Highly effective heterogeneous chemosensors of luminescent silica@coordination polymer core-shell micro-structures for metal ion sensing

Insights on Luminescent Micro- and Nanospheres of Infinite Coordination Polymers

Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto-organize as micro- or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light-emitting devices and bioimaging. In this review, we present the state-of-the-art of ICP-based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.

Nanoconstructs as a versatile tool for detection and diagnosis of Alzheimer biomarkers

The current review focuses towards the advancements made in the past decade in the field of nanotechnology for the early Alzheimer's disease (AD) diagnosis. This review includes the application of nanomaterials and nanosensors for the early detection of the main AD biomarkers (amyloid beta, phosphorylated tau, apolipoprotein E4 allele or APOE4, microRNAs, cholesterol, hydrogen peroxide etc) in biological fluids, to detect the biomarkers at a very low concentration ranging in pico, femto and even atto molar concentrations. The field of drug development has always aimed and is constantly working on developing disease modifying drugs, but these drugs will only succeed when given in the early disease stages. Thus, developing efficient diagnostic tools is of vital importance. Various nanomaterials such as liposomes; dendrimers; polymeric nanoparticles; coordination polymers; inorganic nanoparticles such as silica, manganese oxide, zinc oxide, iron oxide, super paramagnetic iron oxides; quantum dots, silver nanoparticles, gold nanoparticles, and carbon based nanostructures (carbon nanotubes, graphene oxide, nanofibres, nanodiamonds, carbon dots); Up-conversion nanoparticles; 2D nanomaterials; and radioactive nanoprobes have been used in constructing and improving efficiency of nano-sensors for AD biosensing at an early stage of diagnosis.

Luminescent sensing of nitroaromatics by crystalline porous materials

Designing strategies for the syntheses of targeted luminescent MOFs, nanoparticle/MOF composites and COFs described and their application in sensing nitroaromatic compounds and explosives discussed.

Nanonetwork of Coordination Polymer AHMT-Ag for the Effective and Broad Spectrum Detection of 6-Mercaptopurine in Urine and Blood Serum

Nanocrystalline coordination polymers (NCCPs) have been considered as an incredible electrochemical sensor for the effective detection of biologically dynamic drug 6-mercaptopurine (6-MP). In the present report, a significantly stable infinite arrayed coordination polymeric network was self-assembled via metal with efficient organic tecton 4-amino-3-hydrazino-5-mercapto-1,2,4,-triazole (AHMT) in which silver(I) ions are coordinated by AHMT via hydrazino and exocyclic thiol linkage to form AHMT-Ag NCCP. An efficient and highly sensitive detection of 6-MP is attained owing to eminent electron channeling via polymeric nanocrystallite pores. An effective charge transfer leads to an interface of the AHMT-Ag nano-pores and electrolyte anchored electrode via π-π electron coupling and hydrophobic interaction. The voltammogram exposes acute redox behavior of 6-MP and discloses an impeccable illustration for the AHMT-Ag facilitated oxidation of 6-MP. This unique signature was applied in voltammetric detection of 6-MP in blood serum, human urine, and pharmaceutical formulation (tablet) by a considerable high sensitivity of 0.074, 0.058, and 0.036 μA/μM and a detection limit of 87, 97, and 37 nM, respectively. Thus, the prepared AHMT-Ag NCCP can provide a valuable platform for fabrication of highly sensitive electrochemical devices to assay biologically essential drug molecules.

Competitive formation between 2D and 3D metal-organic frameworks: insights into the selective formation and lamination of a 2D MOF

The structural dimension of metal-organic frameworks (MOFs) is of great importance in defining their properties and thus applications. In particular, 2D layered MOFs are of considerable interest because of their useful applications, which are facilitated by unique structural features of 2D materials, such as a large number of open active sites and high surface areas. Herein, this work demonstrates a methodology for the selective synthesis of a 2D layered MOF in the presence of the competitive formation of a 3D MOF. The ratio of the reactants, metal ions and organic building blocks used during the reaction is found to be critical for the selective formation of a 2D MOF, and is associated with its chemical composition. In addition, the well defined and uniform micro-sized 2D MOF particles are successfully synthesized in the presence of an ultrasonic dispersion. Moreover, the laminated 2D MOF layers are directly synthesized via a modified bottom-up lamination method, a combination of chemical and physical stimuli, in the presence of surfactant and ultrasonication.

Classification, Synthesis, and Application of Luminescent Silica Nanoparticles: a Review

Luminescent materials are of worldwide interest because of their unique optical properties. Silica, which is transparent to light, is an ideal matrix for luminescent materials. Luminescent silica nanoparticles (LSNs) have broad applications because of their enhanced chemical and thermal stability. Silica spheres of various sizes could be synthesized by different methods to satisfy specific requirements. Diverse luminescent dyes have potential for different applications. Subject to many factors such as quenchers, their performance was not quite satisfying. This review thus discusses the development of LSNs including their classification, synthesis, and application. It is the highlight that how silica improves the properties of luminescent dye and what role silica plays in the system. Further, their applications in biology, display, and sensors are also described.

Synthesis of Bimetallic Conductive 2D Metal-Organic Framework (Cox Niy -CAT) and Its Mass Production: Enhanced Electrochemical Oxygen Reduction Activity

The development of new electrocatalysts for electrochemical oxygen reduction to replace expensive and rare platinum-based catalysts is an important issue in energy storage and conversion research. In this context, conductive and porous metal-organic frameworks (MOFs) are considered promising materials for the oxygen reduction reaction (ORR) due to not only their high surface area and well-developed pores but also versatile structural features and chemical compositions. Herein, the preparation of bimetallic conductive 2D MOFs (Co_x Ni_y -CATs) are reported for use as catalysts in the ORR. The ratio of the two metal ions (Co²⁺ and Ni²⁺ ) in the bimetallic Co_x Ni_y -CATs is rationally controlled to determine the optimal composition of Co_x Ni_y -CAT for efficient performance in the ORR. Indeed, bimetallic MOFs display enhanced ORR activity compared to their monometallic counterparts (Co-CAT or Ni-CAT). During the ORR, bimetallic Co_x Ni_y -CATs retain an advantageous characteristic of Co-CAT in relation to its high diffusion-limiting current density, as well as a key advantage of Ni-CAT in relation to its high onset potential. Moreover, the ORR-active bimetallic Co_x Ni_y -CAT with excellent ORR activity is prepared at a large scale via a convenient method using a ball-mill reactor.

Improvement in Crystallinity and Porosity of Poorly Crystalline Metal-Organic Frameworks (MOFs) through Their Induced Growth on a Well-Crystalline MOF Template

Porous metal-organic frameworks (MOFs) are interesting materials owing to their interesting structural features and their many useful properties and applications. In particular, the structural features are greatly important to optimize the MOFs' porosities and so properties. Indeed, the MOFs' well-developed micropore and high surface area are the most important structural features, and as such, many practical applications of MOFs originate from these structural features. We herein demonstrate a strategy for improving the crystallinity of MOFs, and so increasing the porosity and surface area of poorly crystalline MOFs by making them in core-shell-type hybrids through the induced growth on the well-crystalline template. Although poorly crystalline versions of MOFs generate naturally in the absence of the well-crystalline template, well-crystalline versions of MOFs produce inductively in the presence of the well-crystalline template. In addition, the crystallinity enhancement of MOFs brings together the improvement in their porosities and surface areas. The surface areas and pore volumes of the well-crystalline versions of MOFs produced through the induced growth on the template are calculated based on this study, indicating that MOF surface areas increase by up to 7 times compared to the poorly crystalline versions.

Construction of flexible metal-organic framework (MOF) papers through MOF growth on filter paper and their selective dye capture

The conjugation of metal-organic frameworks (MOFs) with other materials is an excellent strategy for the production of advanced materials having desired properties and so appropriate applicability. In particular, the integration of MOFs with a flexible paper is expected to form valuable materials in separation technology. Here we report a simple method for the generation of MOF papers through the compact and uniform growth of MOF nanoparticles on the cellulose surface of a carboxymethylated filter paper. The resulting MOF papers show a selective capture ability for negatively charged organic dyes and they can be used for dye separation through simple filtration of a dye solution on the MOF papers. In addition, MOF papers can be reused after a simple washing process without losing their effective dye capture ability.

Fabrication and characterization of dual-functional ultrafine composite fibers with phase-change energy storage and luminescence properties

Ultrafine composite fibers consisting of a thermoplastic polyurethane solid-solid phase-change material and organic lanthanide luminescent materials were prepared through a parallel electrospinning technique as an innovative type of ultrafine, dual-functional fibers containing phase-change and luminescent properties. The morphology and structure, thermal energy storage, and luminescent properties of parallel electrospun ultrafine fibers were investigated. Scanning electron microscopy (SEM) images showed that the parallel electrospun ultrafine fibers possessed the desired morphologies with smaller average fiber diameters than those of traditional mixed electrospun ultrafine fibers. Transmission electron microscopy (TEM) images revealed that the parallel electrospun ultrafine fibers were composed of two parts. Polymeric phase-change materials, which can be directly produced and spun, were used to provide temperature stability, while a mixture of polymethyl methacrylate and an organic lanthanide complex acted as the luminescent unit. Differential scanning calorimetry (DSC) and luminescence measurements indicated that the unique structure of the parallel electrospun ultrafine fibers provides the products with good thermal energy storage and luminescence properties. The fluorescence intensity and the phase-change enthalpy values of the ultrafine fibers prepared by parallel electrospinning were respectively 1.6 and 2.1 times those of ultrafine fibers prepared by mixed electrospinning.

Synthesis of hybrid metal-organic frameworks of {FexMyM'1-x-y}-MIL-88B and the use of anions to control their structural features

The controlled formation of metal-organic frameworks (MOFs) or coordination polymers (CPs) with suitable components and structural features is one of the most important themes in MOF research. In particular, the reliable preparation of hybrid MOFs containing more than two different kinds of metal ions or organic linkers and a comprehensive understanding of the structural flexibility of MOFs are the central issues for the production of MOFs with the desired properties. We report the synthesis of micro-sized hybrid MOF particles [also known as coordination polymer particles (CPPs)] containing two or three kinds of metal ions in each particle: {Fe_xM_yM'_1-x-y}-MIL-88B (MIL stands for Materials of Institut Lavoisier, M and M' = Ga, Co, or Mn). Scanning electron microscopy images revealed the formation of well-defined uniform micro-sized hexagonal rods, and energy-dispersive X-ray spectroscopy and elemental mapping images verified the simultaneous incorporation of two or three kinds of metal ions within the CPPs. Interestingly, the structural features of CPPs made from MIL-88B were controlled by altering the anions involved in the structure. Incorporating large acetylacetonate anions within the structure resulted in the closed MIL-88B structure with a small cell volume. However, the open MIL-88B structure with a large cell volume was obtained when small chloride anions were incorporated. The intermediate semi-open MIL-88B structure was also prepared using nitrate anions. Three different structural forms of MIL-88B were verified by powder X-ray diffraction, whole pattern fitting, and thermogravimetric analysis.

Facile Synthesis of Au or Ag Nanoparticles-Embedded Hollow Carbon Microspheres from Metal-Organic Framework Hybrids and Their Efficient Catalytic Activities

Au or Ag nanoparticles-embedded hollow carbon spheres, which display outstanding catalytic activity and excellent recyclability, are prepared by a one-step pyrolysis of metal-organic framework (MOF) hybrids consisting of polystyrene cores and MOF shells loaded with noble metal ions (polystyrene@ZIF-8/M(n+) ; M(n+) = Au(3+) or Ag(+) ).

Novel core-shell structure microspheres based on lanthanide complexes for white-light emission and fluorescence sensing

A series of new core-shell structure materials based on lanthanide complexes [H2NMe2]3[Ln(dpa)3] (Ln = Eu, Tb, Sm, Dy, Nd, and Yb; [H2NMe2](+) = dimethylamino cation; dpa = 2-dipicolinate) and silica microspheres has been prepared under solvothermal conditions. Electron microscopy reveals that the nanosized materials SiO2@Ln-dpa are spherical with a narrow size distribution and a [H2NMe2]3[Ln(L)3] coating was generated on the surface of silica microspheres successfully. The core-shell structure materials exhibit excellent optical performance. The white-light-emitting material SiO2@(Dy:Eu)-dpa has a potential application in the development of a white-light device, as a result of the fact that its CIE chromaticity coordinate is very close to that of pure white. Then, we selected SiO2@Eu-dpa as a representative sample for sensing experiments. Eventually, we found that the core-shell structure sensors are highly selective and sensitive for acetone and Cu(2+) cations. The detection of Cu(2+) in the human body is an important issue. Interestingly, the core-shell structure materials display better selectivity and higher sensitivity than the pure lanthanide complexes in sensing Cu(2+) and the value of the quenching effect coefficient has increased by more than 20%.

A turn on fluorescent sensor based on lanthanide coordination polymer nanoparticles for the detection of mercury(ii) in biological fluids

Im-quenched fluorescence of Eu/IPA CPNPs can be recovered upon the addition of Hg²⁺ through the formation of a Hg/Im complex.