Colloid Journal

Modern photonics technologies are increasingly dealing with nanostructures of different chemical composition and morphology. DNA- origami is one of the most promising methods of colloidal synthesis since its self- assembling allows creating organic nanoparticles with controlled geometry. Yet the issue remains how to hybridize them with single emitters of light for photonics applications. In the paper we investigate an opportunity of spontaneous interaction of DNA- origami in the form of parallelepiped tiles (61 × 52 × 5.8 nm) containing rectangle apertures (15 × 9 nm) with colloidal core- shell quantum dots (CdSe/CdS/ZnS/oleic acid). We characterize the attachment probability (− 25%) as well as consider single DNA/QD hybrid geometry with atomic force microscopy using deep 2D deconvolution post- processing analysis for correction.

Traditional bacterial identification methods based on cultivation require significant time, which substantially limits their operational efficiency. This paper proposes a rapid and simple method for the quantification of S. aureus 209p and E. coli K12 bacterial cells based on indirect SERS spectroscopy using gold nanostar and nanorod tags conjugated with the 4- nitrothiophenol reporter molecule. The dependence of the SERS signal on the number of nanoparticle- labeled bacterial cells was investigated. The developed method for estimating bacterial cell count demonstrated good performance both for the direct measurement of the signal from the freshly prepared complex and for measuring the signal from the pellet after centrifugation. The most statistically significant results were obtained using gold nanostars under direct, pellet- free measurement conditions of the SERS signal from the bacteria complex.

The Poisson- Helmholtz- Boltzmann model is used to study the properties of a double electric layer formed near a single weakly charged spherical particle surrounded by a 1:1 electrolyte solution. Dividing into Coulomb and non- Coulomb (defined by the Yukawa potential) interactions between ions in solution, as well as between ions and a particle, we obtain mathematical expressions for the profiles of the corresponding potentials near the particle as a function of the main parameters of the model. When varying the values of key parameters, we find both monotonic and nonmonotonic profiles of the electrostatic potential, and we observe a change in the sign of the potential, resulting in the phenomena of inversion and reversal of charge. The conditions under which the inversion and reversal of the sign of the particle potential occur are determined. The dependence of the zero charge potential on the particle size, the concentration of a monovalent electrolyte solution, and the surface density of a non- Coulomb force source is considered.

Composite nanoparticles (CNPs) with a core of a noble metal (Au, Ag) and a silica shell serving as a carrier for different target compounds are of considerable interest for solving various applied problems, including the tumor theranostics, the creation of highly sensitive sensors, super-bright emitters (including nanolasers) and different metamaterials. The conventional precursor in the synthesis of such shells is tetraethoxysilane (TEOS), which is characterized by low affinity for the surface of metal cores and poor solubility in water. In addition, as a result of the hydrolytic condensation of TEOS, a dense network of Si–O–Si bonds is formed, which negatively affects the shell capacity for the target compound. All these drawbacks significantly complicate both the obtaining of CNPs and their subsequent loading. In this paper, the possibilities and advantages of alternative approaches to the creation of CNPs based on the replacement of TEOS with functionalized alkoxysilanes are analyzed. The main attention is paid to particles obtained using γ-mercaptopropyltrimethoxysilane.

The review examines research studies in the field of electrorheology in recent years. The main actively developing research areas are presented. The latest achievements in both the development of novel materials and the theoretical description of the effect are summarized. The progress in the field of practical application is considered and original promising applications of the electrorheological effect are noted.

A new strategy of controlled non- covalent assembly is applied for tuning of the properties of ultrathin film hybrids based on graphene oxide (GO), tetracarboxyphenylporphyrin (TCPP), and polydiacetylene surfactant (PDA). It is shown how, using layer- by- layer deposition or one- step self- assembly of components at the air/water interface, it is possible to influence the mechanisms of energy and charge transfer while maintaining the chemical composition of the ultrathin film. Zinc acetate was used to integrate the active components of the hybrid through coordination bonds with the carboxyl groups of the GO and organic components. Atomic force microscopy showed that layer- by- layer assembly results in an ordered structure with a dense monolayer of GO at the base, an intermediate layer of TCPP, and an upper layer of PDA crystallites. Single- stage assembly leads to the formation of a mixed layer of GO- Zn²⁺- TCPP with a folded GO morphology covered with PDA. Spectroscopic studies revealed Förster resonance energy transfer in both hybrids, in which porphyrin acts as both an energy donor and acceptor depending on the structural form of the polydiacetylene surfactant associated with it. Hybrids obtained by layer- by- layer assembly, when integrated into photovoltaic cells with an electron- hole transport layer, demonstrated pronounced diode properties and significant photoresponse due to effective spatial separation of charges and directed transport in the layered structure. Hybrids obtained in a single stage produce symmetrical volt- ampere curves and low photoresponse due to exciton recombination in a disordered structure. The results demonstrate the fundamental possibility of controlling charge transport in photoactive hybrids by controlling their supramolecular organization through the choice of assembly method.

The paper proposes a capillary model of a charged membrane consisting of a set of separated by impenetrable material plane-parallel slit hydrophilic pores, on the surface of which a zeta potential can be set, or a fixed charge density and a liquid adhesion condition, and hydrophobic pores that differ from hydrophilic ones in size, zeta potential (fixed charge density), and Navier slip condition. The hydrodynamic and electroosmotic permeability of the membrane and its electrical conductivity are derived as functions of relative hydrophilic and hydrophobic porosity, electrolyte concentration, surface charges or potentials, dielectric properties of the solution, ion diffusion coefficients and their charge numbers, and the sizes of both types of pores. In all cases, compliance with the Onsager reciprocity principle for cross coefficients L₁₂ and L₂₁, responsible for the electroosmosis and the streaming current is shown. All boundary value problems for the four types of pores are solved analytically in the Debye-Hückel approximation. It has been established that, under the action of external pressure and electric potential gradients, in the case of aqueous organic mixtures against the background of a weak electrolyte solution, a multidirectional flow of components through the hydrophilic and hydrophobic pores of the membrane is possible. The results obtained make it possible to predict the transport properties of a charged membrane depending on the ratio between the fractions of hydrophilic and hydrophobic pores.

Colloidal systems used as a template in sol- gel synthesis are of great interest owing to their structural diversity, however, they are very sensitive to the experimental conditions. The introduction of a precursor, the release of an organic solvent during hydrolysis, the addition of catalytic additives - acid or alkali, heating lead to rearrangement and phase transformations. As a result, the final state turns out to be significantly changed compared to the initial one, which is not determined a priori. The review is devoted to precursors with ethylene glycol residues, which, unlike tetraethoxysilane used in traditional sol- gel synthesis, are hydrophilic, completely soluble in water, hydrolyzes in neutral aqueous solutions, do not require the addition of a catalyst and heating. Furthermore, unlike ethanol, ethylene glycol, in the quantities in which it is released during hydrolysis, does not lead to the transformation of colloidal systems. The review covers the preparation of the precursors, the issues of sol- gel chemistry and examples of the formation of various functional materials that are synthesized using a simpler protocol in one step under conditions determined by the mineralized template, rather than the sol- gel process. Many of the mentioned silica materials can be synthesized only using ethylene glycol- containing silane.