A new type of fluorescent material is presented, which is called non-conjugated polymer dots (NCPDs). The NCPDs only possess sub-fluorophores (which are groups such as CO, CN, NO) instead of typical conjugated fluorophore groups, and thus these materials should not have strong photoluminescence (PL) in the usual sense. Nevertheless, the PL of these sub-fluorophores can be enhanced by chemical crosslinking or physical immobilization of polymer chains, which is named the crosslink-enhanced emission (CEE) effect. The significant advances achieved by us and other groups on both experimental and theoretical aspects are discussed, and the covalent-bond CEE, rigidity-aggregated CEE, or supramolecular CEE in NCPDs is elaborated. Moreover, synthetic strategies, unique optical properties, and the promise of NCPDs in bio-related fields, such as bioimaging and drug delivery, are systematically discussed.

Nichtkonjugierte Polymerpunkte (NCPDs) werden als neuartiges fluoreszierendes Material vorgestellt. Die NCPDs enthalten anstelle typischer konjugierter fluorophorer Gruppen nur Sub-Fluorophore (das sind Gruppen wie CO, CN, NO), und daher sollten diese Materialien keine starke Photolumineszenz (PL) im herkömmlichen Sinne aufweisen. Allerdings kann die PL dieser Sub-Fluorophore durch chemische Vernetzung oder physikalische Immobilisierung von Polymerketten verstärkt werden. Dieser Effekt wird als gesteigerte Emission durch Vernetzung (CEE) bezeichnet. Außerdem kann CEE über kovalente Bindungen, über Aggregation zu einer starren Struktur und über supramolekulare Wechselwirkungen bei NCPDs realisiert werden. Synthesestrategien, optische Eigenschaften und die Aussichten von NCPDs auf Gebieten wie biologische Bildgebung und Wirkstofftransport werden erörtert.

Recently great progress has been achieved in highly effective hybrid solar cells fabricated using aqueous materials. The state-of-the-art energy conversion efficiency has been close to 5% with high photocurrent. However, charge separation and transport mechanism in the aqueous-processed hybrid solar cells are rarely reported and are usually assumed to be similar to oil-phase processed systems; that is, self-assembly polymers are mainly responsible for charge separation and carrier transport. To date, this assumption has prohibited further improvement of the conversion efficiency in aqueous-processed hybrid systems by adopting any appropriate technique routes. Here, ultrafast carrier dynamics in these hybrid solar cells consisting of poly(p-phenylenevinylene) (PPV)-based aqueous polymers and water-solution CdTe nanocrystals (NCs) are investigated in detail. Self-charge separation in grown CdTe NC partly capped CdS shell layers after anneal treatment is unambiguously identified. Different from their oil-soluble counterparts, these core/shell nanocrystals do not have the restrictions of quantum confinement and surface ligands, form effective charge transport networks, and play a dominant role in the charge separation and carrier transport processes. These findings provide a greater understanding on the fundamental photophysics in aqueous-processed hybrid systems.

A water-soluble conjugated polymer (WCP) poly[(3,4-dibromo-2,5-thienylene vinylene)-co-(p-phenylene-vinylene)] (PBTPV), containing thiophene rings with high charge-carrier mobility and benzene rings with excellent solubility is designed and prepared through Wessling polymerization. The PBTPV precursor can be easily processed by employing water or alcohols as the solvents, which are clean, environmentally friendly, and non-toxic compared with the highly toxic organic solvents such as chloroform and chlorobenzene. As a novel photoelectric material, PBTPV presents excellent hole-transport properties with a carrier mobility of 5 × 10⁻⁴ cm² V⁻¹ s⁻¹ measured in an organic field-effect transistor device. By integrating PBTPV with aqueous CdTe nanocrystals (NCs) to produce the active layer of water-processed hybrid solar cells, the devices exhibit effective power conversion efficiency up to 3.3%. Moreover, the PBTPV can form strong coordination interactions with the CdTe NCs through the S atoms on the thiophene rings, and effective coordination with other nanoparticles can be reasonably expected.

Graphene quantum dots (GQDs) have recently emerged as a promising type of low-toxicity, high-biocompatibility, and chemically inert fluorescence probe with a high resistance to photobleaching. They are a prospective substitution for organic materials in light-emitting devices (LED), enabling the predicted concept of much brighter and more robust carbon LED (CLED). However, the mechanism of GQD emission remains an open problem despite extensive studies conducted so far, which is becoming the greatest obstacle in the route of technical improvement of GQD quantum efficiency. This problem is solved by the combined usage of femtosecond transient absorption spectroscopy and femtosecond time-resolved fluorescence dynamics measured by a fluorescence upconversion technique, as well as a nanosecond time-correlated single-photon counting technique. A fluorescence emission-associated dark intrinsic state due to the quantum confinement of in-plane functional groups is found in green-fluorescence graphene quantum dots by the ultrafast dynamics study, and the two characteristic fluorescence peaks that appear in all samples are attributed to independent molecule-like states. This finding establishes the correlation between the quantum confinement effect and molecule-like emission in the unique green-fluorescence graphene quantum dots, and may lead to innovative technologies of GQD fluorescence enhancement, as well as its broad industrial application.

The bandgap in graphene-based materials can be tuned from 0 eV to that of benzene by changing size and/or surface chemistry, making it a rising carbon-based fluorescent material. Here, the surface chemistry of small size graphene (graphene quantum dots, GQDs) is tuned programmably through modification or reduction and green luminescent GQDs are changed to blue luminescent GQDs. Several tools are employed to characterize the composition and morphology of resultants. More importantly, using this system, the luminescence mechanism (the competition between both the defect state emission and intrinsic state emission) is explored in detail. Experiments demonstrate that the chemical structure changes during modification or reduction suppresses non-radiative recombination of localized electron-hole pairs and/or enhances the integrity of surface π electron network. Therefore the intrinsic state emission plays a leading role, as opposed to defect state emission in GQDs. The results of time-resolved measurements are consistent with the suggested PL mechanism. Up-conversion PL of GQDs is successfully applied in near-IR excitation for bioimaging.

Self-assembly of colloidal microspheres or nanospheres is an effective strategy for fabrication of ordered nanostructures. By combination of colloidal self-assembly with nanofabrication techniques, two-dimensional (2D) colloidal crystals have been employed as masks or templates for evaporation, deposition, etching, and imprinting, etc. These methods are defined as “colloidal lithography”, which is now recognized as a facile, inexpensive, and repeatable nanofabrication technique. This paper presents an overview of 2D colloidal crystals and nanostructure arrays fabricated by colloidal lithography. First, different methods for fabricating self-assembled 2D colloidal crystals and complex 2D colloidal crystal structures are summarized. After that, according to the nanofabrication strategy employed in colloidal lithography, related works are reviewed as colloidal-crystal-assisted evaporation, deposition, etching, imprinting, and dewetting, respectively.

This review article summarizes recent progress in the fabrication methodologies and functional modulations of nanoparticle (NP)–polymer composites. On the basis of the techniques of NP synthesis and surface modification, the fabrication methods of nanocomposites are highlighted; these include surface-initiated polymerization on NPs, in situ formation of NPs in polymer media, and the incorporation through covalent linkages and supramolecular assemblies. In these examples, polymers are foremost hypothesized as inert hosts that stabilize and integrate the functionalities of NPs, thus improving the macroscopic performance of NPs. Furthermore, due to the unique physicochemical properties of polymers, polymer chains are also dynamic under heating, swelling, and stretching. This creates an opportunity for modulating NP functionalities within the preformed nanocomposites, which will undoubtedly promote the developments of optoelectronic devices, optical materials, and intelligent materials.

As one of the most robust and versatile routes to fabricate ordered micro- and nanostructures, soft lithography has been extensively applied to pattern a variety of molecules, polymers, biomolecules, and nanomaterials. This paper provides an overview on recent developments employing soft lithography methods to pattern colloidal crystals and related nanostructure arrays. Lift-up soft lithography and modified microcontact printing methods are applied to fabricate patterned and non-close-packed colloidal crystals with controllable lattice spacing and lattice structure. Combining selective etching, imprinting, and micromolding methods, these colloidal crystal arrays can be employed as templates for fabrication of nanostructure arrays. Realization of all these processes is favored by the solvent swelling, elasticity, thermodecomposition, and thermoplastic characteristics of polymer materials. Applications of these colloidal crystals and nanostructure arrays have also been explored, such as biomimetic antireflective surfaces, superhydrophobic coatings, surface-enhanced Raman spectroscopy substrates, and so on.

Bioinspired organic/inorganic hybrid one-dimensional photonic crystals (1DPCs) are prepared by alternating thin films of titania and poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) (PHEMA-co-PGMA) by spin-coating, which is a simple, reproducible, and low-cost approach. Their optical properties are tuned by changing the number of layers, incident angles, and the thickness of the layers. The color of the 1DPCs can span the entire visible spectral range when the period or the refractive index is changed. Due to the response of PHEMA-co-PGMA to water vapor, the 1DPCs possess fast water-vapor responsiveness and reversible full-color switching. The color of the 1DPCs varies from blue to green, yellow, orange, and red under differing humidities, covering the whole visible range. At high water-vapor concentrations, the color of the 1DPCs rapidly changes from blue to red and comes back to the original state immediately after exposure to air; this behaviour is like that of some animals in nature. The repeatability of the reversible response of the 1DPCs to water vapor is perfect and can be repeated more than 100 times. The as-prepared 1DPCs successfully combine structural color and water-vapor sensitivity, which is promising for use as materials for colorful detection across the full color range.

In this paper a convenient and universal strategy for preparing nanoring arrays of different compositions based on a colloidal-crystal-template strategy is reported. Large-area arrays of polystyrene, magnetite, Au, Si, magnetite nanoparticle/polystyrene and Au/polystyrene double-layer composite nanorings are prepared. Many kinds of nanoring structures, including Fe₃O₄ nanoparticle/polystyrene and Au/polystyrene double-layer nanorings, can be released from the substrates, resulting in free-standing composite nanorings, which might be used as self-assembly building blocks and ultrasensitive bio- and chemical sensors.

In this study, we demonstrate a new insight into the growth stage of aqueous semiconductor nanocrystals (NCs); namely, that the experimental variable-dependent growth rate and photoluminescence quantum yields (PLQYs) are understandable according to electrostatics. In this context, the aqueous NCs possess (from core outwards) an inorganic core, ligand layer, adsorbed layer, and a diffuse layer. The presence of an electric double-layer not only makes the NCs dispersible in the colloidal solution, but also governs the migration of monomers and monomer adsorption on the NC surface. To maintain NC growth, monomers need to migrate through the double-layer. Consequently, the nature of the diffuse layer influences the ability of monomer diffusion and hence the growth rate of NCs. Systematic studies reveal that the experimental variables, including precursor concentrations, pH of the solution, additional NaCl concentrations, ratio of Cd to ligand, and the nature of the ligands significantly govern the nature of the NC electric double-layer. The experimental variables, which reduce the thickness of the diffuse layer, benefit from monomer diffusion and a rapid growth of NCs. However, on the other hand, the diffuse layer also presents a charge-selective transfer of Cd monomers. The neutral monomers, such as the complex of Cd²⁺ and 3-mercaptopropionic acid (MPA) with 1:1 molar ratio [Cd(MPA)], migrate through the diffuse layer more easily than the charged ones [Cd(MPA)₂²⁻ or Cd(MPA)₃⁴⁻], thus facilitating the growth of NCs. The nature of the adsorbed layer inside the diffuse layer, defined as the assumed interface of solid NCs and the liquid environment, also affects the growth rate and especially the PLQYs of NCs through the adsorption and coalescence of monomers on this interface. Strong interaction between the adsorbed layer and Cd monomers provides the opportunity to accelerate NC growth and to obtain NCs with high PLQYs.