive and scalable method, its potential application in biomedical applications requires careful optimization of the electrolyte composition and deposition parameters to achieve desirable structural properties.

Studies on the latest developments in electrochemical deposition techniques used for the preparation of CMX-based nanocomposite reveal a highly dynamic field based on innovative techniques and material designs that are directed toward improving the performance of electrochemical devices. The work by Tóth et al underscores the importance of optimizing the deposition potential of Cu during the electrochemical deposition of multilayer structures. These studies lead to the expectation that the deposition must be carefully controlled to avoid unwanted electrochemical reactions and to maximize the magnetoresistance properties of the resulting materials in an attempt to understand the subtle interactions between the deposition conditions and material properties in multilayer systems.54 The scientists working on this basis have further studied the usage of MXenes, two-dimensional materials that are gaining popularity because of their high surface area and ion transport capability. The development of MXene-based materials for lithium-ion capacitors is promising for energy storage applications. For the structure of materials, such importance is manifested in the synthesis of MXenes and their performance as electrode materials, which is often repeated throughout subsequent studies.54 The synthesis and application of MXene derivatives in energy conversion and storage have demonstrated the unique properties, such as high surface area and excellent conductivity, of MXenes to fit a range of electrochemical applications. Also, the current progress made in the research on MXene identifies challenges that should be addressed to fully exploit those potentials in energy storage technologies.24 A quasi-2D ultra-thin liquid layer is electrochemically deposited to create a Cu2O/SnO2 periodic heterostructure sheet. Research on this material’s photoresponsivity revealed the response behaviours under various lighting situations. According to the tunnelling modulation process, it has a respectable UV photoresponsivity.55,56Figure 6 shows the various steps in the electrochemical deposition methods of (CMX) and represents the schematic diagrams of the process of electrochemical deposition.

Figure 6 Various steps in the electrochemical deposition methods of CMX (Image is created by Biorender.com).

The study on the synthesis of three-dimensional interconnected conductive networks based on CuOx demonstrated that such architectures can lead to improved electrochemical characteristics of electrode materials through enhanced ionic and electronic transport. The unique properties of CuOx-based materials combined with novel structural approaches may provide dominant improvements in the performance of supercapacitors and glucose sensors.23 Specifically, through the demonstration of Cu species efficacy in enhancing electrochemical activity inside asymmetrical supercapacitors, the importance of structural design to achieve superior electrochemical properties possesses much importance. This further supports the concept that the integration of different materials often leads to promising results for energy-storage applications.57 Some strengths of other techniques, arguably cost and scalability considerations in the versatility of electrodeposition as a method to synthesize nanostructured materials.30 Finally, recent works on the optimization of energy storage properties through the in-situ electrodeposition of nickel-cobalt sulphide composites are demonstrated as examples of how strategic design and synthesis methods can lead to enhanced electrochemical performance, representing the potential of hierarchical structures within energy storage applications.58

Microwave-Assisted Synthesis

Microwave-assisted synthesis is a fast and energy-efficient approach to directly synthesizing CMX-based nanocomposite with atomically precise control over particle size and morphology. Rapid, uniform heating facilitated by microwaves can enhance reaction rates and support the formation of highly crystalline nanostructures with desired properties, including increased surface area.20 The reaction time is markedly reduced, and thus, the synthesis times usually fall in the range of minutes under microwave synthesis conditions rather than hours in traditional synthesis. Mass production is highly efficient and scalable using microwave-assisted synthesis. However, there is an optimization need at the scientific level, to optimize microwave power, reaction time and precursor concentration for nanoparticle agglomeration to avoid quality degradation in CMX nanostructures.59

Studies on microwave-assisted synthesis of CMX-based nanocomposite have exemplified progressive evolution in methodologies and applications, with much emphasis on advantages related to microwave technology in the fabrication of nanomaterials. The exploration begins with the use of the microwave irradiation method as a transformative approach for synthesizing nanomaterials, especially copper oxides. These studies demonstrate the efficiency, energy saving and environmental advantage of the proposed method as a basis for the rapid and uniform production of nanostructures via microwave-assisted approaches.17 This being the basis, new research works further explain the method by illustrating the microwave irradiation application in the synthesis of MOFs, emphasizing the ability of the method in terms of promoting growth with controlled particle morphology and size. The kinetic and thermodynamic perspectives presented here highlight the flexibility of microwave-assisted synthesis in material preparation, which has great implications for gas storage and catalytic applications.60 The mechano-synthetic introduction of mechanochemical forces into the toolbox, complementing nanomaterial synthesis, suggests that the combination of mechanochemical methods with microwave techniques could provide better material properties for titanium dioxide photocatalysts. This synergy offers a much wider synthesis optimization scope using innovative approaches.61 The latest studies introduced a new aspect of microwave synthesis by demonstrating how electric discharges derived from metal particles can be used for the rapid production of inorganic nanomaterials, which discusses the capabilities of microwave-induced arcs for the generation of nanoparticles and demonstrates an alternate microwave technology dimension that may also be used for CMX-based nanoarchitectonics synthesis.62 Microwave-assisted hydrothermal synthesis of nanoparticles, particularly copper-substituted spinels, has reinforced the fact that microwave techniques can be impressively applied for precursors targeting advanced catalytic applications and further solidifies the role of microwave synthesis within the framework.29 Because there are currently no effective treatments for bacterial biofilm-related wound infections, human health is at risk. Thus, there is an urgent need to create a unique approach to wound infection care.56

The importance of microwave solution combustion synthesis, describing the efficiencies and versatility of producing metal oxide nanomaterials, articulating the unique heating mechanisms of microwave synthesis and contributing to uniform heat distribution and rapid material preparation. It is regarded in terms of nanomaterials with tailored properties and enhanced potential for applications in various fields.63 Finally, the synthesis of bimetallic Au-Cu nanostructures, mainly focusing on the promising applications of catalysis and photonics, underscores the optical and electronic benefits to be gained from the combination of copper with gold, adding light to the possibility of elaborating advanced nanoarchitectures that exploit the strength points of both metals.64 Hence, microwave-assisted synthesis techniques with a transformative nature and changes in the product and functionality of Cu2MX4-based nanoarchitectonics are very innovative. The introduction of such innovative methodologies opens new avenues toward the creation of advanced materials with various applications, which could be applied in catalysis, energy storage, or both.

Template-Assisted Synthesis and Self-Assembly

Template-assisted synthesis and self-assembly techniques are highly valuable for building CMX-based nanocomposite with precisely defined shapes, sizes and hierarchical structures. Template-assisted synthesis relies on templates, which can include porous materials or nanostructured moulds, to guide the development of CMX nanostructures so that their morphology and uniformity can be controlled. In contrast, self-assembly techniques use organizational processes between molecules and construct ordered architectures for CMX nanoparticles without the use of moulds. Both methods can produce complex and functional nanostructures of particular value for targeted biomedical applications. However, the removal of templates and optimized conditions in self-assembly introduces additional complexity and expense, making large-scale production problematic.65

The field of microwave-assisted synthesis has seen extensive growth recently, particularly in the synthesis of copper-based nanomaterials. A new microwave-assisted polyol route for the production of copper nanocrystals (CuNCs) without the need for supplementary protective or reducing agents has focused attention on these 2 nm CuNCs because of their low resistance and superior catalytic properties for use in printed electronics and catalytic materials.66 This innovative approach of using a non-aqueous solvent was minimized in terms of oxidation, providing a platform for further studies that aim to optimize synthesis conditions to obtain improved material properties. In 2014, the introduction of copper oxide nanomaterials, with special attention to the distinctive properties and potential applications of CuO nanostructures, pointed to the significance of chemical synthetic strategies and their factors in the synthesis process, which is important for realizing practical applications of CuO in various technological fields. This provides a foundation for further explorations of the synthesis techniques that are to follow.17 Discussions were held on the development of microwave synthesis techniques involving electric discharges generated during the microwave irradiation of metal particles. This highlights how microwave synthesis can drastically reduce the reaction time and increase product density and mechanical properties compared to conventional methods. The results demonstrate the effectiveness of microwave-assisted techniques in obtaining high-quality nanomaterials.62 The synthesis of nanostructured Cu-substituted ZnM2O4 spinels via microwave-assisted hydrothermal synthesis was investigated in 2022. This showed the potential of microwave techniques for synthesizing thermally stable Cu catalysts, and this aspect contributed to the discussion on optimizing the synthesis conditions to achieve the desired material characteristics.29 The findings of biogenic synthesis methods, especially plant-mediated approaches for producing copper-based nanomaterials, have underscored the benefits of green synthesis methods and set researchers in new research directions, namely sustainable practices in the production of nanomaterials. This perspective is critical as the field moves toward more environmentally friendly synthesis techniques.41 A novel one-step method for synthesizing copper oxide nanoparticles by arc discharge plasma in liquid, where it demonstrated the possibility of controlling the Cu/O ratio by varying the discharge currents, indicates that this method permits possible tuning of material properties, which are essential for enhancing the photocatalytic applications of copper oxide nanoparticles.67 Anodic aluminium oxide (AAO) was used as a hard template in a simple solvothermal method to create an array of highly ordered quaternary semiconductor Cu2ZnSnS4 nanowires. The nanowires are single-crystalline and homogeneous when prepared. They can grow in either the crystalline [11̅0] or [111̅] direction, and the resulting nanowire array can have comparable structural properties.68,69 These studies have catalysed a robust trajectory of innovation in microwave-assisted synthesis, especially concerning the development and application of Cu2MX4-based nanoarchitectonics.

Sonochemical Synthesis

Sonochemical synthesis is highly effective for the realization of nanoarchitectonics based on copper iodide CMX using ultrasonic waves, where the reaction chemical processes are accelerated by acoustic cavitation. Ultrasound creates cavitation bubbles in a reaction medium at high energies that finally collapse and, therefore, raise localized high temperature and pressure, which in turn accelerate rapid nucleation as well as the growth of nanostructure-related CMX. This usually results in superior surface area and reactivity. Sonochemical synthesis is highly advantageous, particularly through its rapid rate of synthesis and the ability to produce particles of comparable size. However, strict control over ultrasound frequency, power and duration also has to be carried out to not allow agglomeration in biomedical applications and to ensure material quality.70 Because of its many uses in the scientific and medicinal domains; metal complex synthesis and characterisation have attracted a lot of attention. The biological activity, spectroscopic analysis and sonochemical synthesis of novel copper (Cu) complexes were examined. The results indicate that the produced Cu2+-complexes have a great deal of potential for use in cancer treatment and medication administration. This study advances the field of supramolecular chemistry and creates multipurpose materials for a range of scientific and therapeutic uses.71

Recent advances in the sonochemical synthesis of nanoarchitectonics of Cu2MX4 well reflect the versatility and effectiveness of sonochemistry for fabricating functional nanomaterials. Therefore, the nanoparticle synthesis of Cu2SnS3 was possible. The solvothermal methods for the preparation of quantum dots are optimized for near-infrared photodetection, indicating a growing interest in size control and reusability for practical applications.28 Examples include the synthesis of nanomaterials with improved structural and optical properties, such as titania nanoparticles in photocatalysts, demonstrating how novel synthesis methods can lead to favourable material properties.61 Ultrasonic sonochemical aluminium crystal growth and graphitization of PVP demonstrate ultrasound’s ability to increase the quality features of nanostructures and offer a more efficient method of production than classical techniques, underlining the environmental advantages of sonochemistry.72,73 Similarly, sonochemical routes are utilized to synthesize complex Cu(II) and Zn(II) metal-organic frameworks that have potential applications as catalysts in various catalytic applications; this has further demonstrated the versatility of sonochemical synthesis for all sorts of nanomaterials.74 The preparation of MXene derivatives further unifies the relationship between morphology and functionality, demonstrating that controlled size and shape are directly related to the performance of energy storage and conversion.24 Advances in environmental applications for metal and metal oxide nanostructures have driven the emphasis on solid-state methods for synthesizing metal and metal oxide nanostructures. This implies that low-energy, solvent-free syntheses are a cornerstone of sustainable chemistry.75 Microwave-assisted hydrothermal synthesis is an eco-friendly route that generates energy-efficient nanomaterials. Hence, techniques combining sonochemistry probably point toward the development of high-quality, energy-efficient nanomaterials.29 Honeycomb-layered oxides, particularly copper-based ones, are especially promising materials whose properties can be invaluable to photocathodes and transparent conducting, illustrated by coordination chemistry’s impact on the material properties.76 Additionally, a more environmentally friendly synthesis of copper nanomaterials from a biogenic synthesis process using plant extracts has been reported and is further called green nanotechnology.41

Sol-Gel Method

The sol-gel synthesis route provides an excellent pathway for highly versatile and efficient pathways for preparation of nanoarchitectures based on CMX, where the particle size, shape and porosity are focused at perfect control. Initially, a liquid “sol” transforms through a sequence of hydrolysis and polycondensation reactions into a solid “gel”, obtained using metal precursors, and this gel, when dried and calcined, gives CMX nanostructures that are highly pure and stable It provides homogeneous and very finely dispersed particles, which have made the sol-gel process useful for drug delivery and imaging. However, long processing times and strict regulation of reaction conditions are required to achieve the desired material properties. In recent years, sol-gel processing has emerged as an indispensable method for synthesizing nanostructured materials. Among them, the preparation of nanoarchitectures based on Cu2MX4 (CMX) is of particular interest. The sol-gel process has been widely used to synthesize hollow spheres and 1D structures with high-purity products and fine particle sizes with chemical uniformity. These materials have wide applications in energy storage and environmental remediation.77 Various synthetic routes have been used to obtain MXene derivatives, most notably two-dimensional transition metal carbides and nitrides, like Ti3C2Tx. These structures enable zero-dimensional quantum dots and three-dimensional nanoflowers to be used in energy conversion and storage. The study of the formation mechanisms of such nanostructures is of paramount importance for optimizing their shape and performance.24

The Cu2ZnSnS4 (CZTS) absorber is made utilizing the sol-gel process and the spray deposition approach to synthesize an absorber crystalline layer of the solar cell device. The goal of this work is to create stoichiometric CZTS thin films without the need for a hazardous atmosphere or the sulfurization procedure. Given the differences in the observed microstructure at various substrate temperatures, the structural and optical characteristics of all generated CZTS thin films were examined.78

In addition to this, during research on solid-state synthesis to obtain metal and metal oxide nanostructures, eco-friendly synthesis methods were conducted, wherein a new approach in the solid-state method was implemented, which is to produce metallic nanostructures for use in environmental remediation. This method supports the sol-gel technique because it offers various alternative routes for the preparation of nanostructures in many industries.75 The combined energy-saving chemical synthesis and improvement of nanoscale material properties by hydrothermal synthesis under microwave irradiation, along with the sol-gel combine and improve. This step is important for making production sustainable.29 The effectiveness of creating nanostructures with precise accuracy was a showcase of the trends in sol-gel synthesis, according to studies conducted in China. The flexibility of sol-gel processing in designing nanostructures with specific electrochemical properties, particularly for electrodes of lithium-ion batteries, has been emphasized and pointed toward the growing role of materials derived from sol-gel synthesis in meeting modern energy challenges.79 The preparation of Cu2O nanorods using the SILAR method shows that their electrochemical properties are highly dependent on the concentration of the electrolyte used. These findings form excellent cases for Cu2O as a material for photocatalytic applications because the material overcomes a significant challenge in the inconsistency of nanostructured materials.22

Research on honeycomb-layered oxides with the inclusion of copper atoms confirms that such materials can be well-suitable for application in either photocathodes or as transparent conducting oxides to further demonstrate the various capabilities that can be achieved depending on the correct formulation of the material.76,80 The synthesis, properties and applications of MXenes have shown their relevance to energy-conversion and storage systems, particularly supercapacitors and lithium-ion batteries. It deserves further research because further knowledge of its capabilities could lead to massive solutions to energy and environmental challenges.26Figure 7 shows various steps involved in the synthesis of CMX.

Figure 7 Various steps in the sol-gel synthesis of CMX (Image is created by Biorender.com).

Molecular Layer Deposition (MLD) and Atomic Layer Deposition (ALD)

Advanced construction methods for nanoarchitectures based on Cu2MX4 or CMX enable precise atomic control. Atomic Layer Deposition (ALD) is a method that sequentially introduces metal precursors and reactants to form conformal layers on substrates. MLD is an extension of this process, with organic layers included to form hybrid or composite structures. These two techniques provide potential pathways to tailor the surface and structural characteristics of CMX materials, specifically for biomedical applications. These techniques are costly and time-consuming and require expensive equipment.

The scopes of ALD and MLD in CMX nanoarchitectronics. In ALD, in-situ QMS is advantageous for establishing the mechanism of TMA decomposition on copper oxide surfaces, showing how surface interactions enhance the quality of alumina films for nanoarchitectonic applications.81 ALD can also be used to produce materials with tailored morphologies—an important criterion for use in applications for energy storage and conversion, whereas the study has concentrated on optimization of crystallization temperatures and surface coverage to get better quality of deposition.77 MLD has proven to be a route to create ultrathin microporous metal oxide layers. Mass spectrometry and atomic force microscopy were applied in the work toward an understanding of growth dynamics that puts the potential of MLD into the improvement of polymer surfaces for advanced materials.80 Additionally, MLD demonstrates its potential for exact regulation of film properties through the use of bifunctional monomers but indicates difficulties when deposited on parti