High-Efficiency Ternary Polymer Solar Cells with a Gradient-Blended Structure Fabricated by Sequential Deposition.

Acquiring the ideal blend morphology of the active layer to optimize charge separation and collection is a constant goal of polymer solar cells (PSCs). In this paper, the ternary strategy and the sequential deposition process were combined to make sufficient use of the solar spectrum, optimize the energy-level structure, regulate the vertical phase separation morphology, and ultimately enhance the power conversion efficiency (PCE) and stability of the PSCs. Specifically, the donor and acceptor illustrated a gradient-blended distribution in the sequential deposition-processed films, thus resulting in facilitated carrier characteristics in the gradient-blended devices. Consequently, the PSCs based on D18-Cl/Y6:ZY-4Cl have achieved a device efficiency of over 18% with the synergetic improvement of open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF). Therefore, this work reveals a facile approach to fabricating PSCs with improved performance and stability.

Heterostructures of Cut Carbon Nanotube-Filled Array of TiO2 Nanotubes for New Module of Photovoltaic Devices.

In this work, a new photovoltaic device was prepared. The device uses titanium (Ti) foil/TiO2 nanotubes as the photoanode and multi-walled carbon nanotubes (MWCNTs) as a photosensitizer. Titanium dioxide nanotube arrays (TiO2-NTs) were prepared by one-step anodic oxidation. Cut-MWCNTs with a length of less than 100 nm were obtained by the mixed-acid oxidation of MWCNTs. The two materials were combined to form a TiO2-NTs@cut-MWCNT heterostructure by electrophoresis. TiO2-NTs@cut-MWCNTs were characterized by field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), which showed that the two materials were effectively combined. We fabricated the heterostructure into a photovoltaic device, showing an enhanced photocurrent response and an efficiency of 0.0138%, and explained this phenomenon by performing UV-vis absorption spectroscopy and electrochemical tests. It is hoped that this work can provide a reference value for the application of carbon nanotubes in photovoltaic devices.

Ligand-Tuned Multi-Color Luminescence of Single Aluminum (III) Ion Atomic Centers and Their Selective Sensitivity to Different Metal Ions.

Achieving multi-color luminescence with a single atomic center in transition metal complexes is a challenge. In this work, luminescent materials with tunable emission properties were realized by complexation between aluminum (III) ions with the ligands 3-hydroxyflavone (3-HF) and 5,7-dichloro-8-hydroxyquinoline (DCHQ). Aluminum (III) complexes with a single ligand emitted blue from 3-HF and green from DCHQ. High quantum yields (QYs) of 29.42% and 37.00% were also obtained, respectively. DFT calculations revealed details of the photophysical properties of the complexes. Correspondingly, cyan light emission was obtained if these two complexes were mixed together, from which the emission wavelength was located at 470 nm and the QY was 20.52%, under 290 nm excitation. More importantly, the cyan light emitted by the mixtures had selective sensitivity to different metal ions, resulting in either quenching the fluorescence (in the case of Fe3+) or enhancing the fluorescence (in the case of In3+). The fluorescence enhancement effect of In3+ on metal complexes has not been previously reported, neither for transition metal nor lanthanide ions. The linear quenching behavior of Fe3+ functions in the 50-700 µM concentration range, and the linear enhancement behavior of In3+ is demonstrated in the 300-800 mM concentration range.

Lanthanide (Eu3+/Tb3+)-Loaded γ-Cyclodextrin Nano-Aggregates for Smart Sensing of the Anticancer Drug Irinotecan.

The clinical use of anticancer drugs necessitates new technologies for their safe, sensitive, and selective detection. In this article, lanthanide (Eu3+ and Tb3+)-loaded γ-cyclodextrin nano-aggregates (ECA and TCA) are reported, which sensitively detects the anticancer drug irinotecan by fluorescence intensity changes. Fluorescent lanthanide (Eu3+ and Tb3+) complexes exhibit high fluorescence intensity, narrow and distinct emission bands, long fluorescence lifetime, and insensitivity to photobleaching. However, these lanthanide (Eu3+ and Tb3+) complexes are essentially hydrophobic, toxic, and non-biocompatible. Lanthanide (Eu3+ and Tb3+) complexes were loaded into naturally hydrophilic γ-cyclodextrin to form fluorescent nano-aggregates. The biological nontoxicity and cytocompatibility of ECA and TCA fluorescent nanoparticles were demonstrated by cytotoxicity experiments. The ECA and TCA fluorescence nanosensors can detect irinotecan selectively and sensitively through the change of fluorescence intensity, with detection limits of 6.80 µM and 2.89 µM, respectively. ECA can safely detect irinotecan in the cellular environment, while TCA can detect irinotecan intracellularly and is suitable for cell labeling.

Conditionally designed luminescent DNA crystals doped by Ln3+(Eu3+/Tb3+) complexes or fluorescent proteins with smart drug sensing property.

In this work, a designed porous DNA crystal with high intrinsic biocompatibility was used as the scaffold material to load fluorescent guest molecules to detect anti-cancer drugs. It is shown here that the synthesized crystals have the characteristics consistent with the designed large solvent channels, and can therefore accommodate guest molecules such as fluorescent proteins that cannot be accommodated by less porous crystals. Eu(TTA)3phen and Tb(acac)3phen lanthanide complexes were individually noncovalently loaded into the porous crystals, resulting in hybrid luminescent DNA crystals. Emodin, an anti-cancer, anti-tumor, anti-inflammatory drug, was found to quench lanthanide complexes in solution or in crystals. Notably, emodin is the active ingredient of Lianhua Qingwen Capsule, an anti-COVID-19 drug candidate. Therefore, the porous DNA crystals reported here have potential applications as a biocompatible and theranostic delivery biomaterial for functional macromolecules.

Novel Cuboid-like Crystalline Complexes (CLCCs), Photon Emission, Fluorescent Fibers, and Bright Red Fabrics of Eu3+ Complexes Adjusted by Amphiphilic Molecules.

With the growing needs for flexible fluorescence emission materials, emission fibers and related wearable fabrics with bright emission properties have become key factors for wearable applications. In this article, novel cuboid-like crystals of Eu3+ complexes were generated. Except for light-energy-harvesting ligands of thenoyltrifluoroacetone (TTA) and 1,10-phenanthroline hydrate (Phen), the crystal structures were adjusted by other functional amphiphilic molecules. Not only does ETPC-SA, adjusted by stearic acid, have a regular cuboid-like crystal with a size of about 2 µm size, but it also generates the best photon emission property, with a fluorescence quantum yield of 98.4% fluorescence quantum yield in this report. Furthermore, we succeeded in producing novel fluorescent fibers by mini-twin-screw extrusion, and it was easy to form bright red fabrics, which are equipped with strong fluorescence intensity, flexibility, and a smooth hand feeling, with the normal fabricating method in our work. It is worth noting that ETPC-HQ fibers, which carry a crystal complex adjusted by hydroquinone, possess the lowest quantum yield but have the longest average fluorescence lifetime of 1259 µs. This result means that a low-density polyethylene (LDPE) matrix could make excited electrons stand in the excited state for a relatively long time when adjusted by hydroquinone, so as to increase the afterglow property of fluorescent fibers.

An Efficient Cyan Emission from Copper (II) Complexes with Mixed Organic Conjugate Ligands.

Copper (II) complexes containing mixed ligands were synthesized in dimethyl formamide (DMF). The intense cyan emission at an ambient temperature is observed for solid copper (II) complexes with salicylic acid and a 12% quantum yield with a fluorescent lifetime of approximately 10 ms. Hence, copper (II) complexes with salicylic acid are excellent candidates for photoactive materials. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) reveal that the divalent copper metal centers coordinate with the nitrogen and oxygen lone pairs of conjugate ligands. XPS binding energy trends for core electrons in lower-lying orbitals are similar for all three copper (II) complexes: nitrogen 1s and oxygen 1s binding energies increase relative to those for undiluted ligands, and copper 2p3/2 binding energies decrease relative to that for CuCl2. The thermal behavior of these copper complexes reveals that the thermal stability is characterized by the following pattern: Cu(1,10-phenanthroline)(salicylic acid) > Cu(1,10-phenanthroline)(2,2'-bipyridine) > Cu(1,10-phenanthroline)(1-benzylimidazole)2.

Smart Mn7+ Sensing via Quenching on Dual Fluorescence of Eu3+ Complex-Modified TiO2 Nanoparticles.

In this work, titania (TiO2) nanoparticles modified by Eu(TTA)3Phen complexes (ETP) were prepared by a simple solvothermal method developing a fluorescence Mn7+ pollutant sensing system. The characterization results indicate that the ETP cause structural deformation and redshifts of the UV-visible light absorptions of host TiO2 nanoparticles. The ETP also reduce the crystallinity and crystallite size of TiO2 nanoparticles. Compared with TiO2 nanoparticles modified with Eu3+ (TiO2-Eu3+), TiO2 nanoparticles modified with ETP (TiO2-ETP) exhibit significantly stronger photoluminescence under the excitation of 394 nm. Under UV excitation, TiO2-ETP nanoparticles showed blue and red emission corresponding to TiO2 and Eu3+. In addition, as the concentration of ETP in TiO2 nanoparticles increases, the PL intensity at 612 nm also increases. When ETP-modified TiO2 nanoparticles are added to an aqueous solution containing Mn7+, the fluorescence intensity of both TiO2 and ETP decreases. The evolution of the fluorescence intensity ratio (I1/I2) of TiO2 and ETP is linearly related to the concentration of Mn7+. The sensitivity of fluorescence intensity to Mn7+ concentration enables the design of dual fluorescence ratio solid particle sensors. The method proposed here is simple, accurate, efficient, and not affected by the environmental conditions.

Stable Fluorescence of Eu3+ Complex Nanostructures Beneath a Protein Skin for Potential Biometric Recognition.

We designed and realized highly fluorescent nanostructures composed of Eu3+ complexes under a protein coating. The nanostructured material, confirmed by photo-induced force microscopy (PiFM), includes a bottom fluorescent layer and an upper protein layer. The bottom fluorescent layer includes Eu3+ that is coordinated by 1,10-phenanthroline (Phen) and oleic acid (O). The complete complexes (OEu3+Phen) formed higher-order structures with diameter 40-150 nm. Distinctive nanoscale striations reminiscent of fingerprints were observed with a high-resolution transmission electron microscope (HRTEM). Stable fluorescence was increased by the addition of Eu3+ coordinated by Phen and 2-thenoyltrifluoroacetone (TTA), and confirmed by fluorescence spectroscopy. A satisfactory result was the observation of red Eu3+ complex emission through a protein coating layer with a fluorescence microscope. Lanthanide nanostructures of these types might ultimately prove useful for biometric applications in the context of human and non-human tissues. The significant innovations of this work include: (1) the structural set-up of the fluorescence image embedded under protein "skin"; and (2) dual confirmations of nanotopography and unique nanofingerprints under PiFM and under TEM, respectively.

Visible-light excitable Eu3+-induced hyaluronic acid-chitosan aggregates with heterocyclic ligands for sensitive and fast recognition of hazardous ions.

Water-soluble luminescent lanthanide complexes that can be excited with visible light could enable rapid detection of toxic anions and cations in biological systems. Eu3+-induced hyaluronic acid-chitosan aggregates (EIHCA) can improve the stability, biocompatibility, efficiency, and light absorption of luminescent Eu3+ complexes. Visible-range excitation may avoid phototoxicity associated with overexposure to UV light in biological and ecological applications. In this work, we synthesized and characterized series of EIHCA complexes having three N-donor heterocyclic ligands: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Dphen), 2,2': 6',2″-terpyridine (Tpy) and 1,10-phenanthroline monohydrate (Phen). These complexes possessed bright red fluorescence with a visible range excitation maximum. The photophysical properties of one formulation (we denote as EDL6) include fast quenching response (20 s) of the fluorescence, multi-selectivity, low limit of detection, and high quenching (Ksv) values, enabling selective, rapid and sensitive recognition of Cr2O72- and Fe3+ in aqueous solution. Furthermore, EDL6 exhibits cytocompatibility with mammalian cells that make these complexes promising biocompatible candidate as a safe replacement of organic fluorophores for fluorescence sensing applications. Thus, these new EIHCA complexes were successfully employed for the selective detection of hazardous materials in biological and aqueous environment samples.

NIR-Fluorescent Hybrid Materials of Tm3+ Complexes Carried by Nano-SiO2 via Improved Sol-Gel Method.

Tm3+ has obvious emission characteristics in the near-infrared band. Thulium ions combined with different organic ligands lead to different fluorescent properties. In the near-infrared region, Tm3+ is a down-conversion fluorescent material that is unstable under high temperature and acidic conditions. Moreover, in those complex environments, the fluorescence from Tm3+ complex is usually degraded. In this work, two kinds of near-infrared fluorescent complexes, Tm(TTA)3phen and Tm(DBM)3phen, were prepared, and the intensity of their fluorescence is compared. The fluorescence intensity at 802 nm is greatly improved compared with Tm(TTA)3phen, and the intensity of the emission at 1235 nm and 1400-1500 nm is also enhanced. Moreover, the emission lifetime of SiO2-Tm(TTA)3phen is 50.38 µs. Tm(TTA)3phen complex and SiO2-Tm(TTA)3phen hybrid materials have better fluorescence than Tm(DBM)3phen and SiO2-Tm(DBM)3phen. Therefore, HTTA is a better choice of organic ligands for Tm3+. The NIR-fluorescent hybrid materials prepared have stronger fluorescence after combining with nano-SiO2compared with pure Tm3+ complexes, and have stronger structural stability compared with pure nano-SiO2.

Strong enhanced efficiency of natural alginate for polymer solar cells through modification of the ZnO cathode buffer layer.

Sodium alginate (SA), as a natural marine biopolymer, possesses many merits such as super-easy accessibility from the ocean, low cost, nontoxicity, and no synthesis for practical application. For the chemical structure, SA has enough lone electron pairs of oxygen atoms in the backbone and short branched chains, which is expected to passivate oxygen vacancy on the surface of the ZnO cathode buffer layer to improve the photovoltaic performance. Herein, it was applied to modify the surface trap of the ZnO layer in fullerene and non-fullerene polymer solar cells (PSCs). The defects were successfully reduced, and the trap-assisted recombination decreased. In a PTB7-Th:PC71BM system, power conversion efficiency (PCE) was improved from 8.06% to 9.36%. In the PM6:IT-4F system, PCE was enhanced from 12.13% to 13.08%. The addition of SA did not destroy the stability of the device. Overall, this work demonstrates the potential for preparing devices with long-time stability and industrial manufacture of PSCs by using biological materials in the future.

Europium-functionalized luminescent titania nanotube arrays: Utilizing interactions with glucose, cholesterol and triglycerides for rapid detection application.

In this work, titania nanotube arrays (TiO2-NTs) were prepared by anodization, and the Eu(III) complexes (Eu (TTA)3 phen with 2-thenoyltrifluoroacetone (TTA) and 1, 10-phenanthroline (phen)) were successfully coated onto the walls of the nanotubes. When a solution of glucose, cholesterol or triglycerides was dropped onto Eu(III) complex-modified TiO2-NTs, the fluorescence intensity of this material changes (glucose enhances fluorescence, cholesterol and triglycerides quench fluorescence). These phenomena are explained via an energy transfer process. The sensitivity of the fluorescence intensity to glucose, cholesterol or triglycerides concentration enables design of a multifunctional solid sheet-like detector. Under optimized experimental conditions, the change in fluorescence intensity ratio (ΔF/F0) is linear with the concentration of glucose, cholesterol or triglycerides. To test the utility of the detector, glucose in orange juice, cholesterol in milk powder, and triglycerides in coconut oil were measured using this method and the results were in good agreement analytical data provided by a food testing company. The new method proposed here is simple, sensitive, reliable and suitable for practical applications.

Tb3+/Eu3+ Complex-Doped Rigid Nanoparticles in Transparent Nanofibrous Membranes Exhibit High Quantum Yield Fluorescence.

In this study, transparent membranes containing luminescent Tb3+ and Eu3+ complex-doped silica nanoparticles were prepared via electrospinning. We prepared the electrospun fibrous membranes containing Tb(acac)3phen- (acac = acetylacetone, phen = 1,10-phenanthroline) and/or Eu(tta)3phen- (tta = 2-thenoyltrifluoroacetone) doped silica (M-Si-Tb3+ and M-Si-Eu3+) and studied their photoluminescence properties. The fibrous membranes containing the rare earth complexes were prepared by electrospinning. The surface morphology and thermal properties of the fibrous membrane were studied by atomic force microscopy (AFM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. Fluorescence spectroscopy was used to characterize the fluorescence properties of the membranes. During the electrospinning process, the PVDF transitions from the α phase to the ß phase, which exhibits a more rigid structure. The introduction of rigid materials, like PVDF and silica, can improve the fluorescence properties of the hybrid materials by reducing the rate of nonradiative decay. So the emission spectra at 548 nm (Tb) and 612 nm (Eu) were enhanced, as compared to the emission from the pure complex. Furthermore, the fluorescence lifetimes ranged from 0.6 to 1.5 ms and the quantum yields ranged from 32% to 61%. The luminescent fibrous membranes have potential applications in the fields of display panels, innovative electronic and optoelectronic devices.

Fluorescent SiO2@Tb3+(PET-TEG)3Phen Hybrids as Nucleating Additive for Enhancement of Crystallinity of PET.

A hybrid polymer of SiO2@Tb3+(poly(ethylene terephthalate)-tetraglycol)3 phenanthroline (SiO2@Tb3+(PET-TEG)3Phen) was synthesized by mixing of inorganic SiO2 nanoparticles with polymeric segments of PET-TEG, whereas PET-TEG was achieved through multi-step functionalization strategy. Tb3+ ions and ß-diketonate ligand Phen were added in resulting material. The experimental results demonstrated that it was well blended with PET as a robust additive, and not only promoted the crystallinity, but also possessed excellent luminescence properties. An investigation of the mechanism revealed that the SiO2 nanoparticles functioned as a crystallization promotor; the Tb3+ acted as the fluorescent centre; and the PET-TEG segments played the role of linker and buffer, providing better compatibility of PET matrix with the inorganic component. This work demonstrated that hybrid polymers are appealing as multifunctional additives in the polymer processing and polymer luminescence field.

Theory and simulation developments of confined mass transport through graphene-based separation membranes.

Graphene-based membranes exhibit enormous potential in water desalination and purification because of their ultrathin structure, superhigh water flux, tunable physicochemical properties and precise ionic and molecular sieving performance. However, the transport behavior and mechanism of water, ions and other molecules across nanopores and nanocapillaries in the separation process, especially the confined mass transport, remain unclear, imposing severe limitation on many applications. Therefore, extensive experimental studies and theoretical calculation simulations have been carried out to investigate their unique structure and separation properties, particularly to explore the associated confined mass transport mechanism. Herein, an overview of the theory and simulation developments of graphene-based separation membranes based on confined mass transport is provided, attempting to open up an avenue for designing graphene-based materials as a new generation of separation membranes in the water purification field. This perspective focuses on five topics: (1) membrane transport models and simulation methods; (2) comparison between membrane simulations and experiments; (3) confined mass transport studies of graphene-based membranes with the assistance of molecular dynamics (MD) simulations; (4) fabrication of multifunctional composite membranes; and (5) future research trends in graphene-based membranes.

Graphene Oxide Nanofiltration Membranes Containing Silver Nanoparticles: Tuning Separation Efficiency via Nanoparticle Size.

Three types of graphene oxide/silver nanoparticles (GO/AgNPs) composite membranes were prepared to investigate size-effect of AgNPs on nanofiltration ability. The size of AgNPs was 8, 20, and 33 nm, which was characterized by UV-visible spectroscopy and transmission electron microscopy. The morphology and structure of GO and GO/AgNPs composite membranes were characterized by atomic force microscopy, scanning electron microscopy, and X-ray diffraction. The filtration performance of membranes were evaluated on a dead-end filtration device. When the size of AgNPs is 20 nm, the GO/AgNPs composite membrane has the highest water flux (106.1 L m-2 h-1 bar-1) and rejection of Rhodamine B (RhB) (97.73%) among three types of composite membranes. The effect of feed concentration of dye solution and the flux of common solvent was also investigated. The mechanism was discussed, which demonstrated that both interlaying spacing and defect size influence the filtration ability of membrane, which is instructive to future study.

Hybrid ZnO Electron Transport Layer by Down Conversion Complexes for Dual Improvements of Photovoltaic and Stable Performances in Polymer Solar Cells.

Polymer solar cells (PSCs) have shown excellent photovoltaic performance, however, extending the spectral response range to the ultraviolet (UV) region and enhancing the UV light stability remain two challenges to overcome in the development of PSCs. Lanthanide down-conversion materials can absorb the UV light and re-emit it at the visible region that matches well with the absorption of the active layer material PTB7-Th (poly[[2,6'-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene][3-fluoro-2[(2-ethylhexyl)carbony]thieno[3,4-b]thiophenediyl]]) and PBDB-T-2F, thus helping to enhance the photovoltaic performance and UV light stability of PSCs. In this research, a down-conversion material Eu(TTA)3phen (ETP) is introduced into the cathode transport layer (ZnO) in PSCs to manipulate its nanostructure morphology for its application in hyperfine structure of PSCs. The device based on the ZnO/ETP electron transport layer can obtain power conversion efficiencies (PCEs) of 9.22% (PTB7-Th-PC71BM ([6,6]-phenylC71-butyric acid methyl ester) device) and 13.12% (PBDB-T-2F-IT-4F device), respectively. Besides, in the research on PTB7-Th-PC71BM device, the stability of the device based on ZnO/ETP layer is prolonged by 70% compared with the ZnO device. The results suggest that the ZnO/ETP layer plays the role of enhanced photovoltaic performance and prolonged device stability, as well as reducing photo-loss and UV degradation for PSCs.

Classification, Synthesis, and Application of Luminescent Silica Nanoparticles: a Review.

Luminescent materials are of worldwide interest because of their unique optical properties. Silica, which is transparent to light, is an ideal matrix for luminescent materials. Luminescent silica nanoparticles (LSNs) have broad applications because of their enhanced chemical and thermal stability. Silica spheres of various sizes could be synthesized by different methods to satisfy specific requirements. Diverse luminescent dyes have potential for different applications. Subject to many factors such as quenchers, their performance was not quite satisfying. This review thus discusses the development of LSNs including their classification, synthesis, and application. It is the highlight that how silica improves the properties of luminescent dye and what role silica plays in the system. Further, their applications in biology, display, and sensors are also described.

Polyvinylpyrrolidone Nanofibers Encapsulating an Anhydrous Preparation of Fluorescent SiO2⁻Tb3+ Nanoparticles.

A novel anhydrous preparation of silica (SiO2)-encapsulated terbium (Tb3+) complex nanoparticles has been investigated. The SiO2-Tb3+ nanoparticles are incorporated in electrospun polyvinylpyrrolidone hybrid nanofibers. Transmission electron microscopy confirms that Tb3+ complexes are uniformly and stably encapsulated in or carried by nanosilica. The influence of pH on the fluorescence of Tb3+ complexes is discussed. The properties, composition, structure, and luminescence of the resulting SiO2⁻Tb3+ hybrid nanoparticles are investigated in detail. There is an increase in the fluorescence lifetime of SiO2⁻Tb3+ nanoparticles and SiO2⁻Tb3+/polyvinylpyrrolidone (PVP) hybrid nanofibers compared with the pure Tb3+ complexes. Due to the enhanced optical properties, the fluorescent hybrid nanofibers have potential applications as photonic and photoluminescent materials.