Rigid Environment Research Articles

Thermal Activated Reversible Phosphorescence Behavior of Solid Supramolecule Mediated by β‐Cyclodextrin

AbstractA reversible solid thermally responsive deep‐blue pure organic room temperature phosphorescent material is constructed by terephthalic acid (PPA), β‐cyclodextrin (β‐CD), and poly(vinylalcohol) (PVA). Attributed to the host‐guest interaction of β‐CD to isolate PPA chromophore and the rigid environment offered by hydrogen bonds to suppress the nonradiative decays, amorphous supramolecular assembly PPA‐CD/PVA not only induces a deep‐blue phosphorescence at 410 nm that differing from traditional PPA derivatives with green emission but also enhances the quantum yield up to 30.52%. Uncommonly, this film exhibits a unique reversible thermal stimulation response property with blue and cyan phosphorescence color transitions because heating can destroy the binding behavior between β‐CD and PPA, resulting in redshift phosphorescence emission from PPA stacking. Additionally, with the incorporation of Rhodamine B (RhB) or Sulforhodamine 101 (SR101) into the supramolecular film, color‐tunable phosphorescence from blue to white, yellow, and red relying on the thermal stimulation is realized through triplet‐to‐singlet Förster resonance energy transfer (TS‐FRET) platform. These thermochromic phosphorescence materials are successfully applied in multilevel anticounterfeiting and information encryption, which provides a new simple approach for temperature‐responsive TS‐FRET multicolor luminescence supramolecular materials.

Colorful Room‐Temperature Phosphorescence Including White Afterglow from Mechanical Robust Transparent Wood for Time Delay Lighting

The preparation of mechanical robust organic room‐temperature phosphorescence (RTP) materials especially with white afterglow is attractive but rarely reported. Herein, a method to produce mechanical robust colorful RTP transparent wood (PTW) by infiltrating delignified wood with poly (vinyl alcohol) solutions containing arylboronic acids with various π conjugations is reported. The doubly rigid environment provided by the B─O covalent bonds and hydrogen bonds can stabilize the triplet excitons, leading to a ultralong lifetime of up to 2.13 s and excellent RTP emission stability (without obviously quenching over a month) of the target PTW. Besides, as a promising structural material for optical applications, the PTW shows combined advantages of multicolored persistent luminescence (from blue to green and then to red), good optical transmittance (≈90%), and striking mechanical strength (≈154 MPa). More importantly, by introducing appropriate amount of fluorescent dye rhodamine 6 G to the PTW with blue afterglow, white afterglow with a lifetime of 1.85 s is successfully achieve through triplet‐to‐singlet Förster resonance energy transfer. The PTW can function as afterglow window, anticounterfeiting label, and time delay lighting. This success paves the way for the development of mechanical robust, ecofriendly, and practical RTP materials.

Improvement in persistent room temperature phosphorescence of polymeric systems via a melt‐pressing method

AbstractPolymer‐based afterglow materials with persistent room temperature phosphorescence (pRTP) have attracted ever‐increasing attention due to their excellent mechanical property, suitability for large‐area production, and diverse processing methods. However, most pRTP polymers were solution‐processed into the films via casting. Herein, a simple processing method of melt‐pressing was proposed, which can improve the phosphorescence of various emitters when doped into polyamide‐12 (PA12) or its copolymer PA4 matrix. Notably, for Be@PA4 and Ch@PA4 (benzo[c]phenanthrene, Be and chrysene, Ch), their casted films did not show any afterglow, while the melt‐pressed ones exhibited bright afterglow of over 4.0 s, even if there were no hydrogen or ionic interaction between the emitters and the matrix. Detailed investigations demonstrate the melt‐pressing procedure can increase the non‐covalent interaction among the matrix as well as offer a rigid and dense environment. The melt‐pressed RTP improvement strategy was also applied to other polar polymers. Additionally, the melt‐pressing method would be of great potential in high‐level anti‐counterfeiting like preparing colorful camouflage patterns. Therefore, we offered a feasible method of melt‐pressing to improve the phosphorescence of polymeric materials without a change in chemical composition or feeding ratio. This work also gained a deeper understanding of the luminescence of polymer‐based systems.

Combining geometric constraint and redox non-innocence within an ambiphilic PBiP pincer ligand.

The synthesis of the first pincer ligand featuring a strictly T-shaped group 15 element and its coordination behaviour towards transition metals is described. The platform is itself derived from a trianionic redox non-innocent NNN scaffold. In addition to providing a rigid coordination environment to constrain a Bi centre in a T-shaped geometry to manipulate its frontier molecular orbital constitution, the NNN chelate displays highly covalent bonding towards the geometrically constrained Bi centre. The formation of intriguing ambiphilic Bi-M bonding interactions is demonstrated upon formation of a pincer complex as well as a multimetallic cluster. All compounds are comprehensively characterised by spectroscopic methods including X-ray Absorption Near Edge Structure (XANES) spectroscopy and complemented by DFT calculations.

Highly stable color-tunable organic long-persistent luminescence from a single-component exciplex copolymer for in vitro antibacterial.

Developing exciplex-based organic long-persistent luminescence (OLPL) materials with high stability is very important but remains a formidable challenge in a single-component system. Here, we report a facile strategy to achieve highly stable OLPL in an amorphous exciplex copolymer system via through-space charge transfer (TSCT). The copolymer composed of electron donor and acceptor units can not only exhibit effective TSCT for intra/intermolecular exciplex emission but also construct a rigid environment to isolate oxygen and suppress non-radiative decay, thereby enabling stable exciplex-based OLPL emission with color-tunable feature for more than 100 h under ambient conditions. These single-component OLPL copolymers demonstrate robust antibacterial activity against Escherichia coli under visible light irradiation. These results provide a solid example to exploit highly stable exciplex-based OLPL in polymers, shedding light on how the TSCT mechanism may potentially contribute to OLPL in a single-component molecular system and broadening the scope of OLPL applications.

How does Organizational Communication affect Job Satisfaction among Employees of Automotive Companies?

This research aims to find out how organizational communication influences job satisfaction among automotive company employees. The population in this study were all internal employees of companies operating in the automotive sector, or in this case PT Hadji Kalla Toyota, totaling 80 people. The instruments used in the research were observation, documentation, and questionnaires. The data analysis technique used is simple linear regression analysis and partial hypothesis testing using the IBM Statistical for Product and Service Solution (SPSS) version 21 program. Based on the results of statistical tests, it shows that partially the organizational communication variable has a positive and significant effect on employee job satisfaction. Based on the results of this research, PT Hadji Kalla Toyota should maintain and improve organizational communication by creating a work environment that is not rigid, because a rigid work environment can cause communication between employees to decrease. By establishing good communication, this variable can increase job satisfaction. employee.

Illusory percepts of curvilinear self-motion when moving through crowds.

Self-motion generates optic flow, a pattern of expanding visual motion. Heading estimation from optic flow analysis is accurate in rigid environments, but it becomes challenging when other human walkers introduce independent motion to the scene. Previous studies showed that heading perception is surprisingly accurate when moving through a crowd of walkers but revealed strong heading biases when either articulation or translation of biological motion were presented in isolation. We hypothesized that these biases resulted from misperceiving the self-motion as curvilinear. Such errors might manifest as opposite biases depending on whether the observer perceived the crowd motion as indication of his/her self-translation or self-rotation. Our study investigated the link between heading biases and illusory path perception. Participants assessed heading and path perception while observing optic flow stimuli with varying walker movements. Self-motion perception was accurate during natural locomotion (articulation and translation), but significant heading biases occurred when walkers only articulated or translated. In this case, participants often reported a curved path of travel. Heading error and curvature pointed in opposite directions. On average, participants perceived the walker motion as evidence for viewpoint rotation leading to curvilinear path percepts.

Decaf: Monocular Deformation Capture for Face and Hand Interactions

Existing methods for 3D tracking from monocular RGB videos predominantly consider articulated and rigid objects ( e.g. , two hands or humans interacting with rigid environments). Modelling dense non-rigid object deformations in this setting ( e.g. when hands are interacting with a face), remained largely unaddressed so far, although such effects can improve the realism of the downstream applications such as AR/VR, 3D virtual avatar communications, and character animations. This is due to the severe ill-posedness of the monocular view setting and the associated challenges ( e.g. , in acquiring a dataset for training and evaluation or obtaining the reasonable non-uniform stiffness of the deformable object). While it is possible to naïvely track multiple non-rigid objects independently using 3D templates or parametric 3D models, such an approach would suffer from multiple artefacts in the resulting 3D estimates such as depth ambiguity, unnatural intra-object collisions and missing or implausible deformations. Hence, this paper introduces the first method that addresses the fundamental challenges depicted above and that allows tracking human hands interacting with human faces in 3D from single monocular RGB videos. We model hands as articulated objects inducing non-rigid face deformations during an active interaction. Our method relies on a new hand-face motion and interaction capture dataset with realistic face deformations acquired with a markerless multi-view camera system. As a pivotal step in its creation, we process the reconstructed raw 3D shapes with position-based dynamics and an approach for non-uniform stiffness estimation of the head tissues, which results in plausible annotations of the surface deformations, hand-face contact regions and head-hand positions. At the core of our neural approach are a variational auto-encoder supplying the hand-face depth prior and modules that guide the 3D tracking by estimating the contacts and the deformations. Our final 3D hand and face reconstructions are realistic and more plausible compared to several baselines applicable in our setting, both quantitatively and qualitatively. https://vcai.mpi-inf.mpg.de/projects/Decaf

Biomechanical evaluation of multi-rod constructs to stabilize an S1 pedicle subtraction osteotomy (PSO): a finite element analysis.

To develop and validate a finite element (FE) model of a sacral pedicle subtraction osteotomy (S1-PSO) and to compare biomechanical properties of various multi-rod configurations to stabilize S1-PSOs. A previously validated FE spinopelvic model was used to develop a 30° PSO at the sacrum. Five multi-rod techniques spanning the S1-PSO were made using 4 iliac screws and a variety of primary rods (PR) and accessory rods (AR; lateral: Lat-AR or medial: Med-AR). All constructs, except one, utilized a horizontal rod (HR) connecting the iliac bolts to which PRs and Med-ARs were connected. Lat-ARs were connected to proximal iliac bolts. The simulation was performed in two steps with the acetabula fixed. For each model, PSO ROM and maximum stress on the PRs, ARs, and HRs were recorded and compared. The maximum stress on the L5-S1 disc and the PSO forces were captured and compared. Highest PSO ROMs were observed for 4-Rods (HR + 2 Med-AR). Constructs consisting of 5-Rods (HR + 2 Lat-ARs + 1 Med-AR) and 6-Rods (HR + 2 Lat-AR + 2 Med-AR) had the lowest PSO ROM. The least stress on the primary rods was seen with 6-Rods, followed by 5-Rods and 4-Rods (HR + 2 Lat-ARs). Lowest PSO forces and lowest L5-S1 disc stresses were observed for 4-Rod (Lat-AR), 5-Rod, and 6-Rod constructs, while 4-Rods (HR + Med-AR) had the highest. In this first FE analysis of an S1-PSO, the 4-Rod construct (HR + Med-AR) created the least rigid environment and highest PSO forces anteriorly. While 5- and 6-Rods created the stiffest constructs and lowest stresses on the primary rods, it also jeopardized load transfer to the anterior column, which may not be favorable for healing anteriorly. A balance between the construct's rigidity and anterior load sharing is essential.

Confining monochromophore in dynamic polymer network for multi-stimuli responsive fluorescence-phosphorescence dual-emission

Organic fluorescence-phosphorescence dual-emission materials are attracting broad attention for their wide potential applications in information technology, display media, etc. Most reported organic systems rely on the combination of two or more luminogens that emit different-colored phosphorescence and fluorescence respectively. By contrast, the fluorescence-phosphorescence dual-emission from one single luminogen system are especially appealing, as they can offer many advantages such as improved luminescence stability, simplified fabrication process and excellent reproducibility. Nevertheless, it remains challenging to achieve stimuli-responsive fluorescence-phosphorescence dual-emission in monochromophore-based organic material. Herein, we specially designed one new bromine-substituted naphthalimide molecule and incorporated it into a dynamic carboxyl hydrogen-bonded polyacrylic acid (PAA) network to produce the robust multi-stimuli-responsive fluorescence-phosphorescence dual-emission materials. Detailed studies demonstrated that high-density carboxyl hydrogen-bonded crosslinks play important roles in the achievement of intense phosphorescence by providing a rigid environment and efficient oxygen barrier to stabilize the triplet-excited states. On this basis, responsive fluorescence-phosphorescence dual-emission characteristic was guaranteed to realize interesting luminescence color changes, because many environmental stimuli (e.g., temperature, humidity, or alcohol) were known to dissociate the carboxyl hydrogen-bonded crosslinks. This reported strategy is expected to be universal and promising for the future development of powerful organic fluorescence-phosphorescence dual-emission materials with versatile uses.

Highly two‐photon and X‐ray excited long‐persistent luminescence in a crystalline host‐guest aggregate

AbstractAs a unique type of supramolecular self‐assemblies, crystalline host‐guest aggregates have attracted extensive interests in multiple application fields. Herein, a crystalline host‐guest aggregate LIFM‐HG1 was obtained with curcubit[8]uril as the host and carboxypyridinium salt as the guest. Single‐crystal structural analysis indicates that the presence of abundant weak interactions in LIFM‐HG1 provides a rigid environment for the guest molecule and effectively blocks the external quenchers. Spectral analysis and theoretical calculations confirm the presence of robust triplet energy levels in LIFM‐HG1. Even more impressively, the intersystem crossing channels of the guest molecules are greatly opened up after the formation of the crystalline host‐guest aggregate, resulting in a large kisc of 6.70 × 107 s−1 at room temperature for LIFM‐HG1 (which is ∼0 for pure guest), leading to fascinating multichannel (including one‐photon, two‐photon, and X‐ray) excited LPL properties. In addition, the crystalline LIFM‐HG1 has a much higher triplet state luminescence efficiency under X‐ray and two‐photon excitation than that under single‐photon excitation (AP/AF = 86.8, 44.8, 10.7 under the three circumstances, respectively). And the phosphorescent emission intensity of LIFM‐HG1 is 27.6 times higher than that of the crystalline guest under X‐ray excitation. As a result, LIFM‐HG1 shows a long afterglow retention time under both single‐ and two‐photon excitation, and an impressive afterglow retention time of 1 s under X‐ray excitation. Furthermore, the excellent lysosomal targeting and low cytotoxicity by the formation of host‐guest aggregate makes LIFM‐HG1 promising to be used as a novel lysosomal‐targeted two‐photon excited phosphorescent tracer.

Promoting organic room temperature phosphorescence through in situ polymerization

AbstractOrganic room temperature phosphorescence materials (RTP) have attracted much attention for their wide application in organic light‐emitting diodes, anti‐counterfeiting, and sensors. In this work, a series of organic luminogens containing carbonyl and aromatics were fixed in a three‐dimensional polymethyl methacrylate (PMMA) network by in situ polymerization. All organic luminogens‐doped in situ PMMA (s‐PMMA) columns achieved longer RTP lifetimes than those of doped commercial PMMA (c‐PMMA) films, especially, the RTP lifetime of NMP2O in these PMMA matrixes increased from 1.82 ms to 156.34 ms by about 86 times. It is mainly due to the restriction of molecular motions by highly entangled polymer chains and rigid environments to efficiently inhibit the non‐radiative transitions. Also, the excellent shielding effect toward oxygen by the in situ polymerization process can avoid possible quenching effects on triplet excited states, beneficial to RTP emission. Thus, it affords an efficient approach to achieving persistent RTP for three‐dimensional displaying applications.

On intergranular interaction and the crystallographic mechanism of plastically deformed polycrystalline metals

Taylor principle prevailing currently has been proved to be effective only when grains or grain clusters are deformed in a rigid environment, which disagrees with the reality. Grains realize their plastic deformation in elastoplastic environment, and the equilibrium of intergranular stress and strain need to be reached simultaneously and naturally. The intergranular reaction stress (RS) during deformation can be calculated according to Hooke’s law and the yield stress should be the up-limit of the RS. The combinations of constant external stress and changing RS in RS theory induce alternate activation of deformation systems including slips and twinning with different work hardening rates, while grain orientations and inhomogeneous distribution of external stress have important influence. Some additional deformation systems near the boundaries need to be locally activated when the reduced stress up-limits are reached frequently, to balance the intergranular stress and strain incompatibilities in elastoplastic way. Based on the simpler RS theory, the simulation results of rolling texture on aluminium, low carbon steel, austenite stainless steel, titanium are very close to the reality, indicating that the intergranular elastoplastic interactions and the corresponding crystallographic behaviours of plastic deformation have been reasonably and quantitatively described, therefore, Taylor principle becomes no more necessary.

Mixed B-site driven [InBr4]− tetrahedral efficient blue emission

The [InX4]− tetrahedron is a structure with stronger rigidity than the [InX6]3− octahedron, which makes it a possible blue light emitting material. In this study, the method of mixed B-sites is used to control the polyhedral transition in the crystal structure. In3+ ions partially replace Pb2+ ions to form the mixed B sites of Pb-In. The electronegativity difference of both causes clear energy transfer between Pb and In. The movement of the electron cloud causes a change in the polyhedral structure, which promotes the formation of [PbBr5]3− pyramid and [InBr4]− tetrahedra. In this way, we have achieved the efficient blue light emission of [InBr4]− tetrahedron for the first time. Under 372 nm UV light excitation, (PPh3H)4[PbBr5][InBr4] can achieve efficient blue emission, the photoluminescence quantum yield is 74.03 %, and the emission center at 463 nm. The rigid environment and the [InBr4]− tetrahedron are the sources of the minor Stokes shift, and the self-trapping exciton of the zero dimensions [InBr4]− tetrahedron is the source of efficient blue light emission. Meanwhile, we found that there are two optical transition processes between [PbBr5]3− and [InBr4]−. One is the transfer from the excited state of [PbBr5]3− to the excited state of [InBr4]−, and triphenylphosphine acts as the energy transfer medium of the two. The other is the transfer from the ground state of [PbBr5]3− (donor) to the excited state of [InBr4]− (acceptor).

Large-Scale Preparation for Multicolor Stimulus-Responsive Room-Temperature Phosphorescence Paper via Cellulose Heterogeneous Reaction.

The large-scale preparation of sustainable room-temperature phosphorescence (RTP) materials, particularly those with stimulus-response properties, is attractive but remains challenging. This study develops a facile heterogeneous B─O covalent bonding strategy to anchor arylboronic acid chromophores to cellulose chains using pure water as a solvent, resulting in multicolor RTP cellulose. The rigid environment provided by the B─O covalent bonds and hydrogen bonds promotes the triplet population and suppresses quenching, leading to an excellent lifetime of 1.42 s for the target RTP cellulose. By increasing the degree of chromophore conjugation, the afterglow colors can be tuned from blue to green and then to red. Motivated by this finding, a papermaking production line is built to convert paper pulp reacted with an arylboronic acid additive into multicolor RTP paper on a large scale. Furthermore, the RTP paper is sensitive to water because of the destruction of hydrogen bonds, and the stimuli-response can be repeated in response to water/heat stimuli. The RTP paper can be folded into 3D afterglow origami handicrafts and anti-counterfeiting packing boxes or used for stimulus-responsive information encryption. This success paves the way for the development of large-scale, eco-friendly, and practical stimuli-responsive RTP materials.

Nickel(II) Analogues of Phosphorescent Platinum(II) Complexes with Picosecond Excited-State Decay.

Square-planar Ni(II) complexes are interesting as cheaper and more sustainable alternatives to Pt(II) luminophores widely used in lighting and photocatalysis. We investigated the excited-state behavior of two Ni(II) complexes, which are isostructural with two luminescent Pt(II) complexes. The initially excited singlet metal-to-ligand charge transfer (1MLCT) excited states in the Ni(II) complexes decay to metal-centered (3MC) excited states within less than 1 picosecond, followed by non-radiative relaxation of the 3MC states to the electronic ground state within 9 - 21 ps. This contrasts with the population of an emissive triplet ligand-centered (3LC) excited state upon excitation of the Pt(II) analogues. Structural distortions of the Ni(II) complexes are responsible for this discrepant behavior and lead to dark 3MC states far lower in energy than the luminescent 3LC states of Pt(II) compounds. Our findings suggest that if these structural distortions could be restricted by more rigid coordination environments and stronger ligand fields, the excited-state relaxation in four-coordinate Ni(II) complexes could be decelerated such that luminescent 3LC or 3MLCT excited states become accessible. These insights are relevant to make Ni(II) fit for photophysical and photochemical applications that relied on Pt(II) until now.

Nickel(II) Analogues of Phosphorescent Platinum(II) Complexes with Picosecond Excited‐State Decay

AbstractSquare‐planar NiII complexes are interesting as cheaper and more sustainable alternatives to PtII luminophores widely used in lighting and photocatalysis. We investigated the excited‐state behavior of two NiII complexes, which are isostructural with two luminescent PtII complexes. The initially excited singlet metal‐to‐ligand charge transfer (1MLCT) excited states in the NiII complexes decay to metal‐centered (3MC) excited states within less than 1 picosecond, followed by non‐radiative relaxation of the 3MC states to the electronic ground state within 9–21 ps. This contrasts with the population of an emissive triplet ligand‐centered (3LC) excited state upon excitation of the PtII analogues. Structural distortions of the NiII complexes are responsible for this discrepant behavior and lead to dark 3MC states far lower in energy than the luminescent 3LC states of PtII compounds. Our findings suggest that if these structural distortions could be restricted by more rigid coordination environments and stronger ligand fields, the excited‐state relaxation in four‐coordinate NiII complexes could be decelerated such that luminescent 3LC or 3MLCT excited states become accessible. These insights are relevant to make NiII fit for photophysical and photochemical applications that relied on PtII until now.

Visible light-excited full-color phosphorescent material realized by carbon dots dispersed in polyacrylamide and applied to anti-counterfeiting

Carbon dots-based phosphorescent composites have excellent room-temperature phosphorescent properties. However, the development of carbon dots-based phosphorescent materials that are excited by visible light and have adjustable colors remains a challenge. Here, we report on phosphorescent composites based on multicolored fluorescent carbon dots (CDs) and polyacrylamide (PAM) with four phosphorescent colors (blue, green, yellow and red). The phosphorescence of CDs@PAM composites is mainly derived from the C=O bonds of CDs. Electron transition of n-π* in the C=O bonds facilitates the intersystem crossover that are necessary to generate phosphorescence. In addition, the hydrogen bond actions between the amide groups of PAM polymer and the functional groups on CDs surface also promote the intersystem crossover and inhibit the non-radiative relaxation of triple states (T1) in CDs@PAM. Meanwhile, the PAM matrix provides a rigid protective environment (hydrogen bond mesh structure) that inhibits vibrations, rotations and collisions of the CDs' luminescent clusters (C=O), avoiding the rapid decay of phosphorescence. Four kinds of CDs based phosphorescence materials can produce brilliant phosphorescence under the excitation of visible light (flashlight). Finally, their colorful phosphorescent colors were used to achieve a naked-eye observable anti-counterfeit pattern, demonstrating the potential application of these materials.

UV-curing-enhanced Organic Long-Persistent Luminescence Materials.

Amorphous organic long-persistent luminescence materials (OLPLMs) can realize simpler solution processing and large-area uniform luminescence, which luminescent properties are significantly influenced by the rigid environment. However, research on utilizing the rigidity to promote long-persistent luminescence (LPL) properties of amorphous OLPLMs is still relatively rare due to the lack of an unambiguous and effective strategy to construct the rigid environment. Here, we propose a universal strategy to enhance the LPL performance of organic host-guest doping systems by UV curing, which utilizes the rigid environment constructed by UV curing to promote the interaction between host and guest, thus inducing the generation of highly efficient LPL performance. This solution-processable, large-area and "easy to realize" material fabrication strategy can make amorphous OLPLMs show broader application prospects in some fields, such as anti-counterfeiting, non-destructive detection, and pattern marking or indication. This article is protected by copyright. All rights reserved.

Spectroscopic Characterization of Thiacarbocyanine Dye Molecules Adsorbed on Hexagonal Boron Nitride: a Time-Resolved Study.

Physisorption on hexagonal boron nitride (hBN) gained interest over the years thanks to its properties (chemically and thermally stable, insulating properties, etc.) and similarities to the well-known graphene. A recent study showed flat-on adsorption of several cationic thiacarbocyanine dyes on hBN with a tendency to form weakly coupled H- or I-type aggregates, while a zwitterionic thiacarbocyanine dye rather led to a tilted adsorption. With this in-depth time-resolved study using the TC-SPC technique, we confirm the results proven by adsorption isotherms, atomic force microscopy, and stationary state spectroscopy combined with molecular mechanics simulations and estimation of the corresponding exciton interaction. The absence of a systematic trend for the dependence of the decay times, normalized amplitudes of the decay components, and contribution of different components to the stationary emission spectra upon the emission wavelength observed for all studied dyes and coverages suggests the occurrence of a single emitting species. At low coverage levels, the non-mono-exponential character of the decays was attributed to adsorption on different sites characterized by different intramolecular rotational freedom or energy transfer to nonfluorescent traps or a combination of both. The difference between the decay rates of the four dyes reflects a different density of the nonfluorescent traps. Although the decay time of the unquenched dyes was in the order of magnitude of that of dye monomers in a rigid environment, it is also compatible with weakly coupled aggregates such as proposed earlier based on the stationary spectra. Hence, the adsorption leads to a rigid environment of the dyes, blocking internal conversion. Increasing the concentration of the dye solution from which the adsorption on hBN occurs increases not only the coverage of the hBN surface but also the extent of energy transfer to nonfluorescent traps. For TDC (5,5-dichloro-3-3'-diethyl-9-ethyl-thiacarbocyanine) and TD2 (3-3'-diethyl-9-ethyl-thiacarbocyanine), besides direct energy transfer to traps, exciton hopping between dye dimers followed by energy transfer to these traps occurs, which resulted in a decreasing decay time of the longest decaying component. For all dyes, it was also possible to analyze the fluorescence decays as a stretched exponential as would be expected for energy transfer to randomly distributed traps in a two-dimensional (2D) geometry. This analysis yielded a fluorescence decay time of the unquenched dyes similar to the longest decay time obtained by analysis of the fluorescence decays as a sum of three of four exponentials.