Search

Paper-based microfluidic devices are popular for their ability to automate multistep assays for chemical or biological sensing at a low cost, but the design of paper microfluidic networks has largely relied on experimental trial and error. A few mathematical models of flow through paper microfluidic devices have been developed and have succeeded in explaining experimental flow behavior. However, the reverse engineering problem of designing complex paper networks guided by appropriate mathematical models is largely unsolved. In this article, we demonstrate that a two-dimensional paper network (2DPN) designed to sequentially deliver three fluids to a test zone on the device can be computationally designed and experimentally implemented without experimental trial and error. This was accomplished by three new developments in modeling flow through paper networks: (i) coupling of the Richards equation of flow through porous media to the species transport equation, (ii) modeling flow through assemblies of multiple paper materials (test membrane and wicking pad), and (iii) incorporating limited-volume fluid sources. We demonstrate the application of this model in the optimal design of a paper-based signal-enhanced immunoassay for a malaria protein, PfHRP2. This work lays the foundation for the development of a computational design toolbox to aid in the design of paper microfluidic networks. ©

In this report, we documented novel strategy for the synthesis of bioactive polysubstituted 2-amino-4H-chromine derivatives under a heterogeneous Al-MCM-41-LDH@APTES (ALAM) catalysis. A synthetic procedure is developed to prepare Al-MCM-41-LDH@APTES (ALAM) heterogeneous basic catalysts. Mesoporous Al-MCM-41 is functionalized by known grafting chemistry via layered double hydroxide (LDH) nanosheets and (3-aminopropyl)triethoxysilane (APTES) moiety as a basic organocatalyst. The resulting catalysts contain amino group functionality on the external surface as well as inside the layers and the basicity can be tuned by the loading of APTES. The samples were fully characterized by 29Si and 13C CP/MAS NMR, infrared absorption spectroscopy, TEM, XPS, EDX, TGA, XRD, CO2-TPD, N2 adsorption isotherms measurements, and they were successfully examined for the cascade type Knoevenagel–Michael addition reactions. The product yields associated with these substrates were optimized, and key reaction parameters affecting the yields were identified. The present catalytic method is simple and robust for diversity oriented synthesis which proceeds good to excellent yields without generating any hazards waste. The broad substrate scope, excellent functional group compatibility makes this protocol highly useful towards synthesis of polysubstituted α-cyanoacrylates, α-cyanoacrylonitriles and 2-amino-4H-chromenes with an electron-donating or electron-withdrawing group. We have also successfully established a flow reaction system, gram-scale synthesis as well as catalyst recyclability up to six catalytic cycles without appreciable loss of its activity.

A series of ternary Cu(0)/Cu(II)@g-C3N4/MCM-41 composites have been fabricated by varying the different weight percentage of Cu (2, 4, 6 and 8) with the help of wetness impregnation and thermal condensation methods. The different characterization techniques were adopted to evaluate the morphological studies of as prepared composites provides a better support to distribute g-C3N4 on its surface. Again copper was impregnated onto the surface of g-C3N4/MCM-41 surface as co-catalyst. With increase in copper content, it reduces from Cu(II) to Cu(0) without using a reducing agent. The presence of g-C3N4 helps to shift the Fermi level of CuO towards more negative values due to accumulation of photogenerated electrons on the surface of Cu nanoparticle. Due to the surface plasmon resonance effect of Cu(0), more polarized light was absorbed by the composite and also favours charge separation by creating a Schottky barrier at the junction. The 4 wt% Cu loaded over g-C3N4/MCM-41 exhibits highest percentage of phenol oxidation (97%) under visible light irradiation with different byproduct like benzoquinone (BQ), hydroquinone (HQ) and catechol (CT) with selectivity of 92%, 3% and 2% respectively. The enhancement in catalytic activity has been explained on the basis of synergism between g-C3N4 and Cu(II) and the SPR effect of Cu(0) which also acts as a co-catalyst present on the surface.

The abolition of environmental pollutants and production of hydrogen (H2) from water using a heterogeneous photocatalyst is a demanding science of the current scenario to solve the increasing environmental pollution and worldwide energy catastrophe in modern life. To validate this purpose, the design of low-cost and durable semiconductor-based photocatalysts with great light absorption capacity becomes the most challenging issue for researchers. Regarding this, herein the phosphotungstic acid (HPW)-anchored Zr6O4(OH)4(BDC)6 (UiO-66) metal-organic framework (MOF), i.e., HPW@UiO-66, has been prepared by a hydrothermal method and is efficient, stable, and capable of harvesting solar energy toward the degradation of tetracycline hydrochloride (TCH) and H2 production in the presence of a sacrificial donor. The ionic interaction between HPW and UiO-66 plays a key role toward the photostability and charge-transfer mechanism of the composite and is well characterized with X-ray diffraction, UV diffuse-reflectance spectroscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. A total of 30 wt % HPW@UiO-66 shows a maximum degradation of about 87.24% of a 20 ppm TCH solution in 60 min of solar-light irradiation and about 353.89 μmol/h of H2 production. The conduction- and valence-band potentials are well characterized with Mott-Schottky measurement and a delay charge recombination process through electrochemical impedance spectroscopy. The proposed mediator-free Z-scheme-oriented electron-hole migration route is well supported by photoluminescence, and the scavenger test well explains the better charge-carrier separation and high catalytic performance of the prepared composite. This research will bestow an advantageous blueprint to fabricate novel and challenging photocatalysts toward the photocatalytic treatment of environmental pollutants and H2 evolution.

Achieving photocatalytic organic transformation reactions by using a visible light induced semiconductor-based photocatalyst is promising as a green and sustainable approach. In the present study, Au/Pd bimetallic alloy loaded amine (APTES) functionalised LDH (Layered double hydroxide)–MCM-41 composite was prepared through an in situ co-precipitation followed by a co-reduction method. The structural phases, textural properties, optical behaviour, morphological aspects, chemical states and functional groups of the photocatalysts were thoroughly analysed by powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible diffuse reflectance (UV-vis DRS), fourier-transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies. Moreover, the formation of an alloying structure between Au and Pd was confirmed from PXRD, HRTEM and UV-vis absorption spectra. We investigated one-pot synthesis of imines through photoalkylation of benzyl alcohol with nitrobenzene over Au/Pd bimetal alloy loaded on amine functionalised LDH–MCM-41 composite and it demonstrated imine yield of around 3.1 times (68%) more than the parent LDH (22%). The alloy nanoparticless efficiently harvest light and possess higher photocatalytic activity with respect to single Pd and Au nanoparticles. Due to the alloying structure develops charge heterogeneity on the surface of alloyed nanoparticles and enhances the interaction between metal surface with substrate molecule which promotes the coupling between photo generated benzaldehyde with aniline to form imine. Characterisation such as photoluminescence (PL), time-resolved photoluminescence (TRPL), electrical impedance spectroscopy (EIS) and photocurrent density measurements further proved the superior photoactivity towards imine synthesis. These photocatalytic tandem reactions, therefore, have great potential as an effective pathway for the one-pot organic synthesis and transformation of organics in an environmentally friendly way.

In a typical heterogeneous microfluidic immunosensor, the carrier fluid transports the target analytes to the antibodies immobilized on the channel surfaces with a thin liquid layer where they are captured. While single-phase systems (the carrier fluid being a liquid) are well studied, two-phase systems (the carrier fluid being a gas) are less explored. There in particular, the effect of transport parameters on the capture efficiency (a critical performance parameter) has not received much attention, and thus is the subject of study here. Hence, we have investigated the transport and capture of analytes in a two-phase heterogeneous microfluidic immunosensor wherein the target analytes in the gaseous phase are transported to the immobilized antibodies via gas–liquid interfacial mass transfer which strongly depends on flow variables of the gas phase flow. Parametric studies on capture efficiency using the properties of trinitrotoluene (TNT) were used to obtain the effects of important transport parameters on the capture of analyte molecules. The highlight of this work is the development of an empirical correlation between the capture efficiency and the gas-side non-dimensional interfacial mass transfer coefficient (Sherwood number, Shg). This could help design of a two-phase microfluidic device with improved performance parameters to capture gaseous analytes.

Visible light harvesting by heterogeneous photocatalysts and their applications in organic transformation reactions for the synthesis of target molecules are quite demanding science in the current scenario. In this regard, herein, a novel metal (Au/Pd)-functionalized metal organic framework (UiO-66-NH2) was synthesized to carry out the Suzuki–Miyaura coupling (SMC) reaction under visible light irradiation at ambient conditions. In order to justify the claim regarding the formation of alloys, crystallinity, morphology, particle size, proper separation of excitons, elemental content and their environment, various sensitive characterization techniques such as XRD, XPS, HRTEM, BET surface area and UV-vis analysis were employed. A mechanistic approach by means of experimental investigations revealed that the strong LSPR effect of Au facilitated the transfer of electrons to the Pd surface to make the surface negatively charged and suitable for the activation of aryl halides. The formed electropositive Au nanoparticles were converted to Au0 by accepting the photo-induced electrons from pristine UiO-66-NH2 and made available only holes at VB for the activation of phenylboronic acid. Among all the synthesized photocatalysts (1 : 2), Au/Pd@UiO-66-NH2 showed the highest activity (>99%) with TOF = 426 h−1 in an EtOH/H2O medium towards the SMC reaction, and the highest activity of this catalyst was supported by the electron gas model, LSPR effect (UV-vis) and active species separation (PL) analysis. The bimetallic noble nanoparticle-anchored UiO-66-NH2 not only expands the synthesis scope of C–C coupling by the SMC reaction under ambient conditions but will also inspire the further exploration of the activation of various reactants towards a wide range of organic transformation reactions.

Paper-based microfluidic devices are popular for their ability to automate multi-step assays for chemical or biological sensing at a low cost, but the design of paper microfluidic networks has largely relied on experimental trial and error. A few mathematical models of flow through paper microfluidic devices have been developed and have succeeded in explaining experimental flow behaviour. However, the reverse engineering problem of designing complex paper networks guided by appropriate mathematical models is largely unsolved. In this article, we demonstrate that a two-dimensional paper network (2DPN) designed to sequentially deliver three fluids to a test zone on the device can be computationally designed and experimentally implemented without trial and error. This was accomplished by three new developments in modelling flow through paper networks: i) coupling of the Richards equation of flow through porous media to the species transport equation, ii) modelling flow through assemblies of multiple paper materials (test membrane and wicking pad), and iii) incorporating limited-volume fluid sources. We demonstrate the application of this model in the optimal design of a paper-based signal-enhanced immunoassay for a malaria protein, PfHRP2. This work lays the foundation for the development of a computational design toolbox to aid in the design of paper microfluidic networks.

A series of sulphate modified Al-MCM-41 acid catalysts are synthesized following impregnation and co-condensation methods The physico-chemical characterizations of all the samples are done by XRD, FT-IR, TGA/DTA, TPD, N 2 adsorption and desorption study, SEM, HRTEM and EDAX etc. The structural advantages of Al-MCM-41 such as large specific surface area, wide pore size and pore volume and Bronsted and Lewis acid sites favor the coupling reaction. The catalysts endorsed the direct addition of alcohols to alkynes as well as their coupling with styrenes. The various combinations of alcohols with alkynes and styrenes are compatible with diverse functional groups to synthesize a substituted aryl ketones, as well as olefins with good to excellent yields. Additionally, the approach is advantageous in terms using alcohols, discounting the pre-functionalization and generation of waste by-products. Used precursors, alkynes and styrenes, are valuable since they are stable and found in many biologically active compounds. This current research work provides supplements to C C bond formation methodologies as a single step with atom economy and recyclable approach under mild and environmentally benign conditions.

Since Andreas Manz first introduced the microchip technology for chemical applications back in the 1990s, the field of `microfluidics' has expanded widely and microfluidic tools have become ubiquitous in life sciences research. However, pumps and controllers associated with most current microfluidic chips continue to be bulky and costly. A new class of microfluidic devices in which flow channels are composed of multidimensional (2D or 3D) shapes of porous materials is becoming increasingly popular. The ability of porous materials to wick fluids obviates the need for pumps, making such devices portable, low-cost, and ideal for use in low-resource settings. Such devices are broadly referred to as ``paper microfluidic devices''. The ability to manipulate fluids in paper microfluidics has progressively increased over the past decade and such devices are currently being used to develop highly sensitive and multiplexed low-cost diagnostic/sensing devices. In this article, we review the area of paper microfluidics covering the basic fluid physics, methods of fabrication, flow control tools, applications in diagnostics/sensing, and applications in other emerging areas like tissue engineering and power storage. This review is targeted to a broad audience that does not have prior exposure to the field of paper-based microfluidics. Through this article, we wish to invite researchers from multiple backgrounds to contribute to further development in this new and exciting area of research.

Photocatalytic organic transformations driven by functionalised metal organic frameworks (MOFs) are a green perspective for fine chemical synthesis. In the class of highly porous materials, MOFs are unparalleled in their degree of tunability and structural diversity and range of physical and chemical properties such as large surface area, permanent porosity, large void volumes, and framework flexibility, because of which they can act as a sustainable alternative for inorganic semiconductors. MOFs are the latest class of ordered porous solids being intensively studied as a novel class of hybrid organic–inorganic materials as nanophotocatalysts in the field of chemistry, materials science, chemical engineering, etc. Although the photocatalytic application of MOFs is still in the early stages compared with their other applications such as gas storage, separation, and heterogeneous catalysis, the currently available results have revealed that functionalised MOFs are very active as photocatalysts. The present review aims to discuss the various synthetic methods, post-synthetic modifications, MOF catalysed organic reactions and proposed mechanistic pathways for photoinduced organic transformations.

For enhancing solar energy conversion and environmental remediation, noble metal plasmonic photocatalysis originating from the effectual light absorbance and confinement of surface plasmons provides a new promising route. In the present study, by integrating these two aspects, a series of ternary Ag@Ag3VO4/ZnCr LDH heterostructures have been prepared by an in situ hydrothermal followed by co-precipitation method. In this method, there is self-assembling of Ag3VO4 nanoparticles on the brucite surface of the LDH material along with partial reduction of Ag+ to Ag. The phase identity, optical response, and morphological structure of the heterostructure photocatalysts were systematically characterized through PXRD, HRTEM, UV-Vis DRS, PL, and XPS methods. The resulting monodisperse Ag nanoparticles deposited on LDH materials offer a heterogeneous interaction at the interface and exhibit high photocatalytic activity towards generation of O2 and oxidation of phenol. Evaluation of photocatalytic activity showed that 40 wt% of Ag3VO4 modified LDH is the most effective photocatalyst for O2 evolution (571 μmol) and phenol oxidation (93%). The highly improved photocatalytic performance of the composite was ascribed mainly to the SPR effect of Ag nanoparticles, Schottky barriers formed at the interface of LDH and Ag3VO4 nanoparticles, and strong coupling between Ag, Ag3VO4 and LDH. The electrochemical studies such as LSV, CV, EIS and Tafel plots further support the high rate of photoactivity towards O2 evolution and phenol oxidation. These newly designed plasmonic Ag–LDH nanoheterostructures may offer a promising strategy for maximum light absorption and be authoritative in meeting environmental claims in the future.

Potent utilisation of a huge amount of red mud generated from aluminium industries is a threat to the environment. In the present work the red mud is successfully utilised as an effective photo catalyst for removal of Cr (VI) and malachite green from waste water. A series of red mud/MCM-41composite (RMCM) is developed by simple sol-gel method. The materials are characterised by N 2 ads-des studies, XRD, FTIR, UV–vis DRS, PL and electrochemical studies. From the XRD study it is confirmed that red mud contains both hematite (α-Fe 2 O 3 ) and goethite (α-FeOOH) phases of iron. Their synergetic effect develops a p - n junction and expedites the photo catalytic activity of the material. The structural advantages of MCM-41 plays a vital role for suppressing the e − /h + recombination which is confirmed from the PL study. The RMCM (1:1) exhibits the maximum reduction (85%) of 20 mg L −1 of Cr (VI) solution and oxidation of malachite green (97%). The oxidation and reduction processes provide beneficial method for purification of the waste water and environmental restoration. Further the applications of the RMCM can be extended for absorption of heavy metals, generation of H 2 energy by splitting water and photo catalytic organic transformation reactions. The current work will be beneficial for the researchers working in this field.

Porous graphitic carbon nitride (g-C3N4) was synthesized by taking melamine and ammonium bicarbonate through single-step calcination method followed by ultrasonication to obtain exfoliated porous g-C3N4 (2D) nanosheets. Further enhancement of photocatalytic performance, g-C3N4 nanosheet (2D) was further modified with different weight percentage of (1, 3, 5, and 7) of MnO2. The introduction of α-MnO2 onto the g-C3N4 nanosheet establishes an interlayer channels to promote the migration of charge carriers through the valence band and conduction band of the prepared composite MnO2@g-C3N4. The transformation of photo induced charge carriers adopt the Z-scheme mechanism rather band-transfer mechanism. The accumulated photo generated electrons in conduction band of g-C3N4 is more electro negative than the potential of (O2/O2–.) and able to reduce oxygen to superoxide (O2–.) radical. At the same time, the holes in valence band of α-MnO2 are more electro positive than the potential of (OH–/OH.) and help in oxidate OH– to hydroxyl (OH.) radical. Among all the composites, 3 wt% MnO2 modified g-C3N4 shows the best photocatalytic oxidation efficiency towards all the aromatic alcohols. In presence of visible light, heterojuction formation, and formation of active charged species (OH. and O2–.) were mostly responsible for photocatalytic oxidation of aromatic alcohols through free radical mechanism.

The abolition of environmental pollutants and production of hydrogen (H

A series of ternary Cu@CuO–g-C3N4/MCM-41 photocatalysts have been synthesized by varying the percentage of Cu using simple impregnation and co-condensation methods. The physico-chemical characterization of all the samples was determined using XRD, FTIR, UV-Vis DRS, PL, N2 ads–des studies, SEM and XPS HRTEM, EDAX, EIS and MS. The structural advantages of MCM-41, allow the uniform distribution of g-C3N4 and coexistence of Cu2+ along with Cu0 without using a reducing agent. The presence of g-C3N4 helps to shift the Fermi level of CuO towards more negative values due to accumulation of photogenerated electrons on the surface. It favours charge separation by creating a Schottky barrier at the junction. The 4 wt% Cu loaded over g-C3N4/MCM-41 exhibits a maximum 750 μmol 2 h−1 of H2 evolution under visible light irradiation with an apparent energy conversion efficiency of 24.8%. The enhancement in catalytic activity has been explained on the basis of synergism between g-C3N4 and Cu2+ and the SPR effect of Cu which also acts as a co-catalyst present on the surface of photocatalysts.

This work reports an amine modified meso Al2O3@MCM-41, particularly the ordered mesoporous silica, as a catalyst for the formylation of amines with carbon dioxide (CO2) and with dimethylamine-borane (DMAB) as a green reducing source. This newly developed catalytic system represents a heterogeneous and environmentally benign protocol. Besides this, the catalyst could be reused for five consecutive cycles without any significant loss in its catalytic activity towards the synthesis of formamides. The amine modified meso Al2O3@MCM-41 catalysts were well characterized by high and low angle XRD, temperature programmed desorption (TPD), BET-surface area, TGA/DTA and FT-IR analysis techniques. The effect of various reaction parameters such as temperature, CO2 pressure, time and the ratio of substrates to DMAB for the synthesis of formamides has been investigated. The developed protocol can be applicable for the synthesis of most important key intermediates like formoterol, orlistat, leucovarin and iguratimod in biologically active compounds.

Paper-based microfluidic devices are rapidly becoming popular as a platform for developing point-of-care medical diagnostic tests. However, the design of these devices largely relies on trial and error, owing to a lack of proper understanding of fluid flow through porous membranes. Any porous material having pores of multiple sizes contains partially saturated regions, i.e., regions where less than 100% of the pores are filled with fluid. The capillary pressure and permeability of the material change as a function of the extent of saturation. Although methods to measure these relationships have been developed in other fields of study, these methods have not yet been adapted for paper for use by the larger community of analytical chemists. In the current work, we present a set of experimental methods that can be used to measure the relationships between capillary pressure, permeability, and saturation for any commercially available paper membrane. These experiments can be performed using commonly available lab instruments. We further demonstrate the use of the Richards equation in modeling imbibition into two-dimensional paper networks, thus adding new capability to the field. Predictions of spatiotemporal saturation from the model were in strong agreement with experimental measurements. To make these methods readily accessible to a wide community of chemists, biologists, and clinicians, we present the first report of a simple protocol to measure the flow rates considering the effect of partial saturation. Use of this protocol could drastically reduce the trial and error involved in designing paper-based microfluidic devices.

Detection of minute quantities of target antigens in serum samples (consisting of a mixture of proteins/biomolecules) can be achieved by enhancement of the capture efficiencies of heterogeneous immunosensors. An important process parameter which affects the capture of target analytes in such immunosensors is the pH of the solution as the target proteins present in the serum samples are charged molecules. Here, we investigated the capture of prostate-specific antigens (PSAs), first in a mixed-analyte system wherein the solution contained two other non-specific proteins along with the target analyte, using the surface plasmon resonance spectroscopy. There are no reports on the detection of antigens in a mixed system based on the optimization of the pH values of the carrier fluid, and this is the motivation of the present work. Further, we studied interference effects caused by the presence of these non-specific proteins in the mixed-analyte systems by artificially increasing the ratio of the interfering proteins to that of the target protein. Eventually PSA spiked into the rabbit serum samples was captured through the optimization of the pH of the solution. We could detect PSA in the serum samples when diluted to 100 times or more, where the amounts of other interfering proteins were ~ 66 times that of the amount of PSA. This study proposes a heterogeneous immunosensor to detect the target analytes in the diluted serum samples by tuning pH the of solution mixture, which can be utilized to detect disease biomarkers in serum samples.

Coke oven wastewater containing high concentrations of phenol and chemical oxygen demand (COD) was collected from a local steel plant of Odisha. The treatment of coke oven wastewater was ca...

In recent years, metal/metal oxide functionalized mesoporous materials have received increasing attention in science and technology due to their fascinating properties, such as a large surface area, mesoscopic bulky shape, and interconnected porous structures enabling them to be one of the most promising materials for catalysis and photo catalysis. This review summarizes the recent developments in design, preparation and applications of transition metal/metal oxide promoted MCM-41 for production of hydrogen energy and removal of aqueous pollutants. After a brief introduction of these materials and synthetic strategies, their characterizations and applications in aqueous pollutant degradation by photocatalysis/photo-Fenton processes and H2 energy production by photocatalytic water splitting are summarized. Finally, the future perspectives directions for this promising field are also discussed.

Higher capture efficiencies with faster response times are important performance benchmarks for heterogeneous immunosensors which are utilized in recognitions of analytes for disease detection. As the capture involves transport of antigens from the bulk solution to the surface immobilized antibodies and the subsequent binding, the transport and reaction parameters play a critical role. While there are reports on the effect of individual process parameters (temperature, extent of mixing, pH) on the antigen/antibody interaction, we are not aware of any studies on the combined effect of these process parameters, and moreover, there are limited studies on the effect of these process parameters on the reaction and transport parameters. Knowledge of the effect of the process parameters on the transport and reaction parameters is necessary to understand their relative contributions to and the mechanism involved in the capture of the antigens. In this work, we have made an attempt to quantify the transport and reaction parameters and studied their dependencies on the process parameters. Experiments were conducted with three systems – BSA/anti-BSA, PSA/anti-PSA and CRP/anti-CRP, to quantify the captured antigen. The dependencies of the process parameters on the transport and reaction parameters were obtained from the experimental data using a diffusion–convection–electromigration–reaction model. Utilizing these dependency functions, the process parameters were modeled to find the optimal conditions for the highest capture efficiencies. Specifically, the influence of pH on maximizing the antigen capture and the underlying mechanism of the electrostatic interactions based on the surface charges and zeta potentials were elucidated.

Higher capture efficiency in heterogeneous immunosensors is desirable for the detection of cancer biomarkers at low concentrations. The process of the capture of these antigens is transport limited since the rates of antigen/antibody reactions are faster. In the case of non-flow systems, diffusive transport has contributions from both translational and rotational phenomena. Since the contribution of the rotational diffusivity is comparatively less explored in the literature, we have studied the same for three antigens – bovine serum albumin (BSA), prostate specific antigen (PSA) and C-reactive proteins (CRP). We quantified the rotational diffusivities using the time resolved fluorescence anisotropy method, and further quantified the contribution of the rotational diffusivities to the overall diffusivity of the antigens, and also studied the effect of the process parameters – temperature and pH of the solution. With an increase in temperature, the rotational diffusivity increased showing Arrhenius dependence while with the variation of pH, it showed a non-monotonic behavior having maxima closer to the isoelectric point of the corresponding antigens. This interesting behavior of the pH values could be attributed to lesser electro-viscous effects when the antigen molecule is neutral around its isoelectric point. The optimization of the pH and temperature for the immunosensors could be utilized to design efficient immunosensors.

Nowadays, inorganic–organic hybrid materials having pores in the mesoporous range are an intensively studied new category of demanding materials. By template synthesis, the coupling of inorganic and organic components gives pore sizes between 2 and 15 nm with very high surface area. The inorganic–organic hybrid materials were prepared in two ways: one was by co-condensation and the other by post-synthesis method. The inorganic part provides mechanical strength and the organic part shows functional activities. This review gives an overview of the preparation, properties, and potential applications of these materials in the areas of adsorption of pollutant gases like CO2 and heavy metals and in catalysis. Their activity is found to be very impressive in all these fields and it is hoped to be improved in the near future.

The current research paper deals with the study of palladium doped TiO2 based photocatalytic system to remove cyanide from coke oven wastewater. The photocatalytic activity was improved by employing hydroxyapatite nanoparticles, which serves to enhance the concentration of cyanide near the photoactive sites of TiO2 and also prevents its agglomeration. Further, to enhance the rate of photocatalytic degradation of cyanide under visible light irradiation an iron tetracarboxy phenyl porphyrin sensitizer (Fe-TCPP) was employed. The structural and morphological characterization of the synthesized catalysts were carried out by Fourier transformation infrared spectroscopy (FTIR), X-ray diffraction (XRD), photoluminescence (PL) emission spectra, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and ultraviolet diffuse reflectance spectroscopy (UV- DRS). The photocatalytic activity of the TiO2-Pd-HAP-Fe-TCPP- nanocomposite has been evaluated on degradation of cyanide under visible light irradiation using a photocatalytic reactor system. The results demonstrate the existence of synergistic effect between TiO2-Pd-HAP and Fe-TCPP sensitizer on removal of cyanide. Almost 90% of cyanide degradation was achieved at pH 11 within a short time span of 90 min, using the TiO2-Pd-HAP -Fe-TCPP nanocomposite. The photocatalytic degradation of cyanide by the nanocomposite follows pseudo-first order kinetics. The apparent rate constant (kapp) value of the TiO2-Pd-HAP-Fe-TCPP nanocomposite is estimated to be 11.6 and 4.3 time higher than that of bare TiO2 and TiO2-Pd-HAP respectively. Further, at this condition, >90% toxicity removal was achieved in the photocatalytic system even at a very high initial concentration of cyanide. Therefore, the Fe-TCPP-TiO2-Pd-HAP nanocomposite system can be considered as an alternative technique for removal of cyanide from coke oven wastewater.

Capture of higher amount of antigen with higher efficiency by the antibodies in a minimum time is desired for enhanced performance of immunosensors. In this manuscript we report a systematic investigation of the effects of the nature of the silicon surfaces (whether nanotextured or not) on which antibodies are immobilized and the nature of the surface stacks in combination with the state of mixing of the solution (whether mixed or not) containing the antigens, on the kinetics of the antigen–antibody binding in a non-flow system. An important finding here is that the combination of nanotextured surfaces with the mixing of the analyte solution resulted in a higher antigen capture, higher efficiency of capture and a lower process time, compared to other combinations. Computer simulations using a transport-reaction model were used to extract the transport and reaction parameters from the experimental data. Analysis of these parameters (the maximum available antibodies on the surface per unit area, diffusivity, boundary layer thickness, the dissociation constant) helped to provide an understanding of the experimental results and thus the phenomena involved. Applications of this study include improving the sensitivity and response time of immunosensors in both non-flow and flowing systems.

Higher capture efficiency of biomarkers in heterogeneous immunosensors would enable early detection of diseases. Several strategies are used to improve the capture efficiency of these immunosensors including the geometry of the system along with the transport and reaction parameters. Having a prior knowledge of the behavior of the above parameters would facilitate the design of an efficient immunosensor. While the contributions of the transport and reaction parameters toward understanding of the mechanism involved in capture have been well studied in the literature, their effect in combination with the geometry of the sensors has not been explored until now. In this work, we have experimentally demonstrated that the capture efficiency of the antigen-antibody systems is inversely related to the size of the sensor patch. The experimental system was simulated in order to get an in-depth understanding of the mechanism behind the experimental observation. Further, the extent of heterogeneity in the system was analyzed using the Sips isotherm to obtain the heterogeneity index (α) and the reaction rate constant (K(D)) as fitted parameters for a sensor patch of 1.5 mm radius. The experimental kinetic data obtained for the same sensor patch matched reasonably with the simulation results by considering K(D) as the global affinity constant, which indicated that our system can be considered to be homogeneous. Our simulation results associated with the size dependency of the capture efficiency were in agreement with the trends obtained in our experimental observations where an inverse relation was observed owing to the fact that the mass-transfer limitation decreases with the decrease in the size of the sensor patch. The possible underlying mechanism associated with size dependency of capture efficiency was discussed based on the time-dependent radial variation of captured antigens obtained from our simulation results. A study on the parametric variation was further conducted for the nonmixed and mixed systems on the transport (Deff), reaction (K(D)), and geometric parameters (R). Two different correlations were established for the nonmixed and mixed systems between the capture efficiency (f) and a nondimensional number (t(D)/t(R)) consisting of the above-mentioned parameters. Such unified relations will be useful in designing heterogeneous immunosensors and can be extended to microfluidic immunosensors.

The MCM-41 supported Cs2.5H0.5PW12O40 and K2.5H0.5PW12O40 salts were synthesized by incipient wetness impregnation method. The solids were characterized by N2 adsorption–desorption isotherms, FT-IR, XRD, and temperature programmed desorption, etc. This catalyst has been found to exhibit excellent activity for acetylation of phenolic compounds. The catalyst is stable and reusable giving 96% conversion with 100% selectivity towards acetate products.

High surface densities of properly oriented antibodies are desired for enhancing the sensitivity of immunosensors. A systematic investigation of the densities and orientations of antibodies, immobilized without and with intermediate protein molecules (protein-A and streptavidin) on nano-textured silicon surfaces (RMS roughness

A series of Cu salts of heteropoly acid (CuxH3−2xPW12O40) supported MCM-41 catalysts (CuxH3−2xPW12O40/MCM-41) was synthesized by wet impregnation method and thoroughly characterized by using various analytical techniques, viz., X-ray diffraction, UV−vis diffused reflectance spectroscopy (UV−vis DRS), nitrogen adsorption desorption, temperature-programmed reduction (TPR), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). From XRD and FT-IR studies, we confirmed that the Keggin structure of heteropoly acid (HPA) is retained in Cu salt of HPA. Heck vinylation was performed to examine the catalytic properties of the catalysts. The 50 wt % CuxH3−2xPW12O40/MCM-41 showed remarkable catalytic performance of phenyl iodide (98% conversion) to cinnamic acid in aqueous medium compared with MCM-41 and other catalytic systems.

The paper reports the synthesis, surface and textural characterization of copper and amine modified MCM-41 and its application for the single step amination of benzene to aniline at 70 °C. Varying the amount of Cu different Cu/amine modified MCM-41 samples was synthesized by co-condensation and impregnation method. The samples were characterized by nitrogen adsorption–desorption, X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), 29Si magic-angle spinning (MAS) and 13C Nuclear Magnetic Resonance (NMR) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). X-ray diffraction patterns indicate that the modified materials retain the standard MCM-41 structure. FT-IR and DRS results indicated that Cu and amino groups are incorporated into the Si–O framework and frame wall respectively. NMR showed higher degree of condensation of materials in framework position. Cu-amine-MCM-41 samples showed significant catalytic activity for single step amination of benzene in acetic acid–water medium under mild reaction conditions using hydroxylamine as aminating agent. The Cu-amine-MCM-41 (Si/Cu = 20) showed highest benzene conversion (72.2%) and 100% selectivity for aniline.

This paper reports preparation, characterization of amine modified mesoporous crystalline MCM-41 and its application in Knoevenagel condensation reaction. Amine modified MCM-41 was prepared by co-condensation and post-synthesis methods. The samples were characterized by X-ray powder diffraction, Fourier-transfer infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron micrograph (SEM), 29Si magic-angle spinning (MAS), nuclear magnetic resonance (NMR), diffuse reflectance spectra (DRS), nitrogen adsorption–desorption and CHN analysis. X-ray diffraction patterns indicate that the modified materials retain the standard MCM-41 structure. SEM study exhibits that the arrangement of particles for 12.8% amine modified MCM-41 is well ordered and spherical in nature. CHN analysis supports that complete hydrolysis of ethoxy groups take place in 12.8% amine modified sample. From the NMR study it is confirmed that the surface coverage is 40% in 12.8% amine modified sample. The base catalytic activity of hybrid MCM-41 materials such as amine (post-synthesis and co-condensation methods) and surfactant functionalized materials for condensation reaction between benzaldehyde and diethyl malonate in solvent free, room temperature synthesis of cinnamic acid was evaluated and correlated with the surface and textural properties. Sample containing 12.8 wt% amine loaded by co-condensation method showed highest malonic ester conversion (92%) and selectivity (98%) for cinnamic acid.

A series of copper catalysts supported on mesoporous molecular sieves MCM-41 with copper loading varying from 2 wt% to 10 wt% were synthesized by impregnation method using aqueous copper nitrate solution as the precursor. The samples were characterized by nitrogen adsorption–desorption, X-ray powder diffraction, FT-IR, UV-diffuse reflectance spectra and temperature programmed reduction. X-ray diffraction patterns indicate the presence of crystalline CuO phase above 4 wt% copper loading. TPR patterns at low temperatures reveal the presence of highly dispersed copper oxide on the surface of the support and the profiles at high temperatures indicates bulk copper oxide. The catalytic activity of the samples was evaluated towards benzene oxidation using H 2 O 2 as the oxidant in acetic acid solvent at room temperature. The effect of reaction parameters, i.e. time, temperature, catalyst amount, amount of H 2 O 2 , solvent and alkyl substitution on the substrate, were also investigated. Among the catalysts studied, 4 wt% copper loaded MCM-41 showed maximum conversion (21%) and selectivity (94%) towards phenol.

Nowadays, inorganic–organic hybrid materials having pores in the mesoporous range are an intensively studied new category of demanding materials. By template synthesis, the coupling of inorganic and organic components gives pore sizes between 2 and 15 nm with very high surface area. The inorganic–organic hybrid materials were prepared in two ways: one was by co-condensation and the other by post-synthesis method. The inorganic part provides mechanical strength and the organic part shows functional activities. This review gives an overview of the preparation, properties, and potential applications of these materials in the areas of adsorption of pollutant gases like CO2 and heavy metals and in catalysis. Their activity is found to be very impressive in all these fields and it is hoped to be improved in the near future.

The mesoporous molecular sieve MCM-41 was synthesized by sol–gel method using tetraethyl orthosilicate (TEOS), cetyl trimethyl ammonium bromide (CTAB), aqueous NH3 and water. A series of sulfate modified MCM-41 was prepared by incipient wetness impregnation method using H2SO4 as sulfatising agent. The samples were characterized by BET surface area, X-ray diffraction, FT-IR and TG–DTA. The catalytic activity of the samples was evaluated for nitration of phenol with nitric acid in dichloro ethane (DCE) medium, at room temperature. The effect of reaction parameters, i.e. time, concentration of nitric acid and phenol/nitric acid ratio were also investigated. Modification with sulfate opened new opportunities to generate active Bronsted and Lewis acid sites in the stabilized nanostructure MCM-41. Among the catalysts screened, 4 wt.% sulfated MCM-41 showed maximum activity (93%), with 90% selectivity towards ortho-nitrophenol.

The catalysts exhibit excellent activity for the acetylation of phenols and benzyl alcohols.

A series of Cs salt of phosphotungstic acid (Cs-PTA) supported on MCM-41 (Cs-PTA/MCM-41) was synthesized by a wet impregnation method and thoroughly characterized by using various analytical techniques, viz. X-ray diffraction, UV-Vis diffused reflectance spectroscopy (UV-Vis DRS), nitrogen adsorption desorption, scanning electron microscopy (SEM), Infrared spectra (FTIR), temperature programmed reduction (TPR), and temperature programmed desorption (TPD). The spectroscopic results revealed that Cs-PTA is highly dispersed on a MCM-41 surface. The 50 wt.% Cs-PTA supported on MCM-41 showed remarkable catalytic performance toward acylation of anisole reaction. The catalyst is regenerable by simple calcinations without appreciable loss in catalytic activity.

The Mobil Composition of Matter No. 41 (MCM-41) containing Cu and Al with Si/Al ratios varying from 100 to 10 and 1 to 6wt.% of Cu was synthesized under hydrothermal and impregnation conditions, respectively. The samples were characterized by nitrogen adsorption-desorption measurements, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and (29)Si and (27)Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectra. X-ray diffraction patterns indicate that the modified materials retain the standard MCM-41 structure. TPR patterns show the two-step reduction of Cu species. TPD study shows that Cu-impregnated Al-MCM-41 samples are more acidic than Al-MCM-41. From the MAS-NMR it was confirmed that most of the Al atoms are present tetrahedrally within the framework and some are present octahedrally in extraframework position. Impregnation of Cu shifted Al to the extraframework position. The catalytic activity of the samples toward hydroxylation of phenol in aqueous medium was evaluated using H(2)O(2) as the oxidant at 80 degrees C. The effects of reaction parameters such as temperature, catalyst amount, amount of H(2)O(2), and solvent were also investigated. Sample containing 4wt.% copper-loaded Al-MCM-41-100 showed high phenol conversion (78%) with 68% catechol and 32% hydroquinone selectivity.

This study aims towards applying the intrinsic polarized fluorescence technique for obtaining valuable information from human cervical tissue samples. The efficacy of this technique is tested in human tissues by comparing its diagnostic capabilities with the bulk fluorescence. It is seen that biochemical information is hidden due to the presence of distortions by tissue scattering and absorption in the fluorescence spectra. Intrinsic tissue fluorescence provides a complete understanding of the biochemical and/or morphological changes that take place during the progression of disease. Recording of the experimental data and thereafter subsequent extraction of the intrinsic fluorescence serves as fingerprints towards determining the occurrence of these diseases. Here we report a comparative study of intrinsic versus bulk polarized fluorescence in cervical tissues. Intrinsic fluorescence is seen to be a more sensitive technique than bulk fluorescence for diagnosis of cervical cancers. Attempts have been made to study the changes in the amount of different fluorophores found in the epithelial and stromal layer of cervical tissue (both normal and cancerous). It has been seen that collagen decreases and NADH increases as a healthy cervical tissue develops into a cancerous one. Intrinsic fluorescence provides more consistent discriminating results as compared to bulk polarized fluorescence. It is also more sensitive in giving biochemical information from the different layers in cervical tissue. It may be concluded that intrinsic fluorescence shows promise as a viable tool for providing valuable insights towards fruitful diagnosis of the various stages of disease development and changes occurring with age.