Browsing by Author "Sun, Kien Wen"

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A simple pyrene based AIEE active schiff base probe for selective naked eye and fluoresence off-on detection of trivalent cations with live cell application
(2016-08)
Simon, Turibius
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Shellaiah, Muthaiah
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Srinivasadesikan, Venkatesan
;
Lin, Ching-Chang
;
Ko, Fu-Hsiang
A simple pyrene based schiff base derivative 2-((pyren-1-ylmethylene)amino)ethanol (PE) has been synthesized via one-pot reaction and its nano-aggregation induced emission enhancement (AIEE) was reported through UV/PL, TEM and DLS studies. Interestingly, PE in CH3CN revealed the naked eye and fluorescence turn-on sensing responses towards Fe3+, Cr3+ and Al3+ ions, by means of PET and PE-PE* excimer formation. The 2:1 stoichiometry of sensor complexes PE-M3+ (M=Fe/Cr/Al) were calculated from Job\'s plots based on UV-vis absorption titrations and supported by FTIR and ESI (+Ve) mass analysis. In addition, the binding site of PE-M3+ sensor complexes was well established by H-1 NMR titrations and its sensor reversibility was recognized during subsequent addition of M3+ ions and PMDTA, respectively. The detection limits (LODs) and the association constant (K-a) values of PE-M3+ complexes were calculated by standard deviation and linear fittings. Likewise, quantum yield (Phi(f)) calculations, TEM analysis, pH effect and density functional theory (DFT) studies were executed for the PE-M3+ sensor complexes. More importantly, confocal fluorescence microscopy imaging in Raw264.7 cells showed that PE could be used as an effective fluorescent probe for detecting Fe3+, Cr3+ and Al3+ ions in living cells. (C) 2016 Elsevier B.V. All rights reserved.
An Affordable Wet Chemical Route to Grow Conducting Hybrid Graphite-Diamond Nanowires: Demonstration by A Single Nanowire Device
(2017-09-11)
Shellaiah, Muthaiah
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Chen, Tin Hao
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Simon, Turibius
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Li, Liang-Chen
;
Sun, Kien Wen
We report an affordable wet chemical route for the reproducible hybrid graphite-diamond nanowires (G-DNWs) growth from cysteamine functionalized diamond nanoparticles (ND-Cys) via pH induced self-assembly, which has been visualized through SEM and TEM images. Interestingly, the mechanistic aspects behind that self-assembly directed G-DNWs formation was discussed in details. Notably, above self-assembly was validated by AFM and TEM data. Further interrogations by XRD and Raman data were revealed the possible graphite sheath wrapping over DNWs. Moreover, the HR-TEM studies also verified the coexistence of less perfect sp(2) graphite layer wrapped over the sp3 diamond carbon and the impurity channels as well. Very importantly, conductivity of hybrid G-DNWs was verified via fabrication of a single G-DNW. Wherein, the better conductivity of G-DNW portion L2 was found as 2.4 +/- 1.92 x 10(-6) mS/cm and revealed its effective applicability in near future. In addition to note, temperature dependent carrier transport mechanisms and activation energy calculations were reported in details in this work. Ultimately, to demonstrate the importance of our conductivity measurements, the possible mechanism behind the electrical transport and the comparative account on electrical resistivities of carbon based materials were provided.
Carrier dynamics in modulation-doped InAs/GaAs quantum rings
(2013)
Lin, Chien-Hung
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Lin, Shin-Chin
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Sun, Kien Wen
;
Lee, Chien-Ping
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應用化學系
Carrier dynamics in undoped and modulation-doped self-assembled InAs/GaAs quantum rings was comprehensively examined through time-resolved photoluminescence techniques at room temperature. After photoexcitation, the rates of carrier capture and relaxation in the ground state and excited states were equally fast in both the undoped and charged quantum rings. Instead of cascading down through the excited states, the carriers excited in the undoped quantum rings relaxed through the quasicontinuum states via coupling with acoustical phonons and eventually thermalized to the ground state by emitting longitudinal optical phonons. The dynamics of carrier thermalization was governed by cold carriers in the charged quantum rings. In carrier recombination, the undoped quantum rings had a shorter PL decay time and lower luminescence intensity than the charged quantum rings because radiative recombination was suppressed by defects in the matrix and the absence of cold carriers.
Cysteamine-capped gold-copper nanoclusters for fluorometric determination and imaging of chromium(VI) and dopamine
(2019-12-01)
Shellaiah, Muthaiah
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Simon, Turibius
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Thirumalaivasan, Natesan
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Sun, Kien Wen
;
Ko, Fu-Hsiang
Highly emissive cysteamine-capped gold-copper bimetallic nanoclusters (CA-AuCu NCs) with a quantum yield of 18% were synthesized via one-pot anti-galvanic reduction. The CA-AuCu NCs were characterized by HR-TEM, XPS, FTIR, MALDI-TOF mass spectrometry, DLS, and zeta potential analyses. The NCs are shown to be viable fluorescent probes for Cr(VI) ions and dopamine (DA) via quenching of the blue fluorescence, typically measured at excitation/emission wavelengths of 350/436 nm. During DA recognition, a dark brown color appears, which is distinguishable from that of Cr(VI) detection. The aggregation induced quenching due to electron transfer was demonstrated by photoluminescence, HR-TEM, FTIR, DLS, and zeta potential interrogations. In buffer of pH 7, response is linear in the 0.2 100 mu M for Cr(VI) and from 0.4 250 mu M for DA. The respective detection limits are 80 and 135 nM. The method was applied to the determination of both Cr(VI) and DA in (spiked) tap, lake and sea water, and in human urine samples. The low toxicity of CA-AuCu NCs was validated by the MTT assay, and their responses to Cr(VI) ions and DA was also proven by Raw 264.7 cell imaging. Graphical abstract Cysteamine capped Au-Cu nanoclusters (CA-AuCu NCs) were synthesized via one-pot anti-galvanic reduction and utilized in sensing of Cr(VI) ions and dopamine (DA) with demonstrated real/urine and cell imaging applications.
Cysteamine-modified diamond nanoparticles applied in cellular imaging and Hg2+ ions detection
(2019-01-28)
Shellaiah, Muthaiah
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Simon, Turibius
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Venkatesan, Parthiban
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Sun, Kien Wen
;
Ko, Fu-Hsiang
Luminescent cysteamine-modified nanodiamond particles (ND-Cys) have been reported in surface-mediated energy transfer, cell imaging, and metal-ion recognition studies. In normalized photoluminescence (PL) spectral studies, the emission maxima of ND-Cys (at 50 mu g/mL in water) was fixed at 438 nm at 350 nm excitation, producing a blue emission with a quantum yield (Phi) of 0.13. In the dispersion range of 0-800 mu g/mL, ND-Cys exhibited agglomeration-induced energy transfer via red shifting of the PL peak from 438 nm to 451 nm. Analogous to PL studies, Raman interrogations also established the agglomeration and fixed the saturation limit to 500 mu g/mL in water. The low toxicity and biocompatibility of ND-Cys were demonstrated using methyl thiazolyl tetrazolium assay and time-dependent HeLa cell imaging. Subsequently, the Hg2+ selectivity by ND-Cys was revealed by an intense fluorescence peak shift from 440 nm to 463 nm. Fluorescence studies indicated that the detection limit of Hg2+ ions approximated 153 nM. Fourier-transform infrared and X-ray photoelectron spectroscopy (XPS) analyses supported the binding between free thiol (-SH) and amide (-C=O and -NH) groups of ND-Cys to Hg2+. The Hg2+-induced agglomeration and surface graphitization were successfully confirmed by X-ray powder diffraction, XPS, Raman, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, and zeta potential analyses. Effective detection of Hg2+ ions by ND-Cys was validated through HeLa cell imaging at shortened time intervals.
Development of extremely stable dual functionalized gold nanoparticles for effective colorimetric detection of clenbuterol and ractopamine in human urine samples
(2018-09-06)
Simon, Turibius
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Shellaiah, Muthaiah
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Steffi, Perpectual
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Sun, Kien Wen
;
Ko, Fu-Hsiang
New glutamic acid (Glu) and polyethylenimine (PE) functionalized ultra-stable gold nanoparticles (PE-Glu-AuNPs) were developed via a simple NaBH4 reduction method. The low toxicity and biocompatibility of PE-Glu-AuNPs were confirmed via an MTT assay in Raw 264.7 cells. Excitingly, PE-Glu-AuNPs were found to be extremely stable at room temperature up to six months and were utilized in an effective colorimetric naked eye assay of clenbuterol (CLB) and ractopamine (RCT) at pH 5. It was found that the selective assay of CLB and RCT is not affected by any other interferences (such as alanine, phenylalanine, NaCl, CaCl2, threonine, cysteine, glycine, glucose, urea and salbutamol). Furthermore, the detection of these beta-agonists can be visually accomplished through change color from wine red to purple blue. Notably, the aggregation induced detection of CLB and RCT was well confirmed through transmission electron microscopy (TEM) and dynamic light scattering (DLS) studies. DLS investigations, clearly showed, that in the presence of CLB and RCT, the initial size of PE-Glu-AuNPs (12.8 +/- 8.6 nm) was changed to 84.8 +/- 52.3 and 79.5 +/- 47.8 nm, respectively, via aggregation. Furthermore, the colorimetric assays of CLB and RCT with PE-Glu-AuNPs were effective starting from CLB and RCT concentrations of 200 nM and 400 nM, respectively, and could be visualized using the naked eyes. Remarkably, UV-vis titrations of PE-Glu-AuNPs with CLB and RCT could be used to well estimate their sub nanomolar detection limits (LODs) via standard deviation and linear fittings. The contribution of surface functional groups that support the analyte recognition was confirmed by fourier-transform infrared spectroscopy (FTIR) analysis. Moreover, the CLB and RCT assays with PE-Glu-AuNPs were supported by examination of human urine samples. (C) 2018 Elsevier B.V. All rights reserved.
Effect of Metal Ions on Hybrid Graphite-Diamond Nanowire Growth: Conductivity Measurements from a Single Nanowire Device
(2019-03-11)
Shellaiah, Muthaiah
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Chen, Ying-Chou
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Simon, Turibius
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Li, Liang-Chen
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Sun, Kien Wen
Novel Cd2+ ions mediated reproducible hybrid graphite-diamond nanowire (G-DNWs; Cd2+-NDS1 NW) growth from 4-Amino-5-phenyl-4H-1,2,4-triazole-3-thiol (S1) functionalized diamond nanoparticles (NDS1) via supramolecular assembly is reported and demonstrated through TEM and AFM images. FTIR, EDX and XPS studies reveal the supramolecular coordination between functional units of NDS1 and Cd2+ ions towards NWs growth. Investigations of XPS, XRD and Raman data show the covering of graphite sheath over DNWs. Moreover, HR-TEM studies on Cd2+-NDS1 NW confirm the coexistence of less perfect sp(2) graphite layer and sp(3) diamond carbon along with impurity channels and flatten surface morphology. Possible mechanisms behind the G-DNWs growth are proposed and clarified. Subsequently, conductivity of the as-grown G-DNWs is determined through the fabrication of a single Cd2+-NDS1 NW device, in which the G-DNW portion L2 demonstrates a better conductivity of 2.31 x 10(-4) mS/cm. In addition, we investigate the temperature-dependent carrier transport mechanisms and the corresponding activation energy in details. Finally, comparisons in electrical resistivities with other carbon-based materials are made to validate the importance of our conductivity measurements.
Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots
(2011-06-02)
Shih, Ching-I
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Lin, Chien-Hung
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Lin, Shin-Chin
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Lin, Ta-Chun
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Sun, Kien Wen
In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states) on photoluminescence excitation (PLE) spectra of InAs quantum dots (QDs) was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T) were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA) phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate.
Efficiency Enhancement of PEDOT:PSS/Si Hybrid Solar Cells by Using Nanostructured Radial Junction and Antireflective Surface
(2013-08-14)
Chen, Jheng-Yuan
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Con, Celal
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Yu, Ming-Hung
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Cui, Bo
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Sun, Kien Wen
We demonstrate the implementation of a hybrid solar cell that comprises a surface nanostructured n-type Si and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). The Si surface before deposition of the organic layer was nanostructured by using CsCl self-assembled nanoparticles as a hard mask and dry etching to form radial junction architectures and enhance light diffusion and absorption. Apart from the textured Si surface, processing parameters such as from metal-electrode shadow ratio, spin-coating rate, and surfactant addition were properly adjusted to improve overall cell performance. Our hybrid solar cells achieve the best performance under optimized cell parameters with a power conversion efficiency of 8.84% and short-circuit current density of 30.5 mA/cm(2). This combined technique provides a simple, scalable, and cost-effective process for fabricating hybrid solar cells.
Enhanced Performance of Organic Thin Film Solar Cells Using Electrodes with Nanoimprinted Light-Diffraction and Light-Diffusion Structures
(2014-05-14)
Chen, Jheng-Yuan
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Yu, Ming-Hung
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Chang, Chih-Yu
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Chao, Yi-Hsiang
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Sun, Kien Wen
An ITO substrate with periodic surface nanostructures was used to induce strong diffusion and diffraction of incident light. The nanostructures were fabricated using nanoimprint lithography on photoresist followed by coating of the ITO layer and organic materials with uniform morphology. The nanostructures embedded into the ITO layer were found to increase absorption in poly(3-hexylthiophene) : [6,6]-phenyl-C61-butyric acid methyl ester solar devices. The short-circuit current of the nanostructured organic solar cells improved from 7.07 to 10.76 mA/cm(2). This improvement was due to the increased effective optical path of absorbed light resulting from the trapping and scattering by the nanostructures.
Exceptionally low thermal conductivity of poly(3-hexylthiophene) single nanowires
(2015-01-01)
Lee, Yi-Jung
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Jeng, Kai-Sheng
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Chen, Jiun-Tai
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Sun, Kien Wen
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應用化學系
Electrical and thermal conductivity measurements were conducted by using microfabricated four-point probe and T-type nanosensors in a vacuum on poly(3-hexylthiophene) (P3HT) single nanowires prepared by the whisker method. The nanowires had a cross-section of only 5 nm x 15 nm and a length of 0.5-10 mu m. The electrical conductance of nanowires was 3.3 x 10(-7) 1/Omega and remained stable even after exposing the wires to ambient conditions for a few days. The thermal conductivity of a nanowire was 0.055 +/- 0.003 Wm(-1) K-1 which was approximately an order of magnitude lower than other previously reported P3HT single nanowires with a diameter of 120 nm and embedded in anodic aluminum oxide matrix. This thermal conductivity was also approximately four times smaller than that of P3HT amorphous thin films (similar to 0.2 W m(-1) K-1). The exceptionally low thermal conductivity was attributed to increased interface-phonon scattering because heat propagation was confined to an extreme narrow spatial dimension.
Field-effect-dependent thermoelectric power in highly resistive Sb2Se3 single nanowire
(2018-04-01)
Sun, Kien Wen
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Ko, Ting-Yu
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Shellaiah, Muthaiah
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應用化學系
;
電機學院
In this paper, we report the results of our experiments on and measurements of electrical resistivity and thermoelectric power (Seebeck coefficient) from single-crystalline antimony triselenide (Sb2Se3) single nanowires (NWs) with high resistivity (sigma similar to 4.37 x 10(-4) S/m). A positive Seebeck coefficient of approximately 661 mu V/K at room temperature was obtained using a custom-made thermoelectric power probe with an alternating current lock-in method (the 2 omega technique), which indicates that the thermal transport is dominated by holes. The measured Seebeck coefficient of the NWs is a factor of 2-3 lower than their bulk counterparts and is comparable to that of a highly conductive Sb2Se3 single NWs (approximately -750 mu V/K). We observed an increase in the Seebeck coefficients with increased bias voltages by field-effect gating, which cannot be explained by the modulation of the Fermi level in the NWs.
Highly efficient back-junction PEDOT:PSS/n-Si hybrid solar cell with omnidirectional antireflection structures
(2018-04-01)
Chang, Kai Wen
;
Sun, Kien Wen
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應用化學系
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電機學院
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Department of Applied Chemistry
Hybrid planar solar cells based on bulk n-doped Si wafers and poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) with a back-junction geometry demonstrated an excellent power conversion efficiency of more than 11%. When a random pyramid or a Si nanowire antireflection structure was incorporated into the front of the cell surface, the power conversion efficiencies were further enhanced to 13.9% or 14.5%, respectively. Moreover, the cells with the Si nanowire antireflection structure displayed omnidirectional light-trapping characteristics over the random pyramid structures. These cells also maintained a constant power conversion efficiency even at an incident angle of 60 degrees.
Highly efficient poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/Si hybrid solar cells with imprinted nanopyramid structures
(2013-09-23)
Chen, Jheng-Yuan
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Yu, Ming-Hung
;
Chang, Shun-Fa
;
Sun, Kien Wen
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應用化學系
High-efficiency hybrid solar cells based on nanostructured silicon and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate), which were fabricated via a simple nanoimprint fabrication process, demonstrated an excellent power conversion efficiency of 10.86%. The complex and costly high-temperature photolithography and masking steps were replaced by techniques that are low-cost and capable of mass production. The nanopyramid structures fabricated on the silicon surface provided an antireflective effect and have a radial junction architecture that enhanced the light absorption and carrier collection efficiency. The short-circuit current density (J(sc)) of the hybrid solar cell with nanopyramid structures was greatly improved from 24.5 mA/cm(2) to 32.5 mA/cm(2) compared with that of a flat surface device. The highest solar cell efficiency was achieved on a 525 mu m-thick 2.3 Omega cm n-type Czochralski process (CZ) Si substrate with a designated area of 4 cm(2). (C) 2013 AIP Publishing LLC.
Improved morphological characteristics and electronic properties of MAPbI(3) thin film with multiple methylamine spray treatments
(2020-03-01)
Chiao, Guan-Haw
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Li, Liang-Chen
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Shellaiah, Muthaiah
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Sun, Kien Wen
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應用化學系
We demonstrated that the quality of the film can be significantly improved by using multiple treatments with methylamine (CH3NH2, MA) spray to the spin-coated perovskite thin films on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)/ITO glass substrates, leading to more efficient and reproducible photovoltaic and optoelectronic devices. Our X-ray diffraction and scanning electron microscopy measurements indicated an increase in the homogeneity, grain size, and crystallinity of the spin-coated MAPbI(3) thin film after multiple MA vapor treatments. The influence of MA vapor treatments on emission, absorption, energy gap, and carrier lifetime were investigated through the absorption, steady-state, and time-resolved photoluminescence (PL) spectroscopy. The peak position and full width at half maximum of the MA spray-treated film PL were slightly blue shifted and narrowed, respectively, because of the reduced defect states in the band tail and gain boundary. However, the PL intensity of the treated film was lower than that of the untreated one due to the increased carrier diffusivity in larger grains. The carrier type, concentration, mobility, electrical resistivity, and photoconductivity of the MA spray-treated MAPbI(3) thin film was also investigated using the Hall and current-voltage measurements. The improvements in the morphological characteristics and crystallinity of the treated perovskite thin film were reflected in the enhanced carrier mobility, electrical conductivity, photo response, and suppressed carrier recombination.
Laser induced popcornlike conformational transition of nanodiamond as a nanoknife
(2008-07-21)
Chang, Chia-Ching
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Chen, Pei-Hsin
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Chu, Hsueh-Liang
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Lee, Tzu-Cheng
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Chou, Ching-Chung
Nanodiamond (ND) is surrounded by layers of graphite on its surface. This unique structure feature creates unusual fluorescence spectra, which can be used as an indicator to monitor its surface modification. Meanwhile, the impurity, nitroso (C - N = O) inside the ND can be photolyzed by two-photon absorption, releasing NO to facilitate the formation of a sp(3) diamond structure in the core of ND and transforming it into a sp(2) graphite structure. Such a conformational transition enlarges the size of ND from 8 to 90 nm, resulting in a popcornlike structure. This transition reaction may be useful as nanoknives in biomedical application. (c) 2008 American Institute of Physics.
Microwave plasma-assisted photoluminescence enhancement in nitrogen-doped ultrananocrystalline diamond film
(2012-06-01)
Liu, Yu Lin
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Sun, Kien Wen
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Lin, Yi Jie
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Fong, Shih-Chieh
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Lin, I. Nan
Optical properties and conductivity of nitrogen-doped ultrananocrystal diamond (UNCD) films were investigated following treatment with low energy microwave plasma at room temperature. The plasma also generated vacancies in UNCD films and provided heat for mobilizing the vacancies to combine with the impurities, which formed the nitrogen-vacancy defect centers. The generated color centers were distributed uniformly in the samples. The conductivity of nitrogen-doped UNCD films treated by microwave plasma was found to decrease slightly due to the reduced grain boundaries. The photoluminescence emitted by the plasma treated nitrogen-doped UNCD films was enhanced significantly compared to the untreated films. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4727743]
Nanodiamonds conjugated to gold nanoparticles for colorimetric detection of clenbuterol and chromium(III) in urine
(2018-01-01)
Shellaiah, Muthaiah
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Simon, Turibius
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Venkatesan, Parthiban
;
Sun, Kien Wen
;
Ko, Fu-Hsiang
Nanodiamonds were modified such that they carry thiol groups (ND-thiol). Gold nanoparticles were reacted with ND-thiol to obtain a highly stable conjugate of the type ND@AuNPs. Both ND-thiol and the ND@AuNPs were characterized by SEM, TEM, AFM, DLS, zeta potential, XPS, XRD, UV-Vis, Raman, FTIR and cytotoxicity studies. Their biocompatibility was confirmed via an MTT assay with HeLa cells. At a pH value of 6, the ND@AuNPs represent a colorimetric probe that can be used to selectively detect the illegally used beta-adrenergic drug clenbuterol (CLB) and the pollutant chromium(III). Detection can be performed visually by monitoring the color change from wine red to purple blue, or by colorimetric measurement of the so-called SPR peaks at 651 and 710 nm. The color changes are due to aggregation, and this is confirmed by TEM and DLS data. The involvement of surface functional groups that assist in analyte recognition was verified by FTIR. The detection limits are 0.49 nM for CLB, and 0.37 nM for Cr(III). The ND@AuNPs were successfully applied to the determination of Cr(III) and CLB in spiked human urine samples. Notably, the low interference by other ions in the detection of Cr(III) in tap and lake water is confirmed by ICP-MS analyses.
Novel anthracene- and pyridine-containing Schiff base probe for selective "off-on\'\' fluorescent determination of Cu2+ ions towards live cell application
(2016-07-01)
Simon, Turibius
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Shellaiah, Muthaiah
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Srinivasadesikan, Venkatesan
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Lin, Ching-Chang
;
Ko, Fu-Hsiang
The novel anthracene- and pyridine-containing Schiff base derivative 2-(2-(anthracen-9-ylmethylene)-hydrazinyl) pyridine (AP) has been synthesized via one-pot reaction and its fluorescent "off-on\'\' detection of Cu2+ ions, via PET-based mechanism, is reported. The 1 : 1 stoichiometry of AP center dot center dot center dot Cu2+ sensor complex was calculated from Job\'s plot based on PL titrations and supported by ESI (+Ve) mass spectral analysis. In addition, the binding sites of AP center dot center dot center dot Cu2+ sensor conjugate were supported by H-1 NMR titration. The detection limit (LOD) and association constant (Ka) of AP center dot center dot center dot Cu2+ complex were obtained by standard deviation and linear fittings. Furthermore, quantum yield (Ff), SEM analysis, pH effect, FTIR interpretation and density functional theory (DFT) studies were conducted for the AP center dot center dot center dot Cu2+ sensing conjugate. More decisively, confocal fluorescence microscopy imaging from Raw264.7 cells indicated that AP could be used as an effective fluorescent probe for the analysis of Cu2+ ions in living cells.
Novel pyrene containing monomeric and dimeric supramolecular AIEE active nano-probes utilized in selective "off-on" trivalent metal and highly acidic pH sensing with live cell applications
(2016)
Shellaiah, Muthaiah
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Simon, Turibius
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Srinivasadesikan, Venkatesan
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Lin, Chein-Ming
;
Sun, Kien Wen
Two novel pyrene containing monomeric and dimeric Schiff base derivatives PCS1 and PCS2 have been synthesized via one-pot reaction and their nano-J-type aggregation induced emission enhancement (AIEE) was well demonstrated using UV-Vis/PL, transmission electron microscopy (TEM), dynamic light scattering (DLS), time resolved photoluminescence (TRPL), and live cell imaging studies. In contrast to PCS2, PCS1 in CH3CN exhibits fluorescence "off-on" sensor selectivity towards transition trivalent metal ions (Fe3+, Cr3+ and Al3+) among other metals, via PET inhibition with excimer PCS1-PCS1(star) formation. The 2 : 1 stoichiometry of PCS1 center dot center dot center dot M3+ (M = Fe/Cr/Al) sensor complexes was calculated from Job\'s plots based on their PL titrations. In addition, the binding sites of PCS1 center dot center dot center dot M3+ sensor complexes were well recognised from the H-1 NMR titrations and supported by ESI(+ve) mass and FTIR analysis. Additionally, fluorescence reversibilities of PCS1 center dot center dot center dot M3+ were observed via consequent addition of M3+ ions and PMDTA, respectively. Furthermore, the detection limits (LODs) and the association constant (K-a) values of PCS1 center dot center dot center dot M3+ complexes were calculated using standard deviation and linear fittings. Likewise, quantum yield (Phi) measurements, TEM analysis, determination of the effect of pH, density functional theory (DFT) and time resolved photoluminescence (TRPL) studies were performed for the PCS1 center dot center dot center dot M3+ sensor complexes. More importantly, confocal fluorescence microscopy imaging of Raw264.7 cells showed that PCS1 could be used as an effective fluorescent probe for detecting transition trivalent metal ions (Fe3+, Cr3+, and Al3+) in living cells. Impressively, both PCS1 and PCS2 showed "off-on" sensing at highly acidic pH values (1-3) with live cell applications.