RESUMO
Metal-directed interfacial self-assembly of well-defined coordination polymer (CP) ultrathin films can control the metal complex arrangement and distribution at the molecular level, providing a convenient route for the design and fabrication of novel opto-electrical devices and heterogeneous catalysts. Here, we report the assembly of two series of CP multilayers with the transition-metal ions of Fe2+, Co2+, Zn2+ and Tb3+ as connectors and tripodal terpyridyl ligands of 4,4',4â³-(1,3,5-triazine-2,4,6-triyl)tris(1-(4-([2,2':6',2â³-terpyridin]-4'-yl)benzyl)pyridin-1-ium) (TerPyTa) and 4,4',4â³-(benzene-1,3,5-triyl)tris(1-(4-([2,2':6',2â³-terpyridin]-4'-yl)benzyl)pyridin-1-ium) (TerPyBen) as linkers at the air-water interface. The as-prepared Langmuir-Blodgett (LB) films display strong luminescence, with the emission wavelength and relative intensity dependent on both the metal ions and linkers; among them, the Zn-TerPyTa and Zn-TerPyBen CPs give off the strongest luminescent emission centered at about 370 nm with an emission lifetime of approximately 0.2-0.3 ns. The Tb-TerPyTa CPs can give off emission at approximately 490, 546, 586, and 622 nm, attributed to the 5D4 to 7F3-6 electron transitions of typical Tb3+ ions. Finally, these CP LB films can act as efficient heterogeneous photocatalysts for the CO2 reduction to selectively produce CO. The catalytic efficiency can be optimized by adjusting the experimental conditions (light sensitizer, electron donor, and water content) and CP composition (metal ion and ligand) with an excellent yield of up to 248.1 mmol g-1. In particular, it is revealed that, under the same conditions, the catalytic efficiency of the Fe-TerPyTa CP LB film is nearly 2 to 3 orders of magnitude higher than that of the other metalated complexes investigated in the homogeneous system. UV-vis spectroscopy and cyclic voltammetry studies demonstrated that the dual active sites of Fe-terpyridine and TerPyTa units contribute to the enhanced catalytic activity. This work provides an effective method to introduce the earth-abundant metal complexes into CP films to construct efficient noble-metal-free photocatalysts for the CO2 reduction.
RESUMO
Two-dimensional functional metal-organic frameworks and coordination polymers have attracted much attention and have been successfully prepared in solutions and at interfaces through the coordination of ligands to metal ions. However, the preparation of large-area ultrathin ordered films is still a challenge. Here, a modified liquid/liquid interfacial epitaxial growth method has been developed. A planar liquid/liquid interface between a chloroform solution of bipyridine derivatives and pure water was constructed first, and then an aqueous solution of Eu3+ or Cu2+ ions was added dropwise into the water phase. A layered ultrathin film with the size of several hundreds of square micrometers appeared at the liquid/liquid interface after a certain time. The monitoring results showed that the formation of ultrathin films was a result of continuous epitaxial growth of the adsorbed species due to the synergistic effects of hydrophobic effects of the alkyl chains, coordination bonds between the ligands and metal ions, π-π interactions between the ligands, and the restriction of the interface on the vertical growth. This offers a way to fabricate more large-area thin films of amphiphilic molecules.
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The trivalent europium ion (Eu3+) has garnered a great deal of interest for the design of luminescent materials possessing compound-independent emission bands, strong luminescent intensity, and long emission lifetimes. We herein introduce a synthetic methodology capable of constructing visual luminescent probes from Eu3+ complex-functionalized silica nanocomposites and their Langmuir-Blodgett (LB) films at interfaces. In order to facilitate the coordinative stabilization of Eu3+ over carrier surfaces, silica nanoparticles (nanoSiO2) were pregrafted with terpyridyl (TPy) to make nanoSiO2TPy linkers. Then, a well-designed coordination reaction of nanoSiO2TPy with EuCl3 and 2,6-pyridinedicarboxylic acid (DPA) was carried out at solid-liquid and air-water interfaces, where our desired material (denoted as nanoSiO2TPy@EuDPA) and its corresponding LB film are obtained. The presence of TPy and DPA interacting with Eu3+ plays a key role in regulating the chemical nature of the particle surface, hence giving rise to closely packed nanocomposite arrays in the film. As a result, the improvement in uniformity and stability is achieved alongside the enhancement in emission intensity and lifetime. With such advantageous optical properties, we find them workable as facile, green, and affordable luminescent sensors, by which a range of common toxic anions (Cr2O72-, MnO4-, and PO43-) can be visually and quantitatively recognized. Notably, the LB film-based material could afford a higher Ksv value (1.53 × 105 M-1), a lower detection limit (0.157 µM), and better recyclability than its original powder analogue, showcasing its utility as a more promising candidate for practical use.
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To date, there have been only a few studies focusing on the assignment of X-ray diffraction (XRD) patterns in graphitic carbon nitrides (g-C3N4) and contradictory determination for a broad peak around 12°-14° has been perplexing. In this study, assignments are carried out both theoretically and experimentally. The cell parameters for g-C3N4 are determined as a = b = 8.1 Å, c = 6.5 Å, α = ß = 90°, and γ = 120°. Qualitative and semi-quantitative methods such as fast Fourier transform and residual after 1st and 2nd derivatives are used to confirm and search the hidden peaks. Discrete Fourier transform is applied for the extraction of peak profiles and separation of overlapping peaks. In the broad peak around 12°-14° (with Cu Kα as referring source), two peaks are selected and determined as (100) and (001), which is fairly consistent with the (200) diffraction peak and (002) diffraction peak obtained by 2nd derivative method, respectively. In addition, g-C3N4 nanorods, MOF-doped g-C3N4 nanorods, and oxidized bulk g-C3N4 are successively investigated to present the 7.0 Å d-spacing of (100), hexagonal system of bulk g-C3N4, defect (1/2 0 0) structure with 14.0 Å d-spacing, and ABA stacking sequence. The structural transition in the oxidation of bulk g-C3N4 is presented by XRD to show accordance with the interpretation. Specific phenomena reported in other studies are also reinterpreted successfully, such as the appearance of peak at â¼12.4°.
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A metal-directed assembling approach has been developed to encapsulate hydrogenase (H2ase) within a layer-by-layer (LBL) multilayer of carbon nanotube polyelectrolyte (MWNT-PVPMe), which showed efficient biocatalytic oxidation of H2 gas. The MWNT-PVPMe was prepared via a diazonium process and addition reactions with poly(4-vinylpyridine) (PVP) and methyl iodide (MeI). The covalently attached polymers and organic substituents in the polyelectrolyte comprised 60-70% of the total weight. The polyelectrolyte was then used as a substrate for H2ase binding to produce MWNT-PVPMe@H2ase bionanocomposites. X-ray photoelectron spectra revealed that the bionanocomposites included the elements of Br, S, C, N, O, I, Fe, and Ni, which confirmed that they were composed of MWNT-PVPMe and H2ase. Field emission transmission electron microscope images revealed that the H2ase was adsorbed on the surface of MWNT-PVPMe with the domains ranging from 20 to 40 nm. Further, with the use of the bionanocomposites as nanolinkers and Na2PdCl4 as connectors, the (Pd/MWNT-PVPMe@H2ase)n multilayers were constructed on the quartz and gold substrate surfaces by the Pd(II)-directed LBL assembling technique. Finally, the as-prepared LBL multilayers were used as heterogeneous catalysts for hydrogen oxidation with methyl viologen (MV(2+)) as an electron carrier. The dynamic processes for the reversible color change between blue-colored MV(+) and colorless MV(2+) (catalyzed by the LBL multilayers) were video recorded, which confirmed that the H2ase encapsulated within the present LBL multilayers was of much stronger stability and higher biocatalytic activity of H2 oxidation resulting in potential applications for the development of H2 biosensors and fuel cells.
Assuntos
Hidrogênio/química , Hidrogenase/química , Nanocompostos/química , Nanotubos de Carbono/química , Paládio/química , Adsorção , Biocatálise , Cátions Bivalentes , Composição de Medicamentos , Hidrocarbonetos Iodados/química , Oxirredução , Paraquat/química , Polivinil/química , Propriedades de SuperfícieRESUMO
Hydrophilic treatment of bulk graphene-like carbon nitride (g-C3N4) for future applications has aroused extensive interest, due to its enhanced specific surface area and unusual electronic properties. Herein, water-dispersible g-C3N4 with a porous structure can be obtained by chemical oxidation of bulk g-C3N4 with K2Cr2O7-H2SO4. Acid oxidation results in the production of hydroxyl and carboxyl groups on its basal plane and the formation of a porous structure of g-C3N4 at the same time. The porous g-C3N4 appears as networks with tens of micrometers in width and possesses a high specific surface area of 235.2 m(2) g(-1). The final concentration of porous g-C3N4 can be up to 3 mg mL(-1). Compared with bulk g-C3N4, the as-obtained porous g-C3N4 exhibits excellent water dispersion stability and shows great superiority in photoinduced charge carrier separation and transfer. The photocatalytic activities of porous g-C3N4 towards degradation of organic pollutants are much higher than those of the bulk due to the larger band gap (by 0.2 eV) and specific surface areas.
Assuntos
Nitrilas/química , Catálise , Grafite/química , Luz , Nitrilas/síntese química , Fotólise/efeitos da radiação , Porosidade , Dicromato de Potássio/química , Rodaminas/química , Ácidos Sulfúricos/química , Poluentes Químicos da Água/químicaRESUMO
Bionanocomposites of hydrogenase and viologen-functionalized carbon nanotubes (H2ase/V-MWNTs) were prepared and characterized by using infrared spectra and scanning electron microscope. Cyclic voltammograms revealed two couples of redox waves corresponded to the electron transfer processes of viologens and [4Fe-4S]2+/1+ clusters of hydrogenase. The current intensity was enhanced in the H2 atmosphere, which suggested that the present bio-nanocomposites could be used as heterogeneous bio-catalyst to catalyze reversible reaction between protons and H2.
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Eletroforese/métodos , Hidrogênio/química , Hidrogenase/química , Nanocompostos/química , Nanotubos de Carbono/química , Viologênios/química , Enzimas Imobilizadas/química , Teste de Materiais , Nanocompostos/ultraestrutura , Nanotubos de Carbono/ultraestrutura , Oxirredução , Oxigênio/química , Tamanho da Partícula , Propriedades de SuperfícieRESUMO
We report a kinetically-controlled template-free room-temperature production of hollow silica materials with various novel morphologies, including tubes, crutches, ribbons, bundles and bells. The obtained products, which grew in a well-controlled manner, were monodispersed in shape and size. The role of ammonia, sodium citrate, polyvinylpyrrolidone, chloroauric acid and NaCl in shape control is discussed in detail. The oriented growth of these micro-/nanostructures directed by reverse micelles followed a solution-solution-solid (SSS) mechanism, similar to the classic vapor-liquid-solid mechanism. The evolution processes of silica rods, tubes, crutches, bundles and bells were recorded using transmission electron microscopy to prove the SSS mechanism.
RESUMO
Monolayers and Langmuir-Blodgett (LB) films of pyridyldithio-functionalized multiwalled carbon nanotubes (pythio-MWNTs) conjugated with cytochrome c were investigated. Quartz crystal microbalance measurements revealed that monolayers of pythio-MWNTs could be deposited on the substrate surface with a surface density of about 270 ng/cm2. The as-prepared LB films of pythio-MWNTs could act as a support to immobilize cytochrome c with the surface density of about 5.2 microg/cm2. Composition, structure and morphology of the films were characterized by using absorption and X-ray photoelectron spectra as well as atomic force microscope. A reversible redox process for the immobilized cytochrome c was revealed with the cathodic and anionic potentials at about -0.55 and -0.3 V versus Ag/AgCl, respectively.
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Chiral coordination polymers (CPs) have been prepared at the air-water interface by using the ligand of 1,4-bis(9-O-dihydroquininyl)anthraquinone [(DHQ)2AQN] and its enantiomer of 1,4-bis(9-O-dihydroquinidinyl)anthraquinone [(DHQD)2AQN] as linkers and AgNO3 as the connector. Surface pressure-area isotherms indicated that both ligands could form insoluble monomolecular layers on the pure water and AgNO3 subphase surfaces. Compared with the average molecular area on the pure water surface, that of the ligand increased about 10% when its monolayer was formed on the AgNO3 subphase surface due to the formation of Ag-(DHQ)2AQN and Ag-(DHQD)2AQN chiral CPs. These monolayers were deposited on the quartz, Si, and indium tin oxide (ITO) substrate surfaces via the Langmuir-Blodgett (LB) method. The as-prepared LB films were characterized by using UV-vis absorption and fluorescence spectroscopy, circular dichroism and X-ray photoelectron spectroscopy, as well as by using a scanning electron microscope and atomic force microscope. Broad fluorescence emissions were measured at about 365 and 525 nm for the ligands in the methanol solutions. The second emission red shifted to about 555 nm in the LB films of both pure ligands and their Ag-directed CPs. A couple of well-reversible redox waves were recorded and centered at about -0.2 ~ -0.3 V (vs Ag/AgCl) for the ITO electrode covered by the LB films of (DHQ)2AQN, (DHQD)2AQN, or of the Ag(+)-directed CPs, which were designated to one electron transfer process of the ligands. Small aggregates were observed for the LB films prepared at the lower surface pressures, which were compressed to form more uniform two-dimensional layers at the higher surface pressures.
Assuntos
Antraquinonas/química , Polímeros/química , Polímeros/síntese química , Éteres , Ligantes , Estrutura Molecular , Tamanho da Partícula , Propriedades de SuperfícieRESUMO
OBJECTIVE: To describe a new strategy to manage ectopia lentis in ASD patients assessing the visual outcomes and safety of supracapsular scleral sutured intraocular lens implantation and analyzing the accuracy of different intraocular lens (IOL) power calculation formulae. METHODS: Eight patients with ASD (13 eyes) were underwent supracapsular scleral suture fixation of posterior chamber (PC) IOL without capsular extirpation. The preoperative and postoperative clinical features were compared. The prediction error values from four formulae (SRK/T, Holladay 1, Hoffer Q, Haigis), with or without Wang-Koch (WK) adjustment, were calculated for the cases. RESULTS: Zonulodialysis and premature cataracts could be the main reason for the decreased vision in patients with ASD. There was a significant improvement in best corrected visual acuity on 3-month follow-up after applying supracapsular scleral suture fixation of PC IOL. The prediction errors of the different formulae showed a slight tendency towards postoperative myopia. The Haigis formula with WK adjustment showed the best performance. CONCLUSIONS: Supracapsular scleral suture fixation of IOLs for retaining the capsule-zonule barrier is a good option for ASD patients. The Haigis formula is recommended for ASD patients treated with supracapsular scleral suture fixation of IOLs. The predicted IOL power should be reduced based on the effect of the new anatomic position of the IOL to achieve a satisfactory visual outcome.
Assuntos
Ectopia do Cristalino , Lentes Intraoculares , Humanos , Implante de Lente Intraocular , Acuidade Visual , Ectopia do Cristalino/cirurgia , Esclera/cirurgia , Estudos Retrospectivos , Refração OcularRESUMO
Triad hybrid multilayers containing the light sensitizers of zinc tetrapyridylporphyrin (ZnTPyP) and pyridine-functionalized TiO(2) (TiO(2)-Py) nanoparticles were constructed on substrate surfaces with the use of Pd(II) ions as the connectors using the layer-by-layer (LBL) method. The assembly process was monitored using ultraviolet-visible (UV-vis) absorption and X-ray photoelectron spectra as well as scanning electron microscopy and atomic force microscopy. The content of the pyridine substituents in the TiO(2)-Py nanocomposites was about 2% (w/w). The Soret absorption band of ZnTPyP was 24 nm red-shifted in the hybrid multilayers due to a strong intermolecular electronic coupling interaction among porphyrin macrocycles or porphyrin macrocycle/TiO(2)-Py nanoparticles. The average surface density of each ZnTPyP layer was about 1.4 × 10(-10) mol/cm(2). Aggregation of the small TiO(2)-Py nanoparticles to larger domains with sizes up to hundreds of nanometers occurred in the hybrid multilayers; however, such an aggregation behavior was weaker than that in the solutions. The quartz substrate modified with the as-prepared Pd/ZnTPyP/Pd/TiO(2)-Py triad hybrid multilayers was used as a heterogeneous photocatalyst for the degradation of methyl orange (MO) under irradiation (λ > 420 nm) at room temperature with a catalytic efficiency of about 1.3 × 10(-3) MO/ZnTPyP·s. Without the use of the filter, the catalytic efficiency increased because both ZnTPyP and TiO(2)-Py nanocomposites acted as the light sensitizers. It is suggested that the present heterogeneous catalyst has the advantages of facile separation, high stability, structural controllability on the molecular and nanoscale level, and good recyclability.
Assuntos
Metaloporfirinas/química , Nanocompostos/química , Paládio/química , Processos Fotoquímicos , Piridinas/química , Titânio/química , Zinco/química , Compostos Azo/química , Catálise , Espectroscopia FotoeletrônicaRESUMO
The metal-mediated self-assembly of coordination polymers, building blocks, and metal-organic frameworks has been widely used to construct multifunctional novel materials on the molecular level. Here, we developed this technique to build up multilayers of functionalized carbon nanotubes on the basis of both intermolecular electrostatic and coordinative interactions. Positively charged electroactive viologenthiol (VSH) was first immobilized on multiwalled carbon nanotubes (MWNTs) to form MWNT-VSH hybrids with a relative content of â¼9% by weight. Field emission transmission electron microscopy images revealed that the VSH molecules randomly covered the surfaces of MWNTs with a thickness of 1 to 2 nm. Then, the MWNT-VSH hybrids were used as nanoscale multidentate "ligands" (linkers) to construct metal-mediated multilayers with the use of CuAc(2) as the connectors by the layer-by-layer (LBL) method. The assembly process was monitored by absorption and X-ray photoelectron spectroscopy as well as scanning electron and atomic force microscopy after each assembly of Cu(II) ions and MWNT-VSH hybrids. Finally, the electrochemical behaviors of the viologens in the MWNT-VS/Cu LBL multilayers were investigated.
RESUMO
Multilayers of manganese(III) porphyrin-linked poly(vinylpyridinium) (MnTMPyP-PVPMe) polyelectrolyte and poly(styrenesulfonic acid-o-maleic) acid (PSS) have been assembled on gold, quartz, and indium tin oxide surfaces by a layer-by-layer (LBL) technique. The assembly process was monitored by measuring their absorption spectra and frequency change after each assembly, both of which confirmed the formation of three-dimensional MnTMPyP-PVPMe/PSS multilayers. The Soret absorption band of porphyrin red shifted about 8 nm in the multilayer compared with that in the dilute aqueous solution. The average mass changes for each assembly of MnTMPyP-PVPMe and PSS were estimated to be about 2.9 and 0.25 µg/cm(2), respectively. X-ray photoelectron spectra revealed that the as-prepared multilayers were composed of S 2p, C 1s, N 1s, O 1s, and Mn 2p, corresponding to polymers of MnTMPyP-PVPMe and PSS. A rough surface was observed after the assembly of MnTMPyP-PVPMe on the gold surface, but it became smoother when the PSS layer was adsorbed. The significant difference in the mass change and film morphology after the assembly of MnTMPyP-PVPMe compared to those after the assembly of PSS was ascribed to the reason that the MnTMPyP-PVPMe polyelectrolyte contained large metalloporphyrin macrocycles, which were axially coordinated to the pyridyl substituents of the PVP polymeric backbones. The cyclic voltammograms revealed two couples of redox waves in the phosphate electrolyte solution at pH 11, which corresponded to the electron-transfer processes of Mn(II)/Mn(III) and Mn(III)/Mn(IV) of polymeric manganese porphyrin MnTMPyP-PVPMe. The charge-transfer process was also investigated. Finally, the present MnTMPyP-PVPMe/PSS multilayers were used as a heterogeneous catalyst for the decoloration of an azo dye.
Assuntos
Maleatos/química , Manganês/química , Polímeros/química , Poliestirenos/química , Polivinil/química , Porfirinas/químicaRESUMO
Sodium salt of poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA) has been employed to prepare a series of stable nanosized metal colloids such as silver, gold, palladium, platinum, and silver-gold alloy nanostructures. All of the as-synthesized products are very stable in water. The metal nanostructures have been directly confirmed by ultraviolet-visible spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected area electron diffraction (SAED), and also characterized by techniques such as Fourier transform infrared spectroscopy (FT-IR) and (1)H NMR. Intensive study has found that the metal ions are most probably reduced by organic radicals, generated from the thermal degradation of PSSMA.
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Detection of anthrax biomarker dipicolinic acid (DPA) is of great importance upon the crisis of bioterrorism. Development of fluorescent materials for DPA detection, particularly one that fully depends on single luminescent response, faces the challenge of being susceptible to interferences. The accompanying accuracy problems offer great opportunities for the establishment of more reliable ratiometric analysis method. Herein, a ratiometric fluorescent probe based on terbium functionalized graphitic carbon nitride nanosheets (Tb-g-C3N4NS) is attempted for quantitative detection of DPA to address the distinct function of g-C3N4NS as both carrier and reference fluorophore, which is a so-far unexplored option in fluorescent detection approaches. We achieve the incorporation of Tb3+ into framework of g-C3N4NS by using a simple synthetic strategy comprised of thermal pyrolysis and ultrasonic exfoliation. Combining the reference signal over g-C3N4NS at 440 nm (I440) with the response signal of Tb3+ at 546 nm (I546), concentration of DPA can be easily calculated via its linear correlation with the intensity ratio (I546/I440), giving a precise measurement towards DPA with a detection limit as low as 9.9 nM. Besides enabling an excellent self-calibrating detection of DPA, this work also inspires broader use of g-C3N4NS for relevant process.
Assuntos
Antraz , Térbio , Antraz/diagnóstico , Biomarcadores , Fluorescência , Grafite , Humanos , Compostos de NitrogênioRESUMO
Pyridylthio-modified multiwalled carbon nanotubes (pythio-MWNTs) have been prepared by a reaction of the oxidized MWNTs with S-(2-aminoethylthio)-2-thiopyridine hydrochloride. The obtained pythio-MWNTs nanocomposites formed stable floating monolayers at the air-water interface, which were transferred onto substrate surfaces by the Langmuir-Blodgett (LB) method. Compositions and morphologies of the LB films were characterized by absorption, Raman, X-ray photoelectron spectra as well as by scan electron microscopy and atomic force microscopy. These pythio-MWNTs LB films were then used as a support to immobilize hydrogenase (H(2)ase) to form bionanocomposite of pythio-MWNTs-H(2)ase. Cyclic voltammograms for indium tin oxide electrode covered with the pythio-MWNTs-H(2)ase films were investigated in both Ar and H(2) saturated 0.05 M KCl electrolyte solutions at pH from 4.0 to 9.0. A reversible redox couple of [4Fe-4S](2+/1+) clusters of H(2)ase was recorded when the pH value was 6.0 and 9.0, with reduction and oxidation potentials appearing at about -0.70 and -0.35 V vs Ag/AgCl, respectively. It was revealed that the H(2)ase was of high catalytic activity and strong stability in the LB films of pythio-MWNTs-H(2)ase. Hence, we suggested that the present bionanocomposites could be used as heterogeneous biocatalyst to catalyze reversible reaction between protons and H(2), resulting in potential applications in biohydrogen evolution and H(2) biofuel cells.
Assuntos
Enzimas Imobilizadas/química , Hidrogenase/química , Nanotubos de Carbono/química , Biocombustíveis , Técnicas Eletroquímicas , PiridinasRESUMO
Nafion-carbon nanotubes-viologen composites have been immobilized on glass carbon electrode surfaces. The mixtures of Nafion-carbon nanotubes could largely stabilize the viologen-modified films due to their strong adhesion on the electrode surface and the intermolecular electrostatic interaction between Nation (carbon nanotubes) and viologens. Voltammetric measurements revealed well reversible redox couples corresponding to the viologen groups. The potential differences DeltaEp and the product of De(1/2)C were closely dependant on the substituent groups of the viologens co-assembled.
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Light-sensitizer functionalized organic-inorganic hybrid materials have attracted much attention owing to their potential applications in the fields of optoelectronics, heterogeneous catalysis, sensors, and nanotechnology. Here, an interfacial self-assembly of zero-dimensional (0D) silica@multiporphyrin array nanohybrids and their 3D Langmuir-Blodgett (LB) films is reported. Photoactive tetrapyridylporphyrin (TPyP) was first assembled on the silica nanoparticles' surfaces via silane, substitution, and coordination reactions to produce nanoSiO2 @(Pd-TPyP)n hybrids. Then, the Cd2+ -nanoSiO2 @(Pd-TPyP)n monolayers and LB films were constructed on the CdCl2 subphase surface. These monolayers and LB films displayed stronger stability, as well as more uniform and closely packed nanoparticle arrays compared with those prepared on the pure water surface, owing to the formation of strong network-like Pd- and Cd-TPyP coordination units, which significantly enhanced the nanoparticles' interaction. Further, compared with that of the 0D nanoSiO2 @(Pd-TPyP)n hybrids, the degradation efficiency was nearly 20â times higher when the hybrids' LB films were used as light-sensitizers for the photocatalytic degradation of RhB. Finally, flexible photochromic devices were constructed by using the LB films sandwiched between two electrodes, which displayed a reversible photoinduced redox reaction of viologen together with a color change process. Because TPyP was strongly immobilized on the nanoparticles' surfaces and the particles were connected through the Py-Pd2+ -Py and Py-Cd2+ -Py coordination units with the 3D network-like architecture, the present nanohybrids and LB films had good stability and reusability.
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The topography of self-assembled viologen derivatives (VC(8)SH, VC(10)SH, HSC(8)VC(8)SH, and HSC(10)VC(10)SH) molecules on an octanethiol (C(8)) self-assembled monolayer (SAM) modified gold surface was measured using ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). We demonstrate here a novel matrix SAM appropriate for isolation of the viologen molecules. The C(8) was used for a matrix SAM, in which the VC(8)SH, VC(10)SH, HSC(8)VC(8)SH, and HSC(10)VC(10)SH were inserted at molecular lattice defects. The isolated single molecules of viologen derivatives inserted in the matrix SAM were observed as protrusions in STM topography using a constant current mode. We measured the topographic heights (VC(8)SH: 1.53 nm, VC(10)SH: 2.01 nm, HSC(8)VC(8)SH: 2.71 nm, and HSC(10)VC(10)SH: 3.3 nm) of the molecular protrusions using STM. Also, changes in the central axis of viologen molecules were observed as VC(8)SH (0.5-0.73 nm), VC(10)SH (0.4-0.74 nm), HSC(8)VC(8)SH (0.67-0.84 nm), and HSC(10)VC(10)SH (0.67-0.99 nm), respectively.