Hollow Core-shell Nanoparticles Research Articles

Lipid-Polymer Hybrid Nanosystems: A Rational Fusion for Advanced Therapeutic Delivery.

Lipid nanoparticles (LNPs) are spherical vesicles composed of ionizable lipids that are neutral at physiological pH. Despite their benefits, unmodified LNP drug delivery systems have substantial drawbacks, including a lack of targeted selectivity, a short blood circulation period, and in vivo instability. lipid-polymer hybrid nanoparticles (LPHNPs) are the next generation of nanoparticles, having the combined benefits of polymeric nanoparticles and liposomes. LPHNPs are being prepared from both natural and synthetic polymers with various techniques, including one- or two-step methods, emulsification solvent evaporation (ESE) method, and the nanoprecipitation method. Varieties of LPHNPs, including monolithic hybrid nanoparticles, core-shell nanoparticles, hollow core-shell nanoparticles, biomimetic lipid-polymer hybrid nanoparticles, and polymer-caged liposomes, have been investigated for various drug delivery applications. However, core-shell nanoparticles having a polymeric core surrounded by a highly biocompatible lipid shell are the most commonly explored LPHNPs for the treatment of various diseases. In this review, we will shed light on the composition, methods of preparation, classification, surface functionalization, release mechanism, advantages and disadvantages, patents, and clinical trials of LPHNPs, with an emphasis on core-shell-structured LPHNPs.

Synthesis of silica hollow core shell nanoparticles by sacrificial nitrated polystyrene template approach for targeted drug delivery application

Silica hollow core shell nanoparticles (SHCNs) were synthesized by employing nitrated polystyrene as sacrificial template. Polystyrene (PS) nanoparticles were functionalized with nitro functional group to modify the surface properties and to enhance the pore size of SHCNs. Calcination of silica coated nitrated PS nanoparticles lead to the formation of SHCNs and no traces of the polymer particles were found inside SHCNs as analyzed in fourier transform infrared radiation (FTIR). Transmission electron microscope (TEM) images were used to analyze the shell thickness of silica which was tuned between 15 and 35 nm. Specific surface area and average pore sizes of SHCNs were found to vary from 533.6 to 130.5 m2/g and 2.6 to 3.7 nm respectively. SHCNs were loaded with doxorubicin to evaluate the potential release kinetics by varying the silica shell thickness and pH of the release medium. SHCNs showed sustained release for 250 min at a pH of 7.4.

Initial stages of misfit stress relaxation in composite nanostructures through generation of rectangular prismatic dislocation loops

Critical (necessary) conditions of misfit stress relaxation in bulk and hollow core–shell nanoparticles, bulk and hollow core–shell nanowires, and flat bi- and tri-nanolayers (composing of a substrate and one or two thin films, respectively) through generation of rectangular prismatic dislocation loops (PDLs) at the inner and outer interfaces of the composite nanostructures with subsequent extension of the PDLs into cores (substrates) or shells (films) are analyzed theoretically and discussed in detail. The critical conditions are considered for different shapes and places of generation of the PDLs. It is shown that the misfit parameter is the principal factor, which determines the energetic preference of PDL generation: the latter is energetically favorable when the misfit parameter reaches its critical value, which depends on the geometry parameters of a composite nanostructure and the PDL type. Regardless of the place of PDL generation, the most energetically favorable case is when the PDL is elongated along the interface. The generation of PDLs from the free surface is the most preferable for small thicknesses of the shells (films). Growth of the shell (film) leads to a change of places of PDL generation while maintains their preferential shape – elongated along the interface. Among the six composite nanostructures under consideration, the tri-nanolayers are the least stable to the PDL generation. The hollow nanoparticles and nanowires are more stable to the PDL generation than the bulk ones. The bi-nanolayers are the most stable to the PDL generation.

Initial stages of misfit stress relaxation by rectangular prismatic dislocation loops in composite nanostructures

Theoretical models are proposed for describing the initial stages of misfit stress relaxation in bulk and hollow core-shell nanoparticles and nanowires, and in planar bi- and trinanolayers through generation of rectangular prismatic dislocation loops at the inner and outer interfaces. We obtain the changes in the total energy of the system due to the appearance of dislocation loops and calculate the critical conditions of their formation. We also determine the most profitable shape of the loops and the preferred places of their generation. Finally, we choose the nanostructures which are the most stable against dislocation loop generation.

From Ab-Initio Calculations to Multiscale Design of Si/C Core-Shell Particles for Li-Ion Anodes

The design of novel Si-enhanced nanocomposite electrodes, that will successfully mitigate mechanical and chemical degradation, is becoming increasingly important for next generation Li-ion batteries. Recently, Si/C hollow core-shell nanoparticles were proposed as a promising anode architecture, which can successfully sustain thousands of cycles with high coulombic efficiency. As the structural integrity and functionality of these heterogeneous Si materials depend on the strength and fracture energy of the active materials, an in-depth understanding of their interface and intrinsic mechanical properties, such as fracture strength and debonding, is critical for the successful design of such composites. Here, we perform ab-initio simulations to calculate these properties for lithiated a-Si/ a-C interface structures, and we combine these results with linear elasticity expressions to model conditions that will avert fracture and debonding in these heterostructures. We calculate that the a-Si/a-C interface retains good adhesion, even at high stages of lithiation. For average lithiated structures, we predict that the strong Si-C bonding averts fracture at the interface; instead, the structure ruptures within lithiated a-Si. From the calculated values and linear elastic fracture mechanics, we construct a continuum level diagram, which outlines the safe regimes of operation in terms of the core and shell thickness and the state of charge. We believe that this multiscale approach can serve as a foundation for developing quantitative failure models, and for subsequent development of flaw-tolerant anode architectures.

From Ab Initio Calculations to Multiscale Design of Si/C Core–Shell Particles for Li-Ion Anodes

The design of novel Si-enhanced nanocomposite electrodes that will successfully mitigate mechanical and chemical degradation is becoming increasingly important for next generation Li-ion batteries. Recently Si/C hollow core-shell nanoparticles were proposed as a promising anode architecture, which can successfully sustain thousands of cycles with high Coulombic efficiency. As the structural integrity and functionality of these heterogeneous Si materials depend on the strength and fracture energy of the active materials, an in-depth understanding of the interface and their intrinsic mechanical properties, such as fracture strength and debonding, becomes critical for the successful design of such and similar composites. Here, we first perform ab initio simulations to calculate these properties for lithiated a-Si/a-C interface structures and combine these results with linear elasticity expressions to model conditions that will avert fracture and debonding in these heterostructures. We find that the a-Si/a-C interface retains good adhesion even at high stages of lithiation. For average lithiated structures, we predict that the strong Si-C bonding averts fracture at the interface; instead, the structure ruptures within lithiated a-Si. From the calculated values and linear elastic fracture mechanics, we then construct a continuum level diagram, which outlines the safe regimes of operation in terms of the core and shell thickness and the state of charge. We believe that this multiscale approach can serve as a foundation for developing quantitative failure models and for subsequent development of flaw-tolerant anode architectures.

Misfit dislocation loops in hollow core–shell nanoparticles

A theoretical model is suggested to determine the critical conditions for generation of circular prismatic misfit dislocation loops in hollow core–shell nanoparticles. Based on a strict solution of the linear elasticity boundary-value problem for a circular prismatic dislocation loop in a free-surface shell, we examine the loop formation energy in the nanoparticle and show a potential opportunity to fabricate hollow, coherently bonded, i.e. dislocation-free, core–shell nanoparticles by using thin-wall shells with inner-to-outer radii ratio >0.8 as supporting cores.

Hollow Au@Pd and Au@Pt core–shell nanoparticles as electrocatalysts for ethanol oxidation reactions

Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core–shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core–shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core–shell NPs. Along with hollow core–shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core–shell NPs show highest current density in forward scan. Hollow Au@Pt core–shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores.