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The interaction of a presynthesized orange emitting Mn2+ -doped ZnS quantum dots (QDs) with L-Cysteine (L-Cys) led to enhance emission intensity (at 596 nm) and quantum yield (QY). Importantly, the Mn2+ -doped ZnS QDs exhibited high sensitivity towards L-Cys, with a limit of detection of 0.4±0.02 μM (in the linear range of 3.3-13.3 μM) and high selectivity in presence of interfering amino acids and metal ions. The association constant of L-Cys was determined to be 0.36×105 M-1 . The amplified passivation of the surface of Mn2+ -doped ZnS QDs following the incorporation and binding of L-Cys is accounted for the enhancement in their luminescence features. Moreover, the luminescence enhancement-based detection will bring newer dimension towards sensing application.

Herein we report the use of a hue parameter of HSV (Hue, Saturation and Value) color space-in combination with chromaticity color coordinates-for exploring the complexation-induced luminescence color changes, ranging from blue to green to yellow to white, from a non-luminescent Fe-doped ZnS quantum dot (QD). Importantly, the surface complexation reaction helped a presynthesized non-luminescent Fe-doped ZnS QD to glow with different luminescence colors (such as blue, cyan, green, greenish-yellow, yellow) by virtue of the formation of various luminescent inorganic complexes (using different external organic ligands), while the simultaneous blue- and yellow-emitting complex formation on the surface of non-luminescent Fe-doped ZnS QD led to the generation of white light emission, with a hue mean value of 85 and a chromaticity of (0.28,0.33). Furthermore, the surface complexation-assisted incorporation of luminescence properties to a non-luminescent QD not only overcomes their restricted luminescence-based applications such as light-emitting, biological and sensing applications but also bring newer avenues towards unravelling the surface chemistry between QDs and inorganic complexes and the advantage of having an inorganic complex with QD for their aforementioned useful applications.

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.

Herein, we report the sustainable, cost-effective, and greener surface modification strategy of a quantum dot complex (QDC)—comprised of zinc chalcogenide quantum dot (Qdot; for example, undoped ZnS and Mn2+-doped ZnS) and surface zinc quinolate (ZnQ2) complexes—following interaction with bovine serum albumin (BSA) protein. The interaction of BSA with QDC led to an enhancement in their luminescence properties (such as the quantum yield and emission lifetime), solubility, and stability (in water), compared to their bare form. The enhanced luminescence properties of BSA coupled with QDC—also termed herein as the BSA–QDC nanocomposite—are due to the BSA-induced structural rigidity of the ZnQ2 complex (being present on the surface of zinc chalcogenide Qdot). The highly green luminescent nontoxic BSA–QDC nanocomposite—consisting of undoped ZnS and the ZnQ2 complex—showed better imaging capability of HeLa cells in comparison to only QDC and sensing ability of an enzyme (trypsin) with a detection limit of 0.06 μ...

In the present study, plywood dust has been used as precursor to prepare activated carbon and copper as impregnating agent. Two methods have been employed to impregnate copper in activated carbon s...

Herein, we report a complexation reaction between Zn2+ ions present on the surface of an orange-red-emitting environmentally sustainable Mn2+-doped ZnS QD and a non-emitting copper quinolate (CuQ2) complex, which leads to the formation of a greenish blue-emitting surface zinc quinolate (ZnQ2) complex. The synchronous contribution of the surface ZnQ2 complex and Mn2+-doped ZnS QD is directed towards the generation of photostable bright white light (at λex – 355 nm) with chromaticity coordinates of (0.34, 0.42), color rendering index (CRI) of 71 and color-correlated temperature (CCT) of 5046 K. The ZnQ2 complexed Mn2+-doped ZnS QD is herein called as quantum dot complex (QDC). The excitation- and time-dependent tunability in emission, chromaticity, CRI and CCT of QDC revealed their futuristic applications in light-emitting devices with an anticipated color output. The current work also shows the catalytic behavior of Mn2+-doped ZnS QDs towards facilitating the formation of surface ZnQ2 from CuQ2, which is not feasible with regard to the reactivity of CuQ2 under normal conditions according to the Irving–William series. The rate of the reaction was observed to be first order with respect to CuQ2 at 20 °C, and the complexation constant for the formation of ZnQ2 was estimated to be 8.3 × 105 M−1. This is important for understanding the surface chemistry of metal chalcogenide QDs towards complexation reactions.

Herein we report the picomolar level detection of vitamin B12 (VB12) using orange-red emitting ligand-free Mn2+-doped ZnS quantum dots (QDs; λem = 587 nm) in an aqueous dispersion. Sensing was achieved following the quenching of the luminescence of the Mn2+-doped ZnS QDs with an increasing concentration of VB12. The Stern–Volmer constant was determined to be 5.2 × 1010 M−1. Importantly, the Mn2+-doped ZnS QDs exhibited high sensitivity towards VB12, with a limit of detection as low as 1.15 ± 0.06 pM (in the linear range of 4.9–29.4 pM) and high selectivity in the presence of interfering amino acids, metal ions, and proteins. Notably, a Forster resonance energy transfer (FRET) mechanism was primarily proposed for the observed quenching of luminescence of Mn2+-doped ZnS QDs upon the addition of VB12. The Forster distance (Ro) and energy transfer efficiency (E) were calculated to be 2.33 nm and 79.3%, respectively. Moreover, the presented QD-FRET-based detection may bring about new avenues for future biosensing applications.

The present study aims at efficient abatement of pollutants from coke-oven wastewater using environment-friendly and low-cost adsorbents for a green world. The adsorbent used were native laterite soil (NLS), heat-treated laterite soil (HTLS), native shale (NS) and Heat-treated shale (HTS). One factor at a time (OFAT) approach was followed to determine the most effective condition based on the maximum removal. Heat-treated laterite soil and native shale were found most effective among their counterparts. Freundlich model was found best to analyze equilibrium data. The real coke-oven wastewater was collected and experiments were performed in batch mode. The percentage removal of cyanide (88.09% and 95.31%) and ammoniacal-N (87.28% and 92.12%) were found satisfactory when heat-treated laterite soil and native shale were used as adsorbents, respectively.

Herein, we report the fabrication of a single component white light emitting (WLE) nanocomposite – following the formation of a luminescent zinc quinolate complex (using 8-hydroxyquinoline (HQ) as a complexation agent) on the surface of the ZnS shell of CuInS2/ZnS core/shell quantum dots. The synchronous contribution of greenish blue emission by the zinc quinolate surface complex and red emission by the CuInS2/ZnS core/shell quantum dots led to white light generation from the nanocomposite upon UV excitation. The reported nanocomposite exhibited bright natural cool white light emission with chromaticity color coordinates of (0.32, 0.35) and (0.32, 0.33), color rendering indices (CRI) of 91 and 83 and correlated color temperatures (CCT) of 6087 K and 5930 K in the solution and solid phase, respectively. Importantly, the higher temperature (up to 200 °C) sustainable white light emitting nature and long term stability of the solid nanocomposite may have importance for solid state light emitting applications.

Herein we report the generation of synchronous tricolor emission for a single wavelength excitation from a quantum dot complex (QDC). The single-component QDC was formed out of a complexation reaction, at room temperature, between ligand-free Mn(2+)-doped ZnS quantum dots (Qdots) and a mixture of two organic ligands (acetylsalicylic acid and 8-hydroxyquinoline). Furthermore, the tunability in chromaticity color coordinates, which is important for solid-state lighting, was achieved following the synthesis of QDC. Moreover, the photostable QDC emitted white light (λex 320 nm) with (0.30, 0.33) and (0.32, 0.32) chromaticity color coordinates in the liquid and the solid phases, respectively. Hence, the white light-emitting QDC may be a superior material for light-emitting applications.

Herein we report the generation and control of double channel emission from a single component system following a facile complexation reaction between a Mn(2+) doped ZnS colloidal quantum dot (Qdot) and an organic ligand (8-hydroxy quinoline; HQ). The double channel emission of the complexed quantum dot-called the quantum dot complex (QDC)-originates from two independent pathways: one from the complex (ZnQ2) formed on the surface of the Qdot and the other from the dopant Mn(2+) ions of the Qdot. Importantly, reaction of ZnQ2·2H2O with the Qdot resulted in the same QDC formation. The emission at 500 nm with an excitation maximum at 364 nm is assigned to the surface complex involving ZnQ2 and a dangling sulfide bond. On the other hand, the emission at 588 nm-with an excitation maximum at 330 nm-which is redox tunable, is ascribed to Mn(2+) dopant. The ZnQ2 complex while present in QDC has superior thermal stability in comparison to the bare complex. Interestingly, while the emission of Mn(2+) was quenched by an electron quencher (benzoquinone), that due to the surface complex remained unaffected. Further, excitation wavelength dependent tunability in chromaticity color coordinates makes the QDC a potential candidate for fabricating a light emitting device of desired color output.