Sol Concentration Research Articles

Major Role of Voluminosity in the Compressibility and Sol-Gel Transition of Casein Micelle Dispersions Concentrated at 7 °C and 20 °C.

The objective of this work is to bring new information about the influence of temperatures (7 °C and 20 °C) on the equation of state and sol–gel transition behavior of casein micelle dispersions. Casein micelle dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis at 7 °C and 20 °C. The osmotic stress technique measured the osmotic pressures of the dispersions over a wide range of concentrations. Rheological properties of concentrated dispersions were then characterized, respectively at 7 °C and at 20 °C. The essential result is that casein micelle dispersions are less compressible at 7 °C than at 20 °C and that concentration of sol–gel transition is lower at 7 °C than at 20 °C, with compressibility defined as the inverse to the resistance to the compression, and that is proportional to the cost to remove water from structure. From our interpretations, these two features were fully consistent with a release of soluble β-casein and nanoclusters CaP and an increased casein micelle hydration and apparent voluminosity at 7 °C as compared with 20 °C.

Kinetics of the nucleophilic dissolution of hydrophobic and hydrophilic elemental sulfur sols by sulfide

The reaction most directly responsible for polysulfide formation in aquatic settings, as a key part of overall biotic and abiotic sulfur cycling, is the nucleophilic reaction between elemental sulfur and sulfide. The reactivity of elemental sulfur, and therefore the production of polysulfide, is fundamentally tied to a suite of poorly understood surface properties of elemental sulfur, that in natural environments is thought to primarily exist in the most stable state (α-S8), or as biologically produced elemental sulfur (S8bio). Sulfur sols, a group of particles from nanoparticle to colloidal size, can be used as model systems to isolate key characteristics responsible for poorly understood reactivity associated with sulfur cycling. Specifically, Weimarn sols (S8weimarn), as hydrophobic particles, and Raffo sols (S8Raffo) as hydrophilic particles, represent ideal end members for biologically produced elemental sulfur.The reaction most directly responsible for polysulfide formation in aquatic settings, as a key part of overall biotic and abiotic sulfur cycling, is the nucleophilic reaction between elemental sulfur and sulfide. A series of pseudo-first order kinetic batch reactions were performed after development of a technique to measure sulfur sol concentrations with sufficient quality at second time scales on a 96-well microplate UV–Vis spectrophotometer. The experiments facilitated determination of the kinetics of the reaction between elemental sulfur sols and sulfide as a function of specific surface area, sulfide concentration, pH, ionic strength, and temperature for both Raffo and Weimarn sols, and determination of the effect of organic surfactants (using sodium dodecylsulfate, SDS, as an analogue). A broad governing rate law for either sol proved statistically undefinable, likely a result of key back reactions, surface reaction details, and undefined side reactions. However, a series of rate laws for specific conditional variables and defined rates for an array of conditions set a kinetic framework to define these rates. Activation energy for sols are relatively close to that determined for S8bio and significantly lower than those measured for α-S8. Reaction rates as a function of surface character (hydrophilic v hydrophobic) are significantly different, and rates as a function of surfactant concentration suggest enhancement of reaction rates as a surface process, not linked to dissolution of the elemental sulfur by surfactants. An accurate description of kinetic pathways governing intermediate sulfur species thus requires specific definition of the form of elemental sulfur.

Functionalization of polymeric membranes with phosphonic and thiol groups for water purification from heavy metal ions

Membrane technologies are a useful solution for water treatment, especially for removing trace amounts of different pollutants. Current research is focused on improving the removal efficiency of polyvinylidene fluoride (PVDF) membranes to heavy metal ions, such as lead(II), cadmium(II), and chromium(III). The surface chemistry and morphology of PVDF membranes were varied applying the sol–gel approach for functionalization. It involved (1) diethylphosphatoethyltriethoxysilane (DPTES) or 3-mercaptopropyltrimethoxysilane (MPTMS) as functionalizing precursors, (2) different concentrations of the initial sols, and (3) NH4OH or HCl as the catalysts for the hydrolysis and co-condensation reactions. According to the SEM analysis of the surface texture, alkaline catalyst and low sol concentration result in the formation of porous membrane active layers. Membrane weight loss after water filtration under pressure indicated the dependence of layer stability on the conditions of functionalization, namely the membranes with phosphonic groups prepared in an acidic medium are more resistant to rinsing. Functionalized PVDF membranes demonstrated a significant increase in sorption efficiency along with high water flux. Overall, such membranes were sufficient for treating water with ion concentrations lower than 100 mg/L, whereas the applied functionalization technique is promising for adjusting the parameters of the final membranes.

Evaluation of in Vitro and in Vivo Transdermal Absorption of Solifenacin Succinate.

Solifenacin (Sol), an antimuscarinic agent has been widely used for the treatment of overactive bladder. Transdermal formulations can be administered without water as well as absorbed slowly into the blood over a long period of time. The aim of this study was to develop cream and tape formulations of Sol, and evaluate the transdermal permeation and absorption of the drug from the two formulations in vitro and in vivo, respectively. In the preparation of cream formulation, Sol succinate was dissolved in purified water, and the mixture was added to the hydrophilic cream. Then, aqueous sodium hydroxide was added to the cream. In the tape formulation, Sol succinate was dissolved in a solvent with propylene glycol, diisopropanolamine, triethyl citrate, and EUDRAGIT E100. The dissolved solvent was poured onto a polyethylene film. Cream (5%) and tape (15%) formulations demonstrated high skin permeability. Addition of an adsorption enhancer (N-methyl-2-pyrrolidone) did not further increase the level of skin permeability. In subsequent in vivo experiments in rats, both the cream and tape formulations led to slow absorption of Sol into plasma, with increased t1/2 compared with oral administration. Plasma Sol concentrations peaked 24 h after transdermal application and the drug was still detectable in plasma 72 h after application. Additionally, the cream (5%) and tape (15%) formulations resulted in a higher area under the plasma concentration vs. time curve from 0 to 72 h (AUC0-72) compared with oral formulation (30 mg/kg). In conclusion, significant in vitro permeability and in vivo absorption of Sol from the transdermal formulations were observed.

The effects of TiO2 sol concentration on single- and multiple-scratch damage in electroplated Ni–B-TiO2 sol composite coating

The electrodeposited sol-enhanced Ni–B–TiO2 composite coatings were elaborated using a novel electroplating process. This coating was assessed in terms of tribological behavior and corrosion resistance. However, the adhesion strength of this coating has not been discussed so far. The aim of this study is to evaluate the adhesion behavior of this coating, considering different TiO2 sol concentration in the plating solution in order to predict its effectiveness and its sustainability when used in mineral crushing process. A progressive load scratch test and multi-pass scratch test were performed on coatings. The morphology of scratched surfaces was analyzed to identify the scratch failure mechanism. The results indicate that the addition of TiO2 sol significantly enhanced the deposit adhesion to the substrate compared to pure Ni–B coating. No spallation failure was observed on the sol-enhanced coatings after progressive load scratch test, contrary to Ni–B coating. Moreover, the multi-pass scratch test demonstrated that the improvement in adhesion strength depends strongly on the quantity of the TiO2 sol added to the plating solution. For the optimal concentration of TiO2 sol (25 ml/L), the sol-enhanced Ni–B–TiO2sol composite coating boasts the best adhesion strength. However, further increase in TiO2 sol concentration results in a deterioration of coating adhesion.

Vertically aligned ZnO nanorods arrays grown by chemical bath deposition for ultraviolet photodetectors with high response performance

Well-aligned ZnO nanorods (NRs) arrays were grown on ZnO seed layer/ITO substrate using chemical bath deposition (CBD) technique and then fabricating ultraviolet (UV) photodetectors (PDs). The effect of precursor concentration of sols on the properties of ZnO seed layer was investigated, and indicated that the crystallinity and growth orientation of samples depend significantly on precursor concentration. ZnO NRs deposited on seed layer exhibit hexagonal wurtzite structure and found that changing the concentration not only affects seed layer, but also influence the rods growth, making it possible to improve the aspect ratio and crystallinity of ZnO NRs. Moreover, the performance of PDs was further discussed and suggested that the maximum signal-to-noise ratio (SNR) and sensitivity (S) of PDs are 67 dB and 2348, when the concentration is 0.5 mol/L, also the shortest rise time of 0.993 s and fall time of 2.036 s can be obtained in such preparation conditions, which is related to larger aspect ratio and higher crystal quality of ZnO NRs. The fabricated UV PDs with high performance are helpful to its application in ultraviolet astronomy, fire detection, especially in military fields, and also are promising for large-scale production.

Influence of sol–gel-derived ZnO:Al coating on luminescent properties of Y2O3:Eu3+ phosphor

This study deposited transparent and conductive Al-doped ZnO (AZO) thin coating on the surface of Y2O3:Eu3+ phosphor particle via a sol–gel method and analyzed the influence of soaking pretreatment, sol concentration, stabilizers, and coating temperature on the microstructure and luminescent properties of AZO-coated Y2O3:Eu3+ phosphors with the aid of SEM, TEM, cathodoluminescence (CL), and photoluminescence (PL) measurements. A water soaking pretreatment was found to effectively improve the coverage and uniformity of the AZO coating, resulting in a continuous and coherent coating. This result is attributed to the presence of adsorbed water and hydroxyl groups on the Y2O3:Eu3+ particle surface after water soaking. Monoethanolamine as a stabilizer agent and higher sol concentration led to a thicker coating on the phosphors. At 800 V or lower, the CL intensity of AZO coated Y2O3:Eu3+ phosphors is significantly greater than that of the uncoated particles and increases with coating thickness. In addition, the PL emission intensity also rises with increasing coating thickness and is even higher than bare phosphors. Further increases in coating thickness beyond the optimum value led to a decrease in PL intensity. This study thus proposes that AZO coatings with sufficient thickness and surface coverage bring about in a higher electron/UV light transport and less surface defects, resulting in an improvement in emission intensity.

Sol–gel synthesis of PZT thin films on FTO glass substrates for electro-optic devices

The optoferroelectric materials have attracted a great deal of attention in recent years. Lead zirconate titanate (PZT) thin films are fabricated on FTO glass substrates by sol–gel technique to investigate optical properties of the films. Heat treatment conditions and sol parameters are investigated to determine the optimum condition for fabricating the PZT thin films. Crack free almost pure perovskite crystal structure is formed at calcination temperature of 600 °C, for 5 min, and sol concentration of 0.33 mol/l. Increasing thickness of thin films raises the grain size and average roughness from 30 to 105 nm and 2.36 to 5.48 nm, respectively. FTIR analysis shows that 600 °C is an appropriate temperature for crystallization of PZT thin films due to the existence of metallic bond (M–O–M) in the spectrum. The films are characterized at different thicknesses for optical transmission and electrical investigation. Value of bandgap energy is estimated to be about 3.5 eV. It has been shown that the presence of rosette-type perovskite structure in the pyrochlore background has negative effect on capacitance and resistance of PZT films.

Synthesis and optimization of SiO2@SiO2 core-shell microspheres by an improved polymerization-induced colloid aggregation method for fast separation of small solutes and proteins

Recently, superficially porous particles (SPPs) have been intensively studied and employed for highly efficient and fast separations. In this paper, the SiO2@SiO2 SPPs were synthesized by an improved polymerization-induced colloid aggregation (PICA) method using urea-formaldehyde polymer as the template. The agglomeration of silica core during modification with ureidopropyltrimethoxysilane (UPS) can not only be avoided by reflux in neutral ethanol solution, but also the secondary nucleation of the colloidal silica sol can be inhibited via optimizing the reaction conditions including pH, temperature, colloidal silica sol concentration and the reaction time. The shell thickness and pore size of SPPs can be controlled successfully by adjusting the weight ratio of silica core/colloidal silica sol and the particle size of colloidal silica sol, respectively. The SPP-C18 columns packed using octadecyltrichlorosilane (ODS) modified SPPs with different pore sizes were employed to separate small solutes and proteins. The baseline separations of 6 kinds of alkyl benzenes and 5 kinds of aromatic alcohol homologues were achieved within 4 min by the SPP-C18 column with 8 nm pore size. Compared with the commercial BEH-C18 column, more than 50,000/m of the plate number of propylbenzene was obtained, and the former provided higher column efficiency to separate small solutes than the latter. Meanwhile, 6 kinds of proteins were also separated completely within 2 min using the SPP-C18 column with 40 nm pore size. In addition, the SPP-C18 capillary column was applied to separate and identify the BSA/HeLa/mouse liver digests with capillary LC-MSMS, respectively. The results indicate that more proteins and peptides can be identified using SPP-C18 capillary column compared with commercial silica-C18 capillary column. The result demonstrates that the prepared SPP-C18 column provides higher column efficiency and the SPPs synthesized with the improved PICA method shows a great potential application for the fast separation of small solutes and proteins.

Synthesis of SnO2 Thin Layer with a Doping Fluorine by Sol-Gel Spin Coating Method

A thin layer of tin oxide with doping Fluorine was synthesized using the sol-gel spin coating method. The synthesis aims to determine the quality of thin layers formed based on temperature variations and the number of layers. The basic material used is SnCl2.2H2O, while the doping material used is NH4F with variations in concentrations of dopants 0, 5, 10, 15, 20 and 25%. The substrate used is glass with a size of 10 x 10 x 3 mm. The synthesis of the thin layer includes substrate preparation, sol-gel making, thin film making, and heating process. At this stage SnO2:F is deposited on a glass substrate with sol-gel spin coating technique at the concentration of sol 1 M with doping levels of Fluorine 0, 5, 10, 15, 20 and 25%, and treated with maturation for 24 hours. Making a thin layer using a spin coater at a speed of 2000 rpm for 3 minutes. The layer made consists of one layer, two layers, three layers and four layers. The resulting layer shows that the higher the doping percentage, the higher the transparency of the layer. In addition, the more the number of layers, the lower the transparency level. Keywords: Thin Film, Tin Oxide, Fluorine, Sol-gel, Spin Coating

Surface properties, adherence, and photocatalytic activity of sol–gel dip-coated TiO2–ZnO films on glass plates

In this study, TiO 2 –ZnO nanostructured films prepared from different Ti/water mole ratios were deposited on glass plates by a sol–gel dip-coating method. The structural and surface properties, adherence, and photoactivity of synthesized TiO 2 –ZnO coatings in methylene blue degradation were investigated. Among the as-prepared TiO 2 –ZnO coatings from sols with different Ti/water mole ratios (1, 0.66, 0.5, and 0.4), the highest sol concentration (Ti/water mole ratio of 1) showed the highest methylene blue photodegradation of almost 80% after 400 min of UV irradiation. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray (EDX), and UV-vis diffuse reflectance spectra (DRS) confirmed that at high sol concentrations (Ti/water mole ratios of 1 and 0.66), a mixed phase of anatase and rutile is formed, whereas at a Ti/water mole ratio of 0.5, just pure rutile is formed. In detail, decreasing the sol concentration increases the cracks, degree of agglomeration, and the thickness of coatings. UV-vis DRS studies also confirm that decreasing the sol concentration in synthesized TiO 2 –ZnO films leads to a shift in the absorption region of the coating to the UV region. Moreover, decreasing the sol concentration declines the coating adherence onto glass plates. TEM images of the TiO 2 –ZnO coating synthesized from sol with a Ti/water mole ratio of 1 revealed the formation of ZnO nanorods around a spherical TiO 2 , which indicates the presence of strong interaction between TiO 2 and ZnO nanoparticles. The TiO 2 –ZnO coating synthesized from sol with a Ti/water mole ratio of 1 was then evaluated at different methylene blue concentrations, pH values, and number of coatings. After five consecutive runs, no significant decrease in the photodegradation efficiency was observed. Scanning electron microscopy (SEM) picture of used coating showed a smooth and stable layer without any detachment. Thermogravimetric analysis (TG) and sonication test confirmed thermal and mechanical stabilities of this coating as well.

Synthesis of phosphate functionalized highly porous activated carbon and its utilization as an efficient copper (II) adsorbent

Hollow silica microspheres were prepared by emulsion/extraction method, where the changes of particle size distribution and surface state of the final microspheres were examined considering the effects of a number of processing variables. First, silica sols were emulsified by 2-ethyl-1-hexanol and then the formed droplets were water extracted to form the gelled hollow microspheres. Average particle size of the final microspheres decreased with increasing stirring speed in emulsion formation step and decreasing colloid concentration. Higher colloid sol concentration gives smaller hollowness of the final microspheres. Solid microspheres formed at colloidal silica sol concentration over 60wt%. In addition, average particle size of the final microspheres decreases with increasing percentage of Span80, but aggregation of the final microspheres occurred in the excessive addition. Moderate volume ratio of silica sol to dispersing agent was 1:5, where silica sol were completely used to from liquid droplets. Also the effects of sintering temperature and the volume of dehydrating liquid were examined.

Microstructure and properties of sol-enhanced Co-P-TiO2 nano-composite coatings

Co-P coatings have been widely used as the replacement of hexavalent chromium coatings. In order to improve the properties of Co-P coatings, Co-P-TiO2 nano-composite coatings were prepared using a novel sol-enhanced method. The microstructure, mechanical properties and corrosion resistance of sol-enhanced Co-P-TiO2 nano-composite coatings were systematically investigated. The results show that sol-enhanced Co-P-TiO2 coating with a good dispersion of TiO2 nanoparticles can be obtained by adding an appropriate amount of TiO2 sol to the bath. The microhardness of Co-P-12.5 mL/L TiO2 coating was increased by ∼18% compared to that of Co-P coating. Its wear resistance and corrosion resistance were also significantly improved. The effects of TiO2 sol concentration on the microstructure, mechanical properties and corrosion resistance of Co-P-TiO2 nano-composite coatings were discussed in detail.

Optical Properties of Multilayer BaTiO3/SiO2 Film Structures Formed by the Sol–Gel Method

Multi-layer film structures BaTiO3/SiO2 with a thickness of ~1 μm containing up to 14 pairs of layers were synthesized by the sol–gel method with sequential heat treatment. It is shown that the synthesized structures are X-ray amorphous. The formation of bands in the transmission and reflection spectra caused by interference effects is demonstrated. A more regular structure exhibits a photon band gap (opacity band) in the visible range with main minimum at 636 nm and corresponding maximum in the reflection spectra. Dispersion characteristics of barium titanate films with different concentrations of initial sols were studied and an increase in the refractive index with an increase in the concentration of sol was demonstrated. For a sol with a concentration of 60 mg/mL, the refractive index in the spectral range of 390–1600 nm is 1.88–1.81. The prospects of sol–gel technology for the formation of BaTiO3/SiO2 structures for nanophotonics and solar radiation converters are discussed.

Hierarchical porous ZnO films synthesized by sol–gel method using triethylenetetramine stabilizer

Hierarchically porous ZnO films are synthesized through a novel sol–gel method using triethylenetetramine (TETA) as a stabilizer. Highly crystalline hierarchical porous ZnO thin films with different pore sizes are synthesized in various reaction mediums by altering solvents, sol concentration, the molar ratio of TETA to zinc acetate dehydrate (ZAD), and withdrawal speed. FESEM images show the formation of a hierarchical porous film with spherical and agglomerated particles in the optimized condition of ethanol as the solvent, sol concentration of 0.2 M, the molar ratio of [TETA]:[ZAD] = 2, and withdrawal speed of 30 mm/min. Increasing the solvent chain length, increasing the sol concentration, decreasing the TETA content, or increasing the withdrawal speed increases the particle size and porosity. XRD data, UV–Vis, and PL spectroscopy indicate high crystallinity with appropriate optical properties for the optimized sample. The hierarchical porous ZnO film synthesized by this method can be utilized as a photoelectrochemical electrode in devices such as photocatalysis and photoelectrochemical water splitting.

A holistic analysis of surface, chemical bonding states and mechanical properties of sol-gel synthesized CoZn-oxide coatings complemented by finite element modeling

This article presents a comprehensive study on surface chemical bonding states, morphological features, mechanical properties, finite element modeling, and water contact angle measurements of wet chemical based dip-coated CoZn-oxide thin film coatings. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Nanoindentation, finite element method (FEM) modeling, and drop shape analysis techniques were used to carry out the detailed measurements. AFM studies showed that the surface roughness values of all the coatings sturdily increased with the increase in sol concentrations. The gradual increase in sol concentrations and annealing temperature also had a remarkable influence over the Co, and Zn-contents of these coatings given by XPS analysis. The deconvolution of Co 2p3/2 photoelectron lines revealed the formation of Co(OH)2, CoO, Co2O3, and Co3O4 phases from the coatings surface while low intensity satellite peaks developed due to a partial spinel lattice structure of Co-ions. The occurrence of Co3O4, CoO, and ZnO phases were also confirmed from the deconvolution of O 1s photoelectron lines. The elastic modulus, E, of CoZn-oxide thin film coating, varied within the range of 43.7–69.2 GPa was comparable with that in CoCuO thin film coatings. The maximum stress level induced was estimated to be in the range of 4.0–6.5 GPa. However, as the thickness of the coatings is increased, the maximum stress level slightly decreased. The coatings were moderately hydrophobic.

Efficient inverted planar perovskite solar cells based on inorganic hole-transport layers from nickel-containing organic sol

Due to the rough surface of fluorine-doped tin oxide (FTO) conductive glasses, it is challenging to fabricate fully covered ultra-thin hole-transport layer (HTL) with thickness under 100[Formula: see text]nm by a simple solution-processed method. Yet, the quality of HTLs play a key role in determining photovoltaic performance of the inverted planar perovskite solar cells (PSCs) owing to their important functions for effectively extracting holes, blocking electrons, suppressing dark reaction, and so on. Here, we report a facile nickel-containing organic sol (Ni–Sol) route to fabricate fully covered 46[Formula: see text]nm thick NiO HTLs for efficient inverted planar PSCs. Comparing with the pre-synthesized NiO nanocrystals solution, the Ni–Sol is easier to spread around the rough outline of FTO to achieve higher surface coverage. Through optimizing the concentration of nickel-containing organic sol, the champion performance of the inverted planar PSCs can be achieved because of the high transparency and good hole-transport dynamics of the optimized NiO film. This work demonstrates the advanced Ni–Sol route for preparing efficient inverted planar PSCs by the simple solution-processed method.

An experimental investigation on pool boiling heat transfer enhancement using sol-gel derived nano-CuO porous coating

This paper presents an experimental investigation aimed at studying the influence of nano-CuO coating on the pool boiling heat transfer enhancement of SS 316 LN stainless steel. The coating was developed using the sol-gel dip coating technique. The Scanning Electron Microscopic and X-Ray Diffraction apparatus were used to analyze morphological and structural characteristics of the coating. The complex interaction of coating process parameters on the boiling heat transfer coefficient was studied using the concept of design of experiment. The results reveal as much as 30% increase in the boiling heat transfer coefficient for the sol-gel derived CuO coated boiling surface compared to its uncoated counterpart. The coating was found to tailor the porosity, roughness and wettability of the surface. The heat transfer coefficient increased with an increase in porosity, roughness and decrease in wettability of the boiling surface. Analysis of variance results revealed that the molar concentration of the CuO sol was the most significant parameter influencing the heat transfer coefficient while sintering temperature was the least significant parameter.

Оптические свойства многослойных пленочных структур BaTiO-=SUB=-3-=/SUB=-/SiO-=SUB=-2-=/SUB=-, сформированных золь--гель-методом

AbstractMulti-layer film structures BaTiO_3/SiO_2 with a thickness of ~1 μm containing up to 14 pairs of layers were synthesized by the sol–gel method with sequential heat treatment. It is shown that the synthesized structures are X-ray amorphous. The formation of bands in the transmission and reflection spectra caused by interference effects is demonstrated. A more regular structure exhibits a photon band gap (opacity band) in the visible range with main minimum at 636 nm and corresponding maximum in the reflection spectra. Dispersion characteristics of barium titanate films with different concentrations of initial sols were studied and an increase in the refractive index with an increase in the concentration of sol was demonstrated. For a sol with a concentration of 60 mg/mL, the refractive index in the spectral range of 390–1600 nm is 1.88–1.81. The prospects of sol–gel technology for the formation of BaTiO_3/SiO_2 structures for nanophotonics and solar radiation converters are discussed.

Highly Efficient Copper Sulfide-Based Near-Infrared Photothermal Agents: Exploring the Limits of Macroscopic Heat Conversion.

Among the foreseeable therapeutic approaches at the cellular level, nanoplatform-driven photothermal therapy is a thriving tool for the selective eradication of malignant tissues with minimal side effects to healthy ones. Hence, chemically versatile, near-infrared absorbing plasmonic nanoparticles are distinctly appealing and most sought after as efficient photothermal agents. In this work, a straightforward method to synthesize monodisperse PEGylated copper sulfide nanoparticles of pure covellite (CuS) phase, featuring strong localized surface plasmonic resonance absorption in the near-infrared and flexible surface chemistry, imparted by monomethyl ether polyethylene glycol molecules, is developed and optimized. These nanoparticles show a remarkable photothermal heat conversion efficiency (HCE) of 71.4%, which is among the highest for CuS systems and rivals that of plasmonic noble metal nanostructures. Moreover, through critical evaluation and mathematical modeling of the material's properties and measurement methodology, it is assessed that the calculated HCE values drastically depend on experimental conditions such as wavelength-dependent solvent absorption properties, sol concentration, and optical path. These findings are of paramount relevance to the photothermal community, since they call for a standardization of the procedure for the evaluation of the HCE of proposed photothermal agents, in order to make the reported values universally and reliably comparable.