Carbon dots (CDs) are carbon-based zero-dimensional nanomaterials that can be prepared from a number of organic precursors. In this research, they are prepared using fat-free UHT cow milk through the hydrothermal method. FTIR analysis shows C=O and C-H bond presence, as well as nitrogen-based bond like C-N, C=N and –NH2 presence in CDs, while the absorption spectra show the absorption band at 280 ± 3 nm. Next, the Biuret test was performed, with the results showing no presence of unreacted proteins in CDs. It can be said that all proteins are converted in CDs. Photo luminance spectra shows the emission of CDs is 420 nm and a toxicity study of CDs was performed. The Presto Blue method was used to test the toxicity of CDs for murine hippocampal cells. CDs at a concentration of 4 mg/mL were hazardous independent of synthesis time, while the toxicity was higher for lower synthesis times of 1 and 2 h. When the concentration is reduced in 1 and 2 h synthesized CDs, the cytotoxic effect also decreases significantly, ensuring a survival rate of 60–80%. However, when the synthesis time of CDs is increased, the cytotoxic effect decreases to a lesser extent. The CDs with the highest synthesis time of 8 h do not show a cytotoxic effect above 60%. The cytotoxicity study shows that CDs may have a concentration and time–dependent cytotoxic effect, reducing the number of viable cells by 40%.

Carbon dots (CDs) are zero-dimensional nanomaterials composed of carbon and surface groups attached to their surface. CDs have a size smaller than 10 nm and have potential applications in different fields such as metal ion detection, photodegradation of pollutants, and bio-imaging, in this review, the capabilities of CDs in metal ion detection will be described. Quantum confinement is generally viewed as the key factor contributing to the uniqueness of CDs characteristics due to their small size and the lack of attention on the surface functional groups and their roles is given, however, in this review paper, the focus will be on the functional group and the composition of CDs. The surface functional groups depend on two parameters: (i) the oxidation of precursors and (ii) their composition. The mechanism of metal ion detection is still being studied and is not fully understood. This review article emphasizes the current development and progress of CDs, focusing on metal ion detection based on a new perspective.

In this work, we report the synthesis method of carbon quantum dots (CDs) using the one-step method for fast and effective metal ion determination. Ascorbic acid was used as an inexpensive and environmentally friendly precursor. High-pressure and high-temperature reactors were used for this purpose. Microscopic characterization revealed the size of CDs was in the range of 2–6 nm and they had an ordered structure. The photoluminescence properties of the CDs depend on the process temperature, and we obtained the highest PL spectra for 6 h of hydrothermal reaction. The maximum emission spectra depend poorly on synthesis time. Further characterization shows that CDs are a good contender for sensing Fe3+ in aqueous systems and can detect concentrations up to 0.49 ppm. The emission spectra efficiency was enhanced by up to 200% with synthesis time.

Quantum dots (QDs) are zero-dimensional (0D) nanomaterials with charge confinement in all directions that significantly impact various applications. Metal-free organic quantum dots have fascinating properties such as size-dependent bandgap tunability, good optical absorption coefficient, tunability of absorption and emission wavelength, and low-cost synthesis. Due to the extremely small scale of the materials, these characteristics originated from the quantum confinement of electrons. This review will briefly discuss the use of QDs in solar cells and quantum dots lasers, followed by a more in-depth discussion of QD application in photodetectors. Various types of metallic materials, such as lead sulfide and indium arsenide, as well as nonmetallic materials, such as graphene and carbon nanotubes, will be discussed, along with the detection mechanism.

The article contains sections titled: 1 Introduction 2 Fundamentals of Quantum Materials 2.1 Brief Chronicle of Quantum Materials 2.2 Definition 3 Classification of Quantum Materials 3.1 Topological Insulators and Semimetals 3.2 Quantum Spin Liquids 3.3 Superconductors 3.4 Perovskites 3.5 Quantum Dots 3.5.1 Core‐Type QDs 3.5.2 Core–Shell Quantum Dots 3.5.3 Alloyed or Composite QDs 4 Physical and Chemical Properties, Characterization, and Epitaxy 4.1 Hall Effect and Hall Measurement 4.2 Secondary‐Ion Mass Spectrometry 4.3 X‐ray Diffraction 4.4 Photoluminescence and Electroluminescence 4.5 Electron Spin Coherence Characterization 5 Production of Quantum Materials 5.1 Metalorganic Vapor‐Phase Epitaxy 5.2 Solution Growth of Intermetallic Single Crystals 5.3 Vapor Transport Growth of van der Waals Magnets 5.4 Induction Furnace Heating for the Growth of Intermetallic Quantum Materials 5.5 Floating‐Zone Crystal Growth 5.6 Hydrothermal Method 5.7 High‐Throughput Synthesis of Quantum Materials 5.8 Engineering Epitaxial Superconductor–Semiconductor Heterostructures by Molecular‐Beam Epitaxy 6 Applications of Quantum Materials 6.1 Energy Storage 6.2 Solar Cells 6.3 Catalysis 6.4 Biomedical Sensing and Imaging 6.5 Thermoelectric Devices 6.6 LEDs and Display Applications 6.7 Photodetectors 6.8 Magnetic Devices 6.9 Field‐Effect Transistors 7 Future Perspectives Acknowledgments References