Temperature Dependence Of Efficiency Research Articles

Effect of 2-butanone addition to ethylene fuel on soot formation in counterflow diffusion flames using newly proposed soot model

An improved consistent soot model is proposed and applied to evaluate the effect of 2-butanone addition (10 % to 50 % on a volume basis represented as case 1 to case 5) to ethylene fuel on soot formation using a counterflow burner configuration. The predictive capability of the suggested soot model is verified by assessing its performance against existing experimental data on soot formation (SF) configuration-type ethylene counterflow flames at diverse strain rates and various fuel additives. The proposed soot model comprises 55 inception reactions with temperature-dependent collision efficiency and 10 condensation reactions from 10 PAH species (from naphthalene to larger PAHs up to coronene), including modified HACA surface growth and oxidation reactions. 2-butanone is produced as a byproduct during the pyrolysis of biomass and the microbiological fermentation of agricultural waste. It holds various benefits as a prospective biofuel for spark ignition (SI) engines. Limited information exists regarding its sooting characteristics due to a lack of available soot measurements. The simulations are conducted for the soot formation (SF) type counterflow flames with a fixed fuel and oxidizer jet velocity. The proposed soot model can effectively replicate both the qualitative and quantitative aspects of the experimental trends and shows a better agreement than the existing models available in the literature. The soot volume fraction (SVF) and the particle number density (PND) decrease with increasing the 2-butanone concentration in the binary fuel mixture. The PAH concentration decreases with increasing 2-butanone addition in the fuel mixture. The peak SVF and the maximum temperature are reduced by ∼22.7 % and ∼3.6 %, with a 40 % increase in the 2-butanone portion in the fuel mixture from case 1 to case 5. Increasing the 2-butanone content in the fuel mixture decreases the inception rate, HACA rate, and condensation rate while it increases the oxidation rate.

Temperature-dependent electroluminescence of red high-In-content MQWs of dual-wavelength micro-LED

Temperature-dependent electroluminescence (TDEL) measurements have been employed to investigate the carrier transport and recombination processes of InGaN red micro-LED based on dual-wavelength InGaN/GaN MQWs structure. EL peak energy and carrier transport of the red micro-LED both show temperature dependence, due to temperature-induced changes in defect activation. In addition, the current density at which the blue peak of the low-In-content appears in the EL spectrum varies with temperature. As the temperature increases, the blue peak of the low In component tends to appear at higher current densities, which may be attributed to the increase in thermally activated defects hindering the injection of holes into the low-In-content MQWs further away from p-GaN. Furthermore, the IQEs of the high-In-content MQWs are estimated from the TDEL method and then reveal the temperature-dependent efficiency droop. The IQE decreases as temperature increases, particularly above 50 K, where it drops sharply due to temperature-dependent nonradiative recombination. And the two different variation trends in IQE of MQWs with high and low In content reveal a competitive mechanism in carrier distribution, implying that more escaping holes from high-In-content MQWs will further reduce red emission efficiency but enhance carrier injection and blue emission in low-In-content MQWs.

Growth of Ga0.70In0.30N/GaN Quantum-Wells on a ScAlMgO4 (0001) Substrate with an Ex-Situ Sputtered-AlN Buffer Layer.

This study attempted to improve the internal quantum efficiency (IQE) of 580 nm emitting Ga0.70In0.30N/GaN quantum-wells (QWs) through the replacement of a conventional c-sapphire substrate and an in-situ low-temperature GaN (LT-GaN) buffer layer with the ScAlMgO4 (0001) (SCAM) substrate and an ex-situ sputtered-AlN (sp-AlN) buffer layer, simultaneously. To this end, we initially tried to optimize the thickness of the sp-AlN buffer layer by investigating the properties/qualities of an undoped-GaN (u-GaN) template layer grown on the SCAM substrate with the sp-AlN buffer layer in terms of surface morphology, crystallographic orientation, and dislocation type/density. The experimental results showed that the crystallinity of the u-GaN layer grown on the SCAM substrate with the 30 nm thick sp-AlN buffer layer [GaN/sp-AlN(30 nm)/SCAM] was superior to that of the conventional u-GaN template layer grown on the c-sapphire substrate with an LT-GaN buffer layer (GaN/LT-GaN/FSS). Notably, the experimental results showed that the structural properties and crystallinity of GaN/sp-AlN(30 nm)/SCAM were considerably different from those of GaN/LT-GaN/FSS. Specifically, the edge-type dislocation density was approximately two orders of magnitude higher than the screw-/mixed-type dislocation density, i.e., the generation of screw-/mixed-type dislocation was suppressed through the replacement, unlike that of the GaN/LT-GaN/FSS. Next, to investigate the effect of replacement on the subsequent QW active layers, 580 nm emitting Ga0.70In0.30N/GaN QWs were grown on the u-GaN template layers. The IQEs of the samples were measured by means of temperature-dependent photoluminescence efficiency, and the results showed that the replacement improved the IQE at 300 K by approximately 1.8 times. We believe that the samples fabricated and described in the present study can provide a greater insight into future research directions for III-nitride light-emitting devices operating in yellow-red spectral regions.

Temperature-Dependent Efficiency Droop in GaN-Based Blue Micro Light-Emitting Diodes

This work investigates the size-dependent decrease in external quantum efficiency (EQE) of various InGaN/GaN multiple-quantum-well flip-chip blue micro light-emitting diodes (μ-LEDs) of sizes from 10 × 10 μm2 to 250 × 250 μm2 and proposes that the temperature-dependent efficiency droop is the main mechanism for decrease in EQE with reducing dimensions for well-passivated μ-LEDs. Experimental results show that the EQE increases with reducing μ-LED sizes to 50 × 50 μm2. However, the EQE decreases as the μ-LED size is further reduced to 10 × 10 μm2. The measured current-voltage characteristics, the minimum ideality factor, the light-emission patterns by the photon-emission microscope, and the transmission-electron-microscopy images consistently reveal that the decreased EQE of the smallest sized μ-LED is not due to the sidewall leakage: the decreased EQE is rather caused by the temperature-dependent efficiency droop (T-droop), which is systematically found by investigating the blueshift in peak emission wavelength and calculating the thermal resistance (Rth) that increases with the reduced mesa area. The decrease in peak EQE at 440 K compared to 300 K is also presented, which demonstrates that the reduction in peak EQE increases with reducing μ-LED sizes. It is pointed out that the small-sized μ-LEDs suffer from higher junction temperature due to lower heat dissipation caused by higher Rth compared to large-sized μ-LEDs.

Stratified thermal energy storage model with constant layer volume for predictive control — Formulation, comparison, and empirical validation

Recent developments in heating systems have witnessed a significant increase of heat pumps with a highly temperature-dependent efficiency. Optimal real-time operation of these heating systems with predictive control requires a thorough understanding and modeling of the internal temperature distribution of the associated thermal energy storage. At the same time, the thermal energy storage models need to be sufficiently simple to ensure computational tractability in real-time predictive control. Therefore, this article presents a stratified thermal energy storage model with constant layer volume and variable temperature suitable for real-time predictive control. The model employs a novel formulation with quadratic or simpler constraints which enable high accuracy at low computation burden. The proposed model is validated experimentally and compared with other models available in literature. The results show that the proposed stratified thermal energy storage model represents the real-world behavior of a thermal energy storage with great accuracy, while reducing the required computational burden as compared to other models for real-time operation and control. A case study further demonstrates that the increased accuracy of the proposed new model leads to cost and energy savings for the operator.

Chemical Tuning, Pressure, and Temperature Behavior of Mn4+ Photoluminescence in Ga2O3-Al2O3 Alloys.

In this study, we carried out a detailed investigation of the photoluminescence of Mn4+ in Ga2O3-Al2O3 solid solutions as a function of the chemical composition, temperature, and hydrostatic pressure. For this purpose, a series of (Al1-xGax)2O3:Mn4+,Mg phosphors (x = 0, ..., 0.1.0) were synthesized and characterized for the first time. A detailed crystal structure analysis of the obtained materials was done by the powder X-ray diffraction technique. The results of the crystal structure and luminescence studies evidence the transformation of the ambient-pressure-synthesized material from the rhombohedral (α-type) to monoclinic (β-type) phase as the Ga content exceeds 15%. Spectroscopic features of the Mn4+ deep-red emission, including the temperature-dependent emission efficiency and decay time, as well as the possibility of their tuning through chemical pressure in each of these two phases were examined. Additionally, it has been shown that the application of hydrostatic pressure of ≥19 GPa allows one to obtain a corundum-like α-Ga2O3:Mn4+ phase. The luminescence properties of this material were compared with β-Ga2O3:Mn4+, which is normally synthesized at ambient pressure. Finally, we evaluated the possibility of application of the studied phosphor materials for low-temperature luminescence thermometry.

Depth-resolved photochemical production of hydrogen peroxide in the global ocean using remotely sensed ocean color

Hydrogen peroxide (H2O2) is an important reactive oxygen species (ROS) in natural waters, affecting water quality via participation in metal redox reactions and causing oxidative stress for marine ecosystems. While attempts have been made to better understand H2O2 dynamics in the global ocean, the relative importance of various H2O2 sources and losses remains uncertain. Our model improves previous estimates of photochemical H2O2 production rates by using remotely sensed ocean color to characterize the ultraviolet (UV) radiation field in surface water along with quantitative chemical data for the photochemical efficiency of H2O2 formation. Wavelength- and temperature-dependent efficiency (i.e., apparent quantum yield, AQY) spectra previously reported for a variety of seawater sources, including coastal and oligotrophic stations in Antarctica, the Pacific Ocean at Station ALOHA, the Gulf of Mexico, and several sites along the eastern coast of the United States were compiled to obtain a “marine-average” AQY spectrum. To evaluate our predictions of H2O2 photoproduction in surface waters using this single AQY spectrum, we compared modeled rates to new measured rates from Gulf Stream, coastal, and nearshore river-outflow stations in the South Atlantic Bight, GA, United States; obtaining comparative differences of 33% or less. In our global model, the “marine-average” AQY spectrum was used with modeled solar irradiance, together with satellite-derived surface seawater temperature and UV optical properties, including diffuse attenuation coefficients and dissolved organic matter absorption coefficients estimated with remote sensing-based algorithms. The final product of the model, a monthly climatology of depth-resolved H2O2 photoproduction rates in the surface mixed layer, is reported for the first time and provides an integrated global estimate of ∼21.1 Tmol yr−1 for photochemical H2O2 production. This work has important implications for photo-redox reactions in seawater and improves our understanding of the role of solar irradiation on ROS cycling and the overall oxidation state in the oceans.

Assessment of physical soot inception model in normal and inverse laminar diffusion flames

Despite the extensive studies, accurate and reliable modeling of the soot inception process, especially at high pressure conditions, amenable to multi-dimensional flame simulations remains a challenge. In this study, the physical inception model was comprehensively evaluated in the fully-resolved simulations of laminar normal diffusion flame (NDF) and inverse diffusion flame (IDF) at elevated pressures. The effects of inception models on polycyclic aromatic hydrocarbons (PAHs) and soot predictions were quantitatively analyzed, including the selection of soot precursors and collision efficiency models. The results show that the quantitative PAH predicted by different collision efficiency models can differ by an order of magnitude. Compared to the constant efficiency, the temperature-dependent collision efficiency was found to improve the quantitative PAH predictions and the prediction of the spatial soot distribution in NDF, with an increased level of soot on the flame centerline. The inclusion of small-sized PAH species (such as A2, A2R5, and A3) as soot precursors was also found to improve the quantitative prediction of soot volume fraction. The physical inception model performs well in NDF using the optimal parameters. Moreover, simultaneous measurements of PAH and soot were performed in IDF configuration for the evaluation of the physical inception model. Contrary to NDF, PAHs and soot are formed on the outer side of the flame and cannot be oxidized in IDF. The experiment observed that the PAHs concentration increased in the post-flame region, while the soot concentration remained unchanged. However, the opposite trend was obtained in simulations, that is, the PAHs concentration decreased while the soot concentration increased, because the physical inception model predicts the inception behavior in the post-flame area, resulting in persistent transformation of PAHs into soot particles. To improve the predictions in IDF, the radical effects in the inception process need to be considered in the model.

Cost and time effective performance evaluation methods for photovoltaic module cooling techniques: Analytical and experimental study

For assessing the performance of a photovoltaic module (PV) cooler, the temperature-dependent PV efficiency difference factor, FTDED, was introduced earlier. The assessment was accomplished by differentiating whether the PV cooler performance was contributing to the gain or loss to the PV efficiency. That method is costly because it requires the availability of a fixed amount of solar irradiance of 1000 W/m2 that satisfy the PV standard test conditions, and also the use of one unit of a PV without a cooler that has the same solar cell number as a PV with a cooler. This paper proposes new methods that have the flexibility to be applied under various solar irradiance values. The new methods depend on a PV that has a single solar cell only, without a cooler, when executing the performance assessment for a PV with a cooler that has a known number of solar cells. As a result, the assessment cost can be significantly reduced. An experimental work is conducted for three PV cooler types and found that the performance assessment cost can be reduced by up to 33.33 %, by using the new methods, as compared to using the existing method. Hence, the new methods are cost effective. It is also shown that the experimental measurements are the same as the results obtained from the new methods. When the new method (FTDPD) is compared with the temperature-dependent photovoltaic power difference (ΔP) that is defined and derived, it is shown that the computational work can be reduced, because it has less influential parameters, thus, it is also a time-efficient method. PV cooler designers and manufacturers could be the possible users of the new methods.

Effect of Disperse Red 1 Azobenzene Dye Doping and Annealing on the Thermomechanical and Photomechanical Properties of PMMA Fibers

This work studies the effect of azobenzene dye Disperse Red 1 (DR1) doping and annealing on the thermomechanical and photomechanical properties of poly(methyl methacrylate) (PMMA) fibers. The mechanical properties are measured as a function of temperature, pump light intensity, and polarization. We find that doping with DR1 increases the stiffness and the glass transition temperature (Tg) of the PMMA fibers. Moreover, annealing below Tg decreases Young’s modulus and increases Tg. Finally, the photothermal heating contribution to the photomechanical response and the length change during laser exposure are determined in both unannealed and annealed plain PMMA and DR1-doped PMMA fibers. We find that photothermal heating is the dominant mechanism and the effect of photoisomerization is negligible. The temperature-dependent photomechanical efficiencies are also determined.

Platform for transverse evaluation of control strategies for multi-energy smart grids

This paper presents the PEACEFULNESS software platform (Platform for transvErse evAluation of Control stratEgies For mULti-eNErgy Smart gridS), an open framework dedicated to multi-energy smart-grids, based on a techno-economic model that integrates economic considerations (contracts). As such, it is mainly oriented towards the evaluation of multi-energy grid supervision strategies, that is, energy management, and the corresponding policies and legal organization. The main goal is then to highlight the various possible behaviors and strategies to organize the probable future interconnections between the different energy carriers. In particular, it aims at investigating how to maximize the use of renewable energy sources (RES), using Demand Side Management (DSM) techniques and energy storage, in a shared economy context. The open-source tool PEACEFULNESS, written in Python, is described here in detail. It combines a top-down description of the energy networks and connections between the various agents (energy providers, distribution system operators, aggregators, consumers, producers, prosumers, etc.), together with a techno-economic bottom-up description for all devices. Here, both public databases and users’ data (basic heating demands or based on building modeling) can be used, as well as generic or more specific models (e.g., PV panels with constant or temperature-dependent efficiency). One of its major unique features compared with other tools is that it extends the use of DSM techniques to various energy grids which can also interact together. Furthermore, different economic models can be set for both the aggregators and the customers, and even within these groups. As a last competitive advantage, PEACEFULNESS allows the user to simulate the operation and supervision of tens up to hundreds of thousands of agents. It also provides a reporting system giving access to all the data, with a configurable granularity and frequency for the retained indicators. Finally, several validation cases are presented, followed by a series of test cases with increasing size: a smart home, a smart district (2 000 dwellings) and a smart community (50 000 dwellings).

Correction to: A Proposed Temperature-Dependent Photovoltaic Efficiency Difference Factor for Evaluating Photovoltaic Module Cooling Techniques in Natural or Forced Fluid Circulation Mode

Correction to: A Proposed Temperature-Dependent Photovoltaic Efficiency Difference Factor for Evaluating Photovoltaic Module Cooling Techniques in Natural or Forced Fluid Circulation Mode

Simulating Evaluation Method on Heating Performances of Magnetic Nanoparticles with Temperature-Dependent Heating Efficiencies in Tumor Hyperthermia

The magnetic nanoparticles (MNPs) with decreasing heating efficiency (characterized by specific loss power, SLP) with temperature increase, especially around the Curie temperature (TC), are expected to realize the self-regulated temperature hyperthermia of the tumor. However, the actual decrease of the SLP is gradual, resulting in the deviation of self-regulated temperatures from the measured TC. So far, no method is available for evaluating the heating performances of those MNPs. Here, by simulating the temperature-dependent SLP, the heating performances of MNPs are evaluated from three clinically concerning aspects: the capacity for effective heating, the temperature uniformity in the tumor, and the temperature stability under environmental changes such as MNP loss or tumor progression. The developed methods were applied to ZnCoCrFeO, Fe3O4, and γ-Fe2O3 MNPs. It was found that the uniform temperature distribution relies on lowering the heating power in the inner regions of the tumor, and the stable control of temperature depends on the dynamic adaptation of the heating power to the tumor temperature change. The proposed method may be used to predict the heating ability of MNPs and help the selection of MNPs for hyperthermia.

Efficiency Increase through Model Predictive Thermal Control of Electric Vehicle Powertrains

Battery electric vehicles (BEVs) are currently enjoying rising sales figures. However, BEVs still have problems with customer acceptance, partly due to limited driving ranges. To improve the situation, this paper introduces a novel approach utilising temperature-dependent efficiencies using an economic model predictive control approach (MPC) in combination with an active grille shutter in order to accelerate the heating of the permanent magnet synchronous machine. The measurements of temperature-dependent component efficiencies on a powertrain test bench are presented and analysed in detail in the speed/torque range. Thermal models based on the lumped parameter thermal network approach were developed and validated as part of the system-level validation against a US06 wind tunnel measurement. After the build-up and implementation of the MPC, various simulations were conducted. For the investigations, three driving cycles were considered at component start temperatures of 20–80 °C. The results show that using the MPC with the grille shutter can save 0.69–2.02% energy at the HV level compared to the rule-based control with a shutter, of which up to 1.02% is due to temperature-dependent efficiencies. Comparing the MPC with the grille shutter to a vehicle without a shutter, savings of 2.8–4.2% were achieved, while up to 1.67% was achieved due to temperature effects in the powertrain.

Gallium content-dependent efficiency limits of CIGS solar cells at AM1.5G solar irradiance

The gallium content-dependent theoretical limit of the efficiencies of Cu ( In , Ga ) Se2 solar cells were studied using a MATLAB model developed based on the Shockley–Queisser detailed balance. The developed model included the temperature dependence of the bandgap according to the gallium content. The original Shockley–Queisser detailed-balance and the developed model at the ASTM G173-03 AM1.5G solar irradiance were used to calculate the gallium content and solar cell temperature-dependent theoretical efficiency limits of a Cu ( In1 − xGax ) Se2-based solar cell. Due to the spectral distribution of the solar irradiance, there were two “peaks” of efficiency: one at values of x around 0.2 prevails at lower temperatures and the other at values of x around 0.6 higher at temperatures above 0°C. Consequently, there is a “pit” with a minimum at x of around 0.5. Values of x corresponding to these values are higher for the temperature-dependent bandgap model. The calculated relative difference between the ultimate efficiency limit and the theoretical efficiency at x = 0.3 at 310 K is <1 % .

The evolution of darker wings in seabirds in relation to temperature-dependent flight efficiency.

Seabirds have evolved numerous adaptations that allow them to thrive under hostile conditions. Many seabirds share similar colour patterns, often with dark wings, suggesting that their coloration might be adaptive. Interestingly, these darker wings become hotter when birds fly under high solar irradiance, and previous studies on aerofoils have provided evidence that aerofoil surface heating can affect the ratio between lift and drag, i.e. flight efficiency. However, whether this effect benefits birds remains unknown. Here, we first used phylogenetic analyses to show that strictly oceanic seabirds with a higher glide performance (optimized by reduced sink rates, i.e. the altitude lost over time) have evolved darker wings, potentially as an additional adaptation to improve flight. Using wind tunnel experiments, we then showed that radiative heating of bird wings indeed improves their flight efficiency. These results illustrate that seabirds may have evolved wing pigmentation in part through selection for flight performance under extreme ocean conditions. We suggest that other bird clades, particularly long-distance migrants, might also benefit from this effect and therefore might show similar evolutionary trajectories. These findings may also serve as a guide for bioinspired innovations in aerospace and aviation, especially in low-speed regimes.

Design Optimization and Electro-Thermal Modeling of an Off-Board Charging System for Electric Bus Applications

This paper proposes a co-design optimization procedure of a high-power off-board charger for electric vehicle (EV) applications. The primary purpose is to design a 175 kW SiC DC-charging system with high power density to achieve high efficiency at a wide operating range. For the active part of the DC off-board charger, a three-phase active front end (AFE) rectifier topology is considered in the design optimization and the modelling. The design methodology focuses on the optimal design of the passive filters, accurate electro-thermal modelling of the converter, inductor design, capacitor selection, loss and geometric modelling of the passive filters and control system design. The design optimization of the high-power charging system is performed in MATLAB Simulink using a closed-loop dynamic electro-thermal simulation of the off-board charger. The switching frequency, loss and temperature-dependent efficiency of the charger is investigated in parallel. Through this proposed technique, efficiency greater than 96% is achieved at a switching frequency of 40 kHz, along with a smaller size and lower weight of the system. Moreover, it operates with a current total harmonic distortion (THDi) below 3% and a power factor (PF) above 99% at rated power condition.

Transient thermal-electrical performance modelling of solar concentrating photovoltaic (CPV) receiver

The cell efficiency of a solar CPV system can be enhanced by the dissipation of the thermal load from the receiver assembly. The performance of the solar cell is influenced by the incident light and cell operating temperature. In this study, a triple-junction solar cell, under a concentration ratio of 500x and cell dynamic efficiency, is considered for a wide range of operating temperatures (25-80 °C). The key purpose of this work is to simulate both transient and steady-state operating conditions, based on the temperature-dependent conversion efficiency. In this study, a transient model has been developed using COMSOL Multiphysics®. A live-link technique of COMSOL with MATLAB® is used to couple of successive thermal and electrical steady-state models for a fixed timestep. The performance behaviour of electrical parameters Jsc, Voc, P, FF and Pmax are investigated. The results show that a dynamical efficiency, compared with constant efficiency and integrated error, was approximately 12%. The cell cycle steady-state temperature occurs at a maximum cell temperature of 78.4 °C within 30 s at the convective heat transfer coefficient hconv = 1400 W/m2 K and 500x of concentration ratio. Thus, steady-state cell temperature and time to reach it significantly dependence on the values of the environmental parameters of DNI, AM and Tamb. Therefore, we can determine the thermal response of hconv to keep the value of Tcell ≤ 80 °C.

Temperature-dependent energy gain of bifacial PV farms: A global perspective

Bifacial solar panels are perceived to be the technology of choice for next-generation solar farms for their increased energy yield at a marginally increased cost. As the bifacial farms proliferate around the world, it is important to investigate the role of temperature-dependent energy-yield and the levelized cost of energy (LCOE) of bifacial solar farms relative to monofacial farms, stand-alone bifacial modules, and various competing bifacial technologies. In this work, we integrate existing irradiance and light collection models with experimentally validated physics-based temperature-dependent efficiency models to compare the energy yield and LCOE of various bifacial technologies across the world. We find that temperature-dependent efficiency changes the energy yield and LCOE by approximately -10to15%. Indeed, the results differ significantly depending on the location of the farm (defines the illumination and ambient temperature), the elevation of the module (increases light collection), as well as the temperature-coefficients of various bifacial technologies. The analysis presented in this paper will allow us to realistically assess location-specific relative advantage and economic viability of the next generation bifacial solar farms.

Synthesis, Structures, and Photoluminescence of Elongated Face-Centered-Cubic Ag14 Clusters Containing Lipoic Acid and Its Amide Analogue.

Three face-centered-cubic (fcc) silver clusters-namely, [Ag14(LA)2(HLA)4(PPh3)8]2- (1), [Ag14(HLA)6(PPh3)8] (2), and [Ag14(NLA)6(PPh3)8] (3)-that are coprotected by lipoic acid (or its amide derivative) and phosphine ligands have been synthesized and structurally characterized (HLA = (±)-α-lipoic acid, LA = (±)-α-lipoate, and NLA = d,l-6,8-thioctamide). These clusters possess two superatomic electrons (the Jellium model), in harmony with a bonding octahedral Ag6 core capped with 8 Ag atoms. Alternatively, the metal framework of 1-3 can be described as adopting a face-centered cubic (fcc) structure elongated along one of the 3-fold axes. The 12 S atoms from the six bioligands bridge the 12 edges of the (fcc) cube, forming a distorted icosahedron. The counterions, solvent or guest molecules play an important role in dictating the crystal lattices of the products. This is the first report of atom-precise structures of Ag-lipoic acid (or its derivatives) clusters, paving the way for further study of structure-property relationships of these bioligand protected metal nanoclusters. Photoluminescence was observed for cluster 3 with complex temperature-dependent emission patterns and efficiencies.