Albedo Research Articles

Neutral‐Colored Transparent Radiative Cooler by Tailoring Solar Absorption with Punctured Bragg Reflectors

Abstract Daytime radiative cooling (DRC) has emerged as a promising method for temperature reduction of surfaces exposed to sunlight, without energy consumption. Despite advancements in DRC design, existing reflector‐based methodologies often lack transparency because of visible reflection, hindering the widespread application of this technology using glass. Efforts to address this challenge have led to the development of transparent radiative cooling (TRC), although efficient cooling during daylight remains challenging because of the dominant solar energy absorption. This paper proposes a novel TRC design comprising a polydimethylsiloxane (PDMS) emitter atop a transparent dual‐reflector structure. An optimized Bragg reflector (OBR) and a 90 µm‐hole‐punctured Ag window screen reflector (WR) are used to reflect band A of the near‐infrared (NIR) spectrum (0.74 < λ < 1.4 µm) and the overall solar spectrum, respectively. During the daytime, the proposed TRC lowers the temperature by 22.1 °C through the transparent dual reflector system, compared to a PDMS‐coated glass. Thus, this approach optimizes the balance between solar reflection and visibility using a dual reflector, offering an optimal solution for applications requiring both cooling and transparency.

Design of a dynamically switchable metamaterial solar heating and daytime radiative cooling device based on reversible metal electrodeposition

Abstract The combination of daytime radiative cooling and solar heating can regulate the temperature of buildings in all seasons, which is vital to achieving energy savings. However, achieving a dynamic and efficient switch between radiative cooling and solar heating states is still challenging. The reversible metal electrodeposition is a promising electrochromic (EC) technology that can dynamically manipulate the visible and infrared spectrum by depositing a nanoscale metal layer. By combining it with a delicate nanostructure design, reconfigurable daytime radiative cooling and solar heating states can be achieved. In this work, a metamaterial EC device capable of efficiently switching between high solar reflectance (91.73%) and high solar absorptance (95.41%) via reversible silver layer electrodeposition has been developed. This device consists of a top layer, which is a visible transparent electrode of indium tin oxide covered with an ultrathin platinum film, an electrolyte in the middle, and a metamaterial absorber based on a metal/dielectric multilayered structure at the bottom. Afterward, we analyze the spectrum of each part of the device and carry out a parametric study on the practical performance with different ambient temperatures and convective heat transfer coefficients. The average solar reflectance of the device in the radiative cooling state is 93.41% within the range of 0.3–2.5 μm. In the solar heating mode, the average solar absorptance of the device reaches 95.46%. Numerical simulations show that the device in the cooling mode achieves a temperature drop of 5 °C–9.8 °C and an average cooling power of 140.8 W m − 2 . The device in heating mode achieves a maximum temperature rise of 45 °C and a maximum heating power of 700 W m − 2 . This work provides a feasible design for solar heating and daytime radiative cooling switching devices, which is promising in applications like energy-saving buildings, wearable devices, electric vehicles and other outdoors facilities.

Thermal comfort in a two-storey malaysian terrace house: Are passive cooling methods sufficient in present and future climates?

Rising temperatures due to climate change will impact both the indoor thermal comfort of naturally-ventilated housing and the cooling energy needs of air-conditioned housing in tropical regions. This study aims to evaluate the impact of rising temperatures based on the IPCC A2 scenario on indoor thermal comfort and cooling energy in a typical Malaysian terrace house. It addresses three key questions: 1) Can passive cooling (PC) achieve future thermally acceptable conditions? 2) How will PC impact cooling energy with air conditioning (AC)? 3) What is the effectiveness of various PC methods, individually and combined, in controlling indoor climate and saving energy under present and future conditions? We evaluated the effectiveness of eight PC measures—including shading, insulation, solar reflectivity, and nighttime natural ventilation—using EnergyPlus simulations. Results indicate that without PC and AC, indoor temperatures range from 26 to 31 °C, rising to 29–36 °C by the 2050s, often exceeding ASHRAE 55 standards. Currently, combined PC and nighttime ventilation can improve thermal comfort time fraction by up to 87 %. However, by the 2050s, this drops to 38 %, indicating PC alone will be insufficient, and AC systems will be essential. Additionally, in an AC scenario, PC measures reduce cooling energy by 6 % compared to the baseline under future conditions, yet demand is 67 % higher than current conditions. These findings underscore the need for integrating both PC measures and efficient AC systems to mitigate future greenhouse gas emissions from residential sectors in Malaysia and other developing hot climate regions.

Assessing the impact of glazing and window shade systems on view clarity

Windows provide access to daylight and outdoor views, influencing building design. Various glazing and window shade materials are used to mitigate glare, overheating and privacy issues, and they affect view clarity. Among them, we evaluated the effect of window films, electrochromic (EC) glass, and fabric shades on view clarity. We conducted an experiment with 50 participants using visual tests adapted from clinical vision tests (visual acuity, contrast sensitivity, color sensitivity) and images displayed on a computer monitor in a controlled laboratory. Window films and EC glass tints outperformed fabric shades in visual acuity, contrast sensitivity and view satisfaction with the exception of the darkest EC tint state and dark grey VLT 3% shade for color sensitivity and view satisfaction. The EC tints pose internal reflection issues and fabric shades are preferred for visual privacy. Window films and EC glass hinder participants’ blue–green color discrimination while fabric shades also decrease red–yellow color discrimination. Visual acuity predicts view satisfaction and contrast sensitivity is the strongest predictor for visual privacy. Generally, higher visible light transmittance and lower solar reflectance (darker color) enhance human visual performance. The proposed workflow provides an experimental procedure, identifies the primary variables and establishes a predictive framework for assessing view clarity of fenestration.

Honeycomb porous regenerated cellulose aerogel films with enhanced thermal dissipation for agricultural mulch application

Agricultural films, essential to contemporary agricultural production, are mostly made from non-biodegradable petroleum-based materials. The use of such films, especially in high-temperature environments, contributes to elevated internal temperatures in direct sunlight, adversely affecting crop appearance and quality. In this work, rice straw was used as the raw material to prepare biodegradable chemically crosslinked regenerated cellulose aerogel films (RCAF-CC) by combining physical dissolution regeneration, chemical cross-linking, and freeze-drying. The resulting RCAF-CC is notable for its high middle-infrared emissivity and high solar reflectivity, which significantly aid in thermal dissipation for agricultural mulch by enhancing infrared radiation and solar reflection. Compared to traditional polyethylene films, RCAF-CC, with its superior radiative cooling properties and lower water vapor transport rate, has a significant advantage in the growth trend and survival rate of cherry radishes. It is worth noting that the RCAF-CC achieved the degradation rate of 74.4 % in the 100-day soil burial experiment, and the soybean seeds grown in the degraded soil grew well, showing excellent eco-friendliness. These results show that RCAF-CC can be an alternative source of traditional agricultural films, solving the problems of non-biodegradable and high internal temperatures of the films under direct sunlight.

A Flexible Electrochromic Device for All-Season Thermal Regulation on Curved Transparent Building Envelopes.

As one of the least energy-efficient components in buildings, transparent building envelopes are responsible for approximately 60% of the total energy losses. Although controlling solar transmittance through electrochromic modulation is an effective method for temperature management in these structures, a dynamic control strategy for solar light on curved transparent building envelopes is still lacking. In this study, we introduce a dual-mode flexible electrochromic device based on reversible silver deposition for curved transparent building envelopes. The device operates by reversibly depositing and dissolving silver on a flexible polyethylene terephthalate-indium tin oxide (PET-ITO) substrate, controlled through the application and removal of pulsed voltage. This mechanism enables rapid switching between radiative cooling and solar heating modes, leading to modulation of solar reflectance from 89.1% to 15.7% and solar transmittance from 0.02% to 72.9%. Under approximately 700 W/m2 of solar irradiance, the device achieves an average temperature reduction of 1.6 °C (with a maximum reduction of 4.3 °C) compared to ambient temperature in radiative cooling mode. In solar heating mode, the device achieves an average temperature increase of 17.1 °C (with a maximum increment of 23.7 °C) compared to ambient temperature. Simulation results show that the dual-mode flexible electrochromic device could offer all-season thermal regulation for curved transparent building envelopes and achieve a maximum of over 50% annual HVAC energy savings.

The Role of Forcing and Parameterization in Improving Snow Simulation in the Upper Colorado River Basin Using the National Water Model

AbstractThis study assesses snow water equivalent (SWE) simulation uncertainty in the National Water Model (NWM) due to forcing and model parameterization, using data from 46 Snow Telemetry (SNOTEL) sites in the Upper Colorado River Basin (UCRB). We evaluated the newly developed Analysis of Record for Calibration (AORC) forcing data for SWE simulation and examined the impact of bias correction applied to AORC precipitation and temperature. Additionally, we investigated the sensitivity of SWE simulations to choices of physical parameterization schemes through 72 ensemble experiments. Results showed that NWM driven by AORC forcings captured the overall temporal variation of SWE but underestimated its amount. Adjusting AORC precipitation with SNOTEL observations reduced SWE root‐mean‐square error (RMSE) by 66%, adjusting temperature trimmed it by 10%, and adjusting both decreased it by 69%. Among the physical processes, the snow/soil temperature time scheme (STC) demonstrated the highest sensitivity, followed by the surface exchange coefficient for heat (SFC), snow surface albedo (ALB), and rainfall and snowfall partitioning (SNF), while the lower boundary of soil temperature (TBOT) proved to be insensitive. Further optimization of the parameterization combination resulted in a 12% SWE RMSE reduction. When combined with the bias‐corrected AORC precipitation and temperature, this optimization led to a remarkable 78% SWE RMSE reduction. Despite these enhancements, a persistent slow and late spring ablation suggests model deficiencies in snow ablation physics. The study emphasizes the critical need to enhance the accuracy of forcing data in mountainous regions and address model parameterization uncertainty through optimization efforts.

Biologically inspired shell-hollow particles for designing efficient passive all-sky radiative cooling

Passive radiation cooling (PRC), as the most promising technology to meet future cooling needs, has attracted great interest. However, there are still huge challenges in manufacturing high-efficiency and low-cost radiant coolers suitable for all-day use. Here, we report a secondary micro-nano shell-hollow structure based on blending method, inspired by the African white beetle Goliathus goliatus. Due to the difference in reflectance between the shell and the internal air, compared with the homogeneous particles, the scattered light has a changed optical path at the interface of the core (air) and the shell (SiO2), and most of the light escapes from the particles, showing strong total internal reflection. The design ingeniously deposits the nano-sized shell-hollow structure on the surface of the micron-sized shell-hollow structure, achieving high solar reflectance (95 ​%)and excellent long-wave infrared emissivity (94 ​%). Sub-ambient cooling of 7.8 and 4.7 ​°C can be achieved at night and daytime, respectively. Silica microspheres with shell and hollow structure can be prepared by soft template method, which is mature, reliable, simple and cheap.Our work provides new ideas for the design and manufacture of high-performance Passive all-day radiative cooling (PARC).

Fabrication of passive cooling fabric as thermal management curtain for building energy-saving

In the past years, a great deal of attention has been paid to passive cooling envelope materials or smart windows to cope with the increase in building energy consumption due to global warming. However, combining curtains with passive cooling could enable on-demand thermal management based on its dynamically adjustable characteristics. Herein, a superhydrophobic passive cooling cotton fabric with low thermal conductivity (0.0342 W/mK), high solar reflectivity (0.9280) and high infrared emissivity (0.9698) was obtained by wrapping the cotton fabric with a porous SiO2/poly(vinylidene fluoride-hexafluoropropylene) composite coating via solvent exchange phase separation and sanding. The superhydrophobic passive cooling fabrics realized an average of 10.3 °C cooling during the daytime and showed impressive passive cooling performance relative to the pristine cotton. Notably, the superhydrophobic passive cooling fabric demonstrated superior daytime cooling and nighttime insulation performance during outdoor testing and energy consumption simulations compared to commercial curtains. Therefore, superhydrophobic passive cooling cotton fabrics as curtains allow for reducing the energy consumption in building thermal management and broadening the practical application of radiative cooling materials.

State-of-the-Art Review: Effects of Using Cool Building Cladding Materials on Roofs

Cool roofs are roofing systems designed to reflect significant solar radiation, reducing heat absorption and subsequent cooling energy demands in buildings. This paper provides a comprehensive review of cool roof technologies, covering performance standards, material options, energy-saving potential, and hygrothermal considerations. The review examines provisions in current codes and standards, which specify minimum requirements for solar reflectance, thermal emittance, and solar reflectance index (SRI) values. These criteria often vary based on factors like roof slope, climate zone, and building type. Different cool roof materials are explored, including reflective paints and coatings that can be applied to existing roofs as cost-effective solutions. Several studies have demonstrated the energy performance benefits of cool roofs, showing significant reductions in cooling loads, indoor air temperatures, peak cooling demand, and overall cooling energy consumption compared to traditional roofs. However, hygrothermal performance must be evaluated, especially in cold climates, to optimize insulation levels and avoid moisture accumulation risks, as reduced heat absorption can alter moisture migration patterns within the building envelope. While cool roofs provide substantial energy savings in hot climates, further research is needed to validate modeling approaches against real-world studies, investigate the impact of seasonality and green spaces on cool roof efficacy and urban heat island mitigation, and explore energy-saving potential, moisture control, and condensation risks in cold and humid environments.

Printing and dyeing of halloysite nano clay hybrid with natural chlorophyll dye on cotton fabric

This work deals with the synthesis of hybrids formed by the natural dye chlorophyll and halloysite for their subsequent application in the textile field. Once the pigments have been synthesized, with 98 % adsorption, they are used for two textile colouring functions, namely printing and dyeing. In both cases, satisfactory and interesting results were obtained. The hybrids were characterized by FTIR, XRD, TGA, SEM-EDX, BET and all the appropriate colour measurements were carried out to obtain the coordinates in CIELAB space and also to know their total solar reflectance (TSR) 45.98 %. In addition, statistical techniques were used with the use of ANOVA to evaluate the results obtained. The dyeing was carried out by exhaustion and its use was compared with the use of nibbled and non-nibbled fabrics. The textiles were tested for fastness and the results are presented in instrumentally obtained grey scale values, achieving in some cases values of 4–5. Thus, the chlorophyll adsorption capacity of halloysite and its stabilisation for subsequent application in printing and dyeing processes on textile substrates has been demonstrated. This process could be scalable at an industrial level.

Water-efficient evaporative cooling by sunlight-reflective radiative-cooling nanofibers

Evaporative cooling, which has the highest potential for energy transfer, is not sustainable without sufficient water. Here we present the membrane that can be used to protect the moisture from unnecessary evaporation. The membrane is composed of nanofiber non-woven fabric that is breathable and has high solar reflectance and high infrared emissivity for water-efficient evaporative cooling applications. The membrane prevents moisture from evaporating unnecessarily by blocking solar absorption and efficient thermal emission. Specifically, the membrane is composed of ∼400 nm diameter polyurethane fiber, which has a high MIE scattering effect on solar radiation (∼2500 nm wavelength), resulting in over 95% solar reflectance as well as over 95% of total infrared (IR) emissivity and IR transmittance at 50 g/m2 of membrane. In addition, it has sufficient breathability of over 16 mg•cm2•hr that the maximum evaporative cooling is about 100 W/m2. Twice the cooling time and 3 °C cooler surface by tandem of radiative cooling were confirmed in outdoor test of wet fabric covered with nanofiber membrane compared to wet fabric without membrane. This scalable and flexible membrane is applicable where the thermal cooling without energy consumption is required for net-zero energy consumption.

Environmental impact of the variations in solar reflectance index values of some selected dimension stones due to cyclic thermal shock

Natural stones are widely used environmentally appropriate building materials as dimension stone both for exterior cladding and floor coverings in urban areas. Depending on their solar reflectivity, these materials may absorb more solar radiation, especially with noontime summer sunlight exposure, which may cause both increasing cooling costs in commercial buildings and overheating of a city with the formation of urban heat islands. Solar reflectance index (SRI) is defined as the ability of a surface to reject solar heat which tends to change with physical, chemical and biological degradation processes by varying solar reflectance (SR) and thermal emissivity (TE) values. Weakening of the stone matrix structure by physical degradation mechanism, such as thermal shock (T-S) cycles mostly have significant impact on SRI. Within the scope of this study, SRI values were calculated before and after cyclic T-S by measuring the optical properties such as SR and TE values of 30 selected sedimentary and metamorphic originated carbonate-based natural stone types. The changes in surface properties such as color, roughness, and gloss, that may have an impact on the SRI values were also analyzed. In addition, a multivariate regression analysis was established to predict SRI value from such properties with a high degree of accuracy. Finally, it was found that, initial SRI values of 9 natural stone types (mostly metamorphic originated) have been increased considerably by cyclic T-S and tend to increase their ability to reduce urban temperatures by higher SRI values, one of the most important selection criteria in energy consumption for natural stones.

High reflectivity and latent heat synergetic TiO2/Cs0.33WO3-PU double-layer materials with zero transmittance

Passive Cooling Technology, as a method of achieving long-term refrigeration without the need for external energy input, has emerged as an alternative to traditional energy-intensive cooling, garnering increasing attention from academia and industry. However, current passive cooling technology faces challenges such as incomplete solar energy reflection, overcooling, and inevitable absorption of solar radiation and surrounding environmental heat. This paper presents a passive cooling bilayer film with latent heat storage capability, composed of a solid–solid phase change polyurethane (PU) matrix with added TiO2 and Cs0.33WO3.TiO2/Cs0.33WO3-PU exhibits minimal solar transmittance, with reflectance and emissivity rates of 84.46 % and 93.08 %, respectively. The solid–solid phase change matrix effectively mitigates overcooling and heat input issues, reducing temperature fluctuations and peaks, and thereby enhancing passive cooling performance. At the phase transition temperature (306 K), TiO2/Cs0.33WO3-PU achieves cooling powers of 113.77 W/m2(day time) and 173.19 W/m2(night time), the temperature can be reduced by 14.3 °C under 100 mW/cm2sunlight. Additionally, TiO2/Cs0.33WO3-PU demonstrates outstanding thermal stability and reliabitity, hydrophobicity, as well as resistance to UV aging. Moreover, it offers the flexibility to adjust the phase transition temperature and latent heat of the solid–solid phase change matrix according to specific environmental conditions. TiO2/Cs0.33WO3-PU combines passive cooling materials with phase change materials, and complements each other’s advantages. TiO2/Cs0.33WO3-PU not only improves the cooling power, but also provides a new solution to the problem of heat input and supercooling of passive cooling materials. TiO2/Cs0.33WO3-PU also provides new possibilities for the application of passive cooling materials in the fields of long-term outdoor building cooling, human heat management, food preservation and electrical equipment cooling.

Dynamic selective emitter for low infrared signal over wide temperature range based on VO2

The infrared signal intensity of objects contains the thermal radiation from objects themselves and the reflected signal from their surface. Here, we theoretically propose the rule of regulating the infrared signal intensity in mid-wave infrared band, which is influenced by both the reflected solar irradiation and the self-emitted radiation. Then we propose a dynamic selective emitter (DSE) operating in the mid-infrared (MIR) band based on vanadium dioxide (VO2) for lowest infrared signal intensity within the low and high temperature ranges. In the dielectric state of VO2, the selective emitter exhibits the broadband selective absorption attributed to the excitation of magnetic polariton resonance, which can effectively reduce the solar irradiation reflection in 3–4.5 μm band (R‾3–4.5 μm = 0.18) and suppress the thermal radiation in 4.5–5 μm and 8–14 μm band (ε‾4.5–5 μm = 0.28, ε‾8–14 μm = 0.02). In the metallic state of VO2, the resonance absorption disappears and the structure exhibits broadband low emissivity in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) bands (ε‾3–5 μm = 0.28, ε‾8–14 μm = 0.21) for suppression of the thermal radiation. This work highlights the impact of solar irradiation on MWIR camouflage and offers new possibilities for solar and infrared spectral regulation.

Scalable thermochromic superhydrophobic collagen fiber-based wearable materials for all-weather self-adaptive radiative cooling and solar heating

As traditional biomaterials for wearables, collagen fibers (CFs)-based products are widely used in daily life due to their exceptional performance. However, developing CFs-derived products that exhibit seasonal self-adaptive temperature regulation to satisfy the thermal comfort for humans and prolong their service life remains a significant challenge in practical applications. Herein, the smart temperature-adaptive superhydrophobic radiative cooling CFs (STSRC-CFs) were created through a nanoengineering design strategy by a simple and scalable layer-by-layer spraying method. The STSRC-CFs inherit the outstanding properties of natural CFs and maintain high tensile strength (18.2 MPa), air permeability (38.2 mL/cm2∙h), and superhydrophobicity (CA of 161.1°, SA of 2.0°). Moreover, STSRC-CFs possessed a thermal emittance of 0.94, while the solar reflectance could be dynamically modulated in response to the ambient temperature change with a solar reflectance of 0.91 at high temperatures and 0.81 at low temperatures. The synergic effect enables STSRC-CFs to autonomously manage radiative cooling and solar heating, thereby achieving intelligent energy-saving temperature regulation for winter warming and summer cooling. Notably, the superhydrophobic self-cleaning effect of STSRC-CFs prevents from contamination, ensuring sustained spectral modulation and intelligent temperature regulation. Serving as a proof-of-concept for intelligent self-adaptive passive temperature regulation, the STSRC-CFs introduced in this study lay the groundwork for the development of advanced temperature-adaptive radiative cooling and solar heating functional materials.

Polyurethane Based Smart Composite Fabric for Personal Thermal Management in Multi-Mode.

Textiles with thermal/moisture managing functions are of high interest. However, making the textile sensitive to the surrounding environment is still challenging. Herein, a multimodal smart fabric is developed by stitching together the Ag coated thermal-humidity sensitive thermoplastic polyurethane (Ag-THSPU) and the hybrid of polyvinylidene fluoride and polyurethane (PU-PVDF). The porous PU-PVDF layer is used for solar reflection, infrared emissivity, and water resistance. The Ag-THSPU layer is designed for regulating thermal reflection, sweat evaporation as well as convection. In cold and dry state, the Ag domains are densely packed covering the crystalline polyurethane matrix, featuring low water transmission (102.74gm-2·24h-1), high thermal reflection and 2.4°C warmer than with cotton fabric. In the hot and humid state, the THSPU layer is swollen by sweat and expands in area, resulting in the formation of micro-hook faces where the Ag domains spread apart to promote sweat evaporation (2084.88g/m-2·24h-1), thermal radiation and convection, offering 2.5°C cooler than with cotton fabric. The strategy reported here opens a new door for the development of adaptive textiles in demanding situations.

A Janus film coupling radiative cooling and heating for all-day active/passive personal thermal management

Textiles with passive radiative cooling (PRC)/passive radiative heating (PRH) capabilities have been developed to address human thermal comfort in different climate scenarios. Although materials with single PRC/PRH function have been reported, they tended to exhibit only one function of either cooling or heating, which was restrictive in achieving efficient and controllable personal thermal management. Herein, we propose a dual-mode Janus film composed of a PVDF-HFP/ZrO2 cooling layer and a Mxene/CNT heating layer for efficient all-day PRC/PRH. Owing to the natural high refractive index of ZrO2 nanoparticles and the strong scattering of sunlight by the PVDF-HFP nanofibers, the cooling side exhibits a high solar reflectance of 97.1 %. With an infrared emittance of 93 % in atmospheric window, the cooling side achieves subambient cooling temperatures of 8.8 °C during daytime and 7 °C during nighttime. Meanwhile, the Mxene/CNT synergy enables the heating side to exhibit high solar absorbance and electrical conductivity, resulting in a significant PRH capability of up to 19 °C and an outstanding active Joule heating capability as a temperature compensation. The dual-mode Janus film is able to switch cooling/heating modes by simply flipping the interface to alter the sky-facing side, enabling efficient and continuous personal thermal management in complex and changeable environments.

A utility and easily fabricated dual-mode fiber film for efficient and comfortable thermal management

Nowadays, the global climate is constantly being destroyed and the fluctuations in ambient temperature are becoming more frequent. However, conventional single-mode thermal management strategies (heating or cooling) failed to resolve such dynamic temperature changes. Moreover, developing thermal management devices capable of accommodating these temperature variations while remaining simple to fabricate and durable has remained a formidable obstacle. To address these bottlenecks, we design and successfully fabricate a novel dual-mode hierarchical (DMH) composite film featuring a micro-nanofiber network structure, achieved through a straightforward two-step continuous electrospinning process. In cooling mode, it presents a high solar reflectivity of up to 97.7% and an excellent atmospheric transparent window (ATW) infrared emissivity of up to 98.9%. Noted that this DMH film could realize a cooling of 8.1 °C compared to the ambient temperature outdoors. In heating mode, it also exhibits a high solar absorptivity of 94.7% and heats up to 11.9 °C higher than black cotton fabric when utilized by individuals. In practical application scenarios, a seamless transition between efficient cooling and heating is achieved by simply flipping the film. More importantly, the DMH film combining the benefits of composites demonstrates portability, durability, and easy-cleaning, promising to achieve large-scale production and use of thermally managed textiles in the future. The energy savings offered by film applications provide a viable solution for the early realization of carbon neutrality.

Molecular dynamics simulations on TiO2 quantum dots modified asphalt: Impact of size and concentration of quantum dots

With exceptional solar reflectivity and fluorescent characteristics, TiO2 quantum dots (QDs) modified asphalt has been proposed as an innovative cool pavement technology. However, interaction mechanism and thermodynamic properties of TiO2 QDs modified asphalt at microscale have not been well understood. In this study, electronic and optical properties of TiO2 QDs with varied sizes were investigated based on quantum mechanics (QM) calculations. Moreover, molecular dynamics (MD) simulations were implemented to evaluate mechanical moduli and intermolecular dynamics of TiO2 QDs modified asphalt with different quantum sizes and concentrations. The results from QM calculations unveil that as size of TiO2 QDs rises from 6 Å to 12 Å, energy gap and binding energy of TiO2 QDs decreases by 0.928 eV and 526.38 eV, respectively while density of state (DOS) and absorption coefficient of TiO2 QDs increases. Besides, the results from MD simulations reveal that quantum size imposes significant impact on mechanical moduli of modified asphalt while concentration of TiO2 QDs brings notable influence on interaction between quantum dots and asphalt. Specifically, as concentration of QDs rises from 10 % to 30 %, cohesive energy density (CED) and solubility parameter (SP) of modified asphalt is improved by up to 457 % and 136 %, respectively. With increasing quantum size, bulk modulus, shear modulus, and Young’s modulus of modified asphalt is enhanced by up to 372 %, 206 % and 24 %, respectively. The outcomes of this study provide insights into formula and application of advanced asphalt pavement with TiO2 QDs.