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A series of metal–organic frameworks (MOFs) with varying Ni : Co ratios are synthesized by an easy one-step solvothermal method using trimesic acid as an organic linker.

Selective and sensitive detection of dopamine (DA) in the presence of other interfering biomolecules is very challenging in biomedical analysis. Here, we have reported the one-pot synthesis strategy of water-soluble β-cyclodextrin-capped ZnO-doped carbon dot (ZnO-CD) via a simple hydrothermal treatment of β-cyclodextrin (β-CD) and zinc acetate. The as-synthesized ZnO-CDs have a very small size, ∼2–3 nm, and are used as an efficient sensing probe. The aqueous solution of ZnO-CDs exhibits excitation-dependent emission properties. They exhibit the maximum intensity in the blue region of the visible spectrum under excitation at ∼360 nm with the emission maximum at ∼443 nm. The blue emissive ZnO-CDs have shown a high quantum yield (∼18%), good colloidal stability, and photostability under UV light exposure. ZnO-CDs have been used for selective sensing of DA in the presence of other interfering biomolecules with a detection limit of ∼285 nM. Interestingly, DA sensing has also been performed in a mixture of interfering biomolecules. To explore their practical significance as a sensing probe, this fluorescent probe has been used to determine the DA content in spiked blood samples with remarkable accuracy, selectivity, and sensitivity. Based on our results, we propose that selective sensing of DA occurs via the host–guest interaction of DA with β-CD on the ZnO-CD surface, followed by electron transfer through the oxidized form of DA under excitation. Thus, the fluorescence of ZnO-CDs is “turned-off” selectively in the presence of DA.

Herein, a simpler isolation method has been proposed for using the loosely adsorbed surface-adhered waste from the surface of pollutant diesel soot (DS). The simple extraction protocol is based on Soxhlet-purification using acetone to extract the acetone-soluble fluorescent fraction from the bulk DS. The acetone soluble fraction contains some fraction that should be soluble in aqueous medium. So a gel-separation technique was used to separate the highly fluorescent water-soluble fraction of nano-carbons from the bulk. Transmission electron microscopy analysis reveals the carbon dot (CDs) like morphology of the as-extracted blue–green fluorescent water-soluble fraction. These CDs show strong fluorescence photostability (checked up to 4 hours) and have ∼8% quantum yield. The fluorescent water-soluble CDs are used for the selective sensing of Fe(III) and toxic-Hg(II) metal ions among most all the tested metal ions. To determine the plausible quenching mechanism, spectral overlap analysis and time-resolved photoluminescence analysis were performed. The fluorescence quenching by Fe(III) was mainly attributed to the inner filter effect (IFE) mechanism while in the case of Hg(II) ions, quenching was because of the ligand to metal charge transfer (LMCT) mechanism. The sensing of metal ions was additionally supported with the aid of cyclic voltammetry analysis.

The valorization of onion-like carbon nanoparticles (OCNPs) from pollutant soot collected from diesel engine exhaust could be a promising and sustainable approach to develop percolated conductive networks in a poly(lactic acid) (PLA) matrix, which could be used for the design of conductive polymer nanocomposite (CPC)-based quantum resistive sensors (QRS). The aim of the present study is to incorporate these waste materials in the field of structural health monitoring (SHM) of biocomposites. Here, OCNPs have been used in the formulation of QRS and further integrated into unidirectional flax fibers and PLA composites for SHM trials without altering their mechanical properties. QRS transducers made of 1 wt% OCNPs dispersed into a PLA matrix have been prepared via an in situ spray layer-by-layer (sLbL) process during the fabrication of flax–PLA composites by film stacking under vacuum conditions. Their in situ sensing of strain and damage was evaluated by submitting the flax–PLA unidirectional composite samples to various incremental and simultaneous loading–unloading cycles. Most importantly, the piezo-resistive behavior of the OCNP-based QRS has been found to be reproducible, and it exhibits large-amplitude signals with a gauge factor of 6 ± 2, which is two to three times larger than that of commercial strain sensors. Additionally, these waste-derived OCNPs possess interesting ferromagnetic properties at room temperature.

Herein, fabrication of a functionalized graphene aerogel (f-GA) from a biomass (pear fruit)-derived graphene aerogel (GA) is described. Functionalization showed a prominent effect that results in the improved adsorption capacity of f-GA compared to GA, and even better (∼more than double) than commercially available activated carbon (AC). f-GA has been studied for the removal of three different model pollutant dyes, namely crystal violet (CV), methylene blue (MB), rhodamine B (RhB) and their mixtures, along with it also being used for dye removal from unknown real industrial samples. Moreover, a detailed comparative analysis showed the adsorption capacity of f-GA towards CV, MB, and RhB has been improved up to ∼6, ∼7, and ∼10 times, respectively, compared to that of control GA. The recyclability of f-GA was also tested: it works for five cycles without losing its apparent performance.

Herein, we report a simpler functionalization of the CNR by the amine (2,2′-(ethylenedioxy)-bis(ethylamine)) (H 2NCH 2CH 2OCH 2CH 2OCH 2CH 2NH 2 (EDA)) molecules as a surface passivating agent to achieve soluble functionalized carbon nano-rods (f-CNR). The surface-functionalized fluorescent f-CNR exhibited the quantum yield value of ∼16% and were used as a fluorescent probe for the selective detection of the Cr(vi) and Fe(iii) ions in a homogeneous aqueous phase based on fluorescence quenching. In particular, the limits of the detection for both metal ions were obtained to be ∼43 nM for Fe(iii) and ∼11 nM for Cr(vi), which were quite significant in aqueous media. Moreover, the f-CNR showed non-toxicity and was biocompatible with Escherichia coli (E. coli) (ATCC 25922) cells when tested up to 9 mg mL -1.

A hydrazone obtained by the reaction of 2-hydroxynaphthaldehyde with hydrazine hydrate was allowed to react further with 4-diethylamino-2-hdroxybenzaldehyde to provide an unsymmetrical azine derivative (NDEA). The azine has been characterized using spectroscopic techniques and single crystal X-ray crystallography. It selectively detects Al3+ and Cu2+ ions in aqueous methanol (DMSO : H2O : MeOH = 0.1 : 1.9 : 8.0, v/v, HEPES buffer, pH 7.4) and exhibits naked eye visible color changes from greenish yellow to bright yellow and brown on the addition of Al3+ and Cu2+ ions, respectively, with concomitant changes in their absorption spectra. The corresponding solutions containing Al3+ and Cu2+ ions also display changes in their emission spectra via “TURN ON” and “TURN OFF” pathways with a detection limit of 1.65 × 10−7 M and 1.52 × 10−7 M, respectively. NDEA works as a reversible probe towards Al3+ ions and Cu2+ ions by the addition of F− ions and EDTA2− ions, respectively. The complexes of NDEA, separately with Al3+ and Cu2+ ions, have been optimized by DFT (density functional theory). It also exhibits viscochromic and mechanochromic properties. Most importantly, NDEA significantly detects these ions in rat C6 glioma cell lines and displays good cell permeability. It also co-localizes with the commercially available Mitotracker Red and exhibits a unique application as a live cell mitochondrial tracker. Practically, NDEA detects Al3+ and Cu2+ ions in real water samples and blood serum with a high accuracy.

Presently, the doping of carbon dots (CD) with heteroatoms and metal-salts as external dopant is a common practice for enhancing its optical efficiency. This approach can involves the use of biomaterials such as plant leaves since they already possess metals inside as an essential element. In this study, the simple process of carbonization of a leaf extract yielded red-emitting magnesium–nitrogen embedded (self-doped) CD, which were denoted as r-Mg–N-CD, possessing a quantum yield value of ∼41%. Importantly, r-Mg–N-CD was proven to be a biocompatible probe based on the bacteriological test performed on two different bacterial strains, Escherichia coli (E. coli) and Proteus vulgaris (P. vulgaris). In addition to the conventional imaging application, r-Mg–N-CD could also be used for the fluorescence-based selective sensing of Cu(II) metal ions among various heavy metals with a detection limit as low as 50 nM and as red-emitting fluorescent ink.

The effects of nano-carbon interactions on plant growth have recently been the subject of much scientific research. In the past, the use of insoluble nano-carbons on plants led to physical damage to the plant cells due to biochemical incompatibility; at present, the availability of dispersible or soluble forms of several nano-carbons avoids unnecessary physical damage, which could be a possible solution to the continuous increase in the demand for food. These interactions provide a feasible approach that is backed by the long-known results from age-old practices related to the simple addition of charred bio-waste as a carbon source, known as “biochar,” to the soil as a promoter of nutrients. The purposeful use of biochar significantly increases the rate of development of the next generation crop along with the retention of soil fertility. It is known that biochar contains a significant amount of nano-carbons along with micro carbon with oxo-functionality; these are hydrophilic and are readily passed through the plant roots. As such, the potential application of charred carbons/biochar in the growth of plant systems is a time-tested process, and the same can be expected with the nano-carbons. This perspective article provides a summary of the recent advances in the agricultural applications of nano-carbons. In particular, the cellular uptake, translocation, and accumulation of nano-carbons inside the plant, and their significant impacts on the plant physiological parameters are studied. Like plant growth, water uptake and protein expression properties, increasing crop productivity and disease prevention are correlated. The present perspective article also addresses the negative aspects that arise, based on a few reports showing the toxicity of nano-carbons; most of these are physical in nature and care is needed to determine the quality of the nano-carbons, which should be biocompatible.

Two novel square planar complexes [Ni(Hapt)2] (1) and [Ni(btsc)] (2) have been synthesized from acetone N4-phenyl-thiosemicarbazone (Hapt) and benzoyl-3-thiosemicarbazide (Hbtsc) by the reaction of nickel(II) salt. The ligand and complexes have been characterized by various physicochemical methods. Complexes 1 and 2 crystallize in the monoclinic and orthorhombic systems with space group C2/c and Pbcn, respectively. In complexes 1 and 2 the nickel centre is coordinated through the nitrogen and sulphur atoms forming a square planar geometry. Complexes 1 and 2 are stabilized via various types of intermolecular interactions. The course of the thermal degradations of complexes 1 and 2 has been investigated by TGA which indicated that a metal sulphide/oxide is formed as the final residue. Cyclic voltammetric studies show that complex 1 exhibits a reversible Ni(II)/Ni(III) redox process at 0.525 V (E1/2 value at 20 mV s−1) while complex 2 shows reversible redox behavior with an E1/2 value of 0.43 V. Furthermore, efficient electrocatalytic properties of complexes 1 and 2 toward the oxidation of hydrazine and methanol are demonstrated after immobilizing the complexes into Nafion films. The electrocatalytic properties may find applications in industry, in methanol sensing and in methanol fuel cells.

Photoluminescent water-soluble hollow carbon nanorods were synthesized by the pyrolysis of castor oil seeds (Ricinus communis) without the use of a catalyst. Oxidation of the pyrolysed soot produced a water-soluble form of graphitic hollow carbon nanorods. These showed excitation-dependent multicoloured photoluminescent emission from the green to red region of the visible spectrum and extending to the near-infrared region. This photoluminescent behaviour was used to produce a fluorescent turn-off/turn-on sensor for the specific, sensitive and rapid determination of DNA with a detection limit of ∼1.14 nM.

We report here the synthesis and structural characterization of a new discrete bis-dithiolene complex, [PPh4][Cu(DMED)2] (1; DMED = 1,2-dicarbomethoxy-1,2-dithiolate), involving the reaction between a copper polysulfide precursor with activated acetylene. 1 is stable, showing a sulfur-based radical character, as observed by electronic, EPR and cyclic voltammetric studies. This complex, possessing terminal –COOCH3 groups, forms nanospheres by hydrogen bonding in a mixture of solvents containing water as one of the components. These nanospheres further aggregate with water soluble (carboxylated) carbon nanotubes (wsCNTs). These nano-composites are assisted by hydrogen bonding between the carboxylic acid groups of the wsCNTs and the peripheral –COOCH3 groups of the coordinated dithiolenes of the nanospheres, which is promoted by water molecules. Interaction between the nanospheres on wrapping with wsCNTs, in forming the nano-composites, showed a perturbed EPR signal of the sulfur radical originating from the oxidised dithiolate ligand of the discrete complex 1.