Photothermal Energy Research Articles

Sodium acetate trihydrate/melamine foam composite PCM encapsulated by CuS/rGO modified epoxy resin and endowed with light-to-heat conversion properties

In this work, we proposed a novel strategy for the conversion and storage of photothermal energy. This strategy combined hydrothermally prepared CuS/rGO with commercial epoxy resin adhesives. The light-capturing capability of CuS and fast electron transfer rate of rGO was harnessed to endow the modified resin with photothermal conversion capability. Using an inorganic PCM as the energy-storage medium and melamine foam as its support carrier, a form-stabilized composite phase-change material with a latent heat of phase change of 233.7 J/g and a phase-change temperature of 48.7 °C was obtained. In addition, the pre-prepared MER was coated onto the surface of the CPCM. Its purpose was to utilize the photothermal conversion and waterproof properties of modified resins to store solar energy in the internal phase-change materials, while alleviating the leakage problem during the phase-change process of inorganic salt hydrate phase-change materials in the past. The leakage tests showed that the 1.0 mm thick MER provided excellent protection against leakage, significantly reducing leakage of the liquid phase and moisture escape. The composite phase-change material CPCM/MER demonstrated satisfactory results in photothermal conversion experiments. 2% CuS/rGO addition to CPCM/MER can complete the phase change. The samples also showed good stability in the cycling tests. After 100 cycles of testing, the latent heat of the CPCM only decreased by 5.13%. According to the FT-IR results, the CPCM also possessed chemical stability. In this study, a CPCM/MER was successfully prepared, extending the practical application of traditional inorganic phase-change materials in the field of solar energy storage.

Photonic Lithotripsy: Near-Infrared Laser Activated Nanomaterials for Kidney Stone Comminution.

Near-infrared activated nanomaterials have been reported for biomedical applications ranging from photothermal tumor destruction to biofilm eradication and energy-gated drug delivery. However, the focus so far has been on soft tissues, and little is known about energy delivery to hard tissues, which have thousand-fold higher mechanical strength. We present photonic lithotripsy with carbon and gold nanomaterials for fragmenting human kidney stones. The efficacy of stone comminution is dependent on the size and photonic properties of the nanomaterials. Surface restructuring and decomposition of calcium oxalate to calcium carbonate support the contribution of photothermal energy to stone failure. Photonic lithotripsy has several advantages over current laser lithotripsy, including low operating power, noncontact laser operation (distances of at least 10 mm), and ability to break all common stones. Our observations can inspire the development of rapid, minimally invasive techniques for kidney stone treatment and extrapolate to other hard tissues such as enamel and bone.

Heat transfer characteristics of fluids containing paraffin core-metallic shell nanoencapsulated phase change materials for advanced thermal energy conversion and storage applications

The influence of heat transfer characteristics of fluids filled with paraffin core-metallic shell nanoencapsulated phase change material (PCM) on photothermal conversion and storage in a volumetrically heated solar system is numerically analysed. The results show that nanoencapsulated paraffin/Al, paraffin/Au, paraffin/Ag, and paraffin/Cu filled heat transfer fluids enhance the energy storage by 68, 73, 92 and 86 %, respectively as compared with the water-based Al, Au, Ag and Cu nanofluids. It is found that the phase change slurry (PCS) improves the temperature and storage gain, as the utilization of nanoencapsulated PCM and the rise in PCM mass concentration enhance the solar energy absorption power of the slurry. The maximum enhancement in stored energy is also observed for paraffin/Cu PCM filled slurry for a particle diameter of 15 nm. The enhancement in mass concentration of paraffin from 5 to 20 %, improves the thermal performance from 312 to 554 % compared to pure water, respectively. Increasing the size of the core/shell architecture of the PCM, however, reduces the surface area-to-volume ratio of the capsule, causing aggregation of the particles and decreasing the heat transfer between the capsule and the host fluid. This in turn results in decrease in temperature gain. Furthermore, it is noticed that the merger of mono- and hybrid- nanoparticles augments the thermal performance of the PCS. The findings of the study indicate that the paraffin core-metallic shell nanoencapsulated PCMs would significantly enhance the performance of advanced photothermal energy conversion and storage devices.

On-Chip Optical Waveguide Visible-Light Power Detector Based on Photothermal Effect of PPy/SU-8 Photopolymer

In this work, an all-optical on-chip polymer waveguide visible-light power detector is proposed based on photothermal effect of polypyrrole (PPy) nanoparticles. PPy/SU-8 waveguide material is prepared and the strong optical absorption of the photopolymer in the visible-light region is beneficial for efficient photothermal energy conversion. The photothermal characteristics of PPy/SU-8 are analyzed, and through selective absorption specificity of the PPy/SU-8 photopolymer in Vis-NIR region, the performances of the multimode interference (MMI) waveguide device by thermo-optic (TO) tuning are simulated. The photothermal energy conversion coefficient of the PPy/SU-8 waveguide is obtained as 2.5 K/mW. The actual sensitivity of the on-chip light power detector is measured as 2.3 nm/mW. This technique could be used to achieve ultra-compact on-chip all-optical detectors in future.

Intrinsically lighting absorptive PANI/MXene aerogel encapsulated PEG to construct PCMs with efficient photothermal energy storage and stable reusability

Intrinsically lighting absorptive PANI/MXene aerogel encapsulated PEG to construct PCMs with efficient photothermal energy storage and stable reusability

Effects of hydrothermal synthesis conditions on material properties of Cu-Se compounds for thermoelectric and photothermal energy conversion

Copper selenide (CuSe) is a promising material for these applications due to its unique properties such as meaningful electrical conductivity, Seebeck coefficient, and photothermal conversion efficiency. Here, a systematic investigation into the hydrothermal synthesis and characterization of copper selenides (CuSe) was performed for thermoelectric and photothermal applications. Depending on the feeding ratio of the Cu and Se precursors and reducing agent, CuSe2, CuSe, and Cu2Se were synthesized at a relatively low temperature and within a limited time frame. The crystal growth and morphology of the compounds were composition-dependent, which led to variations in their electrical conductivity, Seebeck coefficient, and thermoelectric properties. Synthesized Cu-Se compounds also showed promising photothermal conversion characteristics, which were utilized to increase the energy harvesting of the thermoelectric module under light exposure. This study provide important insights into the relationship between the synthesis conditions and the material properties, as well as the potential of CuSe-based materials for thermoelectric and photothermal applications.

An investigation into the thermo-fluid behavior of volumetrically heated cavities irradiated from the side

Radiation induced natural convection has been extensively researched due to its rife presence in numerous natural flows. Recently, it has seen renewed and resurged interests in context of understanding the photo-thermal energy conversion and its redistribution in direct absorption solar collectors (DASCs). The present work serves to further this objective; in particular, convection induced by direct interaction of the fluid and radiation (irradiated from side) has been critically and comprehensively investigated. In addition to DASCs, the present study has significant applications in various other fields such as nuclear power plants, building design, and laser fusion. A detailed mechanistic theoretical modeling framework has been developed to quantify the impact of various fluid properties and incident flux parameters; viz., Rayleigh number (102 to 108 in the laminar regime), Prandtl number (0.01–1000), optical thickness (0.1–100), convective heat loss from the transmitting wall (controlled in the simulation by varying the modified Biot number, Bi* from 0 to 5), aspect ratio (0.1–10). Furthermore, in addition to magnitude of the incident flux, its distribution (i.e., whether uniform or linearly varying) has also been dealt with. Another distinguishing aspect of the study is the use of the “heatlines” to visualize the flow of energy as it occurs during convection caused due to volumetric heating. Detailed analysis reveals that, while a conduction dominated regime is apparent at Ra ≤ 102, a transition regime occurs at 103 ≤ Ra ≤ 104, and convection is the domineering mechanism when Ra > 104. At higher Rayleigh numbers, the pattern of heatlines begins to resemble that of the streamlines. Nature of the flux distribution at the side wall (along the depth direction) significantly impacts the temperature distribution. Furthermore, there exits an optimum value of optical thickness (for a given Rayleigh number), which ensures minimum heat loss and maximum useful energy gain. Overall, through the present work, we have been able to decipher key design and operational parameters (and quantify their impacts) which dictate the momentum and heat transport in side-irradiated volumetrically heated cavities.

Oriented High Thermal Conductivity Solid-Solid Phase Change Materials for Mid-Temperature Solar-Thermal Energy Storage.

As the global energy crisis intensifies, the development of solar energy has become a vital area of focus for many nations. The utilization of phase change materials (PCMs) for photothermal energy storage in the medium temperature range holds great potential for various applications, but their conventional forms face several challenges. For instance, the longitudinal thermal conductivity of photothermal PCMs is inadequate for effective heat storage on the photothermal conversion surface, and there is a risk of leakage due to repeated solid-liquid phase transitions. Here, we report a solid-solid phase change material, tris(hydroxymethyl)aminomethane (TRIS), which has a phase change temperature of 132 °C in the medium temperature range, enabling high-grade and stable solar energy storage. To overcome the low thermal conductivity problem, we propose a large-scale production of oriented high thermal conductivity composites by compressing a mixture of TRIS and expanded graphite (EG) using the pressure induction method to create in-plane highly thermally conductive channels. Remarkably, the resulting phase change composites (PCCs) exhibit a directional thermal conductivity of 21.3 W/(m·K). Furthermore, the high phase change temperature (132 °C) and large phase change entropy (213.47 J/g) enable a large-capacity high-grade thermal energy to be used. The developed PCCs, when combined with selected photo-absorbers, exhibit efficient integration of solar-thermal conversion and storage. Additionally, we also demonstrated a solar-thermoelectric generator device with an energy output of 93.1 W/m2, which is close to the power of photovoltaic systems. Overall, this work provides a technological route to the large-scale fabrication of mid-temperature solar energy storage materials with high thermal conductivity, high phase change enthalpy, and no risk of leakage, and also offers a potential alternative to photovoltaic technology.

Enhancing optical contrast of sub-wavelength optical image using graphene oxide coated probe in scanning thermal microscopy

Scanning thermal microscopy (SThM) is a powerful technique for obtaining local thermal information on a sample surface using a nano-fabricated thermometer probe. One important application of SThM is sub-wavelength optical imaging, which captures the photothermal response of the probe to light. In this nano-scale imaging technique, optical contrast and spatial resolution are critical performance indicators. The size and material of the thermometer probe play a significant role in determining image quality, as a smaller radius can improve spatial resolution but reduce optical contrast and sensitivity due to decreased light absorption. To address this challenge, we have developed an approach to improve the photothermal energy conversion efficiency by coating the probe with atomically thin graphene oxide (GO). Our results demonstrate that this GO coating can enhance optical sensitivity by more than 1.5 times with linear optical power dependency. Importantly, the coating significantly improves the root mean square contrast of the image by 2.56 times without compromising spatial resolution. Our study highlights the potential of GO-coated probes to improve the sensitivity and quality of SThM-based sub-wavelength optical imaging.

Adsorption of Metformin on Graphene Nanoribbons and Application in Treatment of Oral Cancer Using Photothermal Energy

AbstractGraphene nanoribbons are thin sheets of graphene showing exclusive characteristics such as better drug‐loading capacity, adsorption on mammalian cells, greater surface area, and light‐absorbing ability. The current research work is to develop metformin‐adsorbed carboxyl‐functionalized oxidized graphene nanoribbons and utilize drug repurposing for the treatment of oral cancer by activating photo‐thermal radiation therapy. The nanoribbons are formulated by Hummer's method and evaluated for several characterization parameters like ATR‐ Fourier Transform Infrared (FTIR), Differential scanning calorimetry (DSC), topology, in vitro efficacy, ex vivo and in vitro cell line studies. The ATR‐FTIR spectrum of formulated nanoribbons shows distinctive peak at 3370 cm−1 (NH group) of metformin. The DSC specifies the incidence of steep endothermic crests at 235 °C (CNH3). The in vitro and ex vivo drug release studies show enhanced drug release in acidic pH (6.4) than physiological pH (7.4) with photothermal radiation. The in vitro cell line studies are processed via two‐way ANOVA that exhibits 67.74 ± 0.03% of % inhibition in presence of photothermal radiation. The study demonstrates higher inhibition of cancerous cells at lower concentration of drug and photothermal therapy in comparison to plain drug. The characteristic feature of graphene is used to develop targeted drug delivery system against the oral cancerous cells.

Continuous Photothermal and Radiative Cooling Energy Harvesting by VO2 Smart Coatings with Switchable Broadband Infrared Emission

Extensive use of renewable and clean energy is one of the promising ways to solve energy/environmental problems and promote the sustainable development of our society. As inexhaustible energy sources, the photothermal (PT) and radiative cooling (RC) energy from the sun and outer space have recently attracted tremendous interest. However, these two kinds of energy utilization have distinctly opposite spectral properties, especially in the infrared range, making it extremely difficult to integrate these two energy harvesting modes within a fixed device for continuous energy collection. Thus, in the current study, we have proposed a spectrally self-adaptive broadband absorber/emitter (SSBA/E) based on vanadium dioxide (VO2), a typical phase transition material, to achieve continuous energy harvesting via collecting solar thermal energy in PT mode during the day and obtaining cool energy in wide-band RC mode at night. Experimental results show that owing to the phase transition property of the VO2 layer, these two energy collection modes can be adaptively switched. Specifically, the VO2-based device shows a broadband infrared emissivity modulation from 0.21 to 0.75 and low critical temperatures (58.4 and 49.2 °C) during the phase transition, leading to continuous energy harvesting with high efficiency. Due to the broadband infrared emission, the RC maximum power of the SSBA/E device was estimated to be 58 W m-2. The proposed VO2 smart coatings are also applicable for many other applications such as thermal management of spacecraft, infrared camouflage, or adaptive optical devices.

Ternary mixture thermochromic microcapsules for visible light absorption and photothermal conversion energy storage

Thermochromic microcapsules with photothermal conversion properties were prepared by melamine urea formaldehyde resin (MUF) coated ternary mixtures (color coupler, color developer and solvent). The particle characteristics, chemical structure, heat storage properties, discoloration effect, thermal cycling durability and photothermal conversion properties of microcapsules were analyzed and characterized by ESEM and LPSA, FTIR and XRD, DSC and TGA, SC-10 and UV–Vis, thermal cycling test and solar simulator. The thermochromic and photothermal conversion mechanisms of microcapsules were analyzed. The results showed that the thermochromic microcapsules with a core material ratio of (1:3:60) have the best comprehensive performance. The chromatic aberration value of RTPCMs-C3 and RTPCMs-O3 is 23.35 and 12.14, respectively, which has a certain visible light absorption capacity and excellent thermal cycle durability. The photothermal conversion efficiencies of RTPCMs-C3 and RTPCMs-O3 under simulated solar irradiation were 55.4% and 72.9%, respectively. The conjugated organic polymer core material selectively absorbs the electromagnetic radiation frequency which are matching its internal electronic transition, causing the atomic lattice vibration to generate heat. The heat changes the state of the core material and dissociates the internal conjugated double bonds, eventually causing the microcapsules to change color.

Smart Strategies for Light and Thermal Management in High‐Efficiency Solar Steam Generation

Solar Steam Generation In article number 2201128, Ai Du and co-workers present a comprehensive summary and discussion of light and thermal management strategies in solar steam generation from the perspective of the structure design of ultra-black photo-thermal materials and energy conservation of the system. By using these strategies, evaporators with high evaporation rates and efficiencies that exceed theory values can be achieved.

Polypyrrole‐boosted photothermal energy storage in MOF‐based phase change materials

AbstractInfiltrating phase change materials (PCMs) into nanoporous metal–organic frameworks (MOFs) is accepted as a cutting‐edge thermal energy storage concept. However, weak photon capture capability of pristine MOF‐based composite PCMs is a stumbling block in solar energy utilization. Towards this goal, we prepared advanced high‐performance pristine MOF‐based photothermal composite PCMs by simultaneously integrating photon absorber guest (polypyrrole [PPy]) and thermal storage guest (1‐octadecanol [ODA]) into an MOF host (Cr‐MIL‐101‐NH2). The coated PPy layer on the surface of ODA@MOF not only serves as a photon harvester, but also serves as a phonon enhancer. Resultantly, ODA@MOF/PPy composite PCMs exhibit intense and broadband light absorption characteristic in the ultraviolet–visible–near‐infrared region, and higher heat transfer ability than ODA@MOF. Importantly, the photothermal conversion and storage efficiency of ODA@MOF/PPy‐6% is up to 88.3%. Additionally, our developed MOF‐based photothermal composite PCMs also exhibit long‐standing antileakage stability, energy storage stability, and photothermal conversion stability. The proposed coating strategy and in‐depth understanding mechanism are expected to facilitate the development of high‐efficiency MOF‐based photothermal composite PCMs in solar energy utilization.

Composite Hydrogel for the Targeted Capture and Photothermal Killing of Bacteria toward Facilitating Wound Healing.

Pathogenic infections pose a significant risk to public health and are regarded as one of the most difficult clinical treatment obstacles. A reliable and safe photothermal antibacterial platform is a promising technique for the treatment of bacterial infections. Given the damage that high temperatures cause in normal tissues and cells, a multifunctional hydrogel driven by photothermal energy is created by trapping bacteria to reduce heat transfer loss and conduct low-temperature photothermal sterilization efficiently. The 3-aminobenzene boronic acid (ABA)-modified graphene oxide is combined with carboxymethyl chitosan (CMCS) and cellulose nanocrystalline (CNC) networks to create the ABA-GO/CNC/CMCS composite hydrogel (composite gel). The obtained composite gel displays a uniform three-dimensional network structure, which can be rapidly heated to 48 °C under infrared light irradiation and is beneficial for killing wound infection bacteria and promoting wound healing. The results of animal experiments show that the composite gel significantly reduces inflammation by killing >99.99% of bacteria under near-infrared light irradiation. The result also demonstrates that it increases the granulation tissue thickness and collagen distribution and promotes wound healing. After treatment for 14 days, compared with the remaining 27.73% of the remaining wound area in the control group, the wound area in the composite gel with NIR group is only 0.91%. It significantly accelerates the wound healing process of Staphylococcus aureus infection and shows great potential for clinical application.

Chemical doping of unsubstituted perylene diimide to create radical anions with enhanced stability and tunable photothermal conversion efficiency.

N-doping of perylene diimides (PDIs) to create stable radical anions is significant for harvesting photothermal energy due to their intensive absorption in the near-infrared (NIR) region and non-fluorescence. In this work, a facile and straightforward method has been developed to control the doping of perylene diimide to create radical anions using organic polymer polyethyleneimine (PEI) as a dopant. It was demonstrated that PEI is an effective polymer-reducing agent for the n-doping of PDI toward the controllable generation of radical anions. In addition to the doping process, PEI could suppress the self-assembly aggregation and improve the stability of PDI radical anions. Tunable NIR photothermal conversion efficiency (maximum 47.9%) was also obtained from the radical-anion-rich PDI-PEI composites. This research provides a new strategy to tune the doping level of unsubstituted semiconductor molecules for varying yields of radical anions, suppressing aggregation, improving stability, and obtaining the highest radical anion-based performance.

Adhesive Composite Microspheres with Dual Antibacterial Strategies for Infected Wound Healing.

Skin damage and infection pose a severe challenge to human health. Construction of a novel versatile dressing with good anti-infection and healing-promoting abilities is greatly expected. In this paper, nature-source-based composite microspheres with dual antibacterial mechanisms and bioadhesive features by microfluidics electrospray for infected wound healing is developed. The microspheres enable sustained release of copper ions, which not only show long-term antibacterial properties, but also play important role in wound-healing-related angiogenesis. Additionally, the microspheres are coated with polydopamine via self-polymerization, which renders the microspheres adhesive to the wound surface, and further enhance the antibacterial ability through photothermal energy conversion. Based on the dual antibacterial strategies provided by copper ions and polydopamine as well as the bioadhesive property, the composite microspheres exhibit excellent anti-infection and wound healing performances in a rat wound model. These results, along with the nature-source-based composition and biocompatibility, indicate the great potential of the microspheres in clinical wound repair.

Radially graded metal foams arrangement in heat storage device of photothermal utilization systems

Metal foam was adopted for improving inherent low thermal conductivity of traditional thermal energy storage (TES), which conducted higher solar energy conversion efficiency. With consideration of more energy response and the mixing enhancement effect on heat conduction and natural convection, this work investigated a vertical TES tube in solar energy photothermal utilization systems, embedded in metallic foam with radial gradient porosity and pore density. Experiments and simulations have both been carried out. It is thoroughly examined how the liquid fraction, solid-liquid interface, temperature field, and velocity field evolve, and the properties of energy storage, such as heat transfer density and energy storage quantity, are further assessed. Results demonstrated that the melting duration was shortened by 11.2% for the positive radially graded porosity arrangement and prolonged by 16.8% for the negative, in comparison to the homogeneous structure. Meanwhile, influenced by the varied porosity, the temperature uniformity was enhanced by 4.9% for the positive and was deteriorated by 15.1% for the negative. In addition, positive and negative gradient pore density respectively increased the temperature uniformity of by 15.1% and 16.7%. Based above, metal foam tube with negative gradient porosity and pore density was suggested to build the more efficient photothermal solar energy conversion systems due to faster melting process and more homogeneous temperature uniformity.

MP05-15 PHOTONIC LITHOTRIPSY: EFFECT OF GOLD AND CARBON BASED NANOMATERIALS ON STONE COMMINUTION

You have accessJournal of UrologyCME1 Apr 2023MP05-15 PHOTONIC LITHOTRIPSY: EFFECT OF GOLD AND CARBON BASED NANOMATERIALS ON STONE COMMINUTION Ian Houlihan, Benjamin Kang, Smita De, and Vijay Krishna Ian HoulihanIan Houlihan More articles by this author , Benjamin KangBenjamin Kang More articles by this author , Smita DeSmita De More articles by this author , and Vijay KrishnaVijay Krishna More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003216.15AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Kidney stones affect ∼10% of individuals in the USA. The most common surgical stone treatments include laser lithotripsy by ureteroscopy and extracorporeal shock wave lithotripsy. Photonic lithotripsy (PL) is a novel technology for minimally-invasive, non-contact kidney stone treatment. PL utilizes photonic nanomaterials that convert low-intensity (<5 W), near-infrared laser energy to photothermal and/or photoacoustic energy for kidney stone fragmentation. Herein we investigate the effect of different photonic nanomaterials on PL. METHODS: Human kidney stones with a size range of 2–4 mm and a composition of >70% calcium oxalate (CaOx) were obtained from the Cleveland Clinic Pathology Lab. Five different photonic nanomaterials were evaluated: gold nanoshells (AuNS), gold nanorods (AuNR), multi-walled carbon nanotubes (MWNT), graphene oxide (GO), and polyhydroxy fullerenes (PHF). Each nanomaterial at each laser wavelength and power setting was tested with n=10 stones. Stones were treated with photonic nanomaterials and exposed to a NIR laser (785 nm or 1320 nm) at a distance of 10 mm for three, 3-minute intervals. Multiple intervals were used to observe changes and re-expose stones to the nanomaterial solution. The treatments were considered successful if two or more fragments were produced. RESULTS: Stones predominantly CaOx based were successively fragmented using the different nanomaterials (Figure 1) when irradiated with the 1320 nm and 785 nm NIR lasers. The 1320 nm laser successfully broke >50% of stones across all nanomaterials at 4 W and >30% of stones at 3 W. The 785 nm laser successfully broke >80% of stones across all nanomaterials at 2 W. No stones were fragmented at 1 W as not enough energy was generated for failure to occur. The stones analyzed pre and post PL by FTIR and µCT showed evidence of crack formation and thermal degradation. CONCLUSIONS: Photonic nanomaterials can fragment stones using laser wavelengths that are minimally absorbed by kidney tissue, at low energy and in non-contact mode at a distance of 10 mm. Successful stone comminution with different nanomaterials is dependent upon laser wavelength and laser power. All tested nanomaterials have the ability to fragment kidney stones in an in vitro setting. Source of Funding: LRI Accelerator Grant, Cleveland Clinic Caregiver Catalyst Award, U2Csupport 1U2CDK129440 © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e49 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ian Houlihan More articles by this author Benjamin Kang More articles by this author Smita De More articles by this author Vijay Krishna More articles by this author Expand All Advertisement PDF downloadLoading ...

Co‐Harvest Phase‐Change Enthalpy and Isomerization Energy for High‐Energy Heat Output by Controlling Crystallization of Alkyl‐Grafted Azobenzene Molecules

Photoisomerization‐induced phase change are important for co‐harvesting the latent heat and isomerization energy of azobenzene molecules. Chemically optimizing heat output and energy delivery at alternating temperatures are challenging because of the differences in crystallizability and isomerization. This article reports two series of asymmetrically alkyl‐grafted azobenzene (Azo‐g), with and without a methyl group, that have an optically triggered phase change. Three exothermic modes were designed to utilize crystallization enthalpy (∆Hc) and photothermal (isomerization) energy (∆Hp) at different temperatures determined by the crystallization. Azo‐g has high heat output (275–303 J g−1) by synchronously releasing ∆Hc and ∆Hp over a wide temperature range (−79 °C to 25 °C). We fabricated a new distributed energy utilization and delivery system to realize a temperature increase of 6.6 °C at a temperature of −8 °C. The findings offer insight into selective utilization of latent heat and isomerization energy by molecular optimization of crystallization and isomerization processes.