ONE-DIMENSIONAL MANGANESE DIOXIDE (MnO2) NANOSTRUCTURES SUCH AS NANORODS, NANOWIRES, AND NANOFIBERS HAVE GENERATED INTENSE RESEARCH INTERESTS OVER THE PAST RECENT YEARS DUE TO THEIR SUPERIOR OPTICAL, ELECTRICAL, CATALYTIC, MAGNETIC AND ELECTROCHEMICAL PROPERTIES [1]. SUCH MANGANESE DIOXIDE NANOSTRUCTURES ARE OF CONSIDERABLE IMPORTANCE IN TECHNOLOGICAL APPLICATIONS AND HAVE BEEN INTENSIVELY INVESTIGATED AS PROMISING ELECTRODE MATERIALS IN PRIMARY/SECONDARY BATTERIES AND ELECTROCHEMICAL CAPACITORS DUE TO THEIR EXCELLENT ELECTROCHEMICAL PROPERTIES, LOW-COST, ENVIRONMENTALLY BENIGN, AND EASE OF PREPARATION [2]. VARIOUS APPROACHES HAVE BEEN USED TO FABRICATE MANGANESE DIOXIDE, SUCH AS SELF-REACTING MICROEMULSION, PRECIPITATION, ROOM-TEMPERATURE SOLID REACTION, SONOCHEMICAL AND HYDROTHERMAL METHODS [3]. THE HYDROTHERMAL METHOD IS A POWERFUL SYNTHESIS APPROACH FOR SYNTHESIZING VARIOUS FORMS OF MANGANESE OXIDES AND AFFORDS VARIOUS ADVANTAGEOUS FEATURES INCLUDING THE USE OF MILD SYNTHESIS. IN THIS WORK, NANO-SIZED MANGANESE OXIDE WAS SYNTHESIZED USING HNO3 AND KMNO4 IN THE PRESENCE OF POLYETHYLENE GLYCOL AS A SURFACTANT UNDER HYDROTHERMAL CONDITION. X-RAY DIFFRACTION (XRD) AND SCANNING ELECTRON MICROSCOPE (SEM) WERE USED TO CHARACTERIZE THE STRUCTURE AND MORPHOLOGY OF SYNTHESIZED POWDER.

WELL-DEFINED WORM-LIKE NANOSTRUCTURES OF MnO2 WERE PREPARED VIA PULSE ELECTROCHEMICAL METHOD. THE ELECTROCHEMICAL CELL INCLUDED A STAINLESS STEEL CATHODE (316 L, 100 MM×50 MM×0.5 MM) CENTERED BETWEEN THE TWO PARALLEL GRAPHITE COUNTER ELECTRODES. THE DEPOSITION EXPERIMENTS WERE CONDUCTED AT THE PULSE CURRENT MODE WITH A TYPICAL ON-TIME AND OFF-TIME (TON=5 S AND TOFF=10 S) AND AN AVERAGE CURRENT DENSITY OF 1 MA CM-2 (IA=1 MA CM-2). THE DEPOSITION TIME AND BATH TEMPERATURE WERE 50 MIN AND 80OC, RESPECTIVELY. THE DEPOSITION EXPERIMENTS WERE CONDUCTED USING AN ELECTROCHEMICAL WORKSTATION SYSTEM (POTENTIOSTAT/GALVANOSTAT, MODEL: NCF-PGS 2012, IRAN). AFTER DEPOSITION, THE STEEL SUBSTRATES WERE RINSED WITH WATER SEVERAL TIMES AND DRIED AT 50OC FOR 5 H. THEN, THE DEPOSITS WERE SCRAPED FROM THE SUBSTRATES AND SUBJECTED TO FURTHER ANALYZES. TO OBTAIN OXIDE PRODUCT, THE PREPARED HYDROXIDE POWDER WAS HEAT TREATED AT 600OC FOR 3 H IN DRY AIR ATMOSPHERE. THE PRODUCTS WERE CHARACTERIZED BY XRD, FT-IR AND SEM TECHNIQUES. THE RESULTS REVEALED THAT WELL-CRYSTALLIZED A, G-MnO2 WITH WORM-LIKE TEXTURE HAS BEEN PREPARED (FIG. 1).

SUPER CAPACITORS REPRESENT A NEW CLASS OF ENERGY STORAGE DEVICES THAT HAVE BEEN ATTRACTED MANY RESEARCHERS IN LAST FEW YEARS. GRAPHENE WITH UNIQUE PROPERTIES SUCH AS SUPERIOR ELECTRICAL CONDUCTIVITY AND LARGE SPECIFIC SURFACE AREA IS ONE OF THE MOST SUITABLE MATERIALS IN SUPER CAPACITOR APPLICATIONS [1]. BESIDES, METAL OXIDES ARE BEING USED AS ACTIVE COMPOUNDS IN SUPER CAPACITORS DUE TO THEIR ROLE IN REDOX REACTIONS. IN THIS RESEARCH, SYNTHESIS AND CHARACTERIZATION OF SUPER CAPACITOR ELECTRODES BASED ON GRAPHENE AND MnO2 NANOSTRUCTURED MATERIALS WAS STUDIED UNDER DIFFERENT CONDITIONS. FOR THIS PURPOSE, GRAPHENE OXIDE (GO) WAS SYNTHESIZED BY HUMMERS’ METHOD AND THEN, IT WAS DEPOSITED ON A NICKEL FOAM VIA ELECTROPHORETIC PROCESS WITH APPLIED POTENTIAL OF 5 V IN SOLUTION CONTAINING MGSO4 AND GO [2]. FINALLY, MnO2 ANODICALLY ELECTRODEPOSITED ON REDUCED GO/NI-FOAM BY USING SUCCESSIVE CYCLIC VOLTAMMETRY (CV) AT THE SCAN RATE OF 0.1 VS-1 IN 5 CYCLES. MORPHOLOGY AND CHEMICAL COMPOSITION OF THE PREPARED ELECTRODE WERE INVESTIGATED BY SCANNING ELECTRON MICROSCOPY (SEM) AND X-RAY PHOTOELECTRON SPECTROSCOPY (XPS), RESPECTIVELY. THE ELECTROCHEMICAL AND CAPACITIVE PROPERTIES OF THE SYNTHESIZED SUPER CAPACITOR ELECTRODES WERE STUDIED IN A THREE- ELECTRODES SYSTEM USING VARIOUS TECHNIQUES INCLUDING CV IN THE POTENTIAL WINDOW OF 0 TO 1.0 V (FIG. 1), CHARGE- DISCHARGE (CD) AT A CONSTANT CURRENT OF 6 MA (FIG. 2), AND THE ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS), ALL IN 1.0 M NA2SO4 SOLUTION. THE RESULTS SHOWED THAT THE SYNTHESIZED MnO2/RGO SUPER CAPACITOR ELECTRODE EXHIBITED A CAPACITANCE OF 273 FG-1.

AS GREEN CHEMISTRY IS CURRENTLY A MAJOR CONCERN FOR ORGANIC CHEMISTS, REACTIONS UNDER SOLVENT-FREE CONDITIONS WITH A SOLID CATALYST HAVE RECEIVED MUCH ATTENTION [1]. IT IS KNOWN THAT SUBSTITUTED PYRIMIDINES ARE AN IMPORTANT CLASS OF HETEROCYCLIC COMPOUNDS. A NUMBER OF SYNTHETIC PHARMACOPHORES BASED UPON THE PYRIMIDYL STRUCTURE EXHIBIT BIOLOGICAL ACTIVITIES [2]. WITH REGARD TO THE PHARMACOLOGICAL PROFILE AND OTHER PROMISING MEDICINAL APPLICATIONS OF FUNCTIONALIZED 3, 4-DIHYDROPYRIMIDIN-2 (1H) -ONES AND -THIONES, THEIR SYNTHESIS VIA THE BIGINELLI-LIKE REACTION HAS BEEN THOROUGHLY STUDIED [3].IN THIS PAPER, WE SUCCESSFULLY DEVELOPED A SIMPLE, SOLVENT LESS AND EFFICIENT METHOD FOR THE SYNTHESIS OF DIHYDROPYRIMIDINONE DERIVATIVES BY THE RAPID CONDENSATION OF VARIOUS AROMATIC ALDEHYDES, KETONES AND UREA USING EFFICIENT AND READILY OBTAINABLE MnO2-CNT NANO COMPOSITES AS CATALYST UNDER MICROWAVE IRRADIATION.

INDUSTRIES THAT USE DYES IN DIFFERENT PROCESSES OF THEIR PRODUCTION LINES GENERATE WIDESPREAD WASTEWATER CONTAINING OF SIGNIFICANT AMOUNT OF DYE COMPOUNDS. MOST OF DYES ARE TOXIC AND DIFFICULT TO BIODEGRADE. THEREFORE, IT IS ESSENTIAL TO DEVELOP METHODS THAT CAN LEAD TO DESTRUCTION OF SUCH COMPOUNDS BEFORE THEIR DISCHARGE INTO RIVERS OR ENVIRONMENT. VARIOUS METHODS SUCH AS CHEMICAL, ELECTROCHEMICAL, BIOLOGICAL AND ADSORPTION ARE USED FOR TEXTILE WASTEWATER TREATMENT. AMONG THEM, SORPTION TECHNIQUE EMPLOYING LOW COST ADSORBENTS HAS BEEN PROVED TO BE THE MOST SUITABLE BECAUSE OF ITS EFFICIENCY, FLEXIBILITY, AND ECONOMIC FEASIBILITY [1-3]. IN THE CURRENT WORK, MANGANESE DIOXIDE NANOPARTICLES (MnO2 NPS) WAS PREPARED VIA CHEMICAL ROUTE IN THE LAB AND CHARACTERIZED USING XRD, SEM, AND IR SPECTROSCOPIC TECHNIQUES. THE PREPARED MnO2 NPS THEN WERE USED AS ADSORBENT FOR REMOVAL OF MALACHITE GREEN (MG) DYE FROM AQUEOUS SOLUTIONS. MG IS A BASIC DYE WHICH IS WIDELY USED FOR COLORING VARIOUS FABRICS SUCH AS WOOL, COTTON, LEATHER AND ACRYLIC. THE ADSORPTION EXPERIMENTS WERE CONDUCTED IN BATCH MODE. IN ORDER TO FIND OUT THE MAXIMUM REMOVAL CONDITIONS, THE EFFECT OF IMPORTANT PARAMETERS SUCH AS PH, ADSORBENT DOSE, CONTACT TIME, INITIAL DYE CONCENTRATION, TEMPERATURE AND IONIC STRENGTH, WERE INVESTIGATED. THE EQUILIBRIUM ADSORPTION DATA OBTAINED FROM INITIAL CONCENTRATION, CONTACT TIME AND SOLUTION TEMPERATURE WERE USED FOR ISOTHERM, KINETIC AND THERMODYNAMIC INVESTIGATION RESPECTIVELY. THE KINETICS OF ADSORPTION WAS STUDIED APPLYING THE PSEUDO-FIRST, PSEUDO-SECOND ORDER AND INTRA-PARTICLE DIFFUSION MODELS. THE DATA OBTAINED SHOWS THAT THE SORPTION PROCESS IS OCCURRED VERY FAST (~10 MIN) AND WITH HIGH EFFICIENCY (98%). MAXIMUM ADSORPTION CAPACITY OF 200 MG/G CAN BE ACHIEVED WITH THE INTRODUCED ADSORBENT. WITH REGARD TO THE HIGH PERFORMANCE OF THE ADSORBENT USED IN THE CURRENT STUDY, MnO2 NPS MIGHT BE CONSIDERED AS A PROMISING AND NOVEL ADSORBENT FOR DYE REMOVAL NANOTECHNOLOGY.