Carbon dots (CDs) with small particles less than 10 nm offered unique electrochemical properties. They can be synthesized via various methods using abundant carbon sources. The electrochemical properties of CDs can be optimized via several strategies, including doping with heteroatoms, optimizing the synthesis conditions, and postsynthetic procedures. CDs can be used as suitable electron transporters. They exhibit several advantages, such as a large surface area that offers simple electrode fabrication and enables a high contact area with the investigated analyte. The electrochemical properties of CDs have advanced the analysis of different analytes, including heavy metals ions, biomarkers, hydrogen peroxide, drugs, and other species. The functional groups of CDs provided strong interactions with the vast number of analytes promoting direct electron transfer. CDs offered high sensitivity, good selectivity, and promising properties for analyzing real samples.

Carbon dots (CDs) have been used as a fluorescence probe to sense heavy metal ions. They can be synthesized using cheap sources and offer good optical properties. They provide good photoluminescence properties. The fluorescence emission of CDs can be tuned by controlling particle size, selecting suitable excitation wavelength, and changing the chemical composition via doping with heteroatoms. The synthesis procedure can also affect the optical properties of the synthesized CDs. The unique optical emission enables the sensing of heavy metals, including biological heavy metals (e.g., Fe³⁺, Zn²⁺, Cu²⁺) and toxic metals (e.g., Pb²⁺, As³⁺, Ag⁺, ClO⁻). CDs as fluorescence probes enable a low detection limit and a good linear relationship for a wide concentration range. They can be applied for actual samples with promising properties for assembling electronic devices. This book chapter summarizes the applications of CDs as fluorescence probes to detect heavy metal ions.

Polysaccharides are widely used for several applications, including biomedical science. They can be used in tablet formulation, coating biomedical implants, dental implants, tumor-targeting implants and regenerative medicine, bone and tissue engineering, and drug delivery. They are biocompatible, exhibit low toxicity, and require low cost. Several polysaccharides can be extracted from plants, animals, and microorganisms. Polysaccharides exhibit high performance as implants. Drug loading or release using polysaccharides is optimal compared to conventional polymers. This book chapter summarized the applications of polysaccharides for biomedical implants. It can be a brief introduction for the researchers and scientists looking for biomedical implants using polysaccharides.

The utilization of graphene (G)-based materials e.g., graphene oxide (GO) and reduced GO (rGO) has significantly enhanced the field of mass spectrometry. G-based materials in question constitute a comprehensive collection that offers a wide range of applications, notably in the field of laser desorption/ionization mass spectrometry (LDI-MS). They enable the identification of many biological entities such as proteins, peptides, polysaccharides, and small compounds. G-based matrices offer high sensitivity. Graphene derivatives have been utilized in several advanced techniques, such as surface-assisted LDI-MS (SALDI-MS), surface-enhanced LDI-MS (SELDI-MS), and graphene-assisted LDI-MS (GALDI-MS). These methodologies demonstrate interferences-free spectra within the low mass range (50–1000 Da). They offered soft ionization MS and can be effectively utilized for the analysis of labile biomolecules.

Gene and vaccine delivery offer promising technologies for the treatment of several diseases. However, they suffer from low transfection efficacy, enzyme degradation, and immunogenicity of the gene-based therapeutic agents or vaccines. Thus, several materials were reported as carriers for gene therapeutic agents. Alginates-based materials provide solutions for several challenges of other biomaterials. They exhibit high biocompatibility for many biological cells with low or minimal toxicity, show high stability under different environments, and can proceed quickly into various forms such as beads, capsules, fibers, and hydrogels. Bio-beads of calcium alginate is widely used to encapsulate gene-based therapeutic agents. They can be quickly processed as three-dimensional (3D) scaffolds, hydrogels, capsules, spheres, foams, sponges, and fibers. They can be used as carriers for gene and vaccine delivery. They offer several advantages, such as high biodegradability, good encapsulation efficiency, excellent biocompatibility, and good chelating capacity. The alginate-based system was used for gene delivery for tissue generation, bone generation, cartilage repair, and cancer therapy. Alginate-based biomaterials offered the development of gene-activated bio-inks (GABs) for 3D printing. This book chapter summarizes the applications of alginate as carriers for gene and vaccine delivery.

Hydrogen storage and release using a solid-state material e.g., sodium borohydride (NaBH₄) may fulfill the requirements for the ‘Hydrogen Economy’. This study reported ZnO-based materials for hydrogen release via the hydrolysis of NaBH₄. Two different metal oxides e.g. CeO₂ and TiO₂ with different weight loading (5 wt.% and 10 wt.%) were used during the synthesis via a simple combustion method. The synthesis procedure offered nanocomposites consisting of ZnO-xTiO₂, and ZnO-xCeO₂ (x = 5 wt.% or 10 wt.%). Diffraction techniques (X-ray (XRD) and electron diffraction (ED)) confirm the phase purity of the material. Diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy characterized the optical properties of the materials. The materials displayed a hydrogen generation rate (HGR) of 3000 mL·min⁻¹·g_cat⁻¹. Thermodynamic analysis revealed that ZnO, ZnO-10TiO₂, and ZnO-10CeO₂ catalysts have activation energies of 59.8, 36.8, and 27.5 kJ·mol⁻¹, respectively.

One-pot co-precipitation of target molecules e.g. organic dyes and the synthesis of a crystal containing microporous–mesoporous regimes of zeolitic imidazolate frameworks-8 (ZIF-8) are reported. The synthesis method can be used for cationic (rhodamine B (RhB), methylene blue (MB)), and anionic (methyl blue (MeB)) dyes. The crystal growth of the ZIF-8 crystals takes place via an intermediate phase of zinc hydroxyl nitrate (Zn₅(OH)₈(NO₃)₂) nanosheets that enabled the adsorption of the target molecules i.e., RhB, MB, and MeB into their layers. The dye molecules play a role during crystal formation. The successful encapsulation of the dye molecules was proved via diffuse reflectance spectroscopy (DRS) and electrochemical measurements e.g., cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The materials were investigated for carbon dioxide (CO₂) adsorption and adenosine triphosphate (ATP) biosensing. ZIF-8, RhB@ZIF-8, MB@ZIF-8, and MeB@ZIF-8 offered CO₂ adsorption capacities of 0.80, 0.84, 0.85, and 0.53 mmol g⁻¹, respectively. The encapsulated cationic molecules improved the adsorption performance compared to anionic molecules inside the crystal. The materials were also tested as a fluorescent probe for ATP biosensing. The simple synthesis procedure offered new materials with tunable surface properties and the potential for multi-functional applications.

Metal–organic frameworks (MOFs) have advanced several technologies. However, it is difficult to market MOFs without processing them into a commercialized structure, causing an unnecessary delay in the material's use. Herein, three-dimensional (3D) printing of cellulose/leaf-like zeolitic imidazolate frameworks (ZIF-L), denoted as CelloZIF-L, is reported via direct ink writing (DIW, robocasting). Formulating CelloZIF-L into 3D objects can dramatically affect the material's properties and, consequently, its adsorption efficiency. The 3D printing process of CelloZIF-L is simple and can be applied via direct printing into a solution of calcium chloride. The synthesis procedure enables the formation of CelloZIF-L with a ZIF content of 84%. 3D printing enables the integration of macroscopic assembly with microscopic properties, i.e., the formation of the hierarchical structure of CelloZIF-L with different shapes, such as cubes and filaments, with 84% loading of ZIF-L. The materials adsorb carbon dioxide (CO₂) and heavy metals. 3D CelloZIF-L exhibited a CO₂ adsorption capacity of 0.64–1.15 mmol g⁻¹ at 1 bar (0 °C). The materials showed Cu²⁺ adsorption capacities of 389.8 ± 14–554.8 ± 15 mg g⁻¹. They displayed selectivities of 86.8%, 6.7%, 2.4%, 0.93%, 0.61%, and 0.19% toward Fe³⁺, Al³⁺, Co²⁺, Cu²⁺, Na⁺, and Ca²⁺, respectively. The simple 3D printing procedure and the high adsorption efficiencies reveal the promising potential of our materials for industrial applications.