In this paper, a novel poly-l-lysine (PLL) surface functionalized graphene quantum dots (GQDs) based sensor was developed for detection of cysteine (cys) and homo cysteine (hcys). A fluorescent probe ...(PLL-GQDs) was then fabricated by surface functionalizing GQDs with PLL, a biodegradable polycationic electrolyte to improve the sensitivity and selectivity towards cys and hcys. The detection was based on the specific binding of cys and hcys to PLL at the PLL-GQDs surfaces, which enabled dynamic quenching via electrostatic and hydrophobic interactions. This fluorescent probe provided good linearity for the tested biothiols, ranging from 0 to 150 nM for cys, from 0 to 100 nM for hcys, with limit of detections (LODs) of 2.38 and 1.94 nM, respectively in BPS (pH 7.4). Interestingly, fabricated probe was also able to display a significant selectivity towards cys and hcys against known interfering molecules. The cytotoxicity study confirmed the biocompatibility of PLL-GQDs, enabling its future scope for cell adhesion and other biomedical applications. Besides, confocal study revealed the excellent penetrations of PLL-GQDs into cell cytoplasm and nucleus that validate the practical application of developed probe to detect cys and hcys at cellular level. The method was successfully applied for detection of cys and hcys in human serum sample. We expect the design concept presented here would be broadly used for selective and sensitive estimation of cys and hcys.
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•Waste material (pistachio shells) used for synthesis of graphene quantum dots (GQDs).•Novel poly-l-lysine (PLL) surface functionalized GQDs (PLL-GQDs) based sensor was developed.•The fabricated probe (PLL-GQDs) exhibited low cytotoxicity and excellent biocompatibility.•The probe demonstrated highly sensitive and selective detection of cysteine (cys) and homocysteine (hcys) in real samples.
Surface plasmon resonance (SPR) offers exceptional advantages such as label-free, in-situ and real-time measurement ability that facilitates the study of molecular or chemical binding events. ...Besides, SPR lacks in the detection of various binding events, particularly involving low molecular weight molecules. This drawback ultimately resulted in the development of several sensitivity enhancement methodologies and their application in the various area. Among graphene materials, graphene-based nanocomposites stands out owing to its significant properties such as strong adsorption of molecules, signal amplification by optical, high carrier mobility, electronic bridging, ease of fabrication and therefore, have established as an important sensitivity enhancement substrate for SPR. Also, graphene-based nanocomposites could amplify the signal generated by plasmon material and increase the sensitivity of molecular detection up to femto to atto molar level. This review focuses on the current important developments made in the potential research avenue of SPR and fiber optics based SPR for chemical and biological sensing. Latest trends and challenges in engineering and applications of graphene-based nanocomposites enhanced sensors for detecting minute and low concentration biological and chemical analytes are reviewed comprehensively. This review may aid in futuristic designing approaches and application of grapheneous sensor platforms for sensitive plasmonic nano-sensors.
Graphene nanocomposites based sensitivity enhancement methodologies for chemical and biological sensing. (a) oxidant and reducing gases sensing by oxygen atom of GO with surface reaction mechanism. (b) Protein binding interaction directly on GNC (grapheneous nanocomposites) surface. (c) Antigen: antibody (Ag:Ab) reaction of directly immobilized Ag:Ab on to GNC. (d) pi-pi stacking for planer structure. (e) Hydrogen or electrostatics attraction based binding (f) direct sensing of molecules (shown here for ammonia gas). Display omitted
•Presents graphene nanocomposite based SPR sensors.•Recent progresses in SPR signal enhancement by graphene nanocomposites has been overviewed.•Graphene nanocomposites based sensitivity enhancement methodologies for chemical and biological sensing is reviewed.•In this review, we discussed future trends and perspectives to lay down the future SPR based plasmonic nano-sensors.
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•Intracellular biothiols play important roles in biological systems.•We present the state-of-the-art of CDs and GQDs based fluorescent sensors for biothiols.•The article also ...addresses mechanisms and strategies for fluorescent detection of biothiols using CDs and GQDs.•Sensitivity and selectivity against different biothiol species and other interfering substances are also discussed.•To the best of our knowledge, this review offers the broadest panorama of the state-of-the-art in biothiol sensors.
Fluorescent carbon-based nanomaterials such as carbon dots (CDs) and graphene quantum dots (GQDs) owing to their high aqueous solubility, stable photoluminescence and good biocompatibility are showing greater interest in sensing of biothiols. Biothiols mainly glutathione (GSH), cysteine (Cys), homocysteine (Hcys), considered to be an important tool in the clinical diagnosis of many disorders and diseases. Therefore, the development of new probes has fascinated considerable attention since they are simple, sensitive, rapid and cost effective. Although conventional sensors have been designed and widely applied in biothiols determination, but unfortunately they present many limitations and challenges. In this review, we provide a focused outline on the most recent developments concerning fluorescent based CDs and GQDs nanosensor for detection of biothiols. The most important reaction mechanisms and strategies for detection of biothiols were outlined and compared in terms of their sensitivity and selectivity against different biothiol species and other interfering substances viz. metal ions, amino acids, etc. Future research and challenges in designing of functionalized CDs and GQDs are discussed and elucidated.
The present study aimed to synthesize polyethyleneimine (PEI) surface-functionalized fluorescent carbon dots (CDs)-based biosensor (GP-PEI-CDs) for highly sensitive and selective detection of ...glutathione (GSH). In brief, green pea (GP) shells were utilized for green synthesis of blue luminescent GP-CDs through hydrothermal method. The obtained GP-CDs were surface functionalized with PEI to improve surface defects and quantum confinement effects. The surface functionalization of GP-PEI-CDs was confirmed by different spectroscopic techniques, including FTIR, XPS, etc. Switch “on” of GP-PEI-CDs was quenched by Cu(II) ions (turn “off”), and the limit of detection (LOD) of Cu(II) was found to be 23 nM along with a linearity range as 0 µM to 50 µM. Then, turn “On” process enabled the restoration in fluorescence of surface-functionalized GP-PEI-CDs when different concentrations of GSH in phosphate buffer saline (PBS, pH 7.4) was added. This could be due to split up of Cu(II) from Cu(II)@GP-PEI-CDs complex by presenting selective affinity with thiol (–SH) group of GSH among the various biomolecules. The LOD of GSH was found to be 38 nM and linearity in the range of 0 to 25 µM. The cytotoxicity study confirmed the biocompatibility of surface-functionalized GP-PEI-CDs. Furthermore, a confocal analysis indicated exceptional penetrations of GP-PEI-CDs into the cell cytoplasm and nucleus, demonstrating the created probe's suitability for GSH sensing at the cellular level. The method was successfully applied to determine GSH in in human serum sample.
•Fluorescence and electrochemical sensors for sensitive Tartrazine (Tar) detection in foods are explored.•Advanced carbon-based nanomaterials enhance Tar detection in food, boosting ...safety.•Electrochemical sensors rapidly spot Tar in food with high sensitivity.•This work focuses on refining sensitivity and selectivity, addressing challenges in Tar detection for safer food.•The review highlighted future research, multifunctional sensors & portable device integration.
Azo dyes are widely used as food coloring agents because of their affordability and stability. Examples include brilliant blue, carmoisine, sunset yellow, allura red, and tartrazine (Tar), etc. Notably, Tar is often utilized in hazardous food goods. They are frequently flavoured and combined with food items, raising the likelihood and danger of exposure. Therefore, detecting Tar in food is crucial to prevent health risks. Fluorescence nanomaterials and electrochemical sensors, known for their high sensitivity, affordability, simplicity, and speed, have been widely adopted by researchers for Tar detection. This comprehensive paper delves into the detection of Tar in food products. It extensively covers the utilization of advanced carbon-based nanomaterials, including CDs, doped CDs, and functionalized CDs, for sensitive Tar detection. Additionally, the paper explores the application of electrochemical sensors. The paper concludes by addressing current challenges and prospects, emphasizing efforts to enhance sensitivity, and selectivity for improved food safety.
Organophosphorus pesticide (OPP) is regarded as an important food-chain and environmental contaminant that causes primary acute toxicity and numerous severe health issues. Therefore, the minute ...concentration of OPP present in food materials and environments needs to be identified before it causes any brutal harm to lives. Despite the plenty of merits of qualitative and quantitative sensing methods, the lower sensitivity, poor selectivity, detection speed, etc. towards the interest OPP are major drawbacks. Nanoparticles have attracted a lot of attention because of their unique and intriguing features, which have a variety of applications including sensor development as compared to their bulk counterparts. Recently, the structural design of nanosize-metal–organic framework (MOF) is gaining huge consideration from researchers for sensing applications owing to their versatile and tunable properties. Additionally, MOF-based sensors offer the rapid, simplistic, selective, and sensitive sensing of interest analyte. The present review provides brief information about OPPs and their toxicities. The emerging trends of structural design of nanosize-MOF including their properties have been summarized. Finally, nanosize-MOF-based fluorescent sensors, electrochemical sensors, and colorimetric sensors have been discussed with central focus on sensitivity and selectivity to OPPs. Due to the higher surface area, rich topology, ease of structural tunability and functionalization, tunable pore size, plenty of binding sites, good adsorption potential, excellent charge conductivity, and chemical stability, etc., MOF based sensors are endowed with the ability of OPPs detection upto aM. Hence, MOF as nanoporous sensors can be preferred as an excellent alternative for highly sensitive and selective recognition of OPPs in food and water samples.
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Structural design of nanosize-MOF-based sensor for highly sensitive and selective detection of OPPs in food samples
The Complex permittivity spectra of glycol ether (GE) compounds such as ethylene glycol mono-methyl ether (EGME), ethylene glycol ethyl ether (EGEE) and ethylene glycol butyl ether (EGBE) with water ...mixture over entire concentration range and at 25 °C has been determined using Time Domain Reflectometry technique in the frequency range 10 MHz to 50 GHz. The complex permittivity spectra for GE-water were fitted in Cole-Davidson model. The Static dielectric constant (ε
0
), Relaxation time (τ), effective Kirkwood correlation factor (g
eff
), excess permittivity (
) and Bruggeman factor (f
B
) have been calculated by non-linear least square fit method. The intermolecular interactions between GE-water binary mixtures suggest the non-linear behavior of dielectric parameters. The contribution of hydrogen bonding interactions among the solute-solvent mixtures is confirmed by Excess properties and Bruggeman factor.
•This study analyzes energy rebound, intensity, and output effects.•CES production function is estimated with nonlinear estimation techniques.•The three effects are found significant in both short ...and long-run.•The size of elasticity of substitution shows substitutability among inputs.
The outcomes of energy efficiency are conditional on the size of energy rebound effect, which further promotes energy consumption instead of reducing it. Therefore, evaluating the energy rebound effect is a crucial constituent for environmental sustainability. In that perspective, the present paper examines macroeconomic rebound, intensity, and output effects of exogenous energy efficiency improvements for Pakistan using time series data from 1980 to 2018. For this, constant elasticity of substitution (CES) production function is estimated with two non-linear estimation techniques Nelder and Mead (NM) and Broyden Fletcher Goldfarb Shanno (BFGS). Moreover, three effects of energy efficiency are calculated for long run and short run with both constant returns to scale and variable returns to scale. The study finds about 65% partial energy rebound effect in both cases of NM method while BFGS method provides partial rebound effect (27%) in case of constant returns to scale and backfire (136%) in case of variable returns to scale. Moreover, the magnitudes of three effects in the long run are relatively high as compared to the short run effects. As anticipated, energy efficiency is relatively less effective; therefore, energy and environment policies should incorporate the energy rebound effect to achieve a sustainable economic growth path.
We designed a highly sensitive fluorescent sensor for the early detection of sarcosine, a potential biomarker for prostate cancer. This sensor was based on surface-cobalt-doped fluorescent carbon ...quantum dots (Co-CD) using a FRET-based photoluminescent sensing platform. Blue luminescent carbon quantum dots (CQD) were synthesised through a hydrothermal approach, utilizing
tree pod shells. Cobalt was employed to functionalize the CQD, enhancing the quantum-entrapped effects and minimizing surface flaws. To optimize Co-CD preparation, we employed a Box-Behnken design (BBD), and response surface methodology (RSM) based on single-factor experiments. The Co-CD was then used as a fluorescent probe for selective Cu
detection, with Cu
quenching Co-CD fluorescence through an energy transfer process, referred to as 'turn-off'. When sarcosine was introduced, the fluorescence intensity of Co-CD was restored, creating a 'turn-on' response. The sensor exhibited a Cu
detection limit (LOD) of 2.4 µM with a linear range of 0 μM to 10 µM. The sarcosine detection in phosphate buffer saline (PBS, pH 7.4) resulted in an LOD of 1.54 μM and a linear range of 0 to 10 µM. Importantly, the sensor demonstrated its suitability for clinical analysis by detecting sarcosine in human urine. In summary, our rapid and highly sensitive sensor offers a novel approach for the detection of sarcosine in real samples, facilitating early prostate cancer diagnosis.Communicated by Ramaswamy H. Sarma.
