Tetracarboxylic Acid Research Articles

Green synthesis of polyimide by using an ethanol solvothermal method for aqueous zinc batteries.

Polyimides (PIs) are welcomed by battery researchers because of their exceptional heat resistance, structural design versatility, and ion-bearing capabilities. However, most of the reported PIs are synthesized by using toxic and hazardous reagents, such as ethylenediamine, p-phenylenediamine, 1-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), etc., which are not conducive to environmentally friendly development. In this paper, we aim at employing green solvents and raw materials to prepare PIs using a facile solvothermal method. The reactants are urea and 1,4,5,8-naphthalene tetracarboxylic acid dianhydride (NTCDA). The solvents include pure water, pure ethanol, or water-ethanol mixed solvent. The volume ratio of ethanol in the mixed solvent is regulated to obtain the optimum synthesis condition. Depending on the proportion of ethanol, the polyimide products are labeled as U-PI-0, U-PI-50, U-PI-100, etc. The polymerization degree and structure of synthesized PIs are characterized by gel permeation chromatography (GPC), X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The results indicate that U-PIs exhibit diverse morphological features, including small fragmented, strip-like, and sheet-like structures, and have relative molecular weights ranging from 7500 to 83 000. Notably, the sheet-like U-PI-100 possesses the largest specific surface area, reaching up to 4.20 m2 g-1. When employed as an electrode material in aqueous zinc batteries, U-PI-100 demonstrates superior electrochemical performance compared to others. At a charge-discharge rate of 0.05C, the initial charge/discharge capacity of U-PI-100 is measured to be 314.2/443.7 mA h g-1.

Introducing a Pyrazinoquinoxaline Derivative into a Metal-Organic Framework: Achieving Fluorescence-Enhanced Detection for Cs+ and Enhancing Photocatalytic Activity.

Conventional photoresponsive materials have low photon utilization due to irregular distribution of photoactive groups, which severely limits the related real applications. Metal-organic frameworks (MOFs) can modulate the regular arrangement of functional groups to improve the electron transport paths and enhance the photon utilization, which provides strong support for the development of photoactive materials with excellent performance. In this work, one effective strategy for constructing a photoactive MOF had been developed via the utilization of Cd2+ and pyrazinoquinoxaline tetracarboxylic acid. The structural advantages of the Cd-MOF, such as a porous structure, abundant subject-object interaction sites, and a stable framework, ensure the prerequisite for various applications, while the better synergistic effect of Cd3 clusters and the pyrazinoquinoxaline derivative ensures efficient electron transfer efficiency. Therefore, by virtue of these structural advantages, the Cd-MOF can achieve fluorescence quenching detection for a variety of substrates, such as Fe3+, Cr2O72-, MnO4-, nitrofuran antibiotics, and TNP explosives, while fluorescence enhancement detection can be achieved for halogen ions, Cs+, Pb2+, and NO2-. In addition, the Cd-MOF can be used as a photocatalyst to successfully achieve the photocatalytic conversion of benzylamine to N-benzylbenzimidate under mild conditions. Thus, the Cd-MOF as a whole shows the possibility of application as a diverse fluorescence detection and photocatalyst and also illustrates the feasibility of preparing high-performance photoactive materials using the pyrazinoquinoxaline derivative.

Development of a novel PPTA/cellulose composite insulation paper with low dielectric constant and improved mechanical properties by BTCA crosslinking

AbstractThis study investigates the effect of 1,2,3,4‐butane tetracarboxylic acid (BTCA) crosslinking treatment on the electrical properties of poly‐p‐phenylene terephthalate (PPTA)/cellulose insulation paper to prepare a novel composite insulation paper with low dielectric constant and good electrical performance. Three‐layer PPTA/cellulose composite paper crosslinked by BTCA under various conditions, composite paper without crosslinking, directly mixed composite paper, and conventional Kraft paper are prepared. The morphology and surface chemical composition of the paper samples are characterized. Dielectric, mechanical, and thermal properties are investigated. Results show that the BTCA concentration of 0.2 mol L−1 with a 180°C curing temperature is the relatively superior crosslinking condition to prepare a novel composite with low dielectric constant and good comprehensive performance. The dielectric constant and loss of the novel composite paper decrease to 3.21 and 0.392 at 50 Hz. The tensile strength of the BTCA crosslinked three‐layer PPTA/cellulose composite paper (thickness: 130 μm) has reached 10.01 kN m−1, increased by 41.6% than the directly mixed composite paper. The novel BTCA crosslinked composite paper also shows improved thermal stability. The BTCA crosslinking proves to be a promising method to improve the dielectric properties and electrical performance of the PPTA/cellulose composite paper.

Metal-Organic Framework Based on Pyrazinoquinoxaline Tetracarboxylic Acid for Fluorescence Sensing for Nitro Explosives.

The rapid and selective detection of nitro explosives has become one of the current urgent environmental and safety issues. Fluorescent metal-organic frameworks (MOFs) provide strong support for the development of photoactive materials with excellent sensing performances. In this work, Zn2+ and pyrazinoquinoxaline tetracarboxylic acid with high nitrogen content were selected to construct a MOF structure termed Zn-MOF, which had excellent optical properties. The fluorescence sensing performance of Zn-MOF for nitro explosives was also investigated. The structural advantages of Zn-MOF, such as its porous structure, abundant host-guest interaction sites, and stable framework, ensure the prerequisites for various applications. Zn-MOF is not only capable of responding to a wide range of substrates, such as Fe3+, Cr2O72-, and MnO4-, to achieve fluorescence quenching detection but also able to achieve sensitive fluorescence sensing behavior for nitro explosives. In particular, for trinitrotoluene, the Ksv value can reach 8.72 × 103 M-1. The results show that the introduction of pyrazinoquinoxaline groups into MOFs can be an effective strategy for the preparation of highly efficient fluorescent sensing materials for nitro explosives.

Preparation and properties of electrochromic polyimide hybrid materials containing graphene oxide

The aminosylated graphene oxide was synthesized using the compound E3, three anhydrides (3,3′,4,4′ -diphenyl ether tetracarboxylic acid dianhydride, 3,3′,4,4′ -biphenyl tetracarboxylic acid di anhydride and 1,2,4, 5-phenyl tetracarboxylic acid di anhydride) is a series of electrochromic polyimide hybrid materials containing carbazole groups prepared by polypolymerization with aminated graphene oxide (F2). These PIs not only have good solubility and thermal properties,but also the introduction of 0.5 wt% GO increased the contact area between the film and electrolyte ions, which was beneficial to transport and diffusion of ions, thus improving the response speed of the electrochromic materials. Moreover, its excellent tensile properties make it an ideal material for manufacturing flexible devices. In addition, the polyimide hybrid materials exhibit excellent electrochemical and electrochromic properties as well as electrofluorescent properties. Therefore, the new material will be suitable for hole transmission, electrochromic, chemical sensing and other fields.

Multi-responsive fluorescent sensitivities of a novel 2D Cu-CP with visual turn-off sensing toward nitrofuran antibiotics, Cr(VI) and MnO4− in aqueous solutions

Herein, a novel fluorescent coordination polymer [Cu2(edda)(bpy)2]·6H2O (Cu-CP; H4edda = 5,5′-(ethane-1,2-diylbis(oxy)) diisophthalic acid; bpy = 2,2′-bipyridine) was designed and successfully architected using semi-rigid tetracarboxylic acid ligand H4edda combined with N,N′-donor linker bpy through a hydrothermal method. Single-crystal structural analysis reveals that the adjacent Cu1 centers are linked by 3′- and 5- carboxyl groups of edda4− linker to form a one-dimensional Cu(II)-edda4− chain, which is further strutted by 3- and 5′- carboxyl groups in edda4− ligand to generate a two-dimensional (2D) network with sql topology. Notably, bpy molecules do not actually dedicate to the formation of this 2D network, which merely saturate the configuration of Cu ions. Apart from the great thermal and acid/base stabilities, the π-conjugated nature of H4edda endows Cu-CP with the traits of strong fluorescent emission in both solid state and aqueous solution. Interestingly, Cu-CP can act as a multifunctional platform for effectively detecting nitrofurazone (NFZ), nitrofurantoin (NFT), Cr2O72−, CrO42− and MnO4− via fluorescence quenching effects in an aqueous system. The fabricated Cu-CP fluorescent sensor shows distinguished sensitivity and anti-interference performance as well as low detection limits (3.55 nM for NFZ; 1.02 nM for NFT; 0.58 μM for Cr2O72−, 0.68 μM for CrO42− and 4.59 μM for MnO4−). The underlying quenching mechanisms have been studied through in-depth experimental and computational researches.

Study on water-absorbing behaviors of superabsorbent polymer enhanced by 1,2,3,4-butane tetracarboxylic acid cross-linker

superabsorbent polymers (SAPs) are famous for their excellent water absorption capability. In this work, poly (acrylic acid)-based superabsorbent polymer was developed via free radical polymerization by innovatively using 1,2,3,4-butane tetracarboxylic acid (BTA) as one unique physical cross-linker. Water-soluble BTA molecules contain four carboxyl groups that can interact with poly(acrylic acid) (PAA) polymeric chains through hydrogen bonds. Such force made the products swell but not dissolve in water, determining that BTA took a great role of cross-links. The effects of initiator, catalyzer, neutralizer and cross-linking agent on water-absorbing capacities of as-obtained PAA/BTA-SAP products were explored. The results revealed that swelling ratios of such PAA/BTA-SAP in distilled water was 4480 g/g, in 0.9 wt% NaCl solution was 55 g/g and in 5 wt% urea solution was 1890 g/g. Swelling kinetics indicated that polymer chains of the product in distilled water underwent relaxation and stretching in the swelling stage. The excellent water uptake was attributed to the formation of a well-structured three-dimensional network for SAPs via multiple hydrogen bonds between PAA polymer and BTA molecule. Therefore, the present work provides a new horizon to explore BTA as one unique cross-linker to prepare SAPs with the enhanced water uptake.

Polyamide-imides as novel high performance primary protective coatings of silica optical fibers: Influence of the structure and molecular weight

Polyimides are commonly used as primary protective optical fiber coatings for high-temperature applications. However, a number of significant drawbacks such as thermal and hydrolytic instability of polyamiс acid, its incomplete transformation into polyimide, several deposition cycles of the required thickness and insufficient adhesion of polyimide coatings to the surface complicate the manufacture of special optical fibers and their widespread use. In this study we showed the principal possibility of utilizing polyamide-imides (PAIs) as primary protective coatings of high operational reliability. Two series of high-molecular-weight (Mw = 84–365 kDa) and thermostable (T10% = 490–520 °C) PAIs were synthesized by low temperature polycondensation of terephthaloyl chloride and various tetracarboxylic acid dianhydrides with 9,9-bis(4-aminophenyl)fluorene or 2,2′-bis(trifluoromethyl)benzidine in NMP. Coatings of a thickness of 10–15 μm with good adhesion to the optical fiber were formed from the PAIs solutions in NMP with no any additives and in a single application cycle. Apart from the influence of solution viscosity and drawing parameters on the coating quality, a particular attention was paid to the dependency of the strength and mechanical reliability of the fibers with resulting coatings on the structure and molecular weight of the polymer. It was established that the fibers coated with PAIs prepared from 2,2′-bis(trifluoromethyl)benzidine (Mw = 190–200 kDa) can withstand 3 and 72 h annealing at 350 and 300°С, respectively, retaining >80% of the original strength. Thus, PAIs are considered as a promising candidate for further studies, i.e., for the creation of optical fiber sensors for large-scale applications.

Cellulose Fabrics Functionalized with Sol-Gel Photocatalytic Coatings Based on Iron (III) Phthalocyanine Tetracarboxylic Acids-TiO2-Silica Hybrids.

Photocatalytic coatings are difficult to obtain on textile materials because of the sometimes contradictory properties that must be achieved. In order to obtain a high efficiency of a photocatalytic effect, the metal-oxide semiconductor must be found in the vicinity of the coating-air interface in order to come into direct contact with the contaminant species and allow light radiation access to its surface. Another necessary condition is related to the properties of the covering textile material as well as to the stability of the xerogel films to light and wet treatments. In this sense, we proposed a solution based on hybrid silica films generated by sol-gel processes, coatings that contain as a photocatalyst TiO2 sensitized with tetracarboxylic acid of iron (III) phthalocyanine (FeTCPc). The coatings were made by the pad-dry-cure process, using in the composition a bifunctional anchoring agent (3-glycidoxipropyltrimethoxysilane, GLYMO), a crosslinking agent (sodium tetraborate, BORAX), and a catalyst (N-methylimidazole, MIM) for the polymerization of epoxy groups. The photodegradation experiments performed on methylene blue (MB), utilized as a model contaminant, using LED or xenon arc as light sources, showed that the treatment with BORAX improves the resistance of the coatings to wet treatments but worsens their photocatalytic performances.

Synthesis of Polyamide-Imides by the Interaction of Terephthaloyl Chloride and 3,3',4,4'-Diphenyl Ether Tetracarboxylic Acid Dianhydride with Various Diamines

The effect of temperature, the order and duration of the interaction of terephthaloyl chloride (0.5 mol) and 3,3',4,4'-diphenyl ether tetracarboxylic acid dianhydride (0.5 mol) with 9,9-bis(4-aminophenyl)fluorene or 2,2'-bis(trifluoromethyl)benzidine (1.0 mol) in NMP on the properties of the resulting polyamide-imides was studied. The molecular weights and yields of the resulting polymers were shown to vary in a wide range (Mw = 64–438 kDa, yields 85–97%) and depend on the reaction conditions. The polyamide-imides obtained possess high heat resistance (Tg = 260–360 °C), thermal stability (T10% ~ 500 °C) and form high-strength films (σ = 122–160 MPa, E = 1.3–1.9 GPa, ε = 9–30%).

Coordination Polymers from an Amino-Functionalized Terphenyl-Tetracarboxylate Linker: Structural Multiplicity and Catalytic Properties.

An amino-functionalized terphenyl-tetracarboxylic acid, 2'-amino-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4tpta), was used as an adaptable linker to synthesize, under hydrothermal conditions, eight coordination polymers (CPs). The obtained products were formulated as [Co(μ6-H2tpta)]n (1), [Co(μ3-H2tpta)(2,2'-bipy)]n (2), [M3(μ6-Htpta)2(2,2'-bipy)2]n (M = Mn (3), Cd (4)), [Ni2(μ4-tpta)(phen)2(H2O)4]n (5), [Zn2(μ6-tpta)(phen)2]n (6), {[Zn2(μ6-tpta)(μ-4,4'-bipy)]·H2O}n (7), and [Zn2(μ6-tpta)(μ-H2biim)(H2O)2]n (8), wherein 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), 1,10-phenanthroline (phen), or 2,2'-biimidazole (H2biim) are present as additional stabilizing ligands. The structural types of 1-8 vary from one-dimensional (1D) (2, 5) and two-dimensional (2D) (3, 4, 6) CPs to three-dimensional (3D) metal-organic frameworks (MOFs) (1, 7, and 8) with a diversity of topologies. The products 1-8 were investigated as catalysts in the Knoevenagel condensation involving aldehydes and active methylene derivatives (malononitrile, ethyl cyanoacetate, or tert-butyl cyanoacetate), leading to high condensation product yields (up to 99%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were investigated. This work broadens the application of H4tpta as a versatile tetracarboxylate linker for the generation of diverse CPs/MOFs.

An anionic In(III)-MOF for efficient adsorption of CO2 from CO2/N2 mixture and dye removal

Efficient adsorption of CO2 and dye molecules is crucial for reducing carbon emission and environmental pollution. Metal-Organic Frameworks (MOFs) are considered to be the ideal candidates for gas adsorption material because of their designability. In this work, a new In(III)-MOF (HBU-22) was synthesized by the reaction of a tetracarboxylic acid ligand (H4L, 9,9′-bicarbazole-3,3′,6,6′-tetracarboxylic acid) with In3+ ions, which shows a three-dimensional (3D) coordination network. The saturated adsorption capacity of CO2 and N2 are 21.11 cm3‧g−1 and 0.66 cm3‧g−1 at ambient condition (298 K, 100 kPa). And the higher IAST selectivity of CO2/N2 (v/v, 15:85) reaches 347.37, exceeding that of most MOFs. Furthermore, it can also capture C2H2 with the maximum uptake of 42.80 cm3 g−1. More interestingly, HBU-22 as an anionic framework, which can selectively adsorb Rhodamine B (RhB) within 250 s with the maximum adsorption capacity of 105.04 mg‧g−1. Further studies show that higher gas adsorption capacity is mainly related to the larger Qst of the gas, while its adsorption of Rhodamine B (RhB) is mainly due to ion exchange mechanism.

Lanthanides-based invisible multicolor luminescent hydrogels and films for anti-counterfeiting

Developing high-level luminescent anti-counterfeiting materials with simple preparation and portability is still challenging. Herein, the luminescent anti-counterfeiting hydrogels were acquired via the coordination of 1,2,4,5-benzene tetracarboxylic acid (H4BTC) to Tb(NO3)3 and/or Eu(NO3)3 in water. Multicolor luminescence from green to yellow, orange, and red can be easily obtained by controlling the molar ratio of Tb(NO3)3 to Eu(NO3)3. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the coordination between H4BTC and lanthanides. Emission spectra and optical images confirmed that luminescent hydrogels could be functionalized as luminescent inks for painting and writing with the help of a writing brush. Importantly, the information fabricated by hydrogels cannot be seen under daylight and can only be seen under UV light. Noteworthy, multicolor luminescence can be designed to encode information in multiple ways, resulting in increasing the complexity of information decryption. It can prevent the tampering and forging of information effectively. Moreover, the inks have good stability and adhesion. And the H4BTC-Ln hydrogels can be dried to powders for storage and recovered to hydrogels by adding water. Meanwhile, the multicolor luminescent films were easily prepared by dispersing the corresponding powders of H4BTC-Ln into polyacrylamide (PAAm) matrix. The acquired films have high transmittance as well as good luminescent properties and excellent mechanical properties. They were applied as luminescent anti-counterfeiting labels. This work provides a simple and convenient method for preparing high-level lanthanides-based luminescent anti-counterfeiting materials.

Syntheses, Crystal Structures, and Catalytic Properties of Three Cu(II) and Cobalt(II) Coordination Compounds Based on an Ether-Bridged Tetracarboxylic Acid.

Three new products, [Cu2(μ3-dppa)(2,2'-bipy)2(H2O)]n·2nH2O (1), [Co4(μ4-dppa)2(phen)4(H2O)4]·2H2O (2), and [Co2(μ6-dppa)(μ-4,4'-bipy)(H2O)2]n·3nH2O (3) were synthesized using a hydrothermal method from Cu(II) and Co(II) metal(II) chlorides, 3-(3,4-dicarboxyphenoxy)phthalic acid (H4dppa), and different auxiliary ligands, namely 2,2'-bipyridine (2,2'-bipy),1,10-phenanthroline (phen), and 4,4'-bipyridine (4,4'-bipy). Products 1-3 were characterized by elemental analysis, FTIR, TGA, PXRD, SEM, and single-crystal X-ray crystallography. The structure of 1 features a 1D chain of the 2C1 topological type. Compound 2 shows a discrete tetrameric complex. Product 3 demonstrates a 3D metal-organic framework (MOF) with the new topology. Their structure and topology, thermal stability, and catalytic activity were studied. In particular, excellent catalytic activity was demonstrated for copper(II)-polymer 1 in the cyanosilylation reaction at 35 °C.

Zn-metal organic framework containing electron rich linkers and film preparation for applications in antibiotic detection

A Zn-metal organic framework has been synthesized, [Zn4(ad)3(BPTC)(H2O)4]·0.75ad ·0.25NO3·2.5DMF·2.5H2O (ZnAB MOF) (ad = adenine, BPTC = biphenyl-3,3′,5,5′-tetracarboxylic acid) and characterized by X-ray single crystallography. The crystal structure reveals a 3D framework with two differently sized channels with the structure confirmed by IR, TGA and elemental analysis. This MOF has also been prepared in the form of a MOF film on a Zn metal sheet in situ with one continuous layer 60 μm thick. The materials fluoresce at 352, 433 and 355, 423 nm (λex = 310 nm), for MOF powder and MOF film, respectively. The fluorescence is quenched by nitrofuran antibiotics allowing the MOF to be used in their detection. Specifically, the nitrofuran antibiotics nitrofurazone (NFZ) and nitrofurantoin (NFT) exhibit significant quenching. ZnAB MOF powder shows higher sensitivity than the ZnAB MOF film with higher fluorescence quenching, Stern-Volmer constant (KSV) and limit of detection (LOD). However, the ZnAB MOF film exhibits superior repeatability for nitrofuran detection. Fluorescence quenching of NFZ and NFT may occur via fluorescence resonance energy transfer (FRET) and/or photoinduced electron transfer (PET).

Leveraging the relative strengths of hydrogen and halogen bonds to control nanostructures

Halogen bonds (XBs) and hydrogen bonds (HBs) present a straightforward yet effective strategy for controlling nanostructure morphology. The self-assembled nanopattern, modulated by the relative strengths of XBs and HBs, has rarely been studied using analogous molecules. This research systematically evaluates the relationship between the strengths of Br···O hetero-XBs and N···H HBs in directing the formation of 2D supramolecular co-assembled structures. In this work, tetracarboxylic acid (PEDA), featuring four carboxyl substitutions, forms a stable hydrogen-bonded Rosette network that can function as a template for trapping guest molecules of complementary shape and size. The star-shaped bromine-substituted 1,3,5-tris(3,5-dibromophenyl)benzene (TDB) and 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT) serve as XB donor and HB acceptor respectively, thus capable of acting as guest molecules co-assembly with the PEDA at the heptanoic acid/HOPG interface. Bimolecular co-assembly patterns resulting from these combinations were investigated using scanning tunneling microscopy (STM) and supported by density functional theory (DFT) calculations. The findings indicate that TDB molecules can be accommodated within the triangular cavities of the Rosette network due to the weaker Br···O hetero-XB. Concurrently, the similar star-shaped TPT can co-assemble with PEDA to form an acid–pyridine–acid Ladder-like network based on stronger N···H HBs. Therefore, Br···O hetero-XBs seemingly play no decisive role in the coassembly process of PEDA and TDB. Conversely, N···H HBs hold evident significance in the coassembly of PEDA and TPT. This work potentially holds substantial value for the future design and customization of devices employing the interplay of XBs and HBs.

Design and synthesis of п-conjugated aromatic heterocyclic materials with dual active sites and ultra-high rate performance for aqueous zinc-organic batteries

Acid anhydride cathode materials garner considerable interest for aqueous zinc ion batteries (AZIBs) due to ideal specific capacity and structural diversity, however, serious solubility leads to capacity degradation. Herein, 1,4,5,8-naphthalene tetracarboxylic acid dianhydride − 2,3-diamino phenothiazine (NTDP) featuring multiple active sites (6 with CN and 2 with CO) and large π-conjugated backbone, was designed and synthesized utilizing solid-phase method. The smallest energy gap (ΔE) and the lowest LUMO levels (against monomers) induced by multiple active sites and п-conjugated backbone with high aromaticity, NTDP exhibited excellent specific capacity (307.5 mA h g−1 under 0.05 A/g), ultrahigh rate performance (194.9 mA h g−1 under 20 A/g) and impressive cycling stability (190.0 mA h g−1 over 9000 cycles with a capacity retention of 91.2 % at 15 A/g). The reversible Zn2+ insertion/removal mechanism on multiple active centers (CO and CN) was proposed through XPS, FT-IR, and Raman. The specific capacity of the NTDP//zinc flexible cell was 112.6 mA h g−1 at 3 A/g under various folding angles (45°, 90°, 135°, and 180° bends), suggesting its practical potential for flexible devices. This work will offer opportunities for the rational design of battery structures.

Two new Cd(II)-based coordination polymers: Dual sensor for sulfamethazine antibiotic and ferric ion

The precise combination of basic functionality and luminescence property can deliver multifunctional coordination polymers (CPs) with multifarious applications such as sensitive and selective detection of antibiotics and metal ions sensing. Herein, two new Cd(II)-based CPs having formula [Cd2(L)(bpy)2(H2O)2·4H2O] (1) and [Cd2(L)(phen)(H2O)] (2) have been synthesized and characterized using mixed ligand strategy by solvothermal reaction of Cd(II) salts using 1,1′-biphenyl-2,3,3′,5′-tetracarboxylic acid (H4L) as the main ligand and 2,2′-bipyridyl (bpy) as co-ligand for CP 1 and 1,10-phenanthroline (phen) as co-ligand for CP 2. The CP 1 possesses (4,4)-connected sql topology, while CP 2 displays 2D bilayer network composed of ring-like Cd2(OCO)6 subunits. The sensing studies indicated that both 1 and 2 can behave as luminescent sensor for sensitive and selective detection of sulfamethazine antibiotic with remarkable quenching and low limit of detection. Additionally, both CPs also displayed selective sensing for Fe3+ ions. The possible alleviation in the luminescence intensities of 1 and 2 in presence of antibiotic have been addressed using theoretical calculations which indicated that charge transfer as well as the weak interaction between antibiotic and CP may be responsible for the decline in the emission intensity.

Perylene tetracarboxylic acid (PTA)-based type II heterojunction sensing platform for signal-on photoelectrochemical detection of CEA

The construction of robust photoelectrochemical (PEC) transducing platforms mediates the feasibility and performance of the PEC biosensors. In this work, perylene tetracarboxylic acid (PTA) nanoassemblies were exploited as robust semiconductors to form type II heterojunctions with In2O3. The prepared organic/inorganic heterojunctions show high PEC transducing performances. The carboxyl groups of PTA avoid the additional surface functionalization for covalent immobilization of capturing elements which will diminish the transducing performance. This enables the facile construction of PEC immunosensing platforms. More importantly, Ag@CeO2 nanoparticles were used as energy level matching nanolabels to develop a signal-on PEC immunosensing method. A linear response from 0.1 pg/mL to 100 ng/mL with a detection limit of 63.1 fg/mL was achieved for a typical protein biomarker carcinoembryonic antigen (CEA).

Ratiometric luminescent thermometer based on a mixed Ce/Tb metal-organic framework

A mixed lanthanide metal-organic frameworks Ce1-xTbxFTPTC (x=0.042, 0.022) were synthesized by the simple solvothermal method and its temperature sensing was studied emphatically. The 2′-fluoro-[1,1′:4′,1′′-terphenyl]-3,3′′,5,5′′-tetracarboxylic acid (H4FTPTC) can efficiently sensitize Ce3+ and Tb3+ ions effectively, and it transfers the energy to Ce3+ and Tb3+ ions through resonance coupling. Accordingly, so Ce1-xTbxFTPTC (x=0.042, 0.022) can exhibit strong characteristic fluorescence of Ce3+ and Tb3+ ions. The Ce1-xTbxFTPTC (x=0.042, 0.022), as a proportional type luminescent thermometer shows excellent performance in the temperature range (313K-473K).