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In this paper we elaborate on recently developed molecular switch architectures and how these new systems can help with the realization of new functions and advancement of artificial molecular machines. Progress in chemically and photoinduced switches and motors is summarized and contextualized such that the reader may gain an appreciation for the novel tools that have come about in the past decade. Many of these systems offer distinct advantages over commonly employed switches, including improved fidelity, addressability, and robustness. Thus, this paper serves as a jumping-off point for researchers seeking new switching motifs for specific applications, or ones that address the limitations of presently available systems.

This paper describes the comprehensive molecular characterisation and application of a commercially available, but structurally undefined, photochromic pigment for the development of textile sensors. The commercial pigment was successfully identified using a multianalytical approach, including analysis using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The identified pigment, ethyl-3′-methyl-3′-phenyl-1′-(propan-2-yl)-1′,3′-dihydrospiro[[4,1,2]benzoxadiazine-3,2′-indole], was used to develop a textile sensor by screen printing on a natural fibre fabric surface. The developed sensor exhibited a reversible colour change from white to pink upon exposure to UVA radiation (369 nm). The sensor is characterised by high sensitivity with a linear dose–response of 0–0.005 J/cm2 and a dynamic range of up to 0.05 J/cm2. Furthermore, the sensor’s molecular safety profile was assessed, including elemental composition and cytotoxicity tests on human dermal fibroblasts, which confirmed the sensor’s biocompatibility with occasional skin contact. In addition to its use in decorative and security elements for product authentication, this study demonstrates the sensor’s ability to map the 2D UVA radiation dose distribution. This research highlights the importance of precise molecular identification in the design of functional, safe, and intelligent textile systems.

Inorganic photochromic materials, as emerging photoresponsive materials, have attracted unparalleled interest because of their potential applications in various photoactive devices such as smart windows, optical memories, and photochromic decorations. Over the past decades, great research efforts have been focused on further development of high‐performance photochromic materials, revealing the underlying physical mechanism as well as exploring new advanced applications. However, significant challenges still exist in achieving large photochromic contrast, realizing color‐tunable response, and confirming the detailed photochromic processes. In this review, the latest progress of inorganic photochromic materials is summarized from the aspects of the advance of new materials, the mechanism of photochromism, the techniques for evaluating and revealing photochromism, and the methods for regulating photochromic behavior. The emerging applications of photochromic materials for optical information storage, photocatalysis, optical anti‐counterfeiting, radiation dosimetry and so on are also discussed. The perspectives and challenges of photochromic materials in terms of practical applications are presented. This review aims to provide fundamentals about the mechanism, properties and applications of inorganic photochromic materials and promote the application of photochromic materials in various optical devices. The latest progress of inorganic photochromic materials is summarized from the aspects of the advance of new materials, the mechanism of photochromism, the techniques for evaluating photochromism, the methods for regulating photochromic behavior and various emerging applications. This review aims to promote the application of photochromic materials in photoelectric devices and beyond.

When studying photochromic materials, photostability and endurance are crucial considerations. These characteristics can benefit UV sensors, optical rewritable storage devices, and anti-counterfeiting techniques, as well as the ophthalmic industry. When light irradiates a photochromic system, chromophoric dye molecules, the chromophoric part of the dye, and fatigue resistance refer to how well they hold up against photodegradation, photobleaching, and photooxidation. In our experiment, we examined the photo-fading tendency of a photochromic dye with photochromic textiles. We used the screen-printing technique to create photochromic prints with different dye concentrations. We then continuously exposed the prints to UV light using a spectrophotometer. UV light caused the photochromic dye molecules in these prints to fade and photodegrade. We used three distinct ways to assess UV irradiation over many cycles. We proposed three hypotheses: When photodegraded using various techniques, the UV dosage exhibits additive behaviour during recorded UV irradiance cycles. In addition, a visible light source is more likely to cause photodegradation entirely or partially when the reversion process repeats over several cycles. Next, the prints exhibit photofading when subjected to one UV cycle and multiple irradiance cycles within a single measurement block and numerous irradiance cycles within a single measurement period. The plateau of each measured photochromic cycle adheres to the one-phase dissociation feature for photo-fading behaviour. In contrast, the colour span values for the photochromic system, measured during the development phase of each UV irradiation cycle, fit the one-phase association model.

For the first time a pyrrolidinofullerene salt containing a spiropyran group and an ammonium group, capable of reversibly reacting to UV radiation, has been synthesized. Photoinduced reactions of the synthesized compounds were studied using absorption and luminescence spectroscopies, spectral and kinetic characteristics were measured. The hybrid molecule was found to exhibit intrinsic fluorescence even in the spirocyclic form. The C[sub.60] derivative showed a higher stability and better spectral and luminescent properties than the precursor.

In this paper, the structural, electronic, phonon, and optical properties of lanthanum (La)‐doped yttrium hydrogen selenide (YHSe), along with the effects of pressure variations on its optical properties, are investigated using the density functional theory method. Both the La‐doped and YHSe systems are dynamically stable, as indicated by phonon calculations showing no imaginary frequencies in the Brillouin zone (BZ). The influence of pressure on optical properties is examined, revealing that increased pressure enhances these properties, particularly by improving the absorption coefficient in the ultraviolet (UV) range. Moreover, the bandgap energy of both La‐doped YHSe and YHSe compounds is explored. Increasing La concentration reduces the bandgap and enhances the density of states (DOS) at Fermi energy, inducing metallic characteristics in YHSe. Furthermore, the optical properties are examined at various La concentrations, most of which exhibit a nonlinear relationship as the La concentration increases. Doping under extreme conditions significantly enhances the optical properties of La‐doped YHSe, particularly in the UV‐light wavelength range. Specifically, the absorption coefficient reaches its maximum value in the energy range of 6.678 −13.023 eV within the UV region for all concentrations, indicating strong absorption in this range. This suggests the material’s effectiveness in absorbing electromagnetic radiation, particularly in the UV range, making it a promising candidate for photochromic applications. A thorough exploration of the optical properties under doping reveals prominent peaks, particularly in response to the UV spectrum, with a slight shift toward higher energies beyond the UV range. This suggests that the material under study holds promise as a candidate for sustained photochromic performance over time.

Shape-shifting polymers usually require not only reversible stimuli-responsive ability, but also strong mechanical properties. A novel shape-shifting photochromic hydrogel system was designed and fabricated by embedding hydrophobic spiropyran (SP) into double polymeric network (DN) through micellar copolymerisation. Here, sodium alginate (Alg) and poly acrylate-co-methyl acrylate-co-spiropyran (P(SA-co-MA-co-SPMA)) were employed as the first network and the second network, respectively, to realise high mechanical strength. After being soaked in the CaCl2 solution, the carboxyl groups in the system underwent metal complexation with Ca2+ to enhance the hydrogel. Moreover, after the hydrogel was exposed to UV-light, the closed isomer of spiropyran in the hydrogel network could be converted into an open zwitterionic isomer merocyanine (MC), which was considered to interact with Ca2+ ions. Interestingly, Ca2+ and UV-light responsive programmable shape of the copolymer hydrogel could recover to its original form via immersion in pure water. Given its excellent metal ion and UV light stimuli-responsive and mechanical properties, the hydrogel has potential applications in the field of soft actuators.

Producing ultra-stabilized radicals via light irradiation has raised considerable concern but remains a tremendous challenge in functional materials. Herein, optically actuating ultra-stable radicals are discovered in a sterically encumbered and large π-conjugated tri(4-pyridyl)-1,3,5-triazine (TPT) ligands constructed photochromic compound Cu 3 (H-HEDP) 2 TPT 2 -2H 2 O ( QDU-12 ; HEDP=hydroxyethylidene diphosphonate). The photogeneration of TPT • radicals is the photoactive behavior of electron transfer from HEDP motifs to TPT units. The ultra-long-lived radicals are contributed from strong interchain π-π interactions between the large π-conjugated TPT components, with the radical lifetime maintained for about 18 months under ambient conditions. Moreover, the antiferromagnetic couplings between TPT • radicals and Cu 2+ ions plummeted the demagnetization to 35% of its original state after light irradiation, showing the largest room temperature photodemagnetization in the current radical-based photochromic materials.

The art of dyeing textiles has a long history, as natural dyes have been used since prehistoric times. With the development of synthetic dyes in the 19th century, the focus shifted from natural to synthetic dyes due to their superior properties. Recently, however, interest in natural dyes has increased again due to environmental and health concerns. Among industrial dyes, heterocyclic dyes, especially azo dyes, are of great importance due to their color brilliance and fastness. This review examines the synthesis, application, and analysis of azo dyes, especially heterocyclic dyes. It deals with monoazo, diazo, and polyazo dyes and highlights their structures, synthesis methods, and fastness properties. In addition, the ecological impact of azo dyes and practical solutions for their synthesis and application are discussed.

The emergence of smart windows has been a pivotal innovation in the field of energy efficiency and carbon emission reduction, sparking considerable interest worldwide. This review consolidates the latest research developments in inorganic‐based photochromic materials for smart windows applications, encompassing the design of device architectures, and their implementation in enhancing energy conservation, augmenting comfort levels, and optimizing indoor environmental control. Finally, this review culminates in an insightful analysis of the challenges and constraints in the existing research landscapes, which illuminates guidance for the directions and perspectives of future research. This review details research advances in photochromic (PC) smart windows based on inorganic materials. Buildings are important in global energy demand and carbon emissions and smart windows have considerable potential to improve energy efficiency in buildings. Different types of PC materials and PC devices with different structures are introduced, and the applications of PC smart windows for energy saving and daylight comfort improvement are discussed. In addition, we summarized the challenges and limitations of existing research studies and propose directions and developments for future research studies.