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This investigation was aimed to enhance the dispersibility of multi-walled carbon nanotubes (MWCNT) using sodium polystyrene sulfonate (Na-PSS) polyelectrolyte. Subsequently, electrically conducting, multi-layer thin films are prepared utilizing layer by layer assembly method with poly(vinyl alcohol) as a host matrix. The highest extent of MWCNT dispersion was observed in MWCNT:Na-PSS ratio of 1:9 (wt/wt), which was estimated from UV-Vis spectroscopic analysis. Zeta potential measurements of Na-PSS modified MWCNT dispersion showed large negative potentials ranging from -52 to -64 mV in the most stable pH range of 4 to 10, suggesting the colloidal stability is due to the long-range repulsive nature of electrostatic interactions from negatively charged sulfonate groups. Complementary molecular dynamics simulations showed that adsorption of Na-PSS imparts a large negative potential to the carbon nanotube surface, which increases with an increase in Na-PSS concentration. The multi-layer thin film of (1:9) MWCNT:Na-PSS exhibited a DC electrical conductivity of 2.96 * [10.sup.2] S/m. KEYWORDS conducting thin films, layer by layer assembly, multi-walled carbon nanotubes, poly(sodium 4-styrene sulfonate), zeta potential measurement, 1 | INTRODUCTION Carbon nanotubes (CNTs) with their high aspect ratio and an unique combination of its superior electrical, mechanical, thermal and elastic properties are considered as an ideal nanomaterial [...]

We report here for the first time the role of noncovalently functionalized 2D nanomaterials on the ferroelectric and piezoelectric behavior of poly(vinylidene fluoride) (PVDF) nanocomposites. Graphene oxide (GO), expanded graphite (EG) and hexagonal boron nitride (h‐BN) were noncovalently modified via Li‐salt of 6‐amino hexanoic acid (Li‐AHA), denoted as m‐GO, m‐EG and m‐BN, in order to de‐agglomerate and de‐stack them, which were subsequently incorporated into the PVDF matrix via solution mixing, followed by compression molding. Simultaneously, PVDF nanocomposites with unmodified 0.08 wt% of 2D nanomaterials were also prepared using the same methodology. PVDF/m‐BN nanocomposite showed a higher extent of polar phase (~36%) associated with PVDF phase as compared to PVDF/m‐GO and PVDF/m‐EG nanocomposites. Further, the highest permittivity (~58 at 10−1 Hz) was achieved in PVDF/m‐BN nanocomposite, which was also reflected in higher remnant polarization (~61 nC/cm2) and a significantly higher d33 value (~53 pm/V). Moreover, a higher output peak to peak voltage (~13 V) was obtained for the sensor device fabricated from PVDF/m‐BN nanocomposite. Thus, the role of Li‐AHA‐modified 2D nanomaterials in improving the morphology, dielectric, ferroelectric, and piezoelectric characteristics of the PVDF nanocomposites was clearly established. [ABSTRACT FROM AUTHOR]

The isothermal crystallization behaviour of the polypropylene (PP) phase in PP/multi-walled carbon nanotubes (MWCNTs) composites has been investigated via differential scanning calorimetric analysis, which showed the influence of the varying dispersion level of MWCNTs in the respective PP matrix. PP/MWCNTs composites were prepared via melt-blending technique, wherein two different grades of MWCNTs of varying average 'agglomerate' size and varying entanglements (N-MWCNTs and D-MWCNTs) were utilized. Furthermore, the influence of melt-viscosity of the PP phase was investigated on the crystallization kinetics of the PP/MWCNTs composites. Heterogeneous nucleation ability of MWCNTs has resulted in a decrease in half time of crystallization ([t.sub.1/2]) from ~14 min for pure PP to ~6 min for PP/N-MWCNTs and ~11 min for PP/ D-MWCNTs composites at 1 wt% of MWCNTs at 132[degrees]C. Overall rate of crystallization (k) has significantly increased to 4.9 X [10.sup.-2] [min.sup.-1] for PP/N-MWCNTs composite as compared with 6.2 X [10.sup.-3] [min.sup.-1] for PP/D-MWCNTs composite at 0.5 wt% of MWCNTs at 132[degrees]C. Moreover, the effect of a novel organic modifier, Li-salt of 6-amino hexanoic acid along with a compatibilizer (PP-g-MA) has also been investigated on the crystallization kinetics of the PP phase in PP/ MWCNTs composites., INTRODUCTION The phenomenal discovery of carbon nanotubes (CNTs) in 1991 [1] has led to unprecedented interest in the industrial as well as in the academic community. The outstanding properties associated [...]

Composites of polypropylene (PP) and multi-walled carbon nanotubes (MWCNTs) were prepared via melt-mixing utilizing Li-salt of 6-amino heaxanoic acid (Li-AHA) modified MWCNTs in the presence of a compatibilizer (polypropylene-g-maleic anhydride; PP-g-MA). Improved interaction between the anhydride group of PP-g-MA and the amine functionality of Li-AHA was confirmed via FTIR and Raman spectroscopic analysis. A higher glass transition temperature ([T.sub.g]) of the PP phase has been observed in these composites as compared to pristine MWCNTs-based composites. The crystallization temperature ([T.sub.c]) of the PP phase was increased as a function of pristine MWCNTs concentration in PP/MWCNTs composites indicating heteronucleating action of MWCNTs. However, [T.sub.c] value was decreased in the presence of Li-AHA modified MWCNTs indicating the adsorbed Li-AHA on the MWCNTs surface. Moreover, [T.sub.c] value was higher in the presence of Li-AHA modified MWCNTs with PP-g-MA as compared to that of without PP-g-MA, suggesting the desorbed Li-AHA from the MWCNTs surface due to melt-interfacial reaction. Further, MWCNTs were extracted by hot vacuum filtration technique from PP/MWCNTs composites containing Li-AHA and PP-g-MA. The isothermal crystallization kinetics showed a variation in crystallization behavior of the PP phase in the corresponding composites as compared to the 'extracted MWCNTs.', INTRODUCTION The discovery of carbon nanotubes (CNTs) [1] have led to the development of CNTs-based materials for various applications viz.; EMI shielding [2], super capacitors, memory devices [3], lithium-ion secondary [...]

Undoped and doped poly(2,5-benzimidazole) (ABPBI) membrane was prepared by solvent casting method using methane sulfonic acid as a solvent and phosphoric acid ([H.sub.3]P[O.sub.4]) as a doping agent. The concentration of [H.sub.3]P[O.sub.4] was varied from 0 to 60 vol% to enhance the proton conductivity of the ABPBI membrane at higher temperature. Wide angle X-ray diffraction analysis showed a decrease in crystallinity in ABPBI membrane with increase in [H.sub.3]P[O.sub.4] doping concentration. The molecular signature and the presence of [H.sub.3]P[O.sub.4] was observed in 1000-1500 [cm.sup.-1] in the Fourier transform infrared spectra, which was also supported by a corresponding weight loss at 180°C-200°C in the thermogravimetric analysis. Undoped ABPBI membrane registered the Young's modulus (E) and hardness (H) values of 2.46 and 0.92 GPa, respectively, and the corresponding E and H values for 1.65 doping level of 60 vol% [H.sub.3]P[O.sub.4] doped ABPBI membrane were 0.14 and 0.067 GPa, respectively. The 60 vol% [H.sub.3]P[O.sub.4] doped ABPBI membrane with doping level of 1.65 showed highest proton conductivity value of 2.2 x [10.sup.-2] S/cm. The impedance spectroscopic analysis and the equivalent circuit model were discussed to understand the nature of proton conduction in [H.sub.3]P[O.sub.4] doped ABPBI membrane., INTRODUCTION Polymer electrolyte doped with sulfonic acid group commonly known as perfluorosulfonated solid electrolyte (PFSE) has been utilized for proton conduction. Nafion is one of such type of membrane available [...]

Nanocomposite solid polymer electrolytes (SPEs) have been prepared from polyethylene oxide (PEO), organically modified nanoclay (MNclay), and tetraethylammonium tetrafluoroborate ([TEABF.sub.4]) salt. The concentration of the salt has been varied in the respective SPE, wherein PEO/ MNclay ratio was kept constant. It has been proposed that three types of complex formation could be operative in the SPEs due to the interactions among PEO, MNclay, and the salt. The complex formation mechanism has been postulated on the basis of X-ray diffraction (XRD) analysis, transmission electron microscopic (TEM) observation, differential scanning calorimetric (DSC) analysis, and polarized optical microscopic (POM) observation. 'Complex 1' and 'complex 3' formation could be involved in the crystalline phase as indicated by DSC and XRD analyses, whereas 'complex 2' formation might be restricted in the amorphous phase as suggested by TEM observation. The ionic conductivity of the SPEs has been correlated with the results obtained from XRD, DSC, and POM analyses. The formation of complex 1 and complex 2 could be responsible for the increase in the ionic conductivity, whereas complex 3 formation might decrease the ionic conductivity. An activated carbon-based supercapacitor has been fabricated using SPEs and characterized by cyclic voltammetry, galvanostatic 'charge-discharge' behavior, and impedance spectroscopic analysis., INTRODUCTION In recent years considerable amount of research has been focused on developing solid polymer electrolytes (SPEs) for application in the rechargeable batteries. Polyethylene oxide (PEO) has been extensively studied [...]

The effect of simultaneous addition of multiwall carbon nanotubes (MWNTs) and a reactive compatibilizer (styrene maleic anhydride copolymer, SMA) during melt-mixing on the phase morphology of 80/20 (wt/wt) PA6/ABS blend has been investigated. Morphological analysis through scanning and transmission electron microscopic analysis revealed finer morphology of the blends in presence of SMA + MWNTs. Fourier transform infrared spectroscopic analysis indicated the formation of imide bonds during melt-mixing. Non-isothermal crystallization studies exhibited the presence of a majority faction of MWNTs in the PA6 phase of 80/20 (wt/wt) PA6/ABS blend in presence of SMA + MWNTs. Rheological analysis, dynamic mechanical thermal analysis, and thermogravimetric analysis have demonstrated the compatibilization action of simultaneous addition of a reactive compatibilizer (SMA copolymer) and MWNTs in PA6/ABS blends. An attempt has been made to investigate the role of simultaneous addition of SMA copolymer and MWNTs on the morphology of 80/20 (wt/wt) PA6/ABS blend through various characterization techniques., INTRODUCTION In recent years, carbon nanotubes (CNTs) incorporated binary polymer blends have emerged as a significant research interest in both academic as well as in the industrial community. This is [...]

Multiwall carbon nanotubes (MWNTs) were melt-mixed in polyamide 6 (PA6) and acrylonitrile-butadiene-styrene (ABS) copolymer blends using a simultaneous mixing protocol in order to investigate the state of dispersion of MWNTs in PA6/ABS blends. The blend composition was varied from 40/60 (wt/wt) to 60/40 (wt/wt) in PA6/ABS blends, which showed 'co-continuous' morphology in the presence of MWNTs. State of dispersion of MWNTs in these blends was assessed through bulk electrical conductivity measurements, morphological analysis, solution experiments, and UV-vis spectroscopic analysis. MWNTs were subsequently modified with a novel organic modifier, sodium salt of 6-aminohexanoic acid (Na-AHA), to improve the state of dispersion of MWNTs. Blends with unmodified MWNTs exhibited the DC electrical conductivity in the range [~10.sup.-11] to [~10.sup.-5] S/cm, whereas blends with Na-AHA-modified MWNTs exhibited DC electrical conductivity in the range [~10.sup.-7] to [~10.sup.-5] S/cm. The reduction in MWNTs 'agglomerate' size (~73.7 µm for 40/ 60 blend with unmodified MWNTs to ~59.9 µm in the corresponding blend with Na-AHA-modified MWNTs) was observed through morphological analysis. The rheological studies showed increased complex viscosity and storage moduli in lower frequency region in case of blends with Na-AHA-modified MWNTs confirming a refined 'network-like' structure of MWNTs., INTRODUCTION Polymer blends are of immense commercial interest as high-performance alloys, due to their excellent properties, which can be suited for applications where materials with high thermal stability, good chemical [...]

Polyamide6 (PA6)/acrylonitrile butadiene styrene copolymer (ABS) blends with unmodified multiwall carbon nanotubes (MWNTs) were prepared via melt-blending in a conical twin-screw micro-compounder with varying melt-mixing time. To improve the state of dispersion of MWNTs, non-covalent organic modifiers for MWNTs have been utilized: sodium salt of 6-amino hexanoic acid (Na-AHA) and 1-pyrene-carboxaldehyde (PyCHO). PA6/ABS blends with MWNTs have shown a phase morphology transition from 'matrix-dispersed droplet' type to 'co-continuous' type as a function of melt-mixing time with the exception of 40/60 PA6/ABS blend with PyCHO-modified MWNTs. Non-isothermal crystallization studies revealed the heterogeneous nucleating action of MWNTs through the presence of double crystallization exothermic peaks (at ~192°C and >200°C) while pure PA6 shows bulk crystallization peak at ~192°C. 40/60 and 60/40 (wt/wt) PA6/ABS blends with 5 wt% unmodified MWNTs exhibited electrical conductivity values of ~3.9 x [10.sup.-11] S/cm and ~4.36 x [10.sup.-6] S/cm, respectively. A significant enhancement in electrical conductivity was observed with Na-AHA and PyCHO-modified MWNTs (order of [~10.sup.-6] and [~10.sup.-4] S/cm, respectively)., INTRODUCTION The incorporation of multi wall carbon nanotubes (MWNTs) in the polymer blends via melt-mixing is a well-established strategy to make electrically conducting composites [1-7]. The influence of interfacial tension, [...]

Graphene oxide (GO) incorporated ultra‐high molecular weight polyethylene (UHMWPE) nanocomposites were prepared by encapsulating GO by UHMWPE in an aqueous media via high‐shear mixing, which were subsequently dried and compression molded. Morphological characterizations via scanning electron microscopy revealed the intercalation of UHMWPE chains in the graphitic stacks corresponding to GO. Further, dielectric permittivity of UHMWPE/GO nanocomposite of 1 wt% GO showed a drastic increase (~61) as compared to pure UHMWPE (~2) due to an enhanced interfacial polarization. A significantly higher value of remnant polarization (~10 nC/cm2) and coercive field (~3 kV/cm) was observed in UHMWPE/GO nanocomposite of 1 wt% GO, which showed a strong hysteresis loop of polarization versus electric field plot as compared to pure UHMWPE, which displayed a very weak hysteresis loop. The piezoelectric coefficient (d33) of ~9.5 pm/V was estimated in UHMWPE/GO nanocomposite of 1 wt% GO via piezoresponse force microscopy. Nanocomposite sensor devices were also fabricated and piezoelectric output voltage of ~6 V was recorded in UHMWPE/GO nanocomposite of 1 wt% of GO. We report here for the first time the unique ferroelectric and piezoelectric properties displayed by UHMWPE/GO nanocomposites. [ABSTRACT FROM AUTHOR]

Amine functionalized multiwalled carbon nanotubes (a-MWNT) based polypropylene (PP) composite fibers were prepared in the presence of polypropylene-g-ma-leic anhydride (PP-g-MA) by melt-mixing followed by melt-spinning with subsequent post-drawing of the as-spun fibers of varying draw ratio (DR). In order to enhance the interfacial interaction, a-MWNT were utilized in combination with PP-g-MA during melt-mixing. Fourier transform infrared spectroscopic analysis revealed the formation of imide bonds between MA functionality of PP-g-MA and amine functional group of a-MWNT. Higher tensile properties of PP/a-MWNT/PP-g-MA composite fibers were registered with varying DR of the as-spun fiber. Orientation factors of a-MWNT and PP chains along the fiber axis were correlated with the higher tensile modulus and tensile strength of PP/ a-MWNT/PP-g-MA composite fiber of varying DR. Crystallization studies indicated the role of hetero-nucleating action of a-MWNT in PP/a-MWNT/PP-g-MA composite fiber. POLYM. ENG. SCI., 52:1183-1194, 2012. [C] 2011 Society of Plastics Engineers, INTRODUCTION Polypropylene (PP) is one of the important commodity plastics in view of its consumption in commodity applications. However, PP needs reinforcement in order to achieve high tensile strength and [...]

Multicomponent polymer blends involving polyamide6 (PA6), polypropylene (PP), acrylonitrile-butadiene-sty-rene (ABS) and high density polyethylene (HOPE) with multiwall carbon nanotubes (MWNT) were prepared by melt mixing technique to achieve conducting composites. MWNT were either compounded directly or by employing a masterbatch dilution approach in binary (PA6/ABS), ternary (PA6/PP/ABS) and quaternary (PA6/ PP/ABS/HDPE) blends. To facilitate 'network-like' structure MWNT were pretreated with either sodium salt of 6-aminohexanoic acid or octadecyl tri-phenyl phosponium bromide. Multicomponent blends with pretreated MWNT utilizing masterbatch dilution approach showed significant improvements in the bulk electrical conductivity as compared to blends prepared by direct addition approach at 2 wt % MWNT content Phase morphology of these blends revealed co-continuous type of morphology wherein MWNT were found to be selectively localized in the PA6 phase. The hetero-nucleating action of MWNT was manifested in increased crystallization temperature of mainly PA6 phase of the blends indicating preferential localization of MWNT in the PA6 phase. POLYM. ENG. SCI., 51:1987-2000, 2011. © 2011 Society of Plastics Engineers, INTRODUCTION Blending of polymers is often used to design a material with synergistic combination of desirable properties from each component [l]. The ultimate properties of the blends are strongly influenced [...]

State of dispersion of purified multiwall carbon nano-tubes (p-MWNT) in the presence of neutralized MWNT (n-MWNT) in aqueous solution was assessed through UV-Visible spectroscopy, dynamic light scattering measurements, and solution experiments. Raman spectroscopic analysis revealed that debundling of p-MWNT in the presence of p-MWNT in aqueous solution was persistent even in the solid mixture, which was supported by transmission electron microscopic analysis. The proposed mechanism behind the improved dispersion of p-MWNT in the presence of n-MWNT in aqueous solution has been based on the electrostatic charge repulsion between negatively charged n-MWNT. The state of dispersion of p-MWNT in the presence of n-MWNT in 45/55 polypropylene/acrylonitrile butadiene styrene (PP/ABS) blends was assessed through Raman spectroscopic analysis, bulk electrical conductivity measurements, solution experiment, and crystallization studies. Raman spectroscopic analysis indicated that the state of dispersion of MWNT was improved with increasing n-MWNT content of the mixture. This strategy led to a remarkable increase in the bulk electrical conductivity of 45/55 PP/ABS blends at 3 wt% MWNT content and was strongly dependent on the concentration of n-MWNT in the mixture. Differential scanning calorimetric measurements along with solution experiments revealed the subsequent migration of MWNT from the PP phase to the ABS phase in the blends during melt-mixing in the presence of higher fraction of n-MWNT. POLYM. ENG. SCI., 51:1891-1905, 2011. ©2011 Society of Plastics Engineers, INTRODUCTION The outstanding properties associated with carbon nanotubes (CNT) attract them toward its use in polymer/CNT composites and are exploited for various potential applications viz. electrostatic discharge materials, conducting composites, [...]

Ternary polymer blends of 80/10/10 (wt/wt/wt) polyam-ide6 (PA6)/polypropylene (PP)/acrylonitrile-butadiene-styrene (ABS), PP/PA6/ABS, and ABS/PP/PA6 were prepared in the presence of multiwalled carbon nanotubes (MWCNTs) by melt-mixing technique to investigate the influence of MWCNTs on the phase morphology, electrical conductivity, and the crystallization behavior of the PP and PA6 phases in the respective blends. Morphological analysis showed the 'core-shell'-type morphology in 80/10/10 PA6/PP/ABS and 80/ 10/10 PP/PA6/ABS blends, which was found to be unaltered in the presence of MWCNTs. However, MWCNTs exhibited 'compatibilization-like' action, which was manifested in a reduction of average droplet size of the dispersed phase/s. In contrast, a separately dispersed morphology has been found in the case of 80/10/10 ABS/PP/PA6 blends in which both the phases (PP and PA6) were dispersed separately in the ABS matrix. The electrical percolation threshold for 80/10/10 PA6/PP/ ABS and 80/10/10 PP/PA6/ABS ternary polymer blends was found between 3-4 and 2-3 wt% of MWCNTs, respectively, whereas 80/10/10 ABS/PP/PA6 blends showed electrically insulating behavior even at 5 wt% of MWCNTs. Nonisothermal crystallization studies could detect the presence of MWCNTs in the PA6 and the PP phases. POLYM. ENG. SCI., 51:1550-1563, 2011. ©2011 Society of Plastics Engineers, INTRODUCTION Blending of two or more polymers leads to high-performance materials provided a synergistic interaction between the phases exists. Blending is also an alternative and most inexpensive route to develop [...]

Blends of polypropylene/ethylene octene comonomer (PP/EOC) with conducting fillers viz., carbon black (CB) and multiwall carbon nanotubes (MWNT) were prepared using melt mixing technique with varying filler concentration and blend compositions. Thermo gravimetric analysis studies indicated that presence of filler enhanced the thermal stability of PP/EOC blends. Morphological analysis revealed the formation of matrix-dispersed droplet and co-continuous type of morphology depending on the blend compositions. Significant reduction in droplet size and finer ligament thickness in co-continuous structure were observed in the blends with filler due to compatibilization action. Fillers were found to be aggregated in the EOC phase irrespective of blends compositions and could be related to the affinity of the fillers toward EOC phase. The electrical conductivity of PP/EOC blends with CB and MWNT was found to be highest for 80/20 composition and decreased as EOC content increased. The percolation threshold of CB was between 10 and 15 wt% for the 80/20 and 70/30 blends whereas it was 15-20 wt% for blends with EOC content higher than 30 wt%. The percolation threshold was 2-3 wt% MWNT for PP/EOC blends. This was attributed to the aggregated filler network preferentially in the EOC phase. The melt-rheological behavior of PP/EOC blends was significantly influenced in presence of both the fillers. POLYM. ENG. SCI., 49:1502-1510, 2009. © 2009 Society of Plastics Engineers, INTRODUCTION In recent years conducting fillers (viz., multiwall carbon nanotubes (MWNT), carbon black (CB) etc.) incorporated polymer blends have received immense interest in both academic and industrial fields due to [...]

The mechanical and the crystallization behavior of melt-mixed cocontinuous blends of polyamide6 (PA6) and acrylonitrile butadiene styrene were studied in presence of multiwall carbon nanotubes (MWNT). Young's modulus was observed to be significantly improved with increasing concentration of MWNT, while only moderate improvements were observed in the tensile strength. To overcome the van der Waals' forces between MWNT a unique modifier, sodium salt of 6 amino hexanoic acid (Na-AHA) was employed where it was envisaged that specific interactions between [Na.sup.+] of the modifier and the delocalized 'π-electron' clouds of MWNT would lead to significant debundlling of the tubes. The mechanical properties of the blends with Na-AHA modified MWNT were found to be improved as compared to the blends with purified MWNT however, were found to be adversely affected above certain concentration of Na-AHA in the blends. Dynamic mechanical thermal analysis supported the plasticization effect induced by Na-AHA manifesting in decrease in the glass transition temperature of PA6 in the blends with Na-AHA modified MWNT. Differential scanning calorimetry results showed two crystallization exotherms for PA6 in the blends with both purified and Na-AHA modified MWNT. This unusual crystallization behavior of PA6 was addressed in context to confined crystallization of PA6 in the tube 'network-like' structure. POLYM. ENG. SCI., 49:1533-1543, 2009. [C] 2009 Society of Plastics Engineers, INTRODUCTION The superior electrical, mechanical, and thermal properties of carbon nanotubes (CNT) are intriguing and studies on polymer/CNT composites are rapidly expanding in an intention to develop advanced materials having [...]

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Low band gap photocatalysts are desirable for efficient performance. We report synthesis of cobalt‐doped TiO2 photocatalysts, inside radial pores of nano‐spherical silica (RPNS) particles, having different weight percentages of dopant (0.1 to 4 wt.% Co‐TiO2‐RPNS). Doping decreases both optical band gap and electron‐hole charge separation, with maximum decrease in charge transfer resistance, for 1 wt.% Co‐TiO2‐RPNS (0.74 kΩ.cm−2), compared to TiO2‐RPNS (1.18 kΩ.cm−2). However, it shows only partial degradation of rhodamine B dye. Hence, the 1 wt.% Co‐TiO2‐RPNS catalyst was further investigated with respect to different e−/h+ recombination processes, in presence of any one of the scavengers ‐ e− (K2S2O8) or OH* (butanol) or h+ (EDTA). An e− scavenger shows a higher dye degradation (rate constant 1.24 h−1), while h+ scavenger shows a lower rate (0.38 h−1), in contrast to no scavenger (0.91 h−1). Oxygen purging as a reaction promoter inhibited e−/h+ recombination, doubling overall rate (4.66 h−1). So, scavenger and oxygen purging together can further enhance a low band gap photocatalyst's activity. [ABSTRACT FROM AUTHOR]