The promise of graphene-based transistors for democratizing multiomics studies.

As biological research has synthesized genomics, proteomics, metabolomics, and transcriptomics into systems biology, a new multiomics approach to biological research has emerged. Today, multiomics studies are challenging and expensive. An experimental platform that could unify the multiple omics approaches to measurement could increase access to multiomics data by enabling more individual labs to successfully attempt multiomics studies. Field effect biosensing based on graphene transistors have gained significant attention as a potential unifying technology for such multiomics studies. This review article highlights the outstanding performance characteristics that makes graphene field effect transistor an attractive sensing platform for a wide variety of analytes important to system biology. In addition to many studies demonstrating the biosensing capabilities of graphene field effect transistors, they are uniquely suited to address the challenges of multiomics studies by providing an integrative multiplex platform for large scale manufacturing using the well-established processes of semiconductor industry. Furthermore, the resulting digital data is readily analyzable by machine learning to derive actionable biological insight to address the challenge of data compatibility for multiomics studies. A critical stage of systems biology will be democratizing multiomics study, and the graphene field effect transistor is uniquely positioned to serve as an accessible multiomics platform.

Digital Biosensing by Foundry-Fabricated Graphene Sensors.

The prevailing philosophy in biological testing has been to focus on simple tests with easy to interpret information such as ELISA or lateral flow assays. At the same time, there has been a decades long understanding in device physics and nanotechnology that electrical approaches have the potential to drastically improve the quality, speed, and cost of biological testing provided that computational resources are available to analyze the resulting complex data. This concept can be conceived of as "the internet of biology" in the same way miniaturized electronic sensors have enabled "the internet of things." It is well established in the nanotechnology literature that techniques such as field effect biosensing are capable of rapid and flexible biological testing. Until now, access to this new technology has been limited to academic researchers focused on bioelectronic devices and their collaborators. Here we show that this capability is retained in an industrially manufactured device, opening access to this technology generally. Access to this type of production opens the door for rapid deployment of nanoelectronic sensors outside the research space. The low power and resource usage of these biosensors enables biotech engineers to gain immediate control over precise biological and environmental data.

Lectin- and Saccharide-Functionalized Nano-Chemiresistor Arrays for Detection and Identification of Pathogenic Bacteria Infection.

Improvement upon, and expansion of, diagnostic tools for clinical infections have been increasing in recent years. The simplicity and rapidity of techniques are imperative for their adoption and widespread usage at point-of-care. The fabrication and evaluation of such a device is reported in this work. The use of a small bioreceptor array (based on lectin-carbohydrate binding) resulted in a unique response profile, which has the potential to be used for pathogen identification, as demonstrated by Principal Component Analysis (PCA). The performance of the chemiresistive device was tested with Escherichia coli K12, Enterococcus faecalis, Streptococcus mutans, and Salmonella typhi. The limits of detection, based on concanavalin A (conA) lectin as the bioreceptor, are 4.7 × 10³ cfu/mL, 25 cfu/mL, 7.4 × 104 cfu/mL, and 6.3 × 10² cfu/mL. This shows that the detection of pathogenic bacteria is achieved with clinically relevant concentrations. Importantly, responses measured in spiked artificial saliva showed minimal matrix interference. Furthermore, the exploitation of the distinctive outer composition of the bacteria and selectivity of lectin-carbohydrate interactions allowed for the discrimination of bacterial infections from viral infections, which is a current and urgent need for diagnosing common clinical infections.

Quantifying Small Molecule Binding Interactions with DNA Nanostructures.

DNA nanostructures and hybrid DNA-protein materials are attractive solutions to many applications in biotechnology and material science because of their controllable molecule-level features. Critical to a complete description and characterization of these technologies is the quantification of binding affinity between DNA nanostructures and small molecules relevant to the application at hand. This protocols chapter described a series of experimental and in silico analyses that can be used to described and quantify ligand binding interactions between DNA nanostructures (DNA DX tiles), short double stranded DNA fragments, and arbitrary small molecules. The described methods include microscale thermophoresis, ligand completion assays, circular dichroism spectroscopy, and AutoDock simulations. The protocols use organophosphates and model chemical nerve agents as examples, but the methods described here are broadly applicable.

Enhancing Enzyme Activity and Immobilization in Nanostructured Inorganic-Enzyme Complexes.

Understanding the chemical and physical interactions at the interface of protein surfaces and inorganic crystals has important implications in the advancement of immobilized enzyme catalysis. Recently, enzyme-inorganic hybrid complexes have been demonstrated as effective materials for enzyme immobilization. The precipitation of phosphate nanocrystals in the presence of enzymes creates enzyme-Cu3(PO4)2·3H2O particles with high surface-to-volume ratios, enhanced activity, and increased stability. Here, we begin to develop a mechanistic understanding of enzyme loading in such complexes. Using a series of enzymes including horseradish peroxidase (HRP), a thermostable alcohol dehydrogenase (AdhD), diaphorase, catalase, glucose oxidase (GOx), and the protein bovine serum albumin (BSA), we identified a correlation between particle synthesis temperature, overall enzyme charge, and enzyme loading. The model enzyme HRP has a high predicted pI of ∼7.5 and maintains an overall positive charge under the synthesis conditions, phosphate buffer pH 7.4. HRP loading in HRP-Cu3(PO4)2 complexes was enhanced by 4.2-fold when synthesis was carried out at 37 °C in comparison with synthesis at 4 °C. HRP loading was further enhanced with synthesis at pH 8.0, correlating with a decrease in overall enzyme charge. Proteins with lower predicted pI values and negative overall charge (AdhD, pI of 5.6; diaphorase, pI of 6.8; GOx, pI of 5.2; catalase, pI of 6.9; and, BSA, pI of 5.7) exhibited higher enzyme loadings with 4 °C synthesis, 2.7-, 2.6-, 2.5-, 1.8-, and 1.7-fold protein loading enhancements, respectively. Using HRP as a model system, we also demonstrate that activity increased concomitantly with enzyme loading, and that particle nanostructure was minimally affected by synthesis temperature. Combined, the results presented here demonstrate the control of enzyme loading in enzyme-inorganic particles opening up new possibilities in enzyme and multienzyme catalysis.

DNA Nanostructure Sequence-Dependent Binding of Organophosphates.

Understanding the molecular interactions between small molecules and double-stranded DNA has important implications on the design and development of DNA and DNA-protein nanomaterials. Such materials can be assembled into a vast array of 1-, 2-, and 3D structures that contain a range of chemical and physical features where small molecules can bind via intercalation, groove binding, and electrostatics. In this work, we use a series of simulation-guided binding assays and spectroscopy techniques to investigate the binding of selected organophosphtates, methyl parathion, paraoxon, their common enzyme hydrolysis product p-nitrophenol, and double-stranded DNA fragments and DNA DX tiles, a basic building block of DNA-based materials. Docking simulations suggested that the binding strength of each compound was DNA sequence-dependent, with dissociation constants in the micromolar range. Microscale thermophoresis and fluorescence binding assays confirmed sequence-dependent binding and that paraoxon bound to DNA with Kd's between ∼10 and 300 µM, while methyl parathion bound with Kd's between ∼10 and 100 µM. p-Nitrophenol also bound to DNA but with affinities up to 650 µM. Changes in biding affinity were due to changes in binding mode as revealed by circular dichroism spectroscopy. Based on these results, two DNA DX tiles were constructed and analyzed, revealing tighter binding to the studied compounds. Taken together, the results presented here add to our fundamental understanding of the molecular interactions of these compounds with biological materials and opens new possibilities in DNA-based sensors, DNA-based matrices for organophosphate extraction, and enzyme-DNA technologies for organophosphate hydrolysis.

Mechanisms of Enhanced Catalysis in Enzyme-DNA Nanostructures Revealed through Molecular Simulations and Experimental Analysis.

Understanding and controlling the molecular interactions between enzyme substrates and DNA nanostructures has important implications in the advancement of enzyme-DNA technologies as solutions in biocatalysis. Such hybrid nanostructures can be used to create enzyme systems with enhanced catalysis by controlling the local chemical and physical environments and the spatial organization of enzymes. Here we have used molecular simulations with corresponding experiments to describe a mechanism of enhanced catalysis due to locally increased substrate concentrations. With a series of DNA nanostructures conjugated to horseradish peroxidase, we show that binding interactions between substrates and the DNA structures can increase local substrate concentrations. Increased local substrate concentrations in HRP(DNA) nanostructures resulted in 2.9- and 2.4-fold decreases in the apparent Michaelis constants of tetramethylbenzidine and 4-aminophenol, substrates of HRP with tunable binding interactions to DNA nanostructures with dissociation constants in the micromolar range. Molecular simulations and kinetic analysis also revealed that increased local substrate concentrations enhanced the rates of substrate association. Identification of the mechanism of increased local concentration of substrates in close proximity to enzymes and their active sites adds to our understanding of nanostructured biocatalysis from which we can develop guidelines for enhancing catalysis in rationally designed systems.

MEMS-based shear characterization of soft hydrated samples.

We have designed, fabricated, calibrated and tested actuators for shear characterization to assess microscale shear properties of soft substrates. Here we demonstrate characterization of dry silicone and hydrated polyethelyne glycol. Microscale tools, including atomic force microscopes and nanoindenters, often have limited functionality in hydrated environments. While electrostatic comb-drive actuators are particularly susceptible to moisture damage, through chemical vapor deposition of hexamethyldisiloxane, we increase the hydrophobicity of our electrostatic devices to a water contact angle 90 ± 3°. With this technique we determine the effective shear stiffness of both dry and hydrated samples for a range of soft substrates. Using computational and analytical models, we compare our empirically determined effective shear stiffness with existing characterization methods, rheology and nanoindentation, for samples with shear moduli ranging from 5-320 kPa. This work introduces a new approach for microscale assessment of synthetic materials that can be used on biological materials for basic and applied biomaterials research.

Electronic detection of microRNA at attomolar level with high specificity.

Small RNA (19-23 nucleotides) molecules play an important role in gene regulation, embryonic differentiation, hematopoiesis, and a variety of cancers. Here, we present an ultrasensitive, extremely specific, label-free, and rapid electronic detection of microRNAs (miRNAs) using a carbon nanotubes field-effect transistor functionalized with the Carnation Italian ringspot virus p19 protein biosensor. miRNA-122a was chosen as the target, which was first hybridized to a probe molecule. The probe-miRNA duplex was then quantified by measuring the change in resistance of biosensor resulting from its binding to p19, which selects 21-23 bp RNA duplexes in a size-dependent but sequence-independent manner. The biosensor displayed a wide dynamic range up to 10(-14) M and was able to detect as low as 1 aM miRNA in the presence of a million-fold excess of total RNA, paving the way for simple, point-of-care, low-cost early detection of miRNA as a biomarker in diagnosis of many diseases, including cancer.

Carbon nanotubes-based label-free affinity sensors for environmental monitoring.

Nanostructures, such as nanowires, nanobelts, nanosprings, and nanotubes, are receiving growing interest as transducer elements of bio/chemical sensors as they provide high sensitivity, multiplexing, small size, and portability. Single-walled carbon nanotubes (SWNTs) are one such class of nanostructure materials that exhibit superior sensing behavior due to its large-surface carbon atoms that are highly responsive to surface adsorption events. Further, their compatibility with modern microfabrication technologies and facile functionalization with molecular recognition elements make them promising candidates for bio/chemical sensors applications. Here, we review recent results on nanosensors based on SWNTs modified with biological receptors such as aptamers, antibodies, and binding proteins, to develop highly sensitive, selective, rapid, and cost-effective label-free chemiresistor/field-effect transistor nanobiosensors for applications in environmental monitoring.

Facile approaches to build ordered amphiphilic tris(phthalocyaninato) europium triple-decker complex thin films and their comparative performances in ozone sensing.

Solution processed thin films of an amphiphilic tris(phthalocyaninato) rare earth triple-decker complex, Eu(2)[Pc(15C5)(4)](2)[Pc(OC(10)H(21))(8)], have been prepared from three different methods: self-assembly (SA) annealed in solvent vapor, quasi-Langmuir-Shäfer (QLS) and drop casting methods. In particular, we successfully developed a simple QLS process for fabricating ordered multilayers with a good thickness control. The films prepared from three different methods were characterized by a wide range of methods including electronic absorption spectra, IR, X-ray diffraction, atomic force microscopy (AFM), and current-voltage (I-V) measurements. J-type aggregates have been formed with the increasing degree of order of molecular stacking Cast < QLS < SA films. Moreover, the gas sensing behavior of the three types of films was investigated towards ozone in the 8-300 ppb range. Unexpectedly good sensitive, stable and reproducible responses to O(3) gas are obtained for these kinds of ultra-thin solution processed films in a fast response/recovery cycle of only 1/4 min. The response of Eu(2)[Pc(15C5)(4)](2)[Pc(OC(10)H(21))(8)] films is linearly correlated to the ozone concentration. The interaction between the Eu(2)[Pc(15C5)(4)](2)[Pc(OC(10)H(21))(8)] films and different ozone concentrations was found to follow first-order kinetics. Strikingly, QLS films showed the most stable response and the largest average sensor response rate constant among the three types of films.

Novel pathway to synthesize unsymmetrical 2,3,9,10,16,17,23-heptakis(alkoxyl)-24-mono(dimethylaminoalkoxyl)phthalocyanines.

A new pathway by means of transetherification has been developed to synthesize novel unsymmetrical 2,3,9,10,16,17,23-heptakis(alkoxyl)-24-mono(dimethylaminoalkoxyl)phthalocyanine compounds. Cyclic tetramerization of 4,5-di(alkoxyl)phthalonitrile in refluxing dimethylamino-alcohol with high boiling point such as dimethylaminoethanol (DMAE) and 1-dimethylamino-2-propanol in the presence of lithium and pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile followed by treatment with acetic acid led to the isolation of a series of unsymmetrical metal free 2,3,9,10,16,17,23-heptakis(alkoxyl)-24-mono(dimethylaminoalkoxyl)phthalocyanine compounds H(2){Pc(OR)(7)[OR'N(CH(3))(2)]} [R = C(4)H(9), C(5)H(11), C(8)H(17) and R' = C(2)H(4); R = C(4)H(9) and R' = CH(CH(3))CH(2)] (1-4). Metal insertion into unsymmetrical metal free phthalocyanines (Pc's) using Cu(OAc)(2)·H(2)O in dimethylformamide (DMF) at 140 °C easily afforded corresponding unsymmetrical phthalocyaninato copper complexes Cu{Pc(OR)(7)[OR'N(CH(3))(2)]} (5-8) in good yields. These novel unsymmetrical phthalocyanine compounds have been characterized by a series of spectroscopic methods including (1)H NMR, electronic absorption, IR, and mass spectroscopy in addition to elemental analysis. Their electrochemistry was also studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The present result will be helpful for designing and preparing unsymmetrical phthalocyanines with potential applications in dye-sensitized solar cells.

Bis[1,4,8,11,15,18,22,25-octa(butyloxyl)phthalocyaninato] rare earth double-decker complexes: synthesis, spectroscopy, and molecular structure.

Homoleptic octa-alpha-substituted bis(phthalocyaninato) rare earth double-deckers HM(III)[Pc(alpha-OC(4)H(9))(8)](2) [M = Eu (1), Y (2); Pc(alpha-OC(4)H(9))(8) = 1,4,8,11,15,18,22,25-octa(butyloxyl)phthalocyanine] have been prepared by treating the metal-free phthalocyanine H(2)Pc(alpha-OC(4)H(9))(8) with the corresponding M(acac)(3).nH(2)O (acac = acetylacetonate) in the presence of organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and benzo-18-crown-6/benzo-15-crown-5 in refluxing n-octanol. To the best of our knowledge, it is the first example of homoleptic non-peripherally octa(alkoxyl)-substituted bis(phthalocyaninato) rare earth complexes. Comparative studies on a series of reactions reveal the key role of DBU as catalyst and crown ether as template in the formation of homoleptic rare earth double-decker complexes with structurally highly deformed non-peripherally octa(butyloxy)-substituted phthalocyanine ligand. The molecular structure of complex 1 has been determined by single-crystal X-ray diffraction analysis. The metal center is octa-coordinated by the isoindole nitrogen atoms of the two phthalocyaninato ligands, forming a distorted square antiprism. Despite the extremely non-planar saddle conformation employed by metal free H(2)Pc(alpha-OC(4)H(9))(8) molecule, both the phthalocyanine rings in HEu(III)[Pc(alpha-OC(4)H(9))(8)](2) (1) adopt a conformation that is domed toward the europium center, similar to corresponding unsubstituted or beta-substituted bis(phthalocyaninato) analogues. These two bis(phthalocyaninato) rare earth double-deckers have also been characterized by a wide range of spectroscopic methods including MS, (1)H NMR, UV-vis, IR, and EPR. Structural and spectroscopic studies reveal that the pi-pi interaction between the two Pc(alpha-OC(4)H(9))(8) rings is weaker than that for the corresponding unsubstituted or beta-substituted bis(phthalocyaninato) analogues.

Nonperipherally octa(butyloxy)-substituted phthalocyanine derivatives with good crystallinity: effects of metal-ligand coordination on the molecular structure, internal structure, and dimensions of self-assembled nanostructures.

To investigate the effects of metal-ligand coordination on the molecular structure, internal structure, dimensions, and morphology of self-assembled nanostructures, two nonperipherally octa(alkoxyl)-substituted phthalocyanine compounds with good crystallinity, namely, metal-free 1,4,8,11,15,18,22,25-octa(butyloxy)phthalocyanine H(2)Pc(alpha-OC(4)H(9))(8) (1) and its lead complex Pb[Pc(alpha-OC(4)H(9))(8)] (2), were synthesized. Single-crystal X-ray diffraction analysis revealed the distorted molecular structure of metal-free phthalocyanine with a saddle conformation. In the crystal of 2, two monomeric molecules are linked by coordination of the Pb atom of one molecule with an aza-nitrogen atom and its two neighboring oxygen atoms from the butyloxy substituents of another molecule, thereby forming a Pb-connected pseudo-double-decker supramolecular structure with a domed conformation for the phthalocyanine ligand. The self-assembling properties of 1 and 2 in the absence and presence of sodium ions were comparatively investigated by scanning electronic microscopy (SEM), spectroscopy, and X-ray diffraction techniques. Intermolecular pi-pi interactions between metal-free phthalocyanine molecules led to the formation of nanoribbons several micrometers in length and with an average width of approximately 100 nm, whereas the phthalocyaninato lead complex self-assembles into nanostructures also with the ribbon morphology and micrometer length but with a different average width of approximately 150 nm depending on the pi-pi interactions between neighboring Pb-connected pseudo-double-decker building blocks. This revealed the effect of the molecular structure (conformation) associated with metal-ligand (Pb-N(isoindole), Pb-N(aza), and Pb-O(butyloxy)) coordination on the dimensions of the nanostructures. In the presence of Na(+), additional metal-ligand (Na-N(aza) and Na-O(butyloxy)) coordination bonds formed between sodium atoms and aza-nitrogen atoms and the neighboring butyloxy oxygen atoms of two metal-free phthalocyanine molecules cooperate with the intrinsic intermolecular pi-pi interactions, thereby resulting in an Na-connected pseudo-double-decker building block with a twisted structure for the phthalocyanine ligand, which self-assembles into twisted nanoribbons with an average width of approximately 50 nm depending on the intertetrapyrrole pi-pi interaction. This is evidenced by the X-ray diffraction analysis results for the resulting aggregates. Twisted nanoribbons with an average width of approximately 100 nm were also formed from the lead coordination compound 2 in the presence of Na(+) with a Pb-connected pseudo-double-decker as the building block due to the formation of metal-ligand (Na-N(aza) and Na-O(butyloxy)) coordination bonds between additionally introduced sodium ions and two phthalocyanine ligands of neighboring pseudo-double-decker building blocks.

Design, synthesis, characterization, and OFET properties of amphiphilic heteroleptic tris(phthalocyaninato) europium(III) complexes. The effect of crown ether hydrophilic substituents.

Two amphiphilic heteroleptic tris(phthalocyaninato) europium complexes with hydrophilic crown ether heads and hydrophobic octyloxy tails [Pc(mCn)(4)]Eu[Pc(mCn)(4)]Eu[Pc(OC(8)H(17))(8)] [m = 12, n = 4, H(2)Pc(12C4)(4) = 2,3,9,10,16,17,23,24-tetrakis(12-crown-4)phthalocyanine; m = 18, n = 6, H(2)Pc(18C6)(4) = 2,3,9,10,16,17,23,24-tetrakis(18-crown-6)phthalocyanine; H(2)Pc(OC(8)H(17))(8) = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine] (1, 2) were designed and prepared from the reaction between homoleptic bis(phthalocyaninato) europium compound [Pc(mCn)(4)]Eu[Pc(mCn)(4)] (m = 12, n = 4; m = 18, n = 6) and metal-free H(2)Pc(OC(8)H(17))(8) in the presence of Eu(acac)(3).H(2)O (Hacac = acetylacetone) in boiling 1,2,4-trichlorobenzene. These novel sandwich triple-decker complexes were characterized by a wide range of spectroscopic methods and electrochemically studied. With the help of the Langmuir-Blodgett technique, these typical amphiphilic triple-decker complexes were fabricated into organic field effect transistors (OFET) with top contact configuration on bare SiO(2)/Si substrate, hexamethyldisilazane-treated SiO(2)/Si substrate, and octadecyltrichlorosilane (OTS)-treated SiO(2)/Si substrate, respectively. The device performance is revealed to be dependent on the species of crown ether substituents and substrate surface treatment. OFETs fabricated from the triple decker with 12-crown-4 hydrophilic substituents, 1, allow the hole transfer in the direction parallel to the aromatic phthalocyanine rings. In contrast, the devices of a triple-decker compound containing 18-crown-6 as hydrophilic heads, 2, transfer holes in a direction along the long axis of the assembly composed of face-to-face aggregated triple-decker molecules, revealing the effect of molecular structure, specifically the crown ether substituents on the film structure and OFET functional properties. The carrier mobility for hole as high as 0.33 cm(2) V(-1) s(-1) and current modulation of 7.91 x 10(5) were reached for the devices of triple-decker compound 1 deposited on the OTS-treated SiO(2)/Si substrates, indicating the effect of substrate surface treatment on the OFET performance due to the improvement on the film quality as demonstrated by the atomic force microscope investigation results.

Morphology-controlled self-assembled nanostructures of 5,15-di[4-(5-acetylsulfanylpentyloxy)phenyl]porphyrin derivatives. Effect of metal-ligand coordination bonding on tuning the intermolecular interaction.

Novel metal-free 5,15-di[4-(5-acetylsulfanylpentyloxy)phenyl]porphyrin H2[DP(CH3COSC5H10O)2P] (1) and its zinc congener Zn[DP(CH3COSC5H10O)2P] (2) were designed and synthesized. Single-crystal X-ray diffraction (XRD) analysis confirmed the tetrapyrrole nature of these two compounds, revealing the existence of metal-ligand coordination bond between the carbonyl oxygen in the aryloxy side chain of meso-attached phenyl group in the porphyrin molecule with the zinc center of neighboring porphyrin molecule in the crystal structure of 2. This intermolecular Zn-O coordination bond induces the formation of a supramolecular chain structure in which the porphyrinato zinc moieties are arranged in a "head-to-tail" mode (J-aggregate), which is in contrast to a "face-to-face" stacking mode (H-aggregate) in the supramolecular structure formed depending on the C-H...pi interaction in the crystal of 1. Their self-assembling properties in MeOH and n-hexane were comparatively investigated by scanning electronic microscopy and XRD technique. Intermolecular pi-pi interaction of metal-free porphyrin 1 leads to the formation of hollow nanospheres and nanoribbons in MeOH and n-hexane, respectively. In contrast, introduction of additional Zn-O coordination bond for porphyrinato zinc complex 2 induces competition with intermolecular pi-pi interaction, resulting in nanostructures with nanorod and hollow nanosphere morphology in MeOH and n-hexane. The IR and XRD results clearly reveal the presence and absence of such metal-ligand coordination bond in the nanostructures formed from porphyrinato zinc complex 2 and metal-free porphyrin 1, respectively, which is further unambiguously confirmed by the single-crystal XRD analysis result for both compounds. Electronic absorption spectroscopic data on the self-assembled nanostructures reveal the H-aggregate nature in the hollow nanospheres and nanoribbons formed from metal-free porphyrin 1 due to the pi-pi intermolecular interaction between porphyrin molecules and J-aggregate nature in the nanorods and hollow nanospheres of 2 depending on the dominant metal-ligand coordination bonding interaction among the porphyrinato zinc molecules. The present result appears to represent the first effort toward controlling and tuning the morphology of self-assembled nanostructures of porphyrin derivatives via molecular design and synthesis through introduction of metal-ligand coordination bonding interaction. Nevertheless, availability of single crystal and molecular structure revealed by XRD analysis for both porphyrin derivatives renders it possible to investigate the formation mechanism as well as the molecular packing conformation of self-assembled nanostructures of these typical organic building blocks with large conjugated system in a more confirmed manner.

Effect of peripheral hydrophobic alkoxy substitution on the organic field effect transistor performance of amphiphilic tris(phthalocyaninato) europium triple-decker complexes.

A series of four amphiphilic heteroleptic tris(phthalocyaninato) europium complexes with different lengths of hydrophobic alkoxy substituents on one outer phthalocyanine ligand [Pc(15C5)4]Eu[Pc(15C5)4]Eu[Pc(OCnH(2n+1))8] (n = 4, 6, 10,12) (1, 2, 4, and 5) was designed and prepared. Their film forming and organic field effect transistor properties have been systematically studied in comparison with analogous [Pc(15C5)4]Eu[Pc(15C5)4]Eu[Pc(OC8H17)8] (3). Experimental results showed that all these typical amphiphilic sandwich triple-decker molecules have been fabricated into highly ordered films by the Langmuir-Blodgett (LB) technique, which displays carrier mobility in the direction parallel to the aromatic phthalocyanine rings in the range of 0.0032-0.60 cm2 V(-1) s(-1) depending on the length of the hydrophobic alkoxy substituents. This is rationalized on the basis of comparative morphology analysis results of the LB films by the atomic force microscopy technique.