Dye Assembly Research Articles

Disassembly of Dimeric Cyanine Dye Supramolecular Assembly by Tetramolecular G-quadruplex Dependence on Linker Length and Layers of G-quartet.

Cyanine dyes have been widely applied in various biological systems owing to their specific photochemical properties. Assembly and disassembly process of cyanine dyes were constructed and regulated by special biomolecules. In this paper, dimeric cyanine dyes with different repeat units (oligo-oxyethylene) in linker (TC-Pn) (n = 3–6) were found to form H-aggregates or mixture aggregates in PBS. These aggregates could be disassembled into dimer and/or monomer by (TGnT) tetramolecular G-quadruplexes (n = 3–6, 8), which were affected by the linker length of dimeric cyanine dyes and layers of G-quartets. The 1H-NMR titration results suggest that the binding mode of dimeric cyanine dye with TGnT might be on both ends—stacking like a clip. This binding mode could clearly explain that matching structures between dimeric cyanine dyes and TGnT quadruplexes could regulate the disassembly properties of aggregates. These results could provide clues for the development of highly specific G-quadruplex probes.

A comparative study of assembly and disassembly process of dimeric and monomeric cyanine dyes with DNA templates

Cyanine dyes have attracted more and more interest due to their controllable assembly and disassembly process with biomolecular templates. The self-assembly of cyanine dye not only depend on the environment, but also on their structures. Here, we report assembly and disassembly of two cyanine dyes, a dimeric cyaine dye (TC-P4) and its corresponding monomer (TC). In PBS, these dyes could form aggregates. The parallel c-myc G-quadruplex as a template causes the transformation of TC-P4 from H-aggregates to dimer and monomer; while duplex and single-stranded DNAs could not. The interaction between these DNAs motifs and TC could all induce the appearance of monomer band. Parallel c-myc G-quadruplex could enhance the fluorescence intensity of TC-P4 and TC. The self-assembly and disassembly of TC and TC-P4 could be regulated and used as probes for G-quadruplex recognition from duplex and single-stranded DNAs in solution.

The Versatile SALSAC Approach to Heteroleptic Copper(I) Dye Assembly in Dye-Sensitized Solar Cells

Surface-bound heteroleptic copper(I) dyes [Cu(Lanchor)(Lancillary)]+ are assembled using the “surfaces-as-ligands, surfaces as complexes” (SALSAC) approach by three different procedures. The anchoring and ancillary ligands chosen are ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)-bis(4,1-phenylene))bis(phosphonic acid) (3) and 4,4′-bis(4-iodophenyl)-6,6′-diphenyl-2,2′-bipyridine (4), respectively. In the first SALSAC procedure, the FTO/TiO2 electrode is functionalized with 3 in the first dye bath, and then undergoes ligand exchange with the homoleptic complex [Cu(4)2][PF6] to give surface-bound [Cu(3)(4)]+. In the second method, the FTO/TiO2 electrode functionalized with 3 is immersed in a solution containing a 1:1 mixture of [Cu(MeCN)4][PF6] and 4 to give surface-anchored [Cu(3)(4)]+. In the third procedure, the anchor 3, copper(I) ion and ancillary ligand 4 are introduced in a sequential manner. The performances of the DSSCs show a dependence on the dye assembly procedure. The sequential method leads to the best-performing DSSCs with the highest values of JSC (7.85 and 7.73 mA cm−2 for fully masked cells) and overall efficiencies (η = 2.81 and 2.71%, representing 41.1 and 39.6% relative to an N719 reference DSSC). Use of the 1:1 mixture of [Cu(MeCN)4][PF6] and 4 yields DSSCs with higher VOC values but lower JSC values compared to those assembled using the sequential approach; values of η are 2.27 and 2.29% versus 6.84% for the N719 reference DSSC. The ligand exchange procedure leads to DSSCs that perform relatively poorly. The investigation demonstrates the versatile and powerful nature of SALSAC in preparing dyes for copper-based DSSCs, allowing the photoconversion efficiency of dye to be optimized for a given dye. The SALSAC strategy provides alternative hierarchical strategies where the isolation of the homoleptic [Cu(Lancillary)2]+ is difficult or time-consuming; stepwise strategies are more atom-economic than ligand exchange involving the homoleptic [Cu(Lancillary)2]+.

Structural Heterogeneity in Polynucleotide-Facilitated Assembly of Phenothiazine Dyes.

The assembly of stacked dyes on DNA is of interest for electron transfer, light harvesting, sensing, and catalysis applications. A combination of UV/vis absorption, linear dichroism (LD), and circular dichroism (CD) was applied to characterize thoroughly the aggregation with DNA of the phenothiazine dyes methylene blue, azure B, and thionine. Aggregates of each dye with [poly(dG-dC)]2, [poly(dA-dT)]2, and calf thymus DNA were explored at high dye:DNA binding ratios, where excess dye groove-binds after all intercalation sites are filled. The organization of the aggregates (dimers, trimers, and multimers) with polydeoxynucleotides displays a structural diversity that depends on DNA sequence, extent of methylation of dye exocyclic amine groups, and ionic strength. The dyes typically form right-handed H-aggregates having negative LD, consistent with stepped stacking along the minor groove. However, aggregates in some dye:DNA aggregates show left-handed chirality or positive LD, indicating unusual modes of aggregation such as formation of adventitious dimers between intercalated and minor groove bound dye. In terms of sequence-dependence, methylene blue shows more extensive aggregation with [poly(dA-dT)]2, while thionine aggregates more with [poly(dG-dC)]2. Azure B has distinctive behavior that is unlike either other dyes. Thus, although these phenothiazine dyes possess a common tricyclic framework, the organization of their polynucleotide-facilitated aggregates depends sensitively on the extent of methylation of the exocyclic amines.

Assembly of Macrocycle Dye Derivatives into Particles for Fluorescence and Photoacoustic Applications

Optical imaging is a rapidly progressing medical technique that can benefit from the development of new and improved optical imaging agents suitable for use in vivo. However, the molecular rules detailing what optical agents can be processed and encapsulated into in vivo presentable forms are not known. We here present the screening of series of highly hydrophobic porphyrin, phthalocyanine, and naphthalocyanine dye macrocycles through a self-assembling Flash NanoPrecipitation process to form a series of water dispersible dye nanoparticles (NPs). Ten out of 19 tested dyes could be formed into poly(ethylene glycol) coated nanoparticles 60-150 nm in size, and these results shed insight on dye structural criteria that are required to permit dye assembly into NPs. Dye NPs display a diverse range of absorbance profiles with absorbance maxima within the NIR region, and have absorbance that can be tuned by varying dye choice or by doping bulking materials in the NP core. Particle properties such as dye core load and the compositions of co-core dopants were varied, and subsequent effects on photoacoustic and fluorescence signal intensities were measured. These results provide guidelines for designing NPs optimized for photoacoustic imaging and NPs optimized for fluorescence imaging. This work provides important details for dye NP engineering, and expands the optical imaging tools available for use.

Strategy toward Designing Semiconducting Polymer Nanoparticle–Multichomophoric Dye Assembly

The design of semiconducting polymer nanoparticle based hybrids is promising for light harvesting systems. Here, we design a donor–acceptor system through tuning the energy level alignment of interacting counterparts for an efficient light harvesting system where poly(N-vinyl carbazole) (PVK) nanoparticles (NPs) act as donor and the newly designed bicolor fluorophore ([R6G][HFL]) acts as acceptor. The photophysical interaction between polymer nanoparticle and bicolor fluorophore has been investigated by spectroscopic study and density functional theory (DFT) calculations. Dynamic quenching and the shortening of decay time of PVK polymer nanoparticles are revealed due to the energy and electron transfer process from PVK nanoparticle to the surface attached bicolor fluorophore. Furthermore, an ultrafast spectroscopic study has been undertaken to investigate the decay dynamics of [R6G][HFL] in the presence and absence of PVK. Finally, white light generation with CIE coordinates (0.31, 0.39) is achieved at a ...

Panchromatic Sensitizer for Dye-Sensitized Solar Cells: Unsymmetrical Squaraine Dyes Incorporating Benzodithiophene π-Spacer with Alkyl Chains to Extend Conjugation, Control the Dye Assembly on TiO2, and Retard Charge Recombination.

Metal-free near-infrared (NIR) active unsymmetrical squaraine dyes, RSQ1 and RSQ2, with benzodithiophene (BDT) π-spacer and cyanoacrylic acid acceptor were synthesized by utilizing palladium catalyzed direct (hetero)arylation reaction. Methyl and 2-ethylhexyl groups were strategically placed at the BDT unit for RSQ1 and RSQ2, respectively, to investigate the effect of alkylated π-spacer on dye aggregation on the TiO2 surface and recombination reactions at TiO2/dye/electrolyte interface. These dyes have strong absorption (ε > 105 M-1 cm-1) in near-infrared (NIR) region and exhibit similar optical and electrochemical properties as they have same conjugated framework. RSQ2 performed better than RSQ1 owing to its higher open-circuit voltage (Voc) and fill factor (ff) in spite of having comparable short-circuit current density (Jsc). The panchromatic incident photon-to-current conversion efficiency (IPCE) response was also observed for both the dyes. RSQ2 showed power conversion efficiency (PCE) of 6.72% with short-circuit current density (Jsc) of 18.53 mA/cm2, open circuit voltage (Voc) of 0.538 V, and fill factor (ff) of 67.4%, without any coadsorbent. Attenuation of the charge recombination for RSQ2 was revealed by electrochemical impedance analysis (EIS) and open-circuit potential decay transients (OCVD), which attributes to its higher Voc and ff in comparison to RSQ1.

Assembly of BODIPY-carbazole dyes with liposomes to fabricate fluorescent nanoparticles for lysosomal bioimaging in living cells

Two BODIPY-carbazole dye based fluorescent probes BCA and BCAS were designed, synthesized and encapsulated by liposomes to obtain fluorescent nanoparticles BCA-FNP and BCAS-FNP. The fluorescence imaging showed that BCA-FNP was membrane-permeable and capable of localizing lysosomes in living cells.

Self-Quenching, Dimerization, and Homo-FRET in Hetero-FRET Assemblies with Quantum Dot Donors and Multiple Dye Acceptors

The combination of semiconductor quantum dots (QDs) and Forster resonance energy transfer (FRET) is a powerful tool for bioanalysis and imaging. Through FRET, the dye is able to borrow brightness from the QD, and the FRET efficiency can be tuned through the assembly of multiple acceptor dyes per QD. In principle, the fluorescence intensity from acceptor dyes assembled to a QD donor should always exceed that from the dyes alone, but we observed anomalously low acceptor dye fluorescence intensities in FRET systems with a QD donor and multiple Alexa Fluor 610 (A610) or Alexa Fluor 633 (A633) acceptors. In contrast, fluorescence from Alexa Fluor 555 (A555) or Alexa Fluor 647 (A647) acceptors was well-behaved and agreed with theoretical expectations. The difference between these systems was studied using a combination of UV–visible absorption and fluorescence intensity, lifetime, and anisotropy measurements. Anomalous fluorescence from A610 and A633 arose from the formation of nonfluorescent, H-type dimers of ...

PH-Responsive assembly of metal nanoparticles and fluorescent dyes by diblock copolymer micelles.

Hybrid assemblies consisting of metal nanoparticles (NPs) and fluorophores are quite interesting because the intrinsic properties of fluorophores can be engineered in the assembled structure. In this regard, we utilized the self-segregation properties of block copolymer micelles to organize metal NPs and fluorophores simultaneously in a specific arrangement. From the viewpoint of assembly methods, we first encapsulated Au NPs in the PS cores of polystyrene-block-poly(acrylic acid) (PS-PAA) micelles. Then, positively charged fluorescent dyes of rhodamine 123 (R123) were bound to the negatively charged PAA coronas by electrostatic interactions. Since carboxylic acid in the PAA block is a weak acid, the degree of R123 binding to PS-PAA micelles can be adjusted by varying the pH of the solution. Therefore, by changing the pH, we were able to control the assembly and disassembly of R123 molecules to PS-PAA micelles and the corresponding change in the fluorescence signal.

Multicomponent covalent dye assembly for tight binding and sensitive sensing of L-DOPA.

A mixture of two simple perylene-containing receptors was found to bind bifunctional L-DOPA synergistically and tightly via orthogonal boronate ester and imine bond formation in neutral aqueous solutions, the resulting three-component assembly forming optically active long fibrous aggregates.

Highly sensitive turn-on biosensors by regulating fluorescent dye assembly on liposome surfaces.

We developed a new self-signaling sensory system built on phospholipid liposomes having H-aggregated R6G dyes on their surface. Selective molecular recognition of a target by the phospholipid displaces R6G from the liposome surface to turn on fluorescence signal. Selective and sensitive detection of neomycin down to 2.3 nM is demonstrated.

Manipulation of supramolecular 2D assembly of functional dyes toward artificial light-harvesting systems

Abstract In recent years, excellent research has revealed that light-harvesting systems (LHSs) are composed of beautifully aligned chlorophyll molecules; the regulated alignment of chlorophylls is responsible for the efficient and selective light-harvesting energy transfer processes in purple bacteria. This finding led to the construction of a regularly arranged assembly of functional dyes as a step toward fabricating artificial LHSs. While most approaches toward the construction of dye assemblies have depended on molecular interactions such as covalent, coordination, and hydrogen bonds, my approach involves guest–host interactions using an inorganic nanosheet as the host material. This short review presents the construction of a 2D dye assembly and its effective utilization in artificial light-harvesting applications. Owing to the highly stable and uniform 2D alignment of functional dyes on inorganic nanosheets, nearly 100 % singlet–singlet energy transfer and efficient light-harvesting were achieved. I believe that the results presented herein will contribute to the construction of efficient photochemical reaction systems in supramolecular host–guest assemblies, which may facilitate the realization of artificial photosynthesis.

Factors controlling the photoresponse of copper(i) diimine dyes containing hole-transporting dendrons in dye-sensitized solar cells: substituent and solvent effects

A detailed study of how two factors (substituents on ancillary ligands and solvents during dye assembly) affect performances of copper(i) diimine dyes in DSCs with phosphonic acid anchoring groups is presented.

Influence of a co-adsorbent on the performance of bis(diimine) copper(i)-based dye-sensitized solar cells

The effects of adding chenodeoxycholic acid to copper(i) bis(diimine) dyes in DSCs has been studied, as well as a new stepwise procedure for TiO2-bound dye assembly.

Halos show the path to perfection: peripheral iodo-substituents improve the efficiencies of bis(diimine)copper(i) dyes in DSCs

DSCs containing simple copper(i) dyes with peripheral halo (X) ligands give global efficiencies >3% for X = I; a new strategy for stepwise surface dye assembly is demonstrated.

Spectroscopic and fluorescence properties of silver-dye composite nanoparticles

The aim of this work was to investigate the formation of J-aggregates of thiacyanine dye (TC, 5,5′-disulfopropyl-3,3′-dichlorothiacyanine sodium salt) in the presence of 6 nm spherical silver nanoparticles (Ag NPs) using spectrophotometric and fluorescence methods. The formation of J-aggregates was concentration dependent and characterized by the appearance of the new absorption band with the maximum at 481 nm. Spectrophotometric study of J-aggregate formation and time stability suggested that they were formed on the account of monomer form of TC. Moreover, the stability of J-aggregates increased with the lowering AgNPs concentration. The measurements of fluorescence of the NPs—dye assembly clearly indicated that the fluorescence of TC was quenched by Ag NPs on the concentration dependent manner. The spectrophotometric and fluorescence properties of NPs—dye assembly were found to be quantitatively related to the surface coverage of the dye on the Ag NPs.

Cover Picture: Ultrasound Stimulated Nucleation and Growth of a Dye Assembly into Extended Gel Nanostructures (Chem. Eur. J. 39/2013)

Cover Picture: Ultrasound Stimulated Nucleation and Growth of a Dye Assembly into Extended Gel Nanostructures (Chem. Eur. J. 39/2013)

Ultrasound Stimulated Nucleation and Growth of a Dye Assembly into Extended Gel Nanostructures

A squaraine dye functionalized with a bulky trialkoxy phenyl moiety through a flexible diamide linkage (GA-SQ) capable of undergoing self-assembly has been synthesized and fully characterized. Rapid cooling of a hot solution of GA-SQ to 0 °C results in self-assembled precipitates consisting of two types of nanostructures, rings and ill-defined short fibers. The application of ultrasound modifies the conditions for the supersaturation-mediated nucleation, generating only one kind of nuclei and prompting the formation of crystalline fibrous structures, inducing gelation of solvent molecules. The unique self-assembling behavior of GA-SQ under ultrasound stimulus has been investigated in detail by using absorption, emission, FT-IR, XRD, SEM, AFM and TEM techniques. These studies reveal a nucleation growth mechanism of the self-assembled material, an aspect rarely scrutinized in the area of sonication-induced gelation. Furthermore, in order to probe the effects of nanoscale substrates on the sonication-induced self-assembly, a minuscule amount of single-walled carbon nanotubes was added, which leads to acceleration of the self-assembly through a heterogeneous nucleation process that ultimately affords a supramolecular gel with nanotape-like morphology. This study demonstrates that self-assembly of functional dyes can be judiciously manipulated by an external stimulus and can be further controlled by the addition of carbon nanotubes.

Fluorescence Quenching of 5,5′-Disulfopropyl-3,3′-dichlorothiacyanine Dye Adsorbed on Gold Nanoparticles

Nanoparticles (NPs) modified with fluorescent cyanine dyes can exhibit fluorescent quenching properties due to energy and/or electron transfer, and these systems have many applications in catalysis, drug delivery, nanoelectronics, medical diagnostics, and chemical sensing. The aim of this work was to investigate the adsorption of cyanine dye 5,5′-disulfopropyl-3,3′-dichlorothiacyanine (TC) on the surface of citrate capped gold nanoparticles (AuNPs) with the average core sizes of 9, 17, and 30 nm using various experimental techniques. The measurements of fluorescence corrected for inner filter effects (IFE) of the particle–dye assembly clearly indicated that the fluorescence of TC was quenched by AuNPs on the concentration dependent manner, and the equilibrium constants for the sorption of TC on the NP surface were calculated. Significant increase of fluorescence quenching was noticed when NP size increased, keeping the concentration of NPs of different size constant. By comparing experimental and calculated results for quenching of TC dye fluorescence, we assumed that the maximum quenching was restricted to full monolayer coverage of TC on the NP surface. The conclusion was drawn that the most probable orientation of TC dye molecules on the NP surface was slanted and that the dye approached NP surface with its positively charged thiazole ring.