Morphology Control of Polymer-Inorganic Hybrid Nanomaterials Prepared in Miniemulsion: From Solid Particles to Capsules

The preparation of so-called hybrid nanomaterials has been widely developed in terms of functional and morphological complexity. However, the specific control of the arrangement of organic and inorganic species, which determines the properties of the final material, still remains a challenge. This article offers a review of the strategies that have been used for the preparation of polymer-inorganic hybrid nanoparticles and nanocapsules via processes involving miniemulsions. Different polymer-inorganic nanostructures are classified into four main groups according to the sequential order followed between the synthesis of the polymer and the inorganic species, and the presence or not of their counterpart precursors. The minimization of the energy of the system governs the self-assembly of the different material components and can be addressed by the miniemulsion formulation to reduce the interfacial tensions between the phases involved. The state of the art in the preparation of hybrid nanoparticles is reviewed, offering insight into the structural possibilities allowed by miniemulsion as a versatile synthetic technique.

Development of a mycolic acid-graphene quantum dot probe as a potential tuberculosis biosensor

The development of amine-functionalized graphene quantum dots (GQDs) linked to mycolic acids (MAs) as a potential fluorescent biosensor to detect tuberculosis (TB) biomarkers is described. GQDs have attractive properties: high fluorescence, excellent biocompatibility, good water solubility, and low toxicity. MAs are lipids that are found in the cell wall of Mycobacterium tuberculosis that are antigenic, however, they are soluble only in chloroform and hexane. Chloroform-soluble MAs were covalently linked to synthesized water-soluble GQDs using an amide connection to create a potential fluorescent water-soluble TB biosensor: MA-GQDs. Fluorescence results showed that GQDs had a narrow emission spectrum with the highest emission at 440 nm, while MA-GQDs had a broader spectrum with the highest emission at 470 nm, after exciting at 360 nm. The appearance of the peptide bond (amide linkage) in the Fourier-transform infrared spectrum of MA-GQDs confirmed the successful linking of MAs to GQDs. Powder X-ray diffraction exhibited an increase in the number of peaks for MA-GQDs relative to GQDs, suggesting that linking MAs to GQDs changed the crystal structure thereof. The linked MA-GQDs showed good solubility in water, high fluorescence, and visual flow through a nitrocellulose membrane. These properties are promising for biomedical fluorescence sensing applications.

Preparation and oil absorption performance of ATP/P(MMA-BMA-St)/Fe

In this paper, oil-in-water-in-oil (O/W/O) double Pickering emulsions were prepared by purified and modified attapulgite (ATP), and modified nano-Fe3O4 as stable particles. By using the Pickering emulsion as a template and using methyl methacrylate (MMA), butyl methacrylate ester (BMA) and styrene (St) as monomers, ATP/P(MMA-BMA-St)/Fe3O4 composite porous resins were then prepared. The oil absorption performance of the composites was investigated. The results showed that the composite materials prepared by the double Pickering emulsion template method exhibited a three-dimensional (3D) porous structure. When using the optimal conditions (mMMA:mBMA = 3:2, m(MMA+BMA):mSt = 1:2, initiator = 5.33%, crosslinking agent = 20%, modified attapulgite = 0.33% and oil phase/water phase = 1:4), the prepared porous material had the best oil absorption performance, resulting in a diesel oil absorption rate and oil retention rate of 897.29 and 84.76% respectively. This study provides a simple, economic and environmentally friendly method for the preparation of inorganic–organic composite porous materials, which has great application potential in the field of oil treatment.

Bioactive Graphene Quantum Dots Based Polymer Composite for Biomedical Applications

Today, nanomedicine seeks to develop new polymer composites to overcome current problems in diagnosing and treating common diseases, especially cancer. To achieve this goal, research on polymer composites has expanded so that, in recent years, interdisciplinary collaborations between scientists have been expanding day by day. The synthesis and applications of bioactive GQD-based polymer composites have been investigated in medicine and biomedicine. Bioactive GQD-based polymer composites have a special role as drug delivery carriers. Bioactive GQDs are one of the newcomers to the list of carbon-based nanomaterials. In addition, the antibacterial and anti-diabetic potentials of bioactive GQDs are already known. Due to their highly specific surface properties, π-π aggregation, and hydrophobic interactions, bioactive GQD-based polymer composites have a high drug loading capacity, and, in case of proper correction, can be used as an excellent option for the release of anticancer drugs, gene carriers, biosensors, bioimaging, antibacterial applications, cell culture, and tissue engineering. In this paper, we summarize recent advances in using bioactive GQD-based polymer composites in drug delivery, gene delivery, thermal therapy, thermodynamic therapy, bioimaging, tissue engineering, bioactive GQD synthesis, and GQD green resuscitation, in addition to examining GQD-based polymer composites.

Nanodiamonds synthesis using sustainable concentrated solar thermal energy: applications in bioimaging and phototherapy

There is a renewed interest in nanodiamonds and their applications in biology and medicine, especially in bioimaging and photothermal therapy. This is due to their small size, chemical inertness and unique photo-properties such as bright and robust fluorescence, resistant to photobleaching and photothermal response under near infrared (NIR) irradiation. However, the biggest challenge limiting the wide-spread use of nanodiamonds is the high-energy consuming, dangerous and sophisticated synthetic methods currently adopted by industry named higher temperature high pressure approach, and detonation method. Despite over a decade of research towards the development of new synthetic approaches, most of the methods developed to date require sophisticated instrumentations and have high energy demand. To circumvent the reliance on high energy demanding sophisticated experimental setups, here we present a simple synthetic approach using solar energy as a sustainable sole energy source. Using low-grade coal as carbon precursor, we used high power magnifying glasses to concentrate and focus sunlight to induce synthesis of nanodiamonds. The synthesized nanodiamonds exhibit similar physicochemical and photo-properties as nanodiamonds synthesized using other synthetic approaches.In vitrostudies using macrophage Raw 264.7 cells demonstrated rapid uptake and bright fluorescence of the synthesized nanodiamonds with superior biocompatibility (≥95% cell viability). The synthesized nanodiamonds also exhibited dose dependent photothermal response under NIR irradiation.

Quantum dots as a theranostic approach in Alzheimer's disease: a systematic review

Aim: Quantum dots (QDs) are nanoparticles that have an emerging application as theranostic agents in several neurodegenerative diseases. The advantage of QDs as nanomedicine is due to their unique optical properties that provide high sensitivity, stability and selectivity at a nanoscale range. Objective: To offer renewed insight into current QD research and elucidate its promising application in Alzheimer's disease (AD) diagnosis and therapy. Methods: A comprehensive literature search was conducted in PubMed and Google Scholar databases that included the following search terms: 'quantum dots', 'blood-brain barrier', 'cytotoxicity', 'toxicity' and 'Alzheimer's disease'; PRISMA guidelines were adhered to. Results: Thirty-four publications were selected to evaluate the ability of QDs to cross the blood-brain barrier, potential toxicity and current AD diagnostic and therapeutic applications. Conclusion: QD's unique optical properties and versatility to conjugate to various biomolecules, while maintaining a nanoscale size, render them a promising theranostic tool in AD.

Influence of surface charge of graphene quantum dots on their uptake and clearance in melanoma cells

Graphene quantum dots (GQDs) continue to draw interest in biomedical applications. However, their efficacy gets compromised due to their rapid clearance from the body. On one hand, rapid clearance is desired and considered advantageous in terms of their cytocompatibility, but on the other hand, it is a major limitation for their prolonged use as imaging and therapeutic probes. The uptake and clearance of GQDs have been described in vivo, however, their clearance in vitro is still not understood, one of the main reasons being that their uptake and clearance are a cell type-dependent phenomena. Studies on other types of quantum dots revealed the importance of surface charge in their uptake and retention in different cell types. However, the role of surface chemistry in GQD uptake and clearance has not been described previously. Here, we studied the influence of surface charge on GQDs (anionic and cationic) on their uptake and clearance in melanoma cells. Both cationic and anionic GQDs were synthesized using a hydrothermal method to have a relatively consistent size with an aim to study the role of surface charge in their uptake and clearance in isolation by avoiding size-dependent uptake bias. Both GQDs exhibited excellent biocompatibility with cell viability over 90% even at a high concentration of 200 μg mL-1. Using confocal microscopy and flow cytometry, we observed significantly faster and higher uptake of cationic GQDs compared to anionic GQDs. Consequently, relatively rapid clearance was observed in cells treated with anionic GQDs compared to those treated with cationic GQDs, highlighting the role of surface charge on GQDs in their uptake and clearance. Raman analysis of the cleared exocytosed GQDs revealed no sign of biodegradation of either type.

Influence of Anionic Surfactants on the Fundamental Properties of Polymer/Reduced Graphene Oxide Nanocomposite Films

Surfactants are frequently employed in the fabrication of polymer/graphene-based nanocomposites via emulsion techniques. However, the impact of surfactants on the electrical and mechanical properties of such nanocomposite films remains to be explored. We have systematically studied the impact of two anionic surfactants [sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS)] on intrinsic properties of the nanocomposite films comprising reduced graphene oxide in a matrix of poly(styrene-stat-n-butyl acrylate). Using these ambient temperature film-forming systems, we fabricated films with different concentrations of the surfactants (1-7 wt %, relative to the organic phase). Significant differences in film properties were observed both as a function of amount and type of surfactant. Thermally reduced films exhibited concentration-dependent increases in surface roughness, electrical conductivity, and mechanical properties with increasing SDS content. When compared with SDBS, SDS films exhibited an order of magnitude higher electrical conductivity values at every concentration (highest value of ∼4.4 S m^-1 for 7 wt % SDS) and superior mechanical properties at higher surfactant concentrations. The present results illustrate how the simple inclusion of a benzene ring in the SDS structure (as in SDBS) can cause a significant change in the electrical and mechanical properties of the nanocomposite. Overall, the present results demonstrate how nanocomposite properties can be judiciously manipulated by altering the concentration and/or type of surfactant.

Chiral Graphene Hybrid Materials: Structures, Properties, and Chiral Applications

Chirality has become an important research subject. The research areas associated with chirality are under substantial development. Meanwhile, graphene is a rapidly growing star material and has hard-wired into diverse disciplines. Rational combination of graphene and chirality undoubtedly creates unprecedented functional materials and may also lead to great findings. This hypothesis has been clearly justified by the sizable number of studies. Unfortunately, there has not been any previous review paper summarizing the scattered studies and advancements on this topic so far. This overview paper attempts to review the progress made in chiral materials developed from graphene and their derivatives, with the hope of providing a systemic knowledge about the construction of chiral graphenes and chiral applications thereof. Recently emerging directions, existing challenges, and future perspectives are also presented. It is hoped this paper will arouse more interest and promote further faster progress in these significant research areas.

Synthesis of diamine functionalised graphene oxide and its application in the fabrication of electrically conducting reduced graphene oxide/polymer nanocomposite films

The focus of research in diamine functionalised graphene oxide (GO) has been limited to the use of diamines either as crosslinker or to achieve simultaneous functionalisation, reduction and stitching of GO sheets, especially in the case of ethylene diamine (EDA). Controlling the extent of stitching and functionalisation has to date remained a challenge. In particular, synthesis of colloidally stable monofunctionalised GO-NH2 with dangling amine groups using diamines has remained elusive. This has been the limiting factor towards the utility of EDA functionalised GO (GO-NH2) in the field of polymer-based nanocomposites. We have synthesised colloidally stable GO-NH2 with dangling amine groups and subsequently demonstrated its utility as a surfactant to synthesize colloidally stable waterborne polymer nanoparticles with innate affinity to undergo film formation at room temperature. Thermally annealed dropcast polymer/GO-NH2 nanocomposite films exhibited low surface roughness (∼1 μm) due to the homogeneous distribution of functionalised GO sheets within the polymer matrix as observed from confocal laser scanning microscopy, scanning electron microscopy and transmission electron microscopy. The films exhibited considerable electrical conductivity (∼0.8 S m-1), demonstrating the potential of the GO-NH2/polymer nanocomposite for a wide range of applications.

Miniemulsion polymerization using carboxylated graphene quantum dots as surfactants: effects of monomer and initiator type

The effectiveness of carboxylated graphene quantum dots (cGQDs) as sole surfactants have been investigated in miniemulsion polymerization of 8 different vinyl monomers, initiated by oil-soluble initiator AIBN and water-soluble initiator VA-044.