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A new gadolinium(III)-based coordination polymer (CP), [Gd(3,5-pydc)1.5(CO2)0.5(H2O)4]·3H2O (1, where 3,5-pydc = 3,5-pyridinedicarboxylate), has been successfully synthesized using a slow diffusion method at room temperature. Single-crystal X-ray diffraction study of 1 confirmed its one-dimensional ladder-like structure. The Gd3+ ions are in a distorted tricapped trigonal prismatic geometry. Two types of 3,5-pydc ligands are present in the structures: in one case, the pyridine nitrogen remains vacant, whereas in the other case, the pyridine nitrogen is coordinated with CO2 to form zwitterionic carbamate. The phase purity of 1 has been confirmed by powder X-ray diffraction, thermogravimetric analysis and IR spectroscopic studies. The aqueous dispersion of compound 1 exhibits weak luminescence emission at 385 nm upon excitation at 270 nm. To explore the ligand-sensitized metal-centred luminescence, we have prepared a composite by mixing the CP with Tb3+ ions (Tb@1). The formation of the composite has been confirmed by IR spectroscopic studies in the solid state. The composite showed excellent ligand-sensitized metal-centred luminescence. We have utilized this luminescence property for the sensing of anions in aqueous media. The composite shows luminescence quenching behaviour in the presence of Cr2O72−, CrO42−, and NO2−, with high sensitivity, and their limits of detection are 147 ppb, 142 ppb and 20 ppb, respectively. Selectivity experiments show that the detection of these three anions is highly selective in the presence of other common anions. Detailed experimental studies suggest that the preferable interaction of the three anions with the Tb3+ ions inside the composite and the reduction of the excitation energy are probably responsible for the quenching behaviour. [ABSTRACT FROM AUTHOR]

A new cadmium based MOF [Cd(C5N1S1H4)(C6O5H3)] (C5N1S1H4 = 4MPy, C6O5H3 = HFDA), Cd_1, was synthesized by a solvothermal reaction using 2,5-furandicarboxylic acid (H2FDA) and 4-mercaptopyridine (4MPyH) formed in situ by the S–S bond rupture of the aldrithiol-4 ligand. Single crystal X-ray data of Cd_1 confirmed a two-dimensional structure arranged in an ABAB... fashion in three dimensions where the nitrogen atom of the pyridine ring of 4MPy remains free. The aqueous dispersion of Cd_1 showed room temperature phosphorescence at 520 nm upon excitation at 330 nm. Luminescence lifetime studies revealed that the emission at 520 nm originates from a triplet state which became populated through intersystem crossing (ISC) from the singlet excited state. A trace amount of Hg2+ ions interacted very strongly with Cd_1 and significantly altered its UV-vis absorption and luminescence spectra. After interacting with the Hg2+ ions, the emission of Cd_1 at 520 nm gradually disappeared with a concomitant increase of the low intensity fluorescence at 383 nm. The ISC is hampered by the coordination of Hg2+ ions with two S atoms of the 4MPy moiety of two adjacent 1D chains (inter-layer) and a huge reduction of the structure's flexibility. On the other hand, the interactions between metal ions and Cd_1via the free N atom of the pyridine moiety resulted in the increase of the fluorescence intensity at 383 nm, however the phosphorescence intensity did not change significantly. These studies indicate that the interactions between Hg2+ ions and S atoms are highly selective due to the soft–soft interaction whereas the interactions between the N atoms and all the metal ions are not selective. A ratiometric luminescence approach has been employed to establish Cd_1 as a detector of Hg2+ in aqueous medium selectively over other common metal ions. The estimated quenching constant and detection limit of Cd_1 for Hg2+ were found to be 1.15 × 106 M−1 and 37.5 nM (equivalent to 7.40 ppb) in water. [ABSTRACT FROM AUTHOR]

A new zinc-based two-dimensional coordination polymer, [Zn(5-AIP)(Ald-4)]·H2O (5-AIP = 5-amino isophthalate, Ald-4 = aldrithiol-4), 1, has been synthesized at room temperature by the layer diffusion technique. Single-crystal X-ray diffraction analysis of 1 showed a two-dimensional bilayer structure. An aqueous suspension of 1 upon excitation at 300 nm displayed an intense blue emission at 403 nm. The luminescence spectra were interestingly responsive and selective to Al3+, Cr3+ and Fe3+ ions even in the presence of other interfering ions. The calculated detection limits for Al3+, Cr3+ and Fe3+ were 0.35 μM (≡8.43 ppb), 0.46 μM (≡22.6 ppb) and 0.30 μM (≡15.85 ppb), respectively. Notably, with the cumulative addition of Al3+ ions, the luminescence intensity at 403 nm decreased steadily with a gradual red shift up to 427 nm. Afterward, this red shifted peak showed a turn-on effect upon further addition of Al3+ ions. On the other hand, for Cr3+ and Fe3+ ions, there was only drastic luminescence quenching and a large red shift up to 434 nm. This indicated the formation of a complex between 1 and these metal ions, which was also supported by the UV-Visible absorption spectra of 1 that showed the appearance of a new band at 280 nm in the presence of these three metal ions. The FTIR spectra revealed that these ions interacted with the carboxylate oxygen atom of 5-AIP and the nitrogen atom of the Ald-4 ligand in the structure. The luminescence lifetime decay analysis manifested that a charge-transfer type complex was formed between 1 and Cr3+ and Fe3+ ions that resulted in huge luminescence quenching due to the efficient charge transfer involving the vacant d-orbitals, whereas for Al3+ ions having no vacant d-orbital, turn-on of luminescence occurred because of the increased rigidity of 1 upon complexation. [ABSTRACT FROM AUTHOR]

A terbium doped yttrium based metal–organic framework [Y1.8Tb0.2(CAM)3(H2O)4]·2H2O, 1, {where H2CAM = chelidamic acid}, was successfully synthesized using a hydrothermal technique to be used as a phosphor material along with a large Stokes shift and low self-quenching of luminescence. To confirm the structure and phase purity of compound 1, single-crystals of the isomorphous pure yttrium-based compound [Y2(CAM)3(H2O)4]·2H2O, 1a, were synthesized under similar experimental conditions. The single-crystal X-ray data of compound 1a confirmed a two-dimensional metal–organic framework formed by the connectivity of the Y3+ ion with the carboxylates of chelidamate ligands, while the hydroxyl groups of the chelidamate ligands remain free. The phase purity of compounds 1 and 1a was confirmed by powder X-ray diffraction. Compound 1 was systematically characterized by TGA, IR, SEM, EDX-elemental mapping and BET analysis. The aqueous solution of compound 1 shows a weak visible green emission upon excitation at 280 nm. The emission of compound 1 was utilized to detect the pH response, keeping in mind the favourable presence of free hydroxyl groups. It was observed that the emission intensity increased 4.2 times when the pH was increased from pH 7 to pH 9 along with a sudden jump at pH > 7.5. The luminescence lifetime decay studies also showed a gradual increase in the lifetime of Tb3+ centered emission from 0.75 ms (pH 7) to 0.99 ms (pH 9). The luminescence response of compound 1 in the biologically important pH range of 7–9 based on the free hydroxyl groups may be very much useful for real-life applications. [ABSTRACT FROM AUTHOR]

To study the photophysics and understand the mechanism of metal ion sensing, a luminescent cobalt-based metal–organic compound, [Co(bpds)(bdc)(H2O)2]·bpds (1), was synthesized at room temperature from 4,4′-bipyridyl disulphide (bpds) and 1,4-benzene dicarboxylic acid (bdc) by layer diffusion. Structure determination based on single-crystal X-ray analysis revealed a parallel interpenetrated structure of two-dimensional layers along with a layer of uncoordinated bpds ligand. An aqueous suspension of 1 showed intense blue emission at 421 nm. In the presence of few micromolar of Al3+ ions, a dramatic change in the luminescence spectrum around an isoemissive point was observed with the appearance of a new peak at 380 nm. A similar phenomenon was observed in the presence of Fe3+ ions. For other metal ions, no significant changes in the luminescence spectrum of 1 were observed. Detailed lifetime decay analysis and Fourier-transform infrared spectroscopy revealed that Al3+ ions form charge-transfer complexes (or adducts) with uncoordinated bpds ligands through pyridine nitrogen atoms, resulting in a new emission peak at 380 nm. Time-resolved study revealed that the quenching of luminescence was dynamic in nature and associated with an increase in the non-radiative rate constant. Moreover, the luminescence property of 1 was ultrasensitive to the presence of Al3+ and Fe3+ ions in water, even in a mixture of many other ions, with detection limits of 0.35 and 0.25 μM, respectively. [ABSTRACT FROM AUTHOR]

A terbium-doped yttrium-based metal–organic framework, [Tb0.2Y0.8(FDA)(Ox)0.5(H2O)2]·H2O, 1 {where H2FDA = furan-2,5-dicarboxylic acid and Ox = oxalate}, was successfully synthesized using the hydrothermal technique as a phosphor material along with a large Stokes shift and low self-quenching of luminescence for the rapid visible detection of toxic anions in an aqueous medium. To confirm the structure and phase purity of compound 1, single crystals of the isomorphous pure yttrium-based compound [Y(FDA)(Ox)0.5(H2O)2]·H2O, 1a, were synthesized under similar experimental conditions. The single crystal X-ray data of compound 1a confirmed the three-dimensional metal–organic framework formed by the connectivity of the Y3+ ion with furan-2,5-dicarboxylate and the oxalate moiety. The phase purity of compounds 1 and 1a was confirmed by powder X-ray diffraction. Compound 1 was systematically characterized via TGA, SEM and EDX elemental mapping analysis. The aqueous dispersion of compound 1 showed highly intense visible green emission upon excitation at 265 nm. The emissions of compound 1 were utilized for the luminescence-based visible detection of toxic anions in the aqueous medium through luminescence quenching. The observed limit of detection (LOD) was 1.1 nM, 2.2 nM and 6.5 nM for chromate (CrO42−), permanganate (MnO4−) and phosphates (PO43−, H2PO4− and HPO42−), respectively, and the observed KSV values were superior to those of all other metal–organic frameworks previously reported. More importantly, the LODs are significantly lower than the level recommended for these anions towards human life. [ABSTRACT FROM AUTHOR]

The development of a new generation of multifunctional nanomaterials as a drug delivery system for chemo-photothermal therapy is of great necessity. In this study, we first prepared folic acid-conjugated and doxorubicin-loaded chitosan oligosaccharide encapsulated gold nanorods (FA–COS–TGA–GNRs–DOX) as a new photothermal agent for the delivery of drugs and heat to tumor areas. FA–COS–TGA–GNRs–DOX nanomaterials combine the advantages of COS, GNRs, FA, TGA, and DOX and have excellent biocompatibility, strong absorbance in the near-infrared (NIR) region, photostability, photothermal conversion efficiency, high targeting efficiency, fast drug release under laser irradiation, and tumor cell killing efficiency. FA–COS–TGA–GNRs–DOX exhibited significantly greater cell killing after laser irradiation. The intracellular uptake behavior of the targeted FA–COS–TGA–GNRs–DOX was confirmed by flow cytometry, two-photon fluorescence microscopy (TPFM), and confocal laser scanning microscopy (CLSM). More interestingly, the tumors in the presence of FA–COS–TGA–GNRs–DOX under laser irradiation were efficiently ablated and did not recur, showing an outstanding combined therapy of tumors. The combination of photothermal therapy (PTT) and photoacoustic imaging (PAI) could accurately locate and fully destroy tumor tissues after the intravenous injection of FA–COS–TGA–GNRs–DOX. Hence, this work offers a new avenue to develop a novel class of multifunctional nanomaterials as a drug delivery system for cancer therapy. [ABSTRACT FROM AUTHOR]

The fabrication of nanotherapeutic systems capable of stimuli-responsive drug delivery and photoacoustic imaging (PAI)-guided photothermal therapy (PTT) is considered significant for chemo-photothermal therapy applications in cancer therapy. In the present study, the Prussian blue nanoflake (PBNF) decorated mesoporous silica hybrid nanoparticle (PB@MSH-EDA NPs) is reported for PAI-guided chemo-photothermal therapy applications. The amine group enriched mesoporous silica channels can be used to encapsulate an anticancer drug for chemotherapy, and the surface decorated PBNFs can convert a near-infrared (NIR) laser (808 nm) into heat for photothermal therapy and can also be used for PAI applications. The PB@MSH-EDA NPs show pH-responsive drug release efficiency under acidic pH (pH 5.0 and 4.0) conditions. Furthermore, the PB@MSH-EDA NPs system shows strong NIR laser absorption and photothermal conversion efficiency under 808 nm laser irradiation. The in vitro experimental result shows that the PB@MSH-EDA NPs are biocompatible and could be efficiently taken up by MDA-MB-231 cells. In addition, the in vivo results demonstrate that the tumor-bearing mice fully recovered after injecting the drug (Dox)-loaded PB@MSH-EDA/Dox NPs and being further irradiated with the 808 nm laser. We believe that the PB@MSH-EDA NPs system could be utilized as an efficient PAI-guided chemo-photothermal therapy agent for the detection and treatment of tumors in an emerging cancer therapy application. [ABSTRACT FROM AUTHOR]

Core–shell based, bioactive marine biopolymer-coated drug carriers for high drug loading and efficient drug release response to a specific trigger have received much research interest in cancer therapy. In this study, we present a fucoidan-coated core–shell magnetic mesoporous silica drug carrier (FeNP@SiOH@Fuc NPs) system which consists of a magnetic iron oxide (FeNP) core, a mesoporous silica shell (SiOH), and a marine biopolymer, namely fucoidan (Fuc), coated onto the outer surface as a “gatekeeper” for pH-responsive drug delivery and magnetic hyperthermia applications. Fucoidan coating onto the outer surface of the silica nanoparticles was performed through metal–ligand complex coordination approaches. The drug loaded FeNP@SiOH@Fuc/Dox NPs show good drug retention efficiency under physiological pH conditions and show a pH-responsive drug release behavior under an acidic pH environment and hyperthermia temperature (45 °C) conditions in the presence of an alternating magnetic field (AMF). Furthermore, the MTT assay and the intracellular uptake study results indicate that the synthesized FeNP@SiOH@Fuc NPs have biocompatibility and could be efficiently internalized by MDA-MB-231 cells. In addition, owing to the presence of a magnetic iron oxide core, the FeNP@SiOH@Fuc NPs show an excellent magnetic hyperthermia heating efficiency in the presence of an AMF and reach the hyperthermia temperature (45 °C) within a very short time (approximately ∼4–5 min). Since the FeNP@SiOH@Fuc NP system exhibits pH-stimuli responsive drug release performance, good biocompatibility, and efficient magnetic hyperthermia heating efficiency, the proposed system is expected to be a promising candidate as a drug carrier as well as a hyperthermia agent for chemotherapy and magnetic hyperthermia-based thermal therapy applications in emerging cancer therapy. [ABSTRACT FROM AUTHOR]

Rare-earth-based metal–organic frameworks (ReMOFs) have emerged as an interesting family of compounds, for which new properties are increasingly being found. Based on the potential of ReMOFs, resulting from their optical properties, large numbers of investigations have been carried out during the last decade. Among these investigations, ReMOFs as optical sensors, using their luminescence properties, are increasingly becoming an attractive and useful topic of research. In this study, we have provided the basics of the luminescence behaviour of ReMOFs, various possible sensing mechanisms, and a summary of the uses of ReMOFs for the sensing of nitro explosives, cations, anions, small molecules, pH, and temperature. [ABSTRACT FROM AUTHOR]

A Co(ii) complex of molecular formula C48H96.8N12O22.4Co2Cl2, 1, was synthesized from the Schiff base [H2pydmdp]Cl by a template reaction of pyridoxal (pyd), a vitamer of vitamin B6, N-methyl-1,3-diaminopropane (mdp) and cobalt(ii) acetate. It was characterized by elemental analysis, 1H NMR, IR and UV-Vis spectroscopy, thermal analysis, electrochemistry and single crystal X-ray diffraction. The experimental results suggested that in complex 1, the central Co(ii) is bonded to two phenolato-oxygens, two imine nitrogens and two amine nitrogens in an octahedral geometry. In aqueous media complex 1 exhibits an intense fluorescence emission peak at 506 nm when it was excited at 425 nm. The fluorescence behavior of complex 1 in aqueous media was employed to determine whether it acts as a chemosensor for some selective toxic metal ions. The studies showed that the present complex behaves as a promising sensor for Hg2+ even at the sub-micromolar level. In addition in aqueous solution, complex 1 acts as a sensor for the pH of the medium. A detailed study on the mechanism of sensing behavior established that Hg2+ interacts with complex 1 via weak non-covalent interaction with the N-atom of the pyridine moiety of the molecule. The pyridine nitrogen also plays a vital role in sensing the pH of the medium. [ABSTRACT FROM AUTHOR]

We study the effective polarity of an air/liquid-mixture interface by using interface-selective heterodyne-detected electronic sum frequency generation (HD-ESFG) and vibrational sum frequency generation (HD-VSFG) spectroscopies. With water and N,N-dimethylformamide (DMF) chosen as two components of the liquid mixture, the bulk polarity of the mixture is controlled nearly arbitrarily by the mixing ratio. The effective polarity of the air/mixture interface is evaluated by HD-ESFG with a surface-active solvatochromic molecule used as a polarity indicator. Surprisingly, the interfacial effective polarity of the air/mixture interface increases significantly, when the bulk polarity of the mixture decreases (i.e. when the fraction of DMF increases). Judging from the hydrogen-bond structure at the air/mixture interface clarified by HD-VSFG, this anomalous change of the interfacial effective polarity is attributed to the interface-specific solvation structure around the indicator molecule at the air/mixture interface. [ABSTRACT FROM AUTHOR]

Two isomorphous submicron sized metal–organic network compounds, [Y2(PDA)3(H2O)1]·2H2O (PDA = 1,4-phenylenediacetate), 1 and [Y1.8Tb0.2(PDA)3(H2O)1]·2H2O, Tb@1 have been synthesized by employing solvent assisted liquid grinding followed by heating at 180 °C for 10 min and washing with water. Single crystal X-ray data of bulk 1 confirmed a three dimensional porous structure. The structure and morphology of 1 and Tb@1 were systematically characterized by PXRD, TGA, DSC, IR, SEM and EDX analysis. Dehydrated Tb@1 [Tb@1′] shows a high intense visible green emission upon exposure to UV light. The green emission of Tb@1′ was used for the detection of nitro explosives, such as 2,4,6-trinitrophenol (TNP), 1,3-dinitro benzene (DNB), 2,4-dinitro toluene (DNT), nitro benzene (NB), and 4-nitro toluene (NT) in acetonitrile. The results show that the emission intensity of dehydrated Tb@1′ can be quenched by all the nitro analytes used in the present work. Remarkably, Tb@1′ exhibited a high efficiency for TNP, DNB and DNT detection with KSV [KSV = quenching constant based on linear Stern–Volmer plot] values of 70 920, 44 000 and 35 430 M−1, respectively, which are the highest values amongst known metal–organic materials. Using this material submicromolar level (≡ 0.18 ppm), a detection of nitro explosives has been achieved. [ABSTRACT FROM AUTHOR]

Correction for ‘Prussian blue decorated mesoporous silica hybrid nanocarriers for photoacoustic imaging-guided synergistic chemo-photothermal combination therapy’ by Madhappan Santha Moorthy et al., J. Mater. Chem. B, 2018, DOI: URL10.1039/c8tb01214h/URL. [ABSTRACT FROM AUTHOR]

A new zinc-based two-dimensional coordination polymer, [Zn(5-AIP)(Ald-4)]·H2O (5-AIP = 5-amino isophthalate, Ald-4 = aldrithiol-4), 1, has been synthesized at room temperature by the layer diffusion technique. Single-crystal X-ray diffraction analysis of 1 showed a two-dimensional bilayer structure. An aqueous suspension of 1 upon excitation at 300 nm displayed an intense blue emission at 403 nm. The luminescence spectra were interestingly responsive and selective to Al3+, Cr3+ and Fe3+ ions even in the presence of other interfering ions. The calculated detection limits for Al3+, Cr3+ and Fe3+ were 0.35 μM ([triple bond, length as m-dash]8.43 ppb), 0.46 μM ([triple bond, length as m-dash]22.6 ppb) and 0.30 μM ([triple bond, length as m-dash]15.85 ppb), respectively. Notably, with the cumulative addition of Al3+ ions, the luminescence intensity at 403 nm decreased steadily with a gradual red shift up to 427 nm. Afterward, this red shifted peak showed a turn-on effect upon further addition of Al3+ ions. On the other hand, for Cr3+ and Fe3+ ions, there was only drastic luminescence quenching and a large red shift up to 434 nm. This indicated the formation of a complex between 1 and these metal ions, which was also supported by the UV-Visible absorption spectra of 1 that showed the appearance of a new band at 280 nm in the presence of these three metal ions. The FTIR spectra revealed that these ions interacted with the carboxylate oxygen atom of 5-AIP and the nitrogen atom of the Ald-4 ligand in the structure. The luminescence lifetime decay analysis manifested that a charge-transfer type complex was formed between 1 and Cr3+ and Fe3+ ions that resulted in huge luminescence quenching due to the efficient charge transfer involving the vacant d-orbitals, whereas for Al3+ ions having no vacant d-orbital, turn-on of luminescence occurred because of the increased rigidity of 1 upon complexation.

A terbium-doped yttrium-based metal-organic framework, [Tb0.2Y0.8(FDA)(Ox)0.5(H2O)2]·H2O, 1 {where H2FDA = furan-2,5-dicarboxylic acid and Ox = oxalate}, was successfully synthesized using the hydrothermal technique as a phosphor material along with a large Stokes shift and low self-quenching of luminescence for the rapid visible detection of toxic anions in an aqueous medium. To confirm the structure and phase purity of compound 1, single crystals of the isomorphous pure yttrium-based compound [Y(FDA)(Ox)0.5(H2O)2]·H2O, 1a, were synthesized under similar experimental conditions. The single crystal X-ray data of compound 1a confirmed the three-dimensional metal-organic framework formed by the connectivity of the Y3+ ion with furan-2,5-dicarboxylate and the oxalate moiety. The phase purity of compounds 1 and 1a was confirmed by powder X-ray diffraction. Compound 1 was systematically characterized via TGA, SEM and EDX elemental mapping analysis. The aqueous dispersion of compound 1 showed highly intense visible green emission upon excitation at 265 nm. The emissions of compound 1 were utilized for the luminescence-based visible detection of toxic anions in the aqueous medium through luminescence quenching. The observed limit of detection (LOD) was 1.1 nM, 2.2 nM and 6.5 nM for chromate (CrO42-), permanganate (MnO4-) and phosphates (PO43-, H2PO4- and HPO42-), respectively, and the observed KSV values were superior to those of all other metal-organic frameworks previously reported. More importantly, the LODs are significantly lower than the level recommended for these anions towards human life.