Photo-excitable zinc sulfide nanoparticles: A theranostic nanotool for cancer management

OBJECTIVES

Zinc sulfide nanoparticles (ZnS NPs), as one of the quantum dots less than 10 nm, possess unique size-dependent autofluorescence. Excitation of their valence electrons by energy higher than the bandgap reveals the ZnS NPs' inherited photocatalysis with additive cytotoxic consequences of reactive oxygen species (ROS) release. Coupling the cytotoxicity of photoactivated ZnS NPs with their autofluorescence would be a novel theranostic modality, combating superficially accessible carcinoma.

MATERIAL AND METHODS

After synthesizing and characterization of ZnS NPs, we verified their photocatalysis and electron donation upon UV excitation in degrading organic dye and DNA cleavage, respectively. We then tested the efficacy of UV-activated ZnS NPs to induce ROS-dependent apoptosis in squamous cell carcinoma and breast cancer cell lines.

RESULTS

The energetic electron-hole pairs generated upon UV excitation of ZnS NPs with the consequent cascade of ROS release revealed potent apoptotic cancer cell deaths, compared with single treatment modalities of nonexcited nanoparticles and UV. Moreover, the inherited luminescence of ZnS NPs enabled visualization of their predominant intracytoplasmic uptake with tracking of their cellular response.

CONCLUSION

The intensified luminescence and the fortified cytotoxicity of photoactivated ZnS NPs enhance their theranostic qualifications, boosting their antitumorigenic use.

Investigations on the high performance of InGaN red micro-LEDs with single quantum well for visible light communication applications

In this study, we have demonstrated the potential of InGaN-based red micro-LEDs with single quantum well (SQW) structure for visible light communication applications. Our findings indicate the SQW sample has a better crystal quality, with high-purity emission, a narrower full width at half maximum, and higher internal quantum efficiency, compared to InGaN red micro-LED with a double quantum wells (DQWs) structure. The InGaN red micro-LED with SQW structure exhibits a higher maximum external quantum efficiency of 5.95% and experiences less blueshift as the current density increases when compared to the DQWs device. Furthermore, the SQW device has a superior modulation bandwidth of 424 MHz with a data transmission rate of 800 Mbit/s at an injection current density of 2000 A/cm². These results demonstrate that InGaN-based SQW red micro-LEDs hold great promise for realizing full-color micro-display and visible light communication applications.

On Cordelair-Greil Model about Electrophoretic Deposition

Electrophoretic deposition (EPD) is a facile technique to deposit quantum dots (QDs) films, which can be used as the color conversion layers for display applications. To better understand the EPD process, researchers have built many models of the EPD process. However, most of these models lack solid experimental support. Here, by adopting simple yet effective solvent engineering and well-designed experiments, this study proves the Cordelair-Greil model on EPD processes. Moreover, some supplements about this model are made according to practical experiments. The experimental verification of the Cordelair-Greil model is a solid step toward revealing the dynamics of the EPD process. Furthermore, the formation of cracks in EPD deposited QD films is prevented through solvent engineering. This work proves that besides modifying the intrinsic properties of QDs, solvent engineering is also a simple, effective, and low-cost way to study the EPD process and improve the QD film qualities deposited.

Ultrafast Quenching of Excitons in the ZnxCd1-xS/ZnS Quantum Dots Doped with Mn2+ through Charge Transfer Intermediates Results in Manganese Luminescence

For the first time, a specific time-delayed peak was registered in the femtosecond transient absorption (TA) spectra of Zn_xCd_1−xS/ZnS (x~0.5) alloy quantum dots (QDs) doped with Mn²⁺, which was interpreted as the electrochromic Stark shift of the band-edge exciton. The time-delayed rise and decay kinetics of the Stark peak in the manganese-doped QDs significantly distinguish it from the kinetics of the Stark peak caused by exciton–exciton interaction in the undoped QDs. The Stark shift in the Mn²⁺-doped QDs developed at a 1 ps time delay in contrast to the instantaneous appearance of the Stark shift in the undoped QDs. Simultaneously with the development of the Stark peak in the Mn²⁺-doped QDs, stimulated emission corresponding to ⁴T₁-⁶A₁ Mn²⁺ transition was detected in the subpicosecond time domain. The time-delayed Stark peak in the Mn²⁺-doped QDs, associated with the development of an electric field in QDs, indicates the appearance of charge transfer intermediates in the process of exciton quenching by manganese ions, leading to the ultrafast Mn²⁺ excitation. The usually considered mechanism of the nonradiative energy transfer from an exciton to Mn²⁺ does not imply the development of an electric field in a QD. Femtosecond TA data were analyzed using a combination of empirical and computational methods. A kinetic scheme of charge transfer processes is proposed to explain the excitation of Mn²⁺. The kinetic scheme includes the reduction of Mn²⁺ by a 1Se electron and the subsequent oxidation of Mn¹⁺ with a hole, leading to the formation of an excited state of manganese.

Quantum Dots Based Fluorescent Probe for the Selective Detection of Heavy Metal Ions

Heavy metal ions are one of the primary causes of environmental pollution. A marshal effect of heavy metal ions is a paramount ultimatum to humans, aquatic animals and other organisms present in nature. Multitude arrays of materials have been proclaimed for sensing of heavy metal ions and also many methodologies are applied for heavy metal ion sensing. Due to their toxicity and non-biodegradability, it is required to be perceived immediately prior to its manifestation of harmful effects. Quantum Dots (QDs) are zero-dimensional nanomaterial particles and owing to their distinctive optical and electronic properties, they are utilized as nanosensors. QDs have enriched fluorescence properties which includes broad excitation spectrum, narrow emission spectrum and photostability. QDs offer eclectic and sensitive detection of heavy metal ions due to presence of discrete capping agents and different functional groups present on the surface of the QDs. These capping layers and functional groups attune the sensing capability of the QDs, which leverages the interactions of QDs with various analytes by different mechanisms. This review, comprising of papers from 2011 to 2020,focuses on heavy metal ions sensing potential of various quantum dots and its applicability as a nanosensor for on field heavy metal ions detection in water. Quantum Dots (QDs) based Heavy Metal Detection.

Multimodal polymer encapsulated CdSe/Fe3O4 nanoplatform with improved biocompatibility for two-photon and temperature stimulated bioapplications

Multimodal polymer encapsulated CdSe/Fe₃O₄ nanoplatforms with dual optical and magnetic properties have been fabricated. We demonstrate that CdSe/Fe₃O₄ nanocapsules (NCs) upon excitation with UV radiation or NIR fs-laser excitation exhibit intense one- or two-photon emission at 535 nm, whereas the combination of an alternating magnetic field and 808 nm IR laser excitation results in heat generation. Since anticancer therapies require relatively high doses of Fe₃O₄ nanoparticles (NPs) to induce biologically relevant temperature jumps, the therapeutic effects of 0.1 and 1 mg/mL Fe₃O₄ NCs and CdSe/Fe₃O₄ NCs were investigated using breast cancer cell lines, ER-positive MCF-7, and triple-negative MDA-MB-231 cells. Improved biocompatibility of CdSe/Fe₃O₄ NCs compared to Fe₃O₄ NCs was revealed at higher NCs concentration suggesting safe potential medical applications of CdSe/Fe₃O₄ NCs. In contrast, 1 mg/mL Fe₃O₄ NCs were found to be more cytotoxic to MDA-MB-231 than MCF-7 cells through iron-induced oxidative stress, lipid peroxidation, and concomitant ferroptotic cell death. We believe that Fe₃O₄ NCs-mediated cellular response may be heterogeneous that reflects, at least in part, cancer cell genotype, molecular phenotype, and pathological classification.

Effect of heteroatoms on the optical properties and enzymatic activity of N-doped carbon dots

Carbon dots (CDs) are attractive nanomaterials because of their facile synthesis, biocompatibility, superior physicochemical properties, and low cost of their precursors. Recent advances in CDs have particularly relied on the modulation of their properties by heteroatom doping (e.g., nitrogen). Although nitrogen-doped CDs (N-CDs) have attracted considerable attention owing to their different properties compared to those of the original CDs, the effects of the heteroatom content and types of bonding on the properties of N-doped CDs remain underexplored. In this work, we prepared N-CDs with controlled nitrogen contents, and fully examined their optical properties, enzymatic activity, and toxicity. We demonstrate that (i) the type of carbon–heteroatom bonding (i.e., carbon–oxygen and carbon–nitrogen bonds) can be altered by changing the ratio of carbon to heteroatom sources, and (ii) both the heteroatom content and the heteroatom-bonding character significantly influence the properties of the doped CDs. Notably, N-CDs exhibited higher quantum yields and peroxidase-like activities than the non-doped CDs. Furthermore, the negatively charged N-CDs exhibited negligible cytotoxicity. Such comprehensive investigations on the physicochemical properties of N-CDs are expected to guide the design of N-CDs for targeted applications.

The characteristics of N-CDs suitable for their optical applications or for use as nanozymes were demonstrated by rationalizing the relationship between the dopant content (e.g., the amount of doped N and types of chemical bonding) and physicochemical properties.

A review: recent advances in preparations and applications of heteroatom-doped carbon quantum dots

Carbon quantum dots (CQDs) are widely used in optoelectronic catalysis, biological imaging, and ion probes owing to their low toxicity, stable photoluminescence, and ease of chemical modification. However, the low fluorescence yield and monochromatic fluorescence of CQDs limit their practical applications. This review summarizes the commonly used approaches for improving the fluorescence efficiency of CQDs doped with non-metallic (heteroatom) elements. Herein, three types of heteroatom-doped CQDs have been investigated: (1) CQDs doped with a single heteroatom; (2) CQDs doped with two heteroatoms; and (3) CQDs doped with three heteroatoms. The limitations and future perspectives of doped CQDs from the viewpoint of producing CQDs for specific applications, especially for bioimaging and light emitting diodes, have also been discussed herein.

Carbon quantum dots as fluorescence sensors for label-free detection of folic acid in biological samples

Carbon quantum dots (CQDs) have been fabricated by a facile single-step pyrolysis method from citric acid and ethylene imine polymer. When excited at 359 nm, CQDs show intense blue fluorescence at 434 nm. The fluorescence can be effectively quenched by folic acid (FA), which is attributed to the combination of static quenching and inner filter effect. Thus, the CQDs are developed as an efficient fluorescent sensing platform for label-free sensitive and selective detection of FA. Key parameters influencing the detection were investigated, such as incubation time, salt concentration, selectivity and potential interferences. Under the optimal conditions, a good linearity was observed for the emission intensity against 1.14-47.57 μM with a correlation coefficient of 0.99. The limit of detection was found to be 0.38 μM. The practical application of the sensing system was demonstrated by analyzing FA in human urine samples. The sample recoveries fell in the range of 82.0%-113.1% with RSDs ≤ 10.9%, which presented its reliable and feasible application in real samples.