Selective Nanoprobe Research Articles

Bright yellow fluorescent carbon dots as selective nanoprobe for detection of 2-nitrophenol and 4-nitrophenol in aqueous medium

Different types of phenolic pollutants pose a major risk to the environment and the health of living things. It is therefore crucial for their selective recognition especially nitrophenols. In this work, yellow fluorescent carbon dots (C-dots) were used as selective nanoprobe to efficiently detect 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP). One-pot synthetic method was adopted for making C-dots from o-phenylenediamine and oleic acid mixture. The synthesized C-dots showed an excitation wavelength of 420 nm with Stokes shift of up to 135 nm. These C-dots exhibited instantaneous selective detection of 2-NP and 4-NP in aqueous solution with a detection limit of 6.4 nM and 4.8 nM respectively. Upon incubated with 2-NP and 4-NP, the C-dots’ fluorescence underwent quenching with a maximum extent of respective 80 % and 83 %. By comparing with other analogs of analyte, it was discovered that the emission intensity of the C-dots remained unchanged. Static quenching was proposed behind the changes of fluorescence after the treatment with 2-NP and 4-NP. Such type of C-dots will demonstrate the selective sensing platform in real field application.

Inhibit-AND logic gate enabled versatile BoF-AgNPs as ultrasensitive and selective nanoprobe for Mn(II) ions and nanocatalyst for rapid MB decoloration

There is great interest in fabricating devices that can detect and remove water pollutants, especially heavy metal ions and dyes from wastewater, to promote sustainable water use. In this study, an extract of Borassus flabellifer leaves (BoF-LE) was used to synthesize silver nanoparticles (BoF-AgNPs), with the BoF-LE serving as a reducing and capping agent. The sensitivity and selectivity of BoF-AgNPs for Mn(II) ions were tested by comparing with the control sample and other competent metal ions. Our results showed that BoF-AgNPs are extremely sensitive and selective in detecting Mn(II) ions, with a detection limit of 0.3 ppb. HR-TEM, UV–Vis spectroscopy, and DLS investigations were used to confirm that BoF-AgNPs detect Mn(II) ions by an aggregation-based mechanism. Additionally, it was found that BoF-AgNPs are effective in rapidly decolorizing MB dye, as demonstrated by their ability to decolorize MB by 92.66% within 7 min. This study is the first to report successful synthesis of BoF-AgNPs and their two applications, which are enabled with an Inhibit-AND logic gate. Using BoF-AgNPs to detect and degrade water pollutants may promote sustainable water use.

Nanoscale Carbonate Ion-Selective Amperometric/Voltammetric Probes Based on Ion-Ionophore Recognition at the Organic/Water Interface: Hidden Pieces of the Puzzle in the Nanoscale Phase.

Here, we report on the successful demonstration and application of carbonate (CO32-) ion-selective amperometric/voltammetric nanoprobes based on facilitated ion transfer (IT) at the nanoscale interface between two immiscible electrolyte solutions. This electrochemical study reveals critical factors to govern CO32--selective nanoprobes using broadly available Simon-type ionophores forming a covalent bond with CO32-, i.e., slow dissolution of lipophilic ionophores in the organic phase, activation of hydrated ionophores, peculiar solubility of a hydrated ion-ionophore complex near the interface, and cleanness at the nanoscale interface. These factors are experimentally confirmed by nanopipet voltammetry, where a facilitated CO32- IT is studied with a nanopipet filled with an organic phase containing the trifluoroacetophenone derivative CO32-ionophore (CO32-ionophore VII) by voltammetrically and amperometrically sensing CO32- in water. Theoretical assessments of reproducible voltammetric data confirm that the dynamics of CO32- ionophore VII-facilitated ITs (FITs) follows the one-step electrochemical (E) mechanism controlled by both water-finger formation/dissociation and ion-ionophore complexation/dissociation during interfacial ITs. The yielded rate constant, k0 = 0.048 cm/s, is very similar to the reported values of other FIT reactions using ionophores forming non-covalent bonds with ions, implying that a weak binding between CO32- ion-ionophore enables us to observe FITs by fast nanopipet voltammetry regardless of the nature of bondings between the ion and ionophore. The analytical utility of CO32--selective amperometric nanoprobes is further demonstrated by measuring the CO32- concentration produced by metal-reducing bacteria Shewanella oneidensis MR-1 as a result of organic fuel oxidation in bacterial growth media in the presence of various interferents such as H2PO4-, Cl-, and SO42-.

3-Mercaptopropyl Trimethoxysilane @ Gadolinium Oxide Nanoprobes: An Effective Fluorescence-Sensing Platform for Cysteine

The current work aims to synthesize highly fluorescent and surface-functionalized gadolinium oxide nanoparticles (Gd2O3 NPs) with (3-mercaptopropyl) trimethoxysilane (MPTMS). The surface modification of Gd2O3 nanoparticles with MPTMS enhanced the stability and solubility of the nanoprobe in aqueous media. The size of the nanoprobe was controlled to 7 ± 1 nm using MPTMS coating. These valued points made the MPTMS@Gd2O3 nanoparticles as economical, highly sensitive, selective nanoprobe with a quick response time for the detection of cysteine via the simple fluorescence-based methodology. The proposed strategy has offered the reliable detection of cysteine in the concentration range of 1–100 µm with a detection limit of 42 nm. The selective sensing of cysteine in human serum has jointly acknowledged the potential prospect of developing sensors in body fluids with great accuracy.

LMOF serve as food preservative nanosensor for sensitive detection of nitrite in meat products

Nitrite (NO2−) is widely present in meat products as a vital food preservative, while excessive nitrite is a serious carcinogen to human beings, developing a sensitive and selective nitrite detection method is of great significance for food safety. Herein, a novel luminescent metal organic framework (LMOF) (Rh6G@MOF-5) is prepared through a facile one-pot synthesis as a fluorescent turn-off sensor for NO2− determination. Upon exposure to NO2−, significant fluorescence intensity decreases linearly along with NO2−concentration in the range of 0–200 μmol/L and the detection limit is estimated to be 0.2 μmol/L. The developed nanocomposite has been shown to be an ultrasensitive and selective nanoprobe for detecting NO2− in meat products, with recoveries ranging from 96.1% to 103.2% with the RSDs less than 4%. Rh6G@MOF-5 nanoprobe offers insight into the fabrication of MOF-based sensors with low cost and convenient operation in analyte detection field.

Functional trialkoxysilane mediated controlled synthesis of fluorescent gold nanoparticles and fluoremetric sensing of dopamine

We report herein the synthesis of fluorescent gold nanoparticles (AuNPs) involving the active role of 3-aminopropyltrimethoxysilane (3-APTMS) and 3-glycidoxypropyltrimethoxysilane (3-GPTMS) as active reducing and stabilizing agents. As made, AuNPs showed excellent fluorescent activity with QY∼13%, and the blue fluorescence of nanoparticles is confirmed by CIE Coordinates. The fluorescent AuNPs were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), zeta potential, UV–Visible spectroscopy, X-ray diffraction (XRD), fluorescence spectroscopy (FL), and Edinburgh Instrument. Interestingly, the synthesized fluorescent AuNPs with an average size of 4–10 nm was successfully used as a selective nanoprobe based on fluorescence quenching for the sensing of dopamine (DA). The mechanism of the AuNPs were associated via the electron transfer process. The limit of detection for DA is found to be 0.63 nM with a linear range of 0.05–0.6 mM (R2 = 0.998). Furthermore, the sensing of DA was also investigated in a real sample (CSF) and was found to have good accuracy and recovery, justifying sensitive, selective, and cost-effective techniques for the detection of dopamine in real samples.

Synthesis of fluorescent carbon quantum dots from Jatropha fruits and their application in fluorometric sensor for the detection of chlorpyrifos

In this study, we have synthesized fluorescent carbon quantum dots (J-CQDs) from Jatropha fruit by using a one-pot hydrothermal approach, for the first time. The as-synthesized J–CQDs exhibited bright blue fluorescence emission with a high quantum yield of 13.7 %. Furthermore, the synthesized fluorescent J-CQDs have been used as a fluorometric sensor for the detection of pesticides. The sensing of pesticides is based on the irreversible catalytic inhibition of acetylcholinesterase (AChE) enzyme with a controlled fluorescence quenching process. The thiocholine was mainly triggered by the decomposition of DTNB to form yellow-colored TNBA. Further, TNBA gradually quenched the fluorescence emission spectra of added J-CQDs via dynamic quenching. The catalytic activity of AChE was inhibited in the presence of OPs, leading to the recovery of the fluorescence signal. Thus, a sensitive and selective nanoprobe was designed for the sensing of OPs (chlorpyrifos) along with a detection limit 2.7 ng/mL. Apart from this, the proposed sensing method has been successfully applied for pesticide detection in environmental and agricultural samples with acceptable recovery. Thus, the delivered result suggests that our probe is simple in design, having a short reaction time, and could be proficiently used in further analytical and environmental applications in the future.

Nitrogen/sulfur-co-doped carbon quantum dots: a biocompatible material for the selective detection of picric acid in aqueous solution and living cells.

Here, a fast and eco-friendly one-pot hydrothermal technique is utilized for the synthesis of nitrogen/sulfur-co-doped fluorescent carbon quantum dots (NS-CQDs) from a simple precursor of citric acid (CA) and thiosemicarbazide (TSC). The obtained NS-CQDs exhibited strong blue emission under UV light, with fluorescence quantum yield (QY) of ~37.8%. The Commission internationale de l'eclairage (CIE) coordinates originated at (0.15, 0.07), which confirmed the blue fluorescence of the synthesized NS-CQDs. Interestingly, the prepared NS-CQDs were successfully used as a selective nanoprobe for the monitoring of environmentally hazardous explosive picric acid (PA) in different nitro- and non-nitro-aromatic derivatives of PA. The mechanism of the NS-CQDs was also explored, and was posited to occur via the fluorescence resonance electron transfer (FRET) process and non-fluorescent complex formation. Importantly, this system possesses excellent biocompatibility and low cytotoxicity in HeLa cervical cancer cells; hence, it can potentially be used for PA detection in analytical, environmental, and pathological applications. Furthermore, the practical applicability of the proposed sensing system to pond water demonstrated the feasibility of our system along with good recovery. Graphical abstract.

Amphiphilic fluorescent carbon nanodots as a selective nanoprobe for nitrite and tetracycline both in aqueous and organic solutions

The dispersibility of carbon dots in organic and/or aqueous solvents plays a critical role in various application fields.

Bovine serum albumin encapsulation of near infrared fluorescent nano-probe with low nonspecificity and cytotoxicity for imaging of HER2-positive breast cancer cells

Breast cancer with HER2 overexpressing type links to malignant tumor growth and poor clinical outcome. Successful development of sensitive and selective nano-probe for identification of HER2-positive breast cancer cells is of great importance for breast cancer early diagnosis, subtype classification, and treatment planning. Herein, we report a HER2 antibody conjugated near infrared (NIR) emitted MnCuInS/ZnS qumtun dots (QDs) encapsulated bovine serum albumin (BSA) nano-probe for accurately targeted imaging of HER2-positive breast cancer cells. This NIR nano-probe shows good biocompatibility, low nonspecificity and cytotoxicity, high colloidal stability, and allows HER2-positive breast cancer cell identification with good selectivity. The practicality of this targeted NIR fluorescent nano-probe was proved by successful identifying HER2-positive breast cancer cells from HER2-negative breast cancer cells, which indicates that it can be efficiently applied in selective screening of HER2 overexpressing cancer cells, and provide a platform for the strategy design on the distinction of different breast cancer subtypes.

A Metal-Organic Framework as Selectivity Regulator for Fe3+ and Ascorbic Acid Detection.

Ferric ion (Fe3+) plays a vital role in cellular homeostasis. However, the detection of Fe3+ with rhodamine B (RhB) has potential problems, such as poor selectivity and low photostability. To address these problems, we rationally designed an RhB@MOF nanocomposite-based "on-off-on" fluorescent switching nanoprobe for highly sensitive and selective detection of Fe3+ and ascorbic acid. This RhB@MOF nanoprobe was prepared through a facile one-pot synthesis. Here MOF served as a selectivity regulator for the detection of Fe3+. By embedding RhB into the porous crystalline MOF, enhanced photostability and fluorescence lifetime of RhB to Fe3+ were achieved. The as-prepared RhB@MOF was demonstrated to be an ultrasensitive and selective nanoprobe for the detection of Fe3+ in human serum and ascorbic acid in rat brain microdialysate. Furthermore, inner filter effect (IFE) and photoinduced electron transfer (PET) were proposed and discussed to explain the selectivity and sensitivity of RhB to Fe3+ against other interfering substances. Our novel "on-off-on" nanoprobe provides insight into the rational design of MOF-based biosensors for selective and sensitive detection of analytes.

γ-Aminobutyric acid-modified graphene oxide as a highly selective and low-toxic fluorescent nanoprobe for relay recognition of copper(II) and cysteine.

A sensitive and selective graphene oxide (GO)-based fluorescent nanoprobe has been developed for the relay recognition of Cu2+ and cysteine (Cys) by covalently grafting γ-aminobutyric acid (GABA) onto GO. The fluorescence of the probe (with excitation/emission maxima at 360/445nm) is selectively quenched by Cu2+ via static fluorescence quenching. Fluorescence drops linearly as the concentration of Cu2+ is increased from 50nM to 1.0µM, and the detection limit for Cu2+ is calculated as 15nM. By virtue of the strong interaction between Cys andCu2+, the GO-GABA/Cu2+ complex can further sensitively recognize Cys in a "switch-on" mode. The linear range for Cys detection is from 50nM to 1.0µM, and the detection limit is 38nM. The probe has low cytotoxicity, and it works well inside living cells, which is verified by the successful application in imaging of LLC-PK1 cells. Graphical abstract Gamma-Aminobutyric Acid (GABA) modified graphene oxide (GO) is a highly selective nanoprobe for the fluorometricrelay recognition of Cu2+ and Cys.

Intrinsically fluorescent and highly functionalized polymer nanoparticles as probes for the detection of zinc and pyrophosphate ions in rabbit serum samples

Intrinsically fluorescent polymer nanoparticles (F-PNPs) were synthetized from 2-hydroxy-5-methylisophthalaldehyde and melamine by solvothermal method. F-PNPs can emit strong yellow green fluorescence at 542 nm without the conjugation to any external fluorescent agent and surface modification. Owing to the abundant amino and hydroxyl groups on their surface, the F-PNPs possess multiple binding sites, good biocompatibility and excellent water-solubility. Addition of Zn2+ to the F-PNPs solution resulted in a blue shift (Δλ=40 nm) with obvious enhancement in the fluorescence intensity at 502 nm; while there was negligible change in the presence of other metal ions. The subsequent treatment with pyrophosphate (PPi) can cause fluorescence recovery of F-PNPs by pulling the Zn2+ out of the coordination cavity of F-PNPs-Zn2+ nanocomposites. No interference was observed from other anions and nucleotides, making the F-PNPs-Zn2+ ensembles highly sensitive and selective nanoprobes for PPi. The detection limit is 2.75 × 10−8 M/L and 7.63 × 10−8 M/L for Zn2+ and PPi, respectively. The proposed nanoprobes were then used for detecting the recovery of Zn2+ and PPi in rabbit serum samples, which were found to be 99.4–104.2% and 98.6–104.7%, respectively. The present strategy for the fabrication of nanoparticles may offer a new sight for the preparation of polymer nanostructures. The F-FNPs based probes can provide an accurate method for the detection of Zn2+ and PPi in serum samples.

Phospholipid-Tailored Titanium Carbide Nanosheets as a Novel Fluorescent Nanoprobe for Activity Assay and Imaging of Phospholipase D.

As one of the emerging inorganic graphene analogues, two-dimensional titanium carbide (Ti3C2) nanosheets have attracted extensive attention in recent years because of their remarkable structural and electronic properties. Herein, a sensitive and selective nanoprobe to fluorescently probe phospholipase D activity was developed on the basis of an ultrathin Ti3C2 nanosheets-mediated fluorescence quenching effect. Ultrathin Ti3C2 nanosheets with ∼1.3 nm in thickness were synthesized from bulk Ti3AlC2 powder by a two-step exfoliation procedure and further modified by a natural phospholipid that is doped with rhodamine B-labeled phospholipid (RhB-PL-Ti3C2). The close proximity between RhB and Ti3C2 leads to efficient fluorescence quenching (>95%) of RhB by energy transfer. Phospholipase D-catalyzed lipolysis of the phosphodiester bond in RhB-PL results in RhB moving away from the surface of Ti3C2 nanosheets and subsequent fluorescence recovery of RhB, providing a fluorescent "switch-on" assay for the phospholipase D activity. The proposed nanoprobe was successfully applied to quantitatively determine phospholipase D activity with a low limit of detection (0.10 U L-1) and to measure its inhibition. Moreover, in situ monitoring and imaging the activity of phospholipase D in living cells were achieved using this biocompatible nanoprobe. These results reveal that Ti3C2 nanosheets-based probes exhibit great potential in fluorometric assay and clinical diagnostic applications.

A Luminescent 3d-4f-4d MOF Nanoprobe as a Diagnosis Platform for Human Occupational Exposure to Vinyl Chloride Carcinogen.

A luminescent nanoprobe based on a lanthanide-transition heterometallic metal-organic framework (MOF) is first designed for specific detection of urinary thiodiglycolic acid (TDGA) which is the biomarker of carcinogenic vinyl chloride monomer (VCM) and represents the internal dose of human exposure to VCM. The nanoprobe demonstrates high selectivity to TDGA with about 27.5-fold luminescence enhancement. It also displays excellent sensitivity with a detection limit as low as 89 ng·mL-1 and fast response to TDGA within 4 min, while refraining from the interference of other coexisting species in urine. Such good sensing performance enables the nanoprobe to practically monitor TDGA levels in human urine. Moreover, a portable urine dipstick based on the sensor is developed to conveniently evaluate individuals' intoxication degree of VCM. This fast, sensitive, and selective nanoprobe has promising potential to be a useful tool for point-of-care diagnosis of disease associated with VCM exposure.

Synthesis, characterization and application of modified Pd nanoparticles as preconcentration probes for selective enrichment/analysis of proteins via hydrophobic interactions from real‐world samples using nanoparticle‐liquid‐liquid microextraction coupled to matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

AbstractWe introduce a novel preconcentrating technique by using surface modification of palladium nanoparticles (Pd‐NPs) with octadecane thiol (ODT) prepared in toluene for selective and sensitive extraction of proteins (insulin, ubiquitin, lysozyme) from a variety of real‐world samples including pancreas, mushroom, soybean and milk using nanoparticle‐liquid‐liquid microextraction (NP‐LLME) coupled to matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐MS). The limit of detection (LOD) values obtained for gramicidin D and insulin in water and urine are between 17–37 nM (17–37 fmol) (with RSDs ranging from 5.3–7.2%) which are 10–20‐fold enhancement in detection sensitivity compared with conventional MALDI‐MS. The optimal sample pH for highest extraction efficiency of insulin, ubiquitin and lysozyme from biological samples was observed at sample pH ∼ pI which could be due to the enhancement of hydrophobic interactions between proteins with the hydrophobic ligands of Pd‐ODT NPs. In addition, we also found that with the addition of 1 M NaCl, signals could be significantly enhanced by using the current approach. It is an efficient, straightforward, sensitive and selective nanoprobe which can be widely applied for separation, enrichment and preconcentration of peptides or proteins from complex biological samples in proteome research. Copyright © 2010 John Wiley & Sons, Ltd.

Semiconductor Quantum Dots in Chemical Sensors and Biosensors

Quantum dots are nanometre-scale semiconductor crystals with unique optical properties that are advantageous for the development of novel chemical sensors and biosensors. The surface chemistry of luminescent quantum dots has encouraged the development of multiple probes based on linked recognition molecules such as peptides, nucleic acids or small-molecule ligands. This review overviews the design of sensitive and selective nanoprobes, ranging from the type of target molecules to the optical transduction scheme. Representative examples of quantum dot-based optical sensors from this fast-moving field have been selected and are discussed towards the most promising directions for future research.

Selective nanoprobes for ‘signalling gases’

The use of arrays of chemical detectors has been realized in electronic nose applications.Recently attention has been focused on the application of e-Noses in the medical arena.These are electronic devices that typically employ non-selective gas sensitive elements forthe monitoring of odours and other gaseous analytes. Currently, the lack of relativespecificity to a mixture of gaseous analytes for these sensing elements makes the use ofpattern recognition algorithms to process the signal and match the acquired data profile toa known pattern necessary, thus identifying the signature of the odour or gas detected. Analternative approach to chemical detection through the use of small arrays (two or threeelements) of selective gas sensors made of nanostructured semiconducting filmsand membranes is described in this work. Sensor selectivity is defined here ashigher sensitivity to a given gas or class of gases in the presence of interferinggaseous species. Transition metal oxides are key sensing elements of resistive typechemical detectors. A given oxide may be found in several polymorph phases, eachhaving a distinct structural configuration. Gas–oxide interactions are stronglydependent on the ‘structure sensitivity’ of the polymorph used in sensing. This paperreviews the effect of polymorphism on the gas specificity and the importance ofnanoscale processing for stabilizing the desirable oxide phases, and it introduces agas-polymorph selection library for building the next generation of gas sensingsystems with inherent selectivity to be used as non-invasive disease diagnosis tools.