Carbon dots: synthesis, formation mechanism, fluorescence origin and sensing applications

Advanced synthesis of materials for intermediate-temperature solid oxide fuel cells

This is the first comprehensive review on methods and materials for use in optical sensing of pH values and on applications of such sensors. The Review starts with an introduction that contains subsections on the definition of the pH value, a brief look back on optical methods for sensing of pH, on the effects of ionic strength on pH values and pKa values, on the selectivity, sensitivity, precision, dynamic ranges, and temperature dependence of such sensors. Commonly used optical sensing schemes are covered in a next main chapter, with subsections on methods based on absorptiometry, reflectometry, luminescence, refractive index, surface plasmon resonance, photonic crystals, turbidity, mechanical displacement, interferometry, and solvatochromism. This is followed by sections on absorptiometric and luminescent molecular probes for use pH in sensors. Further large sections cover polymeric hosts and supports, and methods for immobilization of indicator dyes. Further and more specific sections summarize the state of the art in materials with dual functionality (indicator and host), nanomaterials, sensors based on upconversion and 2-photon absorption, multiparameter sensors, imaging, and sensors for extreme pH values. A chapter on the many sensing formats has subsections on planar, fiber optic, evanescent wave, refractive index, surface plasmon resonance and holography based sensor designs, and on distributed sensing. Another section summarizes selected applications in areas, such as medicine, biology, oceanography, bioprocess monitoring, corrosion studies, on the use of pH sensors as transducers in biosensors and chemical sensors, and their integration into flow-injection analyzers, microfluidic devices, and lab-on-a-chip systems. An extra section is devoted to current challenges, with subsections on challenges of general nature and those of specific nature. A concluding section gives an outlook on potential future trends and perspectives.

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

Enhancement of thermal conductivity of kerosene-based Fe3O4 nanofluids prepared via phase-transfer method

Parkinson's disease (PD) is a heterogeneous neurodegenerative disorder that affects an estimated 10 million sufferers worldwide. The two forms of PD include familial and sporadic, and while the etiology of PD is still largely unknown, the condition is likely to be multifactorial with genetic and environmental factors contributing to disease genesis. Diagnosis of the condition is attained through the observation of cardinal clinical manifestations including resting tremor, muscle rigidity, slowness or loss of movement, and postural instability. Unfortunately, by the time these features become apparent extensive neurological damage has already occurred. A cure for PD has not been identified and the current therapy options are pharmaceutical- and/or surgical-based interventions to treat condition symptoms. There is no specific test for PD and most diagnoses are confirmed by a combination of clinical symptoms and positive responses to dopaminergic drug therapies. The prevalence and incidence of PD vary worldwide influenced by several factors such as age, gender, ethnicity, genetic susceptibilities, and environmental exposures. Here, we will present environmental factors implicated in sporadic PD onset. By understanding the mechanisms in which environmental factors interact with, and affect the brain we can stride toward finding the underlying cause(s) of PD.

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Parkinson's Disease and the Environment.

Since the last two decades, protein conjugated fluorescent gold nanoclusters (NCs) owe much attention in the field of medical and nanobiotechnology due to their excellent photo stability characteristics. In this paper, we reported stable, nontoxic and red fluorescent emission BSA-Au NCs for selective detection of L-dopamine (DA) in cerebrospinal fluid (CSF). The evolution was probed by various instrumental techniques such as UV-vis spectroscopy, High resolution transmission electron microscopy (HTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL). The synthesised BSA-Au NCs were showing 4–6 nm with high fluorescent ~8% Quantum yield (QY). The fluorescence intensity of BSA-Au NCs was quenched upon the addition of various concentrations of DA via an electron transfer mechanism. The decrease in BSA-Au NCs fluorescence intensity made it possible to determine DA in PBS buffer and the spiked DA in CSF in the linear range from 0 to 10 nM with the limit of detection (LOD) 0.622 and 0.830 nM respectively. Best of our knowledge, as-prepared BSA-Au NCs will gain possible strategy and good platform for biosensor, drug discovery, and rapid disease diagnosis such as Parkinson’s and Alzheimer diseases.

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Fluorescent Gold Nanoclusters for Selective Detection of Dopamine in Cerebrospinal fluid.

Novel N-doped green-emitting carbon dots (N-GCDs) that were responsive to various external stimuli and had high quantum yields (QYs) for multifaceted applications were synthesized from β-resorcylic acid and ethylenediamine using a hydrothermal process followed by a reflux method. The QYs of the N-GCDs were in the range of 17.36%–48.4% and were associated with different photoluminescent color emission in different solvents. Interestingly, the as-synthesized N-GCDs exhibited strict solvent polarity-dependent switchability (solvatochromism) and multicolor excitation-wavelength-independent emission in different solvents. Sensing of an analyte based on the switching of the photoluminescence (PL) emission maxima (λmax) is always preferred over that based on fluorescence quenching to avoid complexity and confusion regarding the initial fluorescence intensity (I0) and thus make the sensing process simple, rapid, ordered, and reliable. The N-GCDs exhibited blue emission in low-polarity organic solvents, but with the increase of the trace water content in the system, the PL emission peak gradually shifted to a higher wavelength (bathochromic shift) at a single-wavelength excitation. Thus, the N-GCDs are sensitive visual probes for the fluorescence detection of the trace water content in organic solvents without sophisticated processes. They also indicate the pH-response behavior. When the pH decreased from 7.6 to 2.4, the fluorescence emission intensity decreased, with a particularly good linear relationship (R2 = 0.990) in the range of 3.8–6.2. Moreover, the polarity-dependent-emission property was observed in the solid state polymer matrices. Multicolor-emissive N-GCD/polymer films were prepared by integrating N-GCDs with the polymer matrices of different polarity, demonstrating the application of carbon dots for solid-state lighting.

N-doped carbon dots with tunable emission for multifaceted application: solvatochromism, moisture sensing, pH sensing, and solid state multicolor lighting

A unique and facile biosensing system for the detection of low-concentration divalent calcium ions (Ca2+) in human serum was developed using an environmentally benign, blue-colored fluorescent multi-carboxylic acid-functionalized carbon dots (CDs) that were synthesized from ethylenediaminetetraacetic acid (EDTA) via a hydrothermal process. These CDs are termed as ECDs. Our results showed that this newly developed strategy can offer an expeditious, highly sensitive, and selective detection of Ca2+ ions in human serum, with a detection limit as low as 77 pM and a potent working range of 1–10 nM. The Ca2+ ions interact with the carboxylic groups of the ECDs, could be resulting in a strong photoluminescence quenching of the ECDs via a non-radiative electron or energy transfer process. Furthermore, the detection of Ca2+ ions in human serum sample obtained using this sensing system was in good agreement with results derived from inductively coupled plasma-mass spectrometry analysis. No significant PL quenching was observed with other ionic species such as Na+, K+, Mg2+, Fe2+, and Fe3+ owing to their monovalent nature and the fact that they typically exist in human serum at very low concentrations, which disfavors the formation of their corresponding complexes on the surface of the ECDs.

Highly selective and sensitive detection of calcium (II) ions in human serum using novel fluorescent carbon dots

Dopamine is a neurotransmitter of the catecholamine family and has many important roles, especially in human brain. Several diseases of the nervous system, such as Parkinson's disease, attention deficit hyperactivity disorder, restless legs syndrome, are believed to be related to deficiency of dopamine. Several studies have been performed to detect dopamine by using electrochemical analysis. In this study, quantum dots (QDs) were used as sensing media for the detection of dopamine. The surface of the QDs was modified with l-cysteine by coupling reaction to increase the selectivity of dopamine. The fluorescence of cysteine-capped indium phosphide/zinc sulfide QDs was quenched by dopamine with various concentrations in the presence of ascorbic acid. This method shows good selectivity for dopamine detection, and the detection limit was 5 nM.

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Selective detection of dopamine in the presence of ascorbic acid via fluorescence quenching of InP/ZnS quantum dots

Pt thin film was deposited on alumina substrate by using DC sputter and the serpentine pattern was formed by photolithography to fabricate the resistance temperature detector (RTD) The Pt film was thermally treated and the surface structure of the film and its effect on the electrical resistance were studied The sheet resistance of the film depends on the thickness and thermal treatment The developing and etching conditions for serpentine patterning of the film were investigated and various RTD samples were prepared All of the fabricated RTD’s show a good linear variation of resistance with the temperature The temperature coefficient of resistance (TCR) values of RTD’s increased with decreasing film thickness, narrowing pattern line width, and increasing annealing temperature The highest TCR value was obtained from RTD with 1 mm line width thermally treated at 700 ‡C and was 353×103 ppm/‡C

https://www.cheric.org/PDF/KJChE/KC18/KC18-1-0061.pdf

Jongsung Kim

Papers

Fluorescent Gold Nanoclusters for Selective Detection of Dopamine in Cerebrospinal fluid.

N-doped carbon dots with tunable emission for multifaceted application: solvatochromism, moisture sensing, pH sensing, and solid state multicolor lighting

Highly selective and sensitive detection of calcium (II) ions in human serum using novel fluorescent carbon dots

Selective detection of dopamine in the presence of ascorbic acid via fluorescence quenching of InP/ZnS quantum dots

A Study on the Fabrication of an RTD (Resistance Temperature Detector) by Using Pt Thin Film