Recovering hidden quanta of Cu(2+)-doped ZnS quantum dots in reductive environment

Tuning multispectral fluorescence quantum dot-based identification of short-length amyloid β peptides by applying Cu(II) ions

Currently available methods for detecting amyloid β (Aβ) derivatives are mainly dedicated to determining the long forms Aβ1-42 and Aβ1-40. At the same time, the number of physiologically occurring Aβ analogs is much higher, including those truncated at the N- and C-termini. Their identification using standard methods is challenging due to the structural similarity of various Aβ analogs, but could highly benefit from both biomarkers discovery and pathophysiological studies of Alzheimer's disease. Therefore a "chemical tongue" sensing strategy was employed for the detection of seven Aβ peptide derivatives: Aβ1-16, Aβ4-16, Aβ4-9, Aβ5-16, Aβ5-12, Aβ5-9, Aβ12-16. The proposed sensing system is based on competitive interactions between quantum dots, Cu(II) ions, and Aβ peptides, providing unique fluorescence fingerprints useful for the identification of analytes. After carefully evaluating the Aβ sample preparation protocol, perfect determination of all studied Aβ peptides was achieved using partial least square-discriminant analysis (PLS-DA). The developed PLS-DA models are characterized by excellent accuracy, sensitivity, precision, and specificity of analyte determination, emphasizing the potential of the proposed sensing strategy.

Recent development of autonomously driven micro/nanobots for efficient treatment of polluted water

Autonomously propelled micro/nanobots are one of the most advanced and integrated structures which have been fascinated researchers owing to its exceptional property that enables them to be carried out user-defined tasks more precisely even on an atomic scale. The unique architecture and engineering aspects of these manmade tiny devices make them viable options for widespread biomedical applications. Moreover, recent development in this line of interest demonstrated that micro/nanobots would be very promising for the water treatment as these can efficiently absorb or degrade the toxic chemicals from the polluted water based on their tunable surface chemistry. These auto propelled micro/nanobots catalytically degrade toxic pollutants into non-hazardous compounds more rapidly and effectively. Thus, for the last few decades, nanobots mediated water treatment gaining huge popularity due to its ease of operation and scope of guided motion that could be monitored by various external fields and stimuli. Also, these are economical, energy-saving, and suitable for large scale water treatment, particularly required for industrial effluents. However, the efficacy of these bots hugely relies on its design, characteristic of materials, properties of the medium, types of fuel, and surface functional groups. Minute variation for one of these things may lead to a change in its performance and hinders its dynamics of propulsion. It is deemed that nanobots might be a smart choice for using these as the new generation devices for treating industrial effluents before discharging it in the water bodies, which is a major concern for human health and the environment.

Chemical Reactions Involving the Surface of Metal Chalcogenide Quantum Dots

This invited feature article focuses on the chemical reactions involving the surface ions of colloidal quantum dots (Qdots). Emphasis is placed on ion-exchange, redox, and complexation reactions. The pursuit of reactions involving primarily the cations on the surface results in changes in the optical properties of the Qdots and also may confer new properties owing to the newly formed surface species. For example, the cation-exchange reaction, leading to systematic removal of the cations present on the as-synthesized Qdots, enhances the photoluminescence quantum yield. On the other hand, redox reactions, involving the dopant cations in the Qdots, could not only modulate the photoluminescence quantum yield but also give rise to new emission not present in the as-synthesized Qdots. Importantly, the cations present on the surface could be made to react with external organic ligands to form inorganic complexes, thus providing a new species defined as the quantum dot complex (QDC). In the QDC, the properties of Qdots and the inorganic complex are not only present but also enhanced. Furthermore, by varying reaction conditions such as the concentrations of the species and using a mixture of ligands, the properties could be further tuned and multifunctionalization of the Qdot could be achieved. Thus, chemical, magnetic, and optical properties could be simultaneously conferred on the same Qdot. This has helped in externally controlled bioimaging, white light generation involving individual quantum dots, and highly sensitive molecular sensing. Understanding the species (i.e., the newly formed inorganic complex) on the surface of the Qdot and its chemical reactivity provide unique options for futuristic technological applications involving a combination of an inorganic complex and a Qdot.

Copper ion-induced fluorescence band shift of CdTe quantum dots: a highly specific strategy for visual detection of Cu2+ with a portable UV lamp

Visual detection of Cu²⁺ is realized based on a copper-induced fluorescence band shift rather than an intensity change of CdTe QDs.

Redox-Tuned Three-Color Emission in Double (Mn and Cu) Doped Zinc Sulfide Quantum Dots

The photoluminescence characteristics of colloidal Mn(2+) and Cu(2+) (double) doped zinc sulfide (ZnS) quantum dots (Qdots) could be drastically influenced by reactions with redox reagents. Importantly, experiments revealed Cu(+) in ZnS nanocrystals rather than Cu(2+), in conjunction with Mn(2+), as the emitting dopant. Thus, as-synthesized aqueous Qdots emitted orange (with peaks at 460 and 592 nm) due to the host and Mn(2+) dopant emissions. However, upon treatment with a reducing agent, the color changed to yellow with dual peaks positioned at 520 and 590 nm due to Cu(+) and Mn(2+) dopant emissions. The characteristics could be changed reversibly with appropriate redox reagents. Further, treatment with excess of an oxidizing agent led to blue emission with a single peak at 450 nm.