Foams play a critical role in our daily lives and have been extensively applied in numerous areas, like food [1], medicine [2], cosmetics [3], construction [4], fire-fighting [5], mining [6], soil remediation [7], petroleum and the natural gas industry [[8], [9], [10]]. Aqueous foam is a thermodynamically unstable dispersion formed by trapping pockets of gas phase in the continuous aqueous phase. It is also an excellent intermediate structure to build porous solid materials [11,12]. The unique multi-scale structure of interface, films and bubbles endows foam with excellent properties with high viscosity, low density and strong framework and low thermal conductivity [[13], [14], [15]]. However, the natural instability [16] of aqueous foam leads to liquid-gas separation and restricts its performance in various applications. Research has shown that particles can adsorb and accumulate at the liquid-gas boundary of foams and the liquid-liquid boundary of emulsions. The particles' adsorption behavior at the interface is important to stabilize emulsions and foams [[17], [18], [19], [20]]. Particle-stabilized foams are generally known as Pickering foams, which are a promising compound in foam-based applications [[21], [22], [23], [24]]. Lately, as nanotechnology and interfacial modification techniques have progressed, the nanomaterials for Pickering foams have garnered significant attention because of their potential in expanding the application range of foams [[25], [26], [27], [28]]. Fig. 1 summarizes the diverse applications of Pickering foams in various fields.

Pickering foams enhanced by nanomaterials show an ultra-stability, multi-scale morphology and controllable rheological behaviors [[29], [30], [31], [32]]. Nanomaterials, particularly zero-dimensional nanoparticles, possess a notable capability to readily adsorb onto the space between the phases in foam. This adhesion of nanomaterials forms a protective layer akin to an “armor,” enhancing the stability and structural integrity of the foam [30,33,34]. The armored foam shows high resistance to film rupture, bubble coalescence and disproportionation. Additionally, the interwoven three-dimension networks of adsorbed and non-adsorbed nanoparticles weaken the liquid drainage in films. The life of Pickering foam can be prolonged to weeks or months, including under extreme conditions. Dominated mechanisms for nanoparticle stabilized Pickering foams have been described based on the conventional understanding of particle adhesion energy [35], maximum capillary pressure of coalescence, particle-particle interactions [18,36]. Nevertheless, as the nanoparticles become more various in internal components, surface groups, particle sizes and structure, their foam stabilization mechanisms tend to be more complex. For inorganic nanoparticles, in addition to commonly used SiO2 nanoparticles, other types of nanoparticles with single component, including titanium dioxide (TiO2), aluminum oxide (Al2O3), copper oxide (CuO), calcium carbonate (CaCO3), zero-valent iron (Fe0), ferrosoferric oxide (Fe3O4), ferric oxide (Fe2O3), etc., have also been used to produce functional Pickering foams [34,[37], [38], [39], [40]]. With the interfacial modification, nanoparticles with hydrophilicity, hydrophobicity, amphipathicity and even Janus amphipathicity were used for foam enhancement to meet the needs of different environments.

Recently, much more attention has been attracted to nanoparticles with hybrid components and random wettability, particularly those recycled from industrial waste. For example, fly ash nanoparticles produced from coal combustion have been employed to stabilize foam for enhancing oil recovery and reducing air pollutants, which was a promisingly inexpensive method for extremely stable Pickering foams [41,42]. However, many inorganic nanoparticles were unable to meet the requirements for mildness and compatibility in the application of Pickering foam for food, cosmetics, medicine etc. To overcome this problem, attention shifted to organic nanomaterials, especially those of biological origin, including cellulose nanofibers, cellulose nanocrystals, chitin nanofibrils, protein, etc. [[43], [44], [45], [46]] Compared with zero-dimensional inorganic nanoparticles, some of the organic nanomaterials belong to one-dimension. Thus, their distribution behavior and interfacial adsorption behavior vary correspondingly, contributing to a different foam stabilization mechanism [47].

Considering a higher dimensionality of nanomaterials, the utilization of two-dimensional nanosheets for the stability enhancement of Pickering foam and emulsion has recently been confirmed [48,49]. Nanosheets, such as modified graphene oxide and MoS2 nanosheet, could attach to the interface, depending on their amphiphilicity or Janus nature. Unlike conventional nanoparticles, the interfacial adsorption layer of two-dimensional nanosheets is like a “scaly armor”, and exploring the effects of its thickness, width, wettability, and softness on foam stability would be interesting and still requires further exploration.

In addition to the ultrastability of nanomaterial-based Pickering foams, numerous studies have described the multi-scale morphology and rheological behaviors of foams. The morphological characteristics of the interface, bubble, and macroscopic foam can be used not only to help to understand the stabilization mechanism but also to support the analysis of spatial homogeneity, mechanical properties, deformation, and recovery features. Generally, the rheology of Pickering foam fluid depends on its morphology and stability, and it is a crucial parameter to reflect the complex flow behaviors under the self-assembly of nanomaterials in foams films. For 0D nanoparticles, it has recently been recognized that the interfacial roughness of the foam improves because of the relatively enrichment of nanoparticles at the interface. The framework of foams tends to be much stronger, and the foam viscosity could be improved significantly, which demonstrates great potential in drilling, hydraulic fracturing and enhancing oil recovery [[50], [51], [52], [53]]. For 1D nanomaterials, their self-assembly behavior to control the multi-scale morphology of foam has become a focus of attention due to their potential application as an intermediate structure for porous materials with ultra-low density and first-rate mechanical characteristics. For 2D nanosheets, it has recently been discovered that their amphiphilic Janus behavior and large interfacial adsorption area per unit not only change the structure of interfaces but also appreciably impact their rheology.

Over the past few decades, research on nanomaterial-based Pickering foams has driven significant advancements in understanding their stabilization mechanisms and developing novel materials. These foams, characterized by unique multi-scale morphologies and specialized flow behaviors, enable a broad spectrum of applications. In hydraulic fracturing, for instance, the combination of surfactants, nanoparticles, and polymers has yielded foams with improved thermal stability and extended liquid half-life under harsh reservoir conditions. Amani et al. [54] provided an extensive review of Pickering foams, analyzing how particle size, shape, charge, and concentration influence stability, alongside external parameters such as pH, temperature, and salinity. Their findings highlight the increasing industrial applications of Pickering foams in food processing, mining, oil and gas, and wastewater treatment, emphasizing their superior stability due to irreversible particle adsorption. However, their behavior in dynamic systems remains an open research area. Expanding on interfacial stabilization, Bertsch and Fischer [55] investigated the contribution of nanocelluloses in enhancing the stability of emulsions and foams. While unmodified nanocelluloses are highly hydrophilic and ineffective as foam stabilizers, chemical modifications such as covalent hydrophobization or surfactant adsorption significantly enhance their interfacial properties. Moreover, charge screening through salt addition improves adsorption, underscoring the importance of electrostatic interactions in foam stabilization. Furthermore, modifying nanocelluloses through covalent functionalization or surfactant interactions has proven effective in stabilizing both emulsions and foams by influencing interfacial adsorption kinetics and structure [56]. Several works by Sun et al. have summarized the prospects and challenges of cellulose nanomaterial-stabilized foams as oilfield working fluids [57,58]. In food applications, Han et al. [27] explored protein-stabilized Pickering foams, demonstrating how proteins contribute to foam stability via interfacial adsorption, gel-like network formation, and depletion stabilization. Their study emphasizes the potential of protein-based foams in aerated food products while noting challenges in optimizing their functional properties.

With the discovery and improvement of more nanomaterials in different dimensions are becoming more complete. The study of stability, morphology, rheology, and hydrodynamic characteristics of foams stabilized by nanomaterials of different dimensions has become increasingly important. A systematic summary from the perspective of nanomaterial dimensions needs to be carried out. This review seeks to bridge this deficiency by providing a critical and integrative discussion of the latest findings while identifying key unresolved challenges. Specifically, we highlight the need for optimizing interfacial adsorption kinetics, mitigating nanoparticle aggregation in multi-component systems, and fine-tuning foam properties through surface chemistry and morphology modifications. By addressing these issues, we offer suggestions for designing next-generation Pickering foams, unlocking their potential for diverse industrial applications. To achieve this, we first examine recent advancements in nanomaterials across different dimensionalities, 0D, 1D, and 2D, focusing on their roles in Pickering foam stabilization. Next, we analyze the morphology and rheology of these systems, which are pivotal for practical applications. Finally, we outline future research directions that could accelerate innovation in nanomaterial-based Pickering foams, fostering their broader impact in science and industry.