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Doping in semiconductor quantum dots (QDs) using optically active dopants tailors their optical, electronic, and magnetic properties beyond what is achieved by controlling size, shape, and composition. Herein, we synergistically modulated the optical properties of eco‐friendly ZnInSe2/ZnSe core/shell QDs by incorporating Cu‐doping and Mn‐alloying into their core and shell to investigate their use in anti‐counterfeiting and information encryption. The engineered "Cu:ZnInSe2/Mn:ZnSe" core/shell QDs exhibit an intense bright orange photoluminescence (PL) emission centered at 606 nm, with better color purity than the undoped and individually doped core/shell QDs. The average PL lifetime is significantly extended to 201 ns, making it relevant for complex encryption and anti‐counterfeiting. PL studies reveal that in Cu:ZnInSe2/Mn:ZnSe, the photophysical emission arises from the Cu state via radiative transition from the Mn 4T1 state. Integration of Cu:ZnInSe2/Mn:ZnSe core/shell QDs into poly(methyl methacrylate) (PMMA) serves as versatile smart concealed luminescent inks for both writing and printing patterns. The features of these printed patterns using Cu:ZnInSe2/Mn:ZnSe core/shell QDs persisted after 10 weeks of water‐soaking and retained 70 % of PL emission intensity at 170 °C, demonstrating excellent thermal stability. This work provides an efficient approach to enhance both the emission and the stability of eco‐friendly QDs via dopant engineering for fluorescence anti‐counterfeiting applications. [ABSTRACT FROM AUTHOR]

A multi‐stimuli responsive tetraphenyl substituted tripehnylamine‐based aggregation induced emissive (AIE) material coupled with spiropyran was prepared. Owing to the presence of AIE and photochromic moiety, the molecule exhibits emissive aggregates, photochromism, and acidochromism. The multiple stimuli sensitive behavior of the molecule was explored for anti‐counterfeiting behavior on TLC plate and commercial banknotes. The fluorogenic and photogenic response under UV and visible light established the potential of the candidate as a new generation encryption material. [ABSTRACT FROM AUTHOR]

The spatially resolvable multicolored microrods have potential applications in many fields. However, achieving spatially resolved multicolor luminescence tuning on the microrod with a fixed composition remains a daunting challenge. Herein, a strategy is proposed that allows for the tuning of spatially resolved, multicolored upconversion (UC) luminescence (UCL) along a 1D heterogeneous microrod by modifying the pulse width of an external laser. NaYbF4:1 % Ho is identified as an UCL color‐adjustable material, exhibiting pulse width‐dependent multicolored UCL, resulting in a significant regulation of the red/green (R/G) ratio from 0.1 to 10.3 as the pulse width is varied from 0.1 to 10 ms. Such variability can be ascribed to differences in the number of photons incident upon the microrod throughout the period necessary for the UC process to occur. Additionally, NaYbF4:1 %Tm and NaYF4:20 %Yb,1 %Ho are employed as materials that emit blue and green light, respectively, with their UCL colors largely unaffected by changes in the pulse width. Subsequently, a tip‐modified epitaxial growth method is utilized to integrate both UCL color‐adjustable and non‐adjustable segments within the same microrod. Comparing with single‐color or fixed multicolor microrods, our developed multisegmented emissive color adjustable 1D heterogeneous microrods have unique optical characteristics and can carry more optical information. [ABSTRACT FROM AUTHOR]

It is always a challenge to achieve "off–on" luminescent switch by regulating non‐covalent interactions. Herein, we report a unique strategy for constructing high performance "off–on" tunable luminescent materials utilizing a novel molecule (TFPA) consist of pyrene and cyanostilbene. The pristine crystal of TFPA is almost non‐emissive. Upon grinding/UV irradiation, an obvious luminescence enhancement is observed. Theoretical and experimental results revealed the underlying mechanism of this intriguing "off–on" switching behavior. The non‐emissive crystal consists of ordered H‐aggregates, with adjacent two molecules stacked in an anti‐parallel manner and no overlapped area in pyrene moieties. When external force is applied by grinding or internal force is introduced through the photoisomerization, the dimer structures are facilitated with shorter intermolecular distances and better overlapping of pyrene moieties. In addition, the "on" state can recover to "off" state under thermal annealing, showing good reversibility and applicability in intelligence material. The present results promote an in‐depth insight between packing structure and photophysical property, and offer an effective strategy for the construction of luminescence "off–on" switching materials, toward the development of stimuli‐responsive luminescent materials for anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Small organic molecules which can emit fluorescence with tunable dual emission bands are significant for fundamental research and broad applications. In this work, two binaphthyl based arylacrylonitrile derivatives with pyrene and triphenylamine unit (BiNp‐Py and BiNp‐TPA) were designed and synthesized, respectively, featuring chiral backbone and dual AIE‐active cyanostyrene‐linked chromophores. Excellent fluorescence emissions in a range of solution and solid states were observed with high quantum yields, indicative of the solvatochromism and mechanochromism. More interestingly, dual emission bands were found and tunable by the water fraction in THF, and speculatively attributed to the balancing of intramolecular charge transfer (ICT) and locally excited (LE) emission in solution and aggregate states. Furthermore, the potential application in anti‐counterfeiting ink was also explored, indicating the very low concentration (5 ppm) for sufficient distinguishable vision and small colour migration (28 nm) for printing on the filter. The present work provides a new strategy to design organic luminescent structure having widely fluorescent emissions in dual states and a valuable reference for the study of chiral optical materials. [ABSTRACT FROM AUTHOR]

Although remarkable progresses are achieved in the design and development of the mono‐shift in photoluminescence for mechanofluorochromic materials, it is still a severe challenge to explore the opposite mechanofluorochromic materials with both blue‐ and red‐shifted photoluminescence. Herein, two unprecedented 4,5‐bis(TPE)‐1H‐imidazole fused pyridine or quinoline‐based fluorophores X‐1 and X‐2 were designed and synthesized, and X‐1 and X‐2, exhibit completely opposite mechanofluorochromic behavior. Under UV lamp, the color of pristine X‐1 changed from blue to green with reversible redshifted 27 nm in fluorescence emission spectra after ground, while the color of pristine X‐2 changed from red to yellow with reversible blue‐shifted 74 nm after ground. The detailed characterizations (including PXRD, SEM and DSC) confirmed that this opposite mechanofluorochromism was attributed to the transformation of order‐crystalline and amorphous states. The crystal structure analysis and theoretical calculation further explain that opposite mechanofluorochromic behavior take into account different π–π stacking mode by induced π‐extended systems. In addition, these TPE‐based fluorophores (X‐1 and X‐2) exhibited excellent bio‐compatibility and fluorescence properties for bio‐imaging, writable data storage and anti‐counterfeiting materials. [ABSTRACT FROM AUTHOR]

Herein, we propose a rational design strategy by introducing photoactive thienyl and pyridyl groups into an AIE‐active tetraarylethene skeleton to achieve highly efficient photochemistry‐activated fluorescence enhancement from dominantly photo‐physical aggregation‐induced emission behavior, and prove that such photoactivated fluorescence enhancement is perfectly suited for superstable photocontrollable dual‐mode patterning applications in both solution and solid matrix. It is found that the photoactivated fluorescence of designed AIEgen is attributed to the irreversible cyclized‐dehydrogenation reaction under UV irradiation, and the oxidation product has a brighter fluorescence in both solution and solid states owning to its rigid and planar structure. The overall transformation rate of the AIEgen from its opened form to dehydrogenated form is up to nearly 100 % in a short period of UV irradiation, and the fast transformation and the stable product of this photochemical reaction guarantees super stability of photocontrolled patterning, which can be applied in photoactivated dual‐mode patterning and advanced anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

With the development of intellectual properties, concern about advanced anti‐counterfeiting is accumulating, which conventional single‐modal luminescence can no longer satisfy. As one of rapidly developing 0D materials, copper‐based perovskite shows great potential to realize multiple luminescent centers for complex emissions. In this work, Cd was doped into Cs3Cu2I5 and showed resultant emission at 560 nm which surprisingly showed a red‐shifted excitation peak from that of intrinsic self‐trapped emission, resulting in excitation‐wavelength dependent emission. When the excitation wavelength increased from 290 nm to 330 nm, the emission of Cd‐doped Cs3Cu2I5 changed from deep blue to cold white and finally yellow. Afterwards, Cd‐doped Cs3Cu2I5 was mixed with polystyrene to prepare anti‐counterfeiting ink for silk‐screen printing. Meanwhile, Cd‐doped Cs3Cu2I5 maintains outstanding stability after doping, no matter under ambient, continuous UV radiation or high‐temperature environment. The intensity can be almost totally recovered after heating‐and‐cooling cycles. This study lays groundwork for future research into multiple luminescent center manipulation in 0D materials. [ABSTRACT FROM AUTHOR]

Luminescent organic‐inorganic metal halides (OIMHs) are well known as a new materials family in recent years. Novel materials and applications of luminescent OIMHs have been explored by changing either the organic component or the metal halide species. Thereinto, the stimuli‐responsive (SR) phenomena in OIMHs have drawn much attention recently, for not only their attractive application potential but also the helpfulness in understanding the stability of OIMHs to the external environment. Herein, the luminescent OIMHs that are sensitive to external stimuli including contact, pressure, mechanical grinding, light, heat, and gas molecules, are reviewed, with an emphasis on analyses of the structural change during the SR process. The applications of SR luminescent OIMHs in widespread fields, including gas sensing, information encryption, and rewritable luminescent paper are summarized. Finally, the challenges that deserve to be further explored in this research field are discussed, which provides certain guidance for the future study of SR luminescent OIMHs. [ABSTRACT FROM AUTHOR]

Eu2+‐, Mn2+‐ and Eu2+−Mn2+‐doped CaMgSi2O6 phosphors have been prepared by a high‐temperature solid‐state reaction. Systematic investigation of the concentration‐ and temperature‐dependent luminescence of Mn2+ showed that Mn2+ ions occupy two distinct sites in CaMgSi2O6. Electron–vibration interaction (EVI) analyses of Mn2+ ions revealed Huang–Rhys factors of 4.73 and 2.82 as well as effective phonon energies of 313 and 383 cm−1 for the two sites. Eu2+−Mn2+ energy transfer is also discussed, and its efficiency is estimated by lifetime and luminescence spectra. The different thermal quenching behaviours of Eu2+ and Mn2+, the distinct emission colours of Eu2+ (blue, band peak at ∼451 nm) and Mn2+ (yellow–red range, band peaks at ∼583 and 693 nm) endow the co‐doped samples with potential applications in luminescence thermometry and temperature‐/excitation wavelength‐responsive dual anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Two challenges remain for organic thermoresponsive materials; one is to develop high‐performance red‐emissive thermoresponsive materials, while another is to simultaneously achieve high contrast ratio (CR), fast and reversible thermoresponse in a single element. Herein, we not only develop a new deep‐red emissive squaraine‐based AIEgen (TPE‐SQ12) based on a pyrylium end group, which is suitable for fabricating high‐performance thermoresponsive materials, but also show an effective approach to improve both CR (∼ten times increase) and response time (less than 3 seconds), that is, molecularly dispersing AIEgen into an elastomer, attributed to the significantly expanded free volume of elastomer upon increasing the temperature that can activate the AIEgen intramolecular movements more pronouncedly. Double encryption and temperature mapping systems have been separately established by using our designed elastomer/TPE‐SQ12 film, showing the great potential for anti‐counterfeiting and temperature sensing. Finally, white emission is further achieved by co‐doping TPE‐SQ12 with cyan dye into elastomer, which enables fluorescent thermochromism for improving the temperature mapping ability. [ABSTRACT FROM AUTHOR]

We report a general design strategy for a new class of luminogens with dual‐state emission (DSEgens) that are brightly emissive in both the solution and solid state, with solvatochromism properties, by constructing a partially shared donor–acceptor pattern based on a twisted molecule. The DSEgens with bright fluorescence emission in both the solid and solution state demonstrate a unique solvatochromism behaviour depending on solvent polarity and thus may have applications in anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

A strategy is demonstrated to protect valuable items, such as currency, pharmaceuticals, important documents, etc. against counterfeiting, by marking them with luminescent security codes. These luminescent security codes were printed by employing luminescent ink formulated from a cost effective dual-mode luminescent composite pigment of Gd1.7Yb0.2Er0.1O3 and Zn0.98Mn0.02S phosphors using commercially available PVC Gold medium. In the composite, Gd1.7Yb0.2Er0.1O3 and Zn0.98Mn0.02S account for upconversion and downconversion processes, respectively. The synthesis procedure of the composite involves the admixing of Gd1.7Yb0.2Er0.1O3 nanorods and Zn0.98Mn0.02S phosphor, synthesised by hydrothermal and facile solid-state reaction methods, respectively. The structural, morphological, microstructural, and photoluminescent features of Gd1.7Yb0.2Er0.1O3 nanorods, Zn0.98Mn0.02S phosphor and composite were characterised by using XRD, SEM, TEM, and photoluminescence (PL) techniques, respectively. The distribution of PL intensity of the printed pattern was examined by using confocal PL mapping microscopy. The obtained results reveal that security codes printed using ink formulated from this bi-luminescent composite pigment provide dual-stage security against counterfeiting. [ABSTRACT FROM AUTHOR]

Keywords: anti-counterfeiting; organic-inorganic metal halides; photoluminescence; stimuli response; structural transformation EN anti-counterfeiting organic-inorganic metal halides photoluminescence stimuli response structural transformation 1 1 1 07/05/22 20220701 NES 220701 Luminescent organic-inorganic hybrid metal halides are featured as an emerging class of stimuli-responsive materials in the Review by Huang and Wang (DOI: 10.1002/chem.202200609). Anti-counterfeiting, organic-inorganic metal halides, photoluminescence, stimuli response, structural transformation Frontispiece: Luminescent Organic-Inorganic Hybrid Metal Halides: An Emerging Class of Stimuli-Responsive Materials. [Extracted from the article]

Cover Feature: Rational Design of Dual-State Emission Luminogens with Solvatochromism by Combining a Partially Shared Donor-Acceptor Pattern and Twisted Structures (Chem. Eur. J. 70/2019) Keywords: anti-counterfeiting; dual-state emission; solvatochromism; twisted intramolecular charge transfer; twisted structure Anti-counterfeiting, dual-state emission, solvatochromism, twisted intramolecular charge transfer, twisted structure. [Extracted from the article]