Narrow Results

Lead iodide (PbI${}_2)$ nanoparticles in silica have been synthesized using the sol–gel method. The aqueous method of synthesis has been used for undoped PbI₂ nanoparticles. These nanoparticles have been stabilized using thioglycerol acting as the capping agent. The narrow-sized PbI₂ nanoparticles have been obtained, which are characterized by size-dependent properties. The PbI₂ nanoparticles have been characterized and their properties have been investigated by using various experimental techniques like Ultraviolet–Visible (UV–Vis) Absorption Spectroscopy, X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Photoluminescence (PL), Atomic Force Microscopy (AFM), etc. The lateral dimension of PbI₂ nanoparticles in silica varies from 9 Å to 27 Å. PbI₂ thin films were deposited on silicon wafers by using the dip coating method and analyzed by using various characterization techniques like Scanning Electron Microscopy (SEM), Energy Dispersive Analysis by X-rays (EDAX), Mapping, etc. The aim of this work is to synthesize PbI₂ nanoparticles with a size less than or comparable to the Bohr diameter of the exciton. The characterization results showed that the cluster size increases with the increasing film thickness and by the heat treatment in air atmosphere. The PbI₂ nanocrystals embedded in silica films have been studied in this paper. The PbI₂ nanoparticles and the PbI₂ sol–gel thin films can be used in optoelectronic device applications and chemical industrial applications. To the best of our knowledge, there are no studies on the synthesis of PbI₂ nanoparticles in silica using the sol–gel route and on the preparation of PbI₂ thin films using the dip coating method.

Flexible polymer nanocomposite composed of organic methylcellulose (MC) and semiconducting titanium dioxide (TiO₂) films were successfully prepared. The energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) recorded the structure characteristics of the films, proving that MC/TiO₂ nanocomposite were successfully synthesized. The EDX showed that this composite was composed of (28.55% C, 50.90% O, and 20.55% Ti), which displayed the chemical composition of MC/TiO₂. Moreover, the scanning electron microscope (SEM) shows the TiO₂ nanoparticles are loaded homogenously in the nanocomposite films. With increasing the TiO₂, the FTIR intensity of most peaks gradually decreased which may be attributed to that titanium dioxide nanoparticles (TiO₂ NPs) were formed on the methylcellulose (MC). The UV spectrophotometer records the data of absorption (A) for the MC and MC/TiO₂ films between 200nm and 1100nm at the ambient temperature. Using Tauc’s relation, the linear/nonlinear optical characteristics of MC and MC/TiO₂ films were computed. By mixing MC with 2%, 4%, and 6% TiO₂, the Urbach energy of the MC is enhanced from 1.77eV to 1.85, 2.02, and 2.34eV, correspondingly, while the TiO₂ reduced the energy gap of MC from 5.17eV to 3.59, 3.52, or 3.43eV. Moreover, the carbon cluster increased from 44 for MC to 92, 95, and 101 for MC mixed by 2%, 4%, and 6% TiO₂. This study found the MC/TiO₂ hybrid films can potentially be used as optical materials for flexible electronic devices.

Nanodiamonds (NDs) have unique optical and mechanical characteristics, surface chemistry, extensive surface area and biocompatibility, and they are nontoxic, rendering them suitable for a diverse range of applications. Recently, NDs have received significant attention in nano-biomedical engineering. This review discusses the recent advancement of NDs’ biomedical engineering, historical background, basic introduction to nanoparticles and development. We summarize NDs’ synthesis technique, properties and applications. Two methodologies are used in ND synthesis: bottom-up and top-down. We cover synthesis methods, including detonation, ball milling, laser ablation, chemical vapor deposition (CVD) and high pressure and high temperature (HPHT); discuss the properties of NDs, such as fluorescence and biocompatibility. Due to these properties, NDs have potential applications in biomedical engineering, including bioimaging, biosensing, drug delivery, tissue engineering and protein mimics. Further, it provides an outlook for future progress, development and application of NDs in biological and biomedical areas.

The synthesis and visible near-IR region absorption spectra of an 1,6,10,15,19,24,28,33-octaalkylnaphthalocyanine and examples of 3,4,12,13,21,22,30,31-octaalkyl and 3,4,12,13,21,22,30,31-octaalkoxy-2,3-naphthalocyanines are reported.

The synthesis and characterization of three monomeric aluminum porphycenes with anionic or σ-bonded axial ligands is reported. The investigated compounds are represented as (EtioPc)Al(CH³) and (EtioPc)AlX where EtioPc represents the dianion of etioporphycene and X = Cl⁻ or OH⁻. Each synthesized complex was characterized by mass spectrometry. ¹H NMR, IR and UV-visible spectroscopies as well as by electrochemistry. Comparisons are made between the properties of complexes in the aluminum etioporphycene series and related chloro- or methyl σ-bonded Al(III) porphyrins containing octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP) macrocycles. Comparisons are also made between the currently investigated compounds and a previously reported Al(III) μ-oxo dimer, [(EtioPc)Al]₂O. In addition, the crystal and molecular structure of (EtioPc)Al(CH₃) was determined by X-ray diffraction. The molecular structure of this methyl-σ-bonded aluminum etioporphycene provides the first structural data for an aluminum porphycene compound. The aluminum(III) atom in (EtioPc)Al(CH₃) is pentacoordinated and is located 0.54 Å from the plane of the four N-nitrogens.

Unsymmetric push-pull phthalocyanines with a high degree of conjugation achieved by introducing π-delocalized electron substituents were synthesized by statistical condensation of two different diiminoisoindolines. The characterization and spectroscopic properties of these push-pull phthalocyanines are described. These compounds are targeted for the study of their second-order non-linear optical responses.

The synthesis and characterization of oxaporphyrins (OTPP and O₂TPP) containing one and two furan rings in place of pyrrole and a mixed oxathiaporphyrin (OSTPP) is reported. Spectroscopic and electrochemical studies reveal that oxaporphyrins exhibit optical and emission characteristics closer to the parent H₂TPP, while their electrochemical behaviour parallels that reported for mono and dithiaporphyrins. However the characteristics of the mixed oxathia derivative resemble that of monothiaporphyrin. Protonation studies reveal weaker resonance interaction between the β-hydrogens and meso-phenyl substituents in sharp contrast to thiaporphyrins. The reduction potentials for OSTPP and O₂TPP indicate stabilization and destabilization of their LUMOs relative to the parent H₂TPP in the ground and excited states, respectively.

The synthesis, characterization and crystal structure of the octanitro-substituted porphyrin 5,10,15,20-tetrakis(3,5-dinitrophenyl)porphyrin, H₂T(3,5-DNP)P, are described. The solid state structure has two porphyrins in the unit cell with eight pyridine solvates and is made up from columnar arrays of the porphyrins. X-ray crystal structure data: monoclinic, space group P1 2₁/n1, a = 14.9996(9) Å, b = 8.2489(5) Å, c = 24.818(2) Å, α = 90 °, β = 104.172(1) °, γ = 90 °, V = 2977.3(3) ų, d_calc = 1.440 g m^-3, Z = 2.

The synthesis, spectroscopic and electrochemical properties of the Lu(oepz)₂ (oepz ≡ 2,3,7,8,12,13,17,18-octakis(ethyl)-5,10,15,20-porphyrazinato) complex are reported. The complex, as inferred from UV-vis spectra recorded at different concentrations, strongly aggregates in solution, the most likely association mode being dimerization. The complex shows a weak near-IR absorption (λ_max = 834 nm) that is considerably blue-shifted compared with the near-IR absorption of bis(π-radical) lutetium analogues. The Lu(oepz)₂ neutral species is electrochemically stable between 0.73 and -0.98 V (vs Ag/AgCl), which is the largest range of stability for neutral lutetium di- tetrapyrrole complexes. Lu(oepz)₂ shows excellent Type II photodynamic activity, as indicated by the value of the singlet oxygen generation quantum yield φ_Δ of 0.94 obtained by comparison with meso-tetraphenylporphyrin.

A strategy for increasing the yield of long-lived photoinduced charge separation in artificial photosynthetic reaction centers which is based on multiple electron transfer pathways operating in parallel has been investigated. Excitation of the porphyrin moiety of a carotenoid (C)–porphyrin (P)–naphthoquinone (Q) molecular triad leads to the formation of a charge-separated state C^·+–P–Q^·− with an overall quantum yield of 0.044 in benzonitrile solution. Photoinduced electron transfer from the porphyrin first excited singlet state gives C–P^·+–Q^·− with a quantum yield of ~1.0. However, electron transfer from the carotenoid to the porphyrin radical cation to form the final state does not compete well with charge recombination of C–P^·+–Q^·−, reducing the yield. The related pentad C₃–P–Q features carotenoid, porphyrin and quinone moieties closely related to those in the triad. Excitation of this molecule gives a C^·+–P(C₂)–Q^·− state with a quantum yield of 0.073. The enhanced yield is ascribed to the fact that three electron donation pathways operating in parallel compete with charge recombination. The yield does not increase by the statistically predicted factor of three owing to small differences in thermodynamic driving force between the two compounds.

Methyl protopyropheophorbides-a/d were prepared by modification of readily available chlorophyll-a. The key step was oxidation of 13¹-oxo-chlorin to the corresponding porphyrin, and 2,3-dichloro-5,6-dicyano-p-benzoquinone was effective for 17,18-dehydrogenation. A reduction in oxidation potential of the chlorin was necessary for the oxidation. Facile oxidation was achieved by insertion of zinc as the central metal, reduction of the 13-carbonyl group and/or aggregation by high concentration. The synthetic 13¹-oxo-porphyrins had vinyl and formyl groups at the 3-position. These groups were very reactive in the molecule and selectively converted to other functional groups.

Porphyrin-centered star-shaped polymers were synthesized through living cationic ring-opening polymerization of 2-methyl-2-oxazoline employing tetra(p-chloromethylphenyl)porphyrin (CMPP) and its zinc complex as initiators. The polymers were characterized by GPC, ¹H NMR and UV-vis and their properties were examined by fluorescence quenching.

Five novel long-chain-substituted porphyrin derivatives, tetrakis(3,4-dialkylphenyl)porphyrins (abbreviated as (C_n)₈TPPH₂ (n = 8, 12, 18), (C₁₈)₈TPPCu and (C₁₈)₈TPPNi), were synthesized and their mesomorphism was investigated. It was found that the (C_n)₈TPPH₂ (n = 8, 12), derivatives are isotropic liquids at room temperature and that each of the (C₁₈)₈TPPM (M≡H₂, Cu, Ni) derivatives has two liquid crystal phases M₁ and M₂ and two unidentified phases X₁ and X₂. It was revealed by X-ray studies that the M₂ phase is a discotic lamellar (DL) phase. Interestingly, these porphyrin derivatives exhibit not a columnar but a lamellar mesophase, even though they have a disk-like central core with eight alkyl chains in the surroundings.

Octakis(alkoxymethyl) cobalt phthalocyanines with relatively short side chains were synthesized which exhibited no thermotropic liquid crystalline behaviour. The final products as well as the intermediates have been characterized by proton magnetic resonance, infrared and electron spectra and elemental analysis. Cyclic voltammograms were measured for octakis(alkoxymethyl) cobalt phthalocyanines in order to examine their electron transfer properties. The electron transfer properties of octakis (alkoxymethyl) cobalt phthalocyanines depend on the kind and number of substituents and are due to the interaction between the phthalocyanine ring, the central metal which is influenced by the conjugated π electron current of the porphyrazine ring.

Common methods available for the preparation of useful porphyrins from naturally derived heme and by total synthesis from monopyrroles are presented. Such porphyrins can be used for numerous reactivity and structural modification studies of the type which will be presented in minisymposia (including that entitled ‘Syntheses and Chemistry of Porphyrins’) at the First International Conference on Porphyrins and Phthalocyanines (ICPP-1).

This paper provides a review of synthesis of the phthalocyanines containing various macrocycles at the peripheral position of the benzene rings. They are expected to be suitable to change the chemical and physical properties toward the need of technologycal applications. In addition, transition and alkali metal phthalocyanine complexes especially rare-earth bis phthalocyanines, are object of intense investigations for their unique optical and electrochemical properties. The methodology of synthesis, purification and yield varies the structural designation which is restricted and depends on the starting compounds.

An easy synthesis of phthalocyaninatotitanium(IV) compounds substituted with bidentate ligands in the axial position is described. Using strongly chelating oxygen or sulfur donor ligands, the reaction of PcTiO with chelating agents leads to the formation of PcTiX complexes with X ≡ oxalate , catecholate , dithiocatecholate , 2,3-dihydroxynaphthalene and other functionalized catechols (2c–2h). The new compounds possess an enhanced solubility in comparison to PcTiO.

The four compounds in the series from chloro[subphthalocyaninato]boron(III) to chlo-ro[subnaphthalocyaninato]boron(III) were synthesized in a one-pot reaction. To obtain a more soluble set of compounds, the mixture was then reacted with the sodium salt of trihexylsilanol. This mixture was separated by chromatography to provide trihexylsiloxy[subphthalocyaninato]boron(III), trihexylsiloxy[SubN₁P₂]boron(III), trihexylsiloxy[SubN₂P₁]boron(III) and trihexylsiloxy[subnaphthalocyaninato]boron(III). These compounds were characterized by ¹HNMR, EI-MS and UV-vis. They show interesting spectral features in the visible region.

The four compounds in the series from chloro[subphthalocyaninato]boron(III) to chloro[subnaphthalocyaninato]boron (III) where synthesized in a one-pot reaction. To obtain a more soluble set of compounds, the mixture was then reacted with the sodium salt of trihexylsilanol. This mixture was separated by chromatography to provide trihexylsiloxy[subphthalocyaninato]boron(III), trihexylsiloxy[SubN₁P₂]boron(III), trihexylsiloxy[SubN₂P₁]boron(III) and trihexylsiloxy[subnaphthalocyaninato]boron(III). These compounds were characterized by ¹H NMR, EI-MS and UV-vis. They show interesting spectral features in the visible region.

New metal-free 5 and metallophthalocyanines 6-11(M = Cu, Ni, Co, Pb, Zn) fused in peripheral positions with four 24-membered tetraoxatetraaza macrocycles were prepared by cyclotetramerization of 24,25-dicyano-4,10,13,17-tetra(toluene-p-sulfonyl)-1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22-didicontinehydrobenzo[y][3,9,12,18]tetraaza[1,7,16,22]tetraoxatetradicontine in the presence of the corresponding metal salt or a strong organic base. While the N-tosylated derivatives of the phthalocyanines are soluble in common organic solvents, the detosylated derivative of copper phthalocyaninate is soluble in water. The aggregation properties of the phthalocyanines were also investigated as a function of concentration, solvent and oxidative medium. The new compounds are characterized by a combination of elemental analysis and ¹H NMR, ¹³C NMR, IR, UV-vis and MS spectral data.