Nanomaterials have emerged as an amazing class of materials that consists of a broad spectrum of examples with at least one dimension in the range of 1 to 100 nm. Exceptionally high surface areas can be achieved through the rational design of nanomaterials. Nanomaterials can be produced with outstanding magnetic, electrical, optical, mechanical, and catalytic properties that are substantially different from their bulk counterparts. The nanomaterial properties can be tuned as desired via precisely controlling the size, shape, synthesis conditions, and appropriate functionalization. This review discusses a brief history of nanomaterials and their use throughout history to trigger advances in nanotechnology development. In particular, we describe and define various terms relating to nanomaterials. Various nanomaterial synthesis methods, including top-down and bottom-up approaches, are discussed. The unique features of nanomaterials are highlighted throughout the review. This review describes advances in nanomaterials, specifically fullerenes, carbon nanotubes, graphene, carbon quantum dots, nanodiamonds, carbon nanohorns, nanoporous materials, core–shell nanoparticles, silicene, antimonene, MXenes, 2D MOF nanosheets, boron nitride nanosheets, layered double hydroxides, and metal-based nanomaterials. Finally, we conclude by discussing challenges and future perspectives relating to nanomaterials.

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Nanomaterials: a review of synthesis methods, properties, recent progress, and challenges

Neuro-transmitters have been considered to be essential biochemical molecules, which monitor physiological and behavioral function in the peripheral and central nervous systems. Thus, it is of high pharmaceutical and biological significance to analyze neuro-transmitters in the biological samples. So far, researchers have devised a lot of techniques for assaying these samples. It has been found that electro-chemical sensors possess features of robustness, selectivity, and sensitivity as well as real-time measurement. Graphene quantum dots (GQDs) and carbon QDs (CQDs) are considered some of the most promising carbon-based nanomaterials at the forefront of this research area. This is due to their characteristics including lower toxicity, higher solubility in various solvents, great electronic features, strong chemical inertness, high specific surface areas, plenty of edge sites for functionalization, and versatility, in addition to their ability to be modified via absorbent surface chemicals and the addition of modifiers or nano-materials. Hence in the present review, the synthesis methods of GQDs and CQDs has been summarized and their characterization methods also been analyzed. The applications of carbon-based QDs (GQDs and CQDs) in biological and sensing areas, such as biological imaging, drug/gene delivery, antibacterial and antioxidant activity, photoluminescence sensors, electrochemiluminescence sensors and electrochemical sensors, have also been discussed. This study then covers sensing features of key neurotransmitters, including dopamine, tyrosine, epinephrine, norepinephrine, serotonin and acetylcholine. Hence, issues and challenges of the GQDs and CQDs were analyzed for their further development.

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Carbon and graphene quantum dots: a review on syntheses, characterization, biological and sensing applications for neurotransmitter determination

Carbon and graphene quantum dots are prepared using top-down and bottom-up methods. Sustainable synthesis of quantum dots has several advantages such as the use of low-cost and non-toxic raw materials, simple operations, expeditious reactions, renewable resources and straightforward post-processing steps. These nanomaterials are promising for clinical and biomedical sciences, especially in bioimaging, diagnosis, bioanalytical assays and biosensors. Here we review green methods for the fabrication of quantum dots, and biomedical and biotechnological applications.

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Green synthesis, biomedical and biotechnological applications of carbon and graphene quantum dots. A review

Early diagnosis of diseases is of great importance because it increases the chance of a cure and significantly reduces treatment costs Thus, development of rapid, sensitive, and reliable biosensing techniques is essential for the benefits of human life and health As such, various nanomaterials have been explored to improve performance of biosensors, among which, carbon dots (CDs) have received enormous attention due to their excellent performance In this Review, the recent advancements of CD-based biosensors have been carefully summarized First, biosensors are classified according to their sensing strategies, and the role of CDs in these sensors is elaborated in detail Next, several typical CD-based biosensors (including CD-only, enzymatic, antigen-antibody, and nucleic acid biosensors) and their applications are fully discussed Last, advantages, challenges, and perspectives on the future trends of CD-based biosensors are highlighted

Recent Developments of Carbon Dots in Biosensing: A Review.

The updated concepts on the nature of π–π interactions and their use in various fields ranging from crystal engineering to materials science to biochemistry are discussed. This is the opening paper...

The Nature and Applications of π–π Interactions: A Perspective

Carbon and graphene quantum dots (CQDs and GQDs), known as zero-dimensional (0D) nanomaterials, have been attracting increasing attention in sensing and bioimaging. Their unique electronic, fluores...

Review of Carbon and Graphene Quantum Dots for Sensing

π–π stacking interactions, as a kind of attractive and nondestructive noncovalent interaction, have been widely explored for the applications in modern chemistry, molecular biology, and supramolecular armamentarium, among which their bioapplications have attracted tremendous attention due to the unique advantages such as strong binding force, nondestructive fabrication process, and simple operation. Impressively, great achievements have been made in the area of nucleobase stacking, biosensing, controlled drug release, protein folding, molecular recognition, self-assembly, template-directed synthesis. etc. In this review, we first discuss the characterization, geometric configurations, and requirements for π–π stacking interactions, and then focus on their typical bioapplications in material engineering in particular. At the end, the outlook for potential applications of π–π stacking interactions is also discussed.

π–π Stacking Interaction: A Nondestructive and Facile Means in Material Engineering for Bioapplications

In this paper, a facile freeze-drying method was used to prepare composites polyacrylamide/ Nicandra physaloides (L.) gaertn seed gum (PAM/NPG), and it showed high adsorption properties to Congo red (CR) in the aqueous solution. The properties of the materials were investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy, specific surface area analysis (BET) and thermogravimetric analysis. The adsorption properties of CR were inves- tigated at different temperature, contact time, dosage of adsorption, pH, and initial concentration. The experimental results show that the maximum removal of CR from PAM/NPG aerogel is 684.931 mg/g when the temperature is 298 K and pH is 6. The pseudo-first-order kinetic model and Freundlich isothermal model are the best model to describe the adsorption behavior and the adsorption process is exothermic and spontaneous.

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Meixiu Li

Papers

Review of Carbon and Graphene Quantum Dots for Sensing

π–π Stacking Interaction: A Nondestructive and Facile Means in Material Engineering for Bioapplications

Adsorption properties of polyacrylamide/Nicandra physaloides (L.) gaertn gel to Congo red