Sabyasachi Pramanik - Academia.edu (original) (raw)
Papers by Sabyasachi Pramanik
Sensing and Biosensing with Optically Active Nanomaterials, 2022
Physical Chemistry Chemical Physics, 2021
The generation of white light based on the facilitation of an unprecedented complexation reaction... more The generation of white light based on the facilitation of an unprecedented complexation reaction on the surface of a doped quantum dot, with the exploration of their physical insights, is reported herein.
Nanoscale Advances, 2020
The picomolar level detection of vitamin B12 using orange-emitting Mn2+-doped ZnS quantum dots is... more The picomolar level detection of vitamin B12 using orange-emitting Mn2+-doped ZnS quantum dots is described herein.
Chemistry – An Asian Journal, 2020
Herein we report the interaction of a presynthesized orange emitting Mn2+-doped ZnS quantum dots ... more Herein we report the interaction of a presynthesized orange emitting Mn2+-doped ZnS quantum dots (QDs) with L-Cysteine (L-Cys) led to enhance their 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 mM (in the linear range of 3.3-13.3 mM) and high selectivity in presence of interfering amino acids and metal ions. The association constant of L-Cys was determined to be 0.36 x105 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.
Advanced Optical Materials, 2020
Engineering the surface of luminescent quantum dots (QDs) plays a significant role in altering th... more Engineering the surface of luminescent quantum dots (QDs) plays a significant role in altering their physicochemical properties such as emission characteristics, stability, and solubility, which in turn affects their utility in biological and optoelectronic applications. [1-7] Various surface modifying strategies such as ion exchange, ligand exchange, and complexation have been reported to improve the optical performance of QDs in numerous applications, such as light-emitting devices (LEDs), biological imaging, optical sensors, and other energy devices of QDs. [1-7] For example, modification of the surface of QDs with a luminescent inorganic complex helped to fabricate an environmentally sustainable WLE composite that showed a perfect white light nature, which has applications in neurotransmitters and reversible pH sensing. [5-7] Overall, the action of a surface-modifying agent is crucial for the successful fabrication of a luminescent composite demanded by an enduse application. Fabrication of a highly efficient and stable WLE composite, with properties close to bright daytime light, is of paramount interest because of the growing demand for energy-efficient lighting and display systems. [5-10] In general, WLE systems are fabricated either by i) mixing red-, green-, and blue-emitting QDs, which are toxic metal-based or ii) using expensive and multi-step surface modification strategies. [5-10] However, their uses are limited due to the problems linked to nonradiative energy transfer, unwanted changes in chromaticity, self-absorption, high cost, and low environmental sustainability. [5-10] Thus, the inexpensive and eco-friendly surface modification strategies and agents have received the most attention for fabricating highly efficient WLE composites. Recently, ionic liquids (ILs), due to their application friendly properties, have been used as a surface modifying agent and solvent. [11-15] However, their use as a surface modifying agent for fabricating WLE composite is limited. [11-15] For example, the chemical combination of blue-emitting 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF 4) IL with yellowemitting ZnO nanocrystals results in white light generation, Herein, a new and straightforward approach for the fabrication of a stable and multifunctional white light emitting (WLE) hydrogel is reported. For the first time, the utility of such hydrogels for protein packaging with enhanced activity and stability is presented. Initially, a WLE composite with color chromaticity of (0.33, 0.27) is fabricated by engineering the surface of an orange light emitting Mn 2+-doped ZnS quantum dot (QD) using a blue-emitting cholinetosylate ionic liquid (IL). The color chromaticity can be tuned by altering the concentration of the IL and excitation wavelengths. The WLE hydrogel is constructed through the conjugation of the WLE QD-IL composite with an alginate biopolymer. Remarkably, the WLE QD-IL composite and WLE hydrogel show preservation of their structural and luminescence properties for an extended time and thus indicate a potential for storage applications. When cytochrome c (Cyt C) is caged within the WLE hydrogel matrix, the peroxidase activity increases by more than 1.7-times compared with native Cyt C and a Cyt C-loaded QD hydrogel at room temperature. Also, Cyt C-immobilized WLE hydrogel shows a 3.5-fold increase in activity (compared with native Cyt C) at a higher temperature (120 °C) and in the presence of a denaturation agent.
Advanced Materials Interfaces, 2020
high photoluminescence quantum yield as well as excellent carrier mobility and should also facili... more high photoluminescence quantum yield as well as excellent carrier mobility and should also facilitate a balanced ambipolar conduction (both electron and hole conduction), which is crucial for efficient exciton recombination through radiative pathways. [5,10] However, there is always a trade-off between carrier mobility and luminescence in case of organic semiconductors. [11] Colloidal semiconductor nanocrystal or quantum dots (Qdots) are reported to be excellent light emitters and have exhibited high charge transport capability. [12-15] Importantly, Qdot-integrated LETFT are efficient in terms of both emissive and switching properties. [9,13] However, most of the devices are based on toxic metal chalcogenides such as PbS, PbSe, and CdSe Qdots. [14,16-18] These heavy metals cause adverse oxidative stress in human body. [19,20] The toxic nature of these Qdots puts limitations to their practical usability and thus supports the development of environmentally benign ones. The principal bottleneck for the fabrication of devices using Qdots is single step deposition of high quality and defect free layer. Generally, Qdots capped with insulating long organic chains induce a potential barrier to proficient charge transport and electronic coupling between Qdots in thin films and thus restrict their application in the field of electronics. [21] To reduce the interdot spacing and enhance the electronic coupling between the Qdots, a large number of surface modification strategies have been already employed and among them, ligand exchange with halides, [22,23] pseudohalides, [24,25] chalogenides, [26] oxoanion, [27] chalcogenideometallate complex, and halometallates is popular. It has been established that the nature of the capping ligand controls the mobility of carriers and transport characteristics. Typically, the type of ligand might influence the type of channel-whether n-type, p-type or ambipolar-in field effect transistors. [23,28] The ambipolar nature of the transistor is due to near-intrinsic doping of the Qdot. Recently, tetrabutylammonium iodide-treated PbS Qdots, [13] metal chalcogenide complex (Na 4 Sn 2 S 6 •14H 2 O, Na 4 Sn 2 Se 6 , and KInSe 2)-capped CdSe Qdots, [14] and 3-mercaptopropionic acid ligand-exchanged PbS Qdots [9] have been used in thin film transistors to achieve efficient charge transport and high carrier mobilities. However, ligand exchange with compact organic or inorganic ligands in Qdots do not always assure high carrier mobility and better charge transport in Qdot thin films. On the other hand, the ligand exchange may introduce additional Ambipolar transport characteristics of thin film transistors fabricated from nontoxic white light emitting quantum dot complexes (QDCs) are herein reported to exhibit efficient carrier mobilities. The QDCs are synthesized by forming bluish green emitting zinc quinolate complex on the surface of orange emitting Mn 2+-doped ZnS quantum dots (Qdots) using 8-hydroxyquinoline 5-sulfonic acid as the chelating ligand. The device exhibits efficient ambipolar transport characteristics with high I ON /I OFF ratio of 10 4 and electron mobility and hole mobility of 2.95 × 10 −02 and 1.06 × 10 −02 cm 2 V −1 s −1 , respectively. The subthreshold slope of Qdot complex-integrated thin film transistor increases from that of Mn 2+-doped ZnS Qdot-integrated thin film transistor from 0.35 to 0.79 V dec −1 in p-field effect transistor (FET) and from 0.59 to 0.97 V dec −1 in n-FET operations, which annotates an increase in trap state density due to surface complexation of the Qdot. These results suggest that white light emitting QDC can be used as an efficient transport as well as an emissive material, which open up new paradigm for advanced optoelectronic applications.
Chemistry – An Asian Journal, 2019
ACS Applied Nano Materials, 2019
Herein, we report the sustainable, cost-effective and greener surface modification strategy of qu... more Herein, we report the sustainable, cost-effective and greener surface modification strategy of quantum dot complex (QDC)-comprised of Zn-chalcogenide quantum dot (Qdot; for example undoped ZnS and Mn 2+-doped ZnS) and surface Zn-quinolate (ZnQ) complex-following the interaction with bovine serum albumin (BSA) protein. The interaction of BSA to QDC led to enhancement in their luminescence properties (such as quantum yield and emission life time), solubility and stability (in water), compared to their bare form. The enhanced luminescence properties of BSA coupled QDC-also termed herein as BSA-QDC nanocomposite-is due to the BSA induced structural rigidity of the ZnQ 2 complex (being present on the surface of Znchalcogenide Qdot). The highly green luminescent nontoxic BSA-QDC nanocompositeconsisted of undoped ZnS and ZnQ 2 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 M. Interestingly, the interaction of BSA to a dual emitting QDC (consisted of orange emitting Mn 2+-doped ZnS Qdot and green emitting surface ZnQ 2 complex) resulted the generation of white light (which is hard to achieve from only dual emitting QDC at ex-330 nm), with chromaticity coordinates of (0.33, 0.35) and (0.29, 0.35), color rendering index (CRI) of 86 and 80, and correlated color temperature (CCT) of 5646 and 7377 K, in liquid and solid phases respectively. This may open up a new paradigm towards sustainable and user-friendly surface modification strategies for fabricating advanced nanoscale materials, with anticipated uses in imaging, sensing and light emitting applications.
Chemical Communications, 2019
Ratiometric pH sensing in the physiological range of pH 6.5–10.3 by a white light emitting quantu... more Ratiometric pH sensing in the physiological range of pH 6.5–10.3 by a white light emitting quantum dot complex – following the changes in luminescence intensity ratio, color and chromaticity – is described herein.
Langmuir, 2017
Herein we report, the formation of blue emitting Zn(MSA)2 complex on the surface of a yellow emit... more Herein we report, the formation of blue emitting Zn(MSA)2 complex on the surface of a yellow emitting ZnO quantum dot (Qdot)-out of a complexation reaction between N-methylsalicylaldimine (MSA) and ZnO Qdot. This led to formation of a highly luminescent, photostable, single component nanocomposite that emit bright natural white light, with (i) chromaticities of (0.31, 0.38) and (0.31, 0.36), (ii) color rendering indices (CRI) of 74 and 82 and (iii) correlated color temperatures (CCT) of 6505 K and 6517 K, in their solution and solid phases, respectively. Importantly, the control over the chromaticity and CCT-depending upon the degree of complexation-makes the reported nanocomposite a potential new advanced material in fabricating cost-effective single component white light emitting devices (WLED) of choice and design in near future.
Journal of Materials Chemistry C, 2017
Formation of a zinc-quinolate complex on the surface of CuInS2/ZnS core shell quantum dots leadin... more Formation of a zinc-quinolate complex on the surface of CuInS2/ZnS core shell quantum dots leading to the fabrication of an advanced white light emitting nanocomposite.
ACS Applied Materials & Interfaces, 2016
We report the synthesis of a biofriendly highly luminescent white-light-emitting nanocomposite. T... more We report the synthesis of a biofriendly highly luminescent white-light-emitting nanocomposite. The composite consisted of Au nanoclusters and ZnQ2 complex (on the surface of ZnS quantum dots) embedded in protein. The combination of red, green, and blue luminescence from clusters, complex, and protein, respectively, led to white light generation.
The Journal of Physical Chemistry Letters, 2015
Herein we report the generation of synchronous tricolor emission for a single wavelength excitati... more 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 ligandfree 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 (λ ex 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.
Langmuir, 2014
Herein we report the generation and control of double channel emission from a single component sy... more 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 dotcalled the quantum dot complex (QDC)originates from two independent pathways: one from the complex (ZnQ 2) formed on the surface of the Qdot and the other from the dopant Mn 2+ ions of the Qdot. Importantly, reaction of ZnQ 2 •2H 2 O 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 ZnQ 2 and a dangling sulfide bond. On the other hand, the emission at 588 nmwith an excitation maximum at 330 nmwhich is redox tunable, is ascribed to Mn 2+ dopant. The ZnQ 2 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.
Langmuir, 2014
Chemical reaction between oleate-capped Zn(x)Cd(1-x)S quantum dots (Qdots) and 8-hydroxyquinoline... more Chemical reaction between oleate-capped Zn(x)Cd(1-x)S quantum dots (Qdots) and 8-hydroxyquinoline (HQ) led to formation of a surface complex, which was accompanied by transfer of hydrophobic Qdots from nonpolar (hexane) to polar (water) medium with high efficiency. The stability of the complex on the surface was achieved via involvement of dangling sulfide bonds. Moreover, the transferred hydrophilic Qdots--herein called as quantum dot complex (QDC)--exhibited new and superior optical properties in comparison to bare inorganic complexes with retention of the dimension and core structure of the Qdots. Finally, the new and superior optical properties of water-soluble QDC make them potentially useful for biological--in addition to light emitting device (LED)--applications.
Chemistry – An Asian Journal, 2019
Sensing and Biosensing with Optically Active Nanomaterials, 2022
Physical Chemistry Chemical Physics, 2021
The generation of white light based on the facilitation of an unprecedented complexation reaction... more The generation of white light based on the facilitation of an unprecedented complexation reaction on the surface of a doped quantum dot, with the exploration of their physical insights, is reported herein.
Nanoscale Advances, 2020
The picomolar level detection of vitamin B12 using orange-emitting Mn2+-doped ZnS quantum dots is... more The picomolar level detection of vitamin B12 using orange-emitting Mn2+-doped ZnS quantum dots is described herein.
Chemistry – An Asian Journal, 2020
Herein we report the interaction of a presynthesized orange emitting Mn2+-doped ZnS quantum dots ... more Herein we report the interaction of a presynthesized orange emitting Mn2+-doped ZnS quantum dots (QDs) with L-Cysteine (L-Cys) led to enhance their 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 mM (in the linear range of 3.3-13.3 mM) and high selectivity in presence of interfering amino acids and metal ions. The association constant of L-Cys was determined to be 0.36 x105 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.
Advanced Optical Materials, 2020
Engineering the surface of luminescent quantum dots (QDs) plays a significant role in altering th... more Engineering the surface of luminescent quantum dots (QDs) plays a significant role in altering their physicochemical properties such as emission characteristics, stability, and solubility, which in turn affects their utility in biological and optoelectronic applications. [1-7] Various surface modifying strategies such as ion exchange, ligand exchange, and complexation have been reported to improve the optical performance of QDs in numerous applications, such as light-emitting devices (LEDs), biological imaging, optical sensors, and other energy devices of QDs. [1-7] For example, modification of the surface of QDs with a luminescent inorganic complex helped to fabricate an environmentally sustainable WLE composite that showed a perfect white light nature, which has applications in neurotransmitters and reversible pH sensing. [5-7] Overall, the action of a surface-modifying agent is crucial for the successful fabrication of a luminescent composite demanded by an enduse application. Fabrication of a highly efficient and stable WLE composite, with properties close to bright daytime light, is of paramount interest because of the growing demand for energy-efficient lighting and display systems. [5-10] In general, WLE systems are fabricated either by i) mixing red-, green-, and blue-emitting QDs, which are toxic metal-based or ii) using expensive and multi-step surface modification strategies. [5-10] However, their uses are limited due to the problems linked to nonradiative energy transfer, unwanted changes in chromaticity, self-absorption, high cost, and low environmental sustainability. [5-10] Thus, the inexpensive and eco-friendly surface modification strategies and agents have received the most attention for fabricating highly efficient WLE composites. Recently, ionic liquids (ILs), due to their application friendly properties, have been used as a surface modifying agent and solvent. [11-15] However, their use as a surface modifying agent for fabricating WLE composite is limited. [11-15] For example, the chemical combination of blue-emitting 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF 4) IL with yellowemitting ZnO nanocrystals results in white light generation, Herein, a new and straightforward approach for the fabrication of a stable and multifunctional white light emitting (WLE) hydrogel is reported. For the first time, the utility of such hydrogels for protein packaging with enhanced activity and stability is presented. Initially, a WLE composite with color chromaticity of (0.33, 0.27) is fabricated by engineering the surface of an orange light emitting Mn 2+-doped ZnS quantum dot (QD) using a blue-emitting cholinetosylate ionic liquid (IL). The color chromaticity can be tuned by altering the concentration of the IL and excitation wavelengths. The WLE hydrogel is constructed through the conjugation of the WLE QD-IL composite with an alginate biopolymer. Remarkably, the WLE QD-IL composite and WLE hydrogel show preservation of their structural and luminescence properties for an extended time and thus indicate a potential for storage applications. When cytochrome c (Cyt C) is caged within the WLE hydrogel matrix, the peroxidase activity increases by more than 1.7-times compared with native Cyt C and a Cyt C-loaded QD hydrogel at room temperature. Also, Cyt C-immobilized WLE hydrogel shows a 3.5-fold increase in activity (compared with native Cyt C) at a higher temperature (120 °C) and in the presence of a denaturation agent.
Advanced Materials Interfaces, 2020
high photoluminescence quantum yield as well as excellent carrier mobility and should also facili... more high photoluminescence quantum yield as well as excellent carrier mobility and should also facilitate a balanced ambipolar conduction (both electron and hole conduction), which is crucial for efficient exciton recombination through radiative pathways. [5,10] However, there is always a trade-off between carrier mobility and luminescence in case of organic semiconductors. [11] Colloidal semiconductor nanocrystal or quantum dots (Qdots) are reported to be excellent light emitters and have exhibited high charge transport capability. [12-15] Importantly, Qdot-integrated LETFT are efficient in terms of both emissive and switching properties. [9,13] However, most of the devices are based on toxic metal chalcogenides such as PbS, PbSe, and CdSe Qdots. [14,16-18] These heavy metals cause adverse oxidative stress in human body. [19,20] The toxic nature of these Qdots puts limitations to their practical usability and thus supports the development of environmentally benign ones. The principal bottleneck for the fabrication of devices using Qdots is single step deposition of high quality and defect free layer. Generally, Qdots capped with insulating long organic chains induce a potential barrier to proficient charge transport and electronic coupling between Qdots in thin films and thus restrict their application in the field of electronics. [21] To reduce the interdot spacing and enhance the electronic coupling between the Qdots, a large number of surface modification strategies have been already employed and among them, ligand exchange with halides, [22,23] pseudohalides, [24,25] chalogenides, [26] oxoanion, [27] chalcogenideometallate complex, and halometallates is popular. It has been established that the nature of the capping ligand controls the mobility of carriers and transport characteristics. Typically, the type of ligand might influence the type of channel-whether n-type, p-type or ambipolar-in field effect transistors. [23,28] The ambipolar nature of the transistor is due to near-intrinsic doping of the Qdot. Recently, tetrabutylammonium iodide-treated PbS Qdots, [13] metal chalcogenide complex (Na 4 Sn 2 S 6 •14H 2 O, Na 4 Sn 2 Se 6 , and KInSe 2)-capped CdSe Qdots, [14] and 3-mercaptopropionic acid ligand-exchanged PbS Qdots [9] have been used in thin film transistors to achieve efficient charge transport and high carrier mobilities. However, ligand exchange with compact organic or inorganic ligands in Qdots do not always assure high carrier mobility and better charge transport in Qdot thin films. On the other hand, the ligand exchange may introduce additional Ambipolar transport characteristics of thin film transistors fabricated from nontoxic white light emitting quantum dot complexes (QDCs) are herein reported to exhibit efficient carrier mobilities. The QDCs are synthesized by forming bluish green emitting zinc quinolate complex on the surface of orange emitting Mn 2+-doped ZnS quantum dots (Qdots) using 8-hydroxyquinoline 5-sulfonic acid as the chelating ligand. The device exhibits efficient ambipolar transport characteristics with high I ON /I OFF ratio of 10 4 and electron mobility and hole mobility of 2.95 × 10 −02 and 1.06 × 10 −02 cm 2 V −1 s −1 , respectively. The subthreshold slope of Qdot complex-integrated thin film transistor increases from that of Mn 2+-doped ZnS Qdot-integrated thin film transistor from 0.35 to 0.79 V dec −1 in p-field effect transistor (FET) and from 0.59 to 0.97 V dec −1 in n-FET operations, which annotates an increase in trap state density due to surface complexation of the Qdot. These results suggest that white light emitting QDC can be used as an efficient transport as well as an emissive material, which open up new paradigm for advanced optoelectronic applications.
Chemistry – An Asian Journal, 2019
ACS Applied Nano Materials, 2019
Herein, we report the sustainable, cost-effective and greener surface modification strategy of qu... more Herein, we report the sustainable, cost-effective and greener surface modification strategy of quantum dot complex (QDC)-comprised of Zn-chalcogenide quantum dot (Qdot; for example undoped ZnS and Mn 2+-doped ZnS) and surface Zn-quinolate (ZnQ) complex-following the interaction with bovine serum albumin (BSA) protein. The interaction of BSA to QDC led to enhancement in their luminescence properties (such as quantum yield and emission life time), solubility and stability (in water), compared to their bare form. The enhanced luminescence properties of BSA coupled QDC-also termed herein as BSA-QDC nanocomposite-is due to the BSA induced structural rigidity of the ZnQ 2 complex (being present on the surface of Znchalcogenide Qdot). The highly green luminescent nontoxic BSA-QDC nanocompositeconsisted of undoped ZnS and ZnQ 2 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 M. Interestingly, the interaction of BSA to a dual emitting QDC (consisted of orange emitting Mn 2+-doped ZnS Qdot and green emitting surface ZnQ 2 complex) resulted the generation of white light (which is hard to achieve from only dual emitting QDC at ex-330 nm), with chromaticity coordinates of (0.33, 0.35) and (0.29, 0.35), color rendering index (CRI) of 86 and 80, and correlated color temperature (CCT) of 5646 and 7377 K, in liquid and solid phases respectively. This may open up a new paradigm towards sustainable and user-friendly surface modification strategies for fabricating advanced nanoscale materials, with anticipated uses in imaging, sensing and light emitting applications.
Chemical Communications, 2019
Ratiometric pH sensing in the physiological range of pH 6.5–10.3 by a white light emitting quantu... more Ratiometric pH sensing in the physiological range of pH 6.5–10.3 by a white light emitting quantum dot complex – following the changes in luminescence intensity ratio, color and chromaticity – is described herein.
Langmuir, 2017
Herein we report, the formation of blue emitting Zn(MSA)2 complex on the surface of a yellow emit... more Herein we report, the formation of blue emitting Zn(MSA)2 complex on the surface of a yellow emitting ZnO quantum dot (Qdot)-out of a complexation reaction between N-methylsalicylaldimine (MSA) and ZnO Qdot. This led to formation of a highly luminescent, photostable, single component nanocomposite that emit bright natural white light, with (i) chromaticities of (0.31, 0.38) and (0.31, 0.36), (ii) color rendering indices (CRI) of 74 and 82 and (iii) correlated color temperatures (CCT) of 6505 K and 6517 K, in their solution and solid phases, respectively. Importantly, the control over the chromaticity and CCT-depending upon the degree of complexation-makes the reported nanocomposite a potential new advanced material in fabricating cost-effective single component white light emitting devices (WLED) of choice and design in near future.
Journal of Materials Chemistry C, 2017
Formation of a zinc-quinolate complex on the surface of CuInS2/ZnS core shell quantum dots leadin... more Formation of a zinc-quinolate complex on the surface of CuInS2/ZnS core shell quantum dots leading to the fabrication of an advanced white light emitting nanocomposite.
ACS Applied Materials & Interfaces, 2016
We report the synthesis of a biofriendly highly luminescent white-light-emitting nanocomposite. T... more We report the synthesis of a biofriendly highly luminescent white-light-emitting nanocomposite. The composite consisted of Au nanoclusters and ZnQ2 complex (on the surface of ZnS quantum dots) embedded in protein. The combination of red, green, and blue luminescence from clusters, complex, and protein, respectively, led to white light generation.
The Journal of Physical Chemistry Letters, 2015
Herein we report the generation of synchronous tricolor emission for a single wavelength excitati... more 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 ligandfree 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 (λ ex 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.
Langmuir, 2014
Herein we report the generation and control of double channel emission from a single component sy... more 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 dotcalled the quantum dot complex (QDC)originates from two independent pathways: one from the complex (ZnQ 2) formed on the surface of the Qdot and the other from the dopant Mn 2+ ions of the Qdot. Importantly, reaction of ZnQ 2 •2H 2 O 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 ZnQ 2 and a dangling sulfide bond. On the other hand, the emission at 588 nmwith an excitation maximum at 330 nmwhich is redox tunable, is ascribed to Mn 2+ dopant. The ZnQ 2 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.
Langmuir, 2014
Chemical reaction between oleate-capped Zn(x)Cd(1-x)S quantum dots (Qdots) and 8-hydroxyquinoline... more Chemical reaction between oleate-capped Zn(x)Cd(1-x)S quantum dots (Qdots) and 8-hydroxyquinoline (HQ) led to formation of a surface complex, which was accompanied by transfer of hydrophobic Qdots from nonpolar (hexane) to polar (water) medium with high efficiency. The stability of the complex on the surface was achieved via involvement of dangling sulfide bonds. Moreover, the transferred hydrophilic Qdots--herein called as quantum dot complex (QDC)--exhibited new and superior optical properties in comparison to bare inorganic complexes with retention of the dimension and core structure of the Qdots. Finally, the new and superior optical properties of water-soluble QDC make them potentially useful for biological--in addition to light emitting device (LED)--applications.
Chemistry – An Asian Journal, 2019