Microstructure of Polyelectrolyte Nanoaggregates Studied by Fluorescence Probe Method

The microstructure of water soluble nanoaggregates based on polyelectrolyte complex formed by the cationic comb-type copolymer poly(acrylamide -co-[3- (methacryloyl-amino)propyl] trimethylammonium chloride)-graft- polyacrylamide [P(AM-co-MAPTAC)-g-PAM] and the anionic linear polyelectrolyte sodium polyacrylate (NaPA) was investigated using the fluorescence probe technique. The fluorescence probe were 1-anilinonaphthalene-8-sulfonic acid (ANS), pyrene (Py) and 1,10-bis(1-pyrene) decane (PD). The fluorescence properties in polyelectrolyte complex solutions, which are sensitive to either micropolarity (ANS, Py) or microviscosity (PD), were related to the quantities obtained in different pure or mixed solvents. Micropolarities were quantified utilizing the polarity common index (Reichardt) E _T(30). ANS and Py showed a variation of the micropolarity with the charge ratio of the two polymers, with the lowest polarity reached at the complex neutralization. The PD probe, by its excimer-to-monomer fluorescence intensities ratio, enabled us to evidence the effect of the composition and the comb-type copolymer grafting density on the microviscosity of the interpolyelectrolytes aggregates. It has been found that the microviscosity increased with the density of the grafting PAM chains.     

Studies upon Qualification of Meat from Animals Irradiated and Contaminated with Radiocaesium

Abstract

The problem concerning qualification of food originated from animals irradiated and contaminated with ¹³⁷caesium appeared especially after the Chernobyl accident. So, it was a reason to undertake respective studies on 108 rabbits divided into three groups: group I – non-irradiated rabbits, group II – irradiated with a dose of 103 mCkg^?1 (400 R), group III – irradiated with a dose of 206 mCkg^?1 (800 R). All animals were contaminated intragastrically with an aqueous solution of ¹³⁷CsCl. After slaughter samples of the muscles were cured in 1, 3, 5, 10, and 15% brine or were cooked for 2 hrs. In the case of curing the radioactivities of meat and brine, and the concentrations of salt in cured meat were estimated after 7, 14, and 21 days. The radioactivities of cooked meat, broth, and condensed water vapour were estimated after 1 and 2 hrs. Taking into account the decrease of the radioactivities, duration of curing, and concentrations of salt in cured meat the optimum results were achieved when the meat from non-irradiated rabbits was cured for 7 days in 3% brine, and that of irradiated rabbits in 5% brine with regard to a lower stability of this meat. The decontamination effectiveness of cooking was similar in all examined rabbits. Radiocaesium penetrates into the brine or broth and escapes with water vapour thereafter.     

Evaluation of ultrasound and microbubbles effect on pork meat during brining process

In this study combined effect of ultrasound-induced acoustic cavitation and microbubbles during meat brining on pork loin (Longissimus dorsi) was evaluated. Cylindrical shape (diameter 15 mm, height 80 mm) pork loin samples were cut and immersed in 200 g L^-1 NaCl brine and treated with the following brining methods for 180 min: static brining (SB), ultrasound assisted brining (US) and ultrasound combined with microbubbles in brine (USMB). Ultrasound was generated with 20 kHz frequency, 5,09 W/cm² maximum intensity and 100 W maximum power. Microbubbles in brine were produced by a gas–liquid mixing pump. Effect of ultrasound and microbbubles on NaCl content and diffusion in pork loin, mass balance, water binding capacity (WBC), protein denaturation and meat tissue microstructure were evaluated. The US and USMB brinings enhanced the NaCl diffusion into meat compared to meat brined under static conditions. The constant diffusion coefficient (D) model precisely described the NaCl diffusion kinetics during brinings. The ultrasound and microbbubles resulted in microscopic pores on the surface of myofibers. Decreasing WBC was observed for all brining methods. Myosin was not detectable in any of the brining methods. Denaturation temperature of actin showed a decreasing tendency with increasing brining time independently the brining methods.     

Flexible polyethylene terephthalate (PET) electrodes based on single-walled carbon nanotubes (SWCNTs) for supercapacitor application

Flexible polyethylene terephthalate (PET) electrodes based on pristine single-walled carbon nanotubes (SWCNTs) and acid-treated single-walled carbon nanotubes (A-SWCNTs) were prepared by spray coating technique. Flexible A-SWCNTs electrodes showed enhanced electrochemical properties compared to the pristine SWCNTs electrodes. The electrochemical properties of the flexible A-SWCNTs electrodes were optimized with various types of aqueous electrolytes including sulfuric acid (H₂SO₄), sodium sulfate (Na₂SO₄), potassium chloride (KCl), sodium hydroxide (NaOH), and potassium hydroxide (KOH). The electrochemical performance of the A-SWCNTs electrodes as a function of bending to 30° were evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) measurements in 1 M H₂SO₄. The specific capacitance value of the unbent A-SWCNTs electrode was 67 F g^?1, which decreased to 63 F g^?1 (94% retention) after 1000 GCD cycles. Interestingly, the specific capacitance of the unbent A-SWCNTs electrode with application of the 1000 GCD cycles was retained even after 500 bending to 30° with 6000 GCD cycles.     

Effect of swift heavy ion irradiation on thermal,optical and structural properties of poly vinylidene chloride

Poly vinylidene chloride (PVDC) irradiated with lithium (50 MeV), carbon (85 MeV), nickel (120 MeV) and silver ions (120 MeV) having fluence range of 1 × 10¹¹ ions/cm² to 3 × 10¹² ions/cm² have been studied using different techniques i.e. XRD (X-ray diffraction), FTIR (Fourier transform infrared), UV–Visible and TGA (thermo-gravimetric analysis). In XRD analysis, the intensity of diffraction peaks of PVDC irradiated with lithium ions was enhanced at lower fluence as compared to pristine. The shift in optical absorption edge in irradiated PVDC was correlated with the decrease in optical band gap energy. The distinguishable characteristic peaks were observed due to UV–Vis analysis, in lithium irradiated samples of PVDC at higher fluences. The % age decrease in optical band gap energy for the respective ions were 30.9%, 34.16%, 81.1%, 87.02% respectively. Formation of double carbon bonds and breaking of C–O and C–Cl bonds with the release of Cl in irradiated PVDC was observed in FTIR spectra. In Thermogravimetric analysis (TGA), the % age weight loss observed for irradiated samples with increase in ion fluence was lesser than the % age weight loss observed in pristine sample.     

Rapid and controlled transformation of nitrate in water and brine by stabilized iron nanoparticles

Highly reactive zero-valent iron (ZVI) nanoparticles stabilized with carboxymethyl cellulose (CMC) were tested for reduction of nitrate in fresh water and brine. Batch kinetic tests showed that the pseudo first-order rate constant (k _obs) with the stabilized nanoparticles was five times greater than that for non-stabilized counterparts. The stabilizer not only increased the specific surface area of the nanoparticles, but also increased the reactive particle surface. The allocation between the two reduction products, NH₄ ⁺ and N₂, can be manipulated by varying the ZVI-to-nitrate molar ratio and/or applying a Cu–Pd bimetallic catalyst. Greater CMC-to-ZVI ratios lead to faster nitrate reduction. Application of a 0.05 M HEPES buffer increased the k _obs value by 15 times compared to that without pH control. Although the presence of 6% NaCl decreased k _obs by 30%, 100% nitrate was transformed within 2 h in the saline water. The technology provides a powerful alternative for treating water with concentrated nitrate such as ion exchange brine.     

Silver nanostructure arrays abundant in sub-5 nm gaps as highly Raman-enhancing substrates

Two types of highly Raman-enhancing arrays substrates were fabricated using anodic aluminum oxide (AAO) templates by controlling the AAO template temperature and evaporated silver thickness during e-beam evaporating: complex patterned Ag nanoparticle arrays abundant in sub-5 nm gaps (type I); hexagonal Ag nanopore arrays (type II). The surface enhanced Raman scattering (SERS) enhancement factors (EF) of both substrates are estimated experimentally to exceed 10⁵, especially that of type I reaches 10⁷ due to the existence of numerous sub-5 nm gaps. The simulation using finite-difference time-domain (FDTD) method confirmed that gap effect has significantly improved the substrates’ SERS activity.     

Statistical optimization of process parameters for improvement of phycobiliproteins (PBPs) yield using ultrasound-assisted extraction and its kinetic study

The present study is mainly concerned for the development of an optimal ultrasound-assisted extraction (UAE) condition for phycobiliproteins (PBPs) from Oscillatoria sp. (BTA 170) using Taguchi methodology. Four process parameters viz. solid to liquid ratio, duty cycle, electrical acoustic intensity, and pH, for UAE were optimized using Taguchi methodology for enhanced PBPs extraction. The ratio of signal to noise (S/N) was used to compute the optimized condition required to attain a higher yield of PBPs, the average performance of individual parameter and corresponding interactive effects. The statistically significant parameters with their contribution were assessed using Analysis of variance (ANOVA). Results showed that duty cycle contributed the maximum influence (30.81%) on phycocyanin (PC) extraction followed by a solid liquid ratio (28.62%), pH (22.46%) and electrical acoustic intensity (18.10%). The highest contribution on the extraction of phycoerythrin (PE) was found from pH (33.16%), followed by duty cycle (31.57%), solid to liquid ratio (22.83%) and electrical acoustic intensity (12.45%). For extraction of allophycocyanin (APC), the duty cycle, solid to liquid ratio, pH and electrical acoustic intensity contributed 29.47, 29.07, 29.03, and 12.43% respectively. Results obtained from Taguchi methodology indicated that enhanced PC (94.10%), PE (95.20%) and APC (90.54%) can be achieved with solid–liquid ratio (0.2 g/ml), electrical acoustic intensity (16.99 w/cm²), duty cycle (75%), and pH 7 than the yield of PBPs obtained under unoptimized condition. In the present study, higher yield of PC (38.99%), PE (20.84%), and APC (11.93%) were attained with UAE compared to yield obtained from homogenized Oscillatoria sp. BTA 170 using 0.05 M phosphate buffer. Batch extraction data of PBPs under UAE was fitted well with the second order model. The values of second-order rate constant (k) were computed as 6.66 × 10⁻⁴, 64.09 × 10⁻⁴ and 1.49 × 10⁻⁴ L/mg/min for extraction of PC, PE and APC respectively. The PBPs exhibited significant antioxidant property and hydrogen peroxide scavenging activity, which were increased with the enhancement of PBPs concentration.     

Preparation and Property of Poly(N-isopropylacrylamide) (PNIPAAm)/Clay/Linear Polyacrylamide (PAAm) Nanocomposite Hydrogels

In this study, a linear polyacrylamide (PAAm) with an average viscosimetric molecular weight 3.97 × 10³ kg mol^?1 was added to the prereaction solution for the preparation of poly(N-isopropylacrylamide) (PNIPAAm)/clay nanocomposite hydrogels. The effects of the linear PAAm on the optical transparency and tensile property of the resulting PNIPAAm/clay/linear PAAm hydrogels were systematically investigated. The results revealed that the optical transparency and mechanical tensile properties of the resultant hydrogels strongly depended on the linear PAAm content. In particular, 5 wt% loading of linear PAAm led to almost fivefold decreases of transmittance at 25°C and a onefold increase of the tensile elongation at break. These characteristic changes were explained by a typical interpenetrating microstructure, which was formed by PNIPAAm due to the incorporation of linear PAAm in the PNIPAAm/clay network. The dynamic rheological test and infrared spectroscopy analysis on the mixed solutions consisting of linear PAAm and clay platelets further confirmed the interaction.     

Spectroscopic studies on the interaction and sonodynamic damage of neutral red (NR) to bovine serum albumin (BSA)

In this paper, the interaction of neutral red (NR) with bovine serum albumin (BSA) and the sonodynamic damage to BSA under ultrasonic irradiation was studied by means of ultraviolet-visible (UV-vis) and fluorescence spectra. The quenching constant (K_SV=5.749×10⁴ L/mol), binding constant (K_A=3.19×10⁴ L/mol) and binding site number (n=0.9462) were measured. The binding distance (r=2.47 nm) between NR and BSA was obtained according to Föster’s non-radiative energy transfer theory. The damage process of BSA molecules was detected by the hyperchromic effect of UV-vis spectra and quenching of intrinsic fluorescence spectra. In addition, the influencing factors such as ultrasonic irradiation time and NR concentration on the damage to BSA molecules were also considered. The results showed that the damage degree is enhanced with the increase of ultrasonic irradiation time and NR concentration. The possible mechanism of sonodynamic damage to BSA molecules was mainly mediated by singlet oxygen (¹O₂). Otherwise, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. The results indicated that the NR is more vicinal to tryptophan (Trp) residue than to tyrosine (Tyr) residue and the damage site is also mainly at Trp residues. The research result will bring a certain significance to use sonosensitive drugs in the fields of tumor treatment.     

Rheological Behavior of Blends of Poly(Phenylene Sulfide) with a Thermotropic Liquid Crystalline Aromatic Poly(Ether Ester)

A new type of thermotropic liquid crystalline aromatic poly(ether ester) (PEE) was prepared from 1,3-bis(4′-carboxyphenoxy)benzene, 1,4-diacetoxybenzene, and p-acetoxybenzoic acid through a melt transesterification process. The rheological behavior of blends of poly(phenylene sulfide) (PPS) with PEE was studied using a high-pressure capillary rheometer with the shear rate range of 50 s^?1 to 3000 s^?1. The results show that according to the range of shear rate, the flow curves of PEE/PPS blends can be divided into three zones: a first shear-thinning zone (n < 1, “n” represents non-Newtonian indexes), a shear-thickening zone (n > 1), and a second shear-thinning zone (n < 1), and the former two zones are more obvious with the increase of PEE content or elevated temperature. In the second shear-thinning zone, the PPS melt is close to a Newtonian fluid at high temperature and high shear rate; meanwhile the non-Newtonian behavior of the PPS melt at high temperature is enhanced with the addition of PEE. The apparent viscosity of PPS melts sharply dropped after adding PEE, especially at relatively low temperature and low shear rate. The curve of apparent viscosity vs. shear rate starts to flatten out after adding PEE, suggesting that the addition of PEE lowers the sensitivity of PPS to shear rate. As the content of PEE increases, the activation energy of the viscous flow, ΔE_η, of PPS decreases, which means that adding PEE weakens the temperature sensitivity of the apparent viscosity of the PPS melt. It can clearly be seen that the addition of PEE is beneficial to the processing of PPS.     

Sensitive determination of enoxacin by its enhancement effect on the fluorescence of terbium(III)-sodium dodecylbenzene sulfonate and its luminescence mechanism

The fluorescence system of enoxacin-Tb³⁺-sodium dodecylbenzene sulfonate (SDBS) was investigated in this paper. The experiments indicated that the fluorescence intensity of Tb³⁺-SDBS was greatly enhanced by enoxacin. Accordingly, a sensitive fluorimetric method for determining enoxacin was established. The fluorescence intensity was measured by a 1-cm quartz cell with an excitation wavelength of 290 nm and an emission wavelength of 545 nm. The enhanced fluorescence intensity of the system (ΔF) showed a good linear relationship with the concentration of enoxacin in the range of 5.0×10⁻⁹ to 2.0×10⁻⁶ mol L⁻¹, its correlation coefficient was 0.9992 and the detection limit (S/N=3) was 2.8×10⁻⁹ mol L⁻¹. The presented method was used to determine enoxacin in real pharmaceutical samples. The luminescence mechanism was also discussed in detail. In the fluorescence system of enoxacin-Tb³⁺-SDBS, SDBS not only acted as the surfactant but also acted as the energy donor.     

Chemical and structural analysis of low-temperature excimer-laser annealing in indium-tin oxide sol-gel films

We investigated the influence of excimer-laser annealing (ELA) on the electrical, chemical, and structural properties of indium–tin oxide (ITO) films prepared by a solution process. The ITO film was prepared by the sol-gel method and annealed by excimer-laser pulses with an energy density up to 240?mJ/cm². Hall measurements showed that the ELA substantially enhanced the electrical properties of the ITO films, including their resistivity, carrier density, and mobility, as increasing the laser energy density. In-depth x-ray photoelectron spectroscopy analysis of the chemical states in the film surface showed that the ELA reduced carbon species and promoted both an oxidation and crystallization. These changes were consistent with results of x-ray diffraction and transmission electron microscopy measurements, where expansions in the microcrystal growth were observed for higher laser energy density. We comprehensively understand that the chemical rearrangement and concomitant crystallization are the main factors for achieving the electrical properties during the ELA. These results suggest the potential of the ELA-treated sol-gel films for providing high-quality ITO films at low temperatures toward the flexible device applications.     

Hyperthermal scattering of Cs from Pt(1 1 1): the effect of image charge on the ion-surface energy transfer

We have studied the energy exchange between hyperthermal (5-100 eV) Cs⁺ projectiles and a Pt(1 1 1) surface by measuring the kinetic energy of the scattered ions. The scattering geometry was chosen to be in-plane with specular scattering angles, and the energy of the scattered ions was analyzed as functions of incidence energy and angle. For low incidence energy (<40 eV), the energy transfer to the Pt surface is substantially enhanced due to the attractive image charge force between Cs⁺ and the surface. The image charge effects are highlighted by the different energy transfer on Pt(1 1 1) and Si(1 1 1) surfaces. Analysis of the experimental results using two- and three-dimensional theoretical models revealed a well depth of 1 eV for the image charge potential. Hyperthermal Cs⁺ ions scatter from Pt(1 1 1) predominantly via double collisions with Pt atoms, though the scattering phenomena are insensitive to the impact site at the surface.     

Study on the New Fluorescence Enhancement System of Tb –N-(2 - Pyridinyl) Ketoacetamide-Et<Subscript>3</Subscript>N-Zn and its Application

A sensitive fluorescence enhancement system was developed for the determination of zinc (II). The fluorescence intensity of the Tb- N- (2 - Pyridinyl) ketoacetamide (PKA) system was greatly enhanced by the addition of triethylamine (Et₃N) and zinc nitrate in the methanol solution. The excitation and emission wavelengths were 329 nm and 546 nm, respectively. Under optimal conditions, the fluorescence intensities varied linearly with the concentration of Zn²⁺ in the range of 8.0×10⁻⁷−5.0×10⁻⁶ M with a detection limit of 9.9×10⁻⁸ M. The interferences of some substances were described. This method was applied to the determination of amounts of Zn²⁺ in soybean, rice, and wheat, respectively. The results showed that the proposed procedure is a high selective, simple, and rapid method to the determination of Zn²⁺ ion. The mechanism of fluorescence enhancement was also studied.     

Sensitive Determination of Norfloxacin by the Fluorescence Probe of Terbium (III)- Sodium Dodecylbenzene Sulfonate and Its Luminescence Mechanism

The fluorescence system of the norfloxacin-Tb³⁺- sodium dodecylbenzene sulfonate (SDBS) was investigated in this paper. The experiments indicated that the fluorescence intensity of the Tb³⁺-SDBS was greatly enhanced by the norfloxacin. On the basis of the above findings, a sensitive fluorimetric method for determining the norfloxacin was established. The fluorescence intensity was measured by a 1-cm quartz cell with the excitation wavelength of 290 nm and the emission wavelength of 545 nm. The enhanced fluorescence intensity of the system (Δ F) showed a good linear relationship with the concentration of norfloxacin in the range of 5.0×10⁻⁹ mol L⁻¹–2.0×10⁻⁶ mol L⁻¹, its correlation coefficient was 0.9991 and the detection limit (S/N=3) was 1.2×10⁻⁹ mol L⁻¹. The presented method was used to determine the norfloxacin in real pharmaceutical samples. The luminescence mechanism was also discussed in detail. In the fluorescence system of the norfloxacin-Tb³⁺-SDBS, the SDBS not only acted as the surfactant, but also acted as the energy donor.     

Structural Characterization of Hydroxyl-Terminated Polybutadiene-Bound 2, 2-Thiobis(4-methyl-6-tert-butylphenol) and Its Thermo-Oxidative Aging Resistance for Natural Rubber Vulcanizates

A novel polymeric antioxidant, hydroxyl-terminated polybutadiene-bound 2,2-thiobis(4-methyl-6-tert-butylphenol) (HTPB-IPDI-TPH), was prepared by binding 2, 2-thiobis(4-methyl-6-tert-butylphenol) (TPH) onto hydroxyl-terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI). Fourier-transform infrared spectroscopy (FTIR), ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR), and gel permeation chromatography (GPC) were used to characterize the structure of HTPB-IPDI-TPH. The thermal stability of HTPB-IPDI-TPH was studied by thermogravimetry analysis (TGA). The effect of HTPB-IPDI-TPH on thermo-oxidative aging resistance of NR vulcanizates was investigated, and the mechanism of thermo-oxidative aging resistance was preliminarily discussed. The results showed that HTPB-IPDI-TPH contributed better thermal stability and thermo-oxidative aging resistance to NR vulcanizates than TPH. The thermo-oxidative aging resistance of HTPB-IPDI-TPH was more remarkable in the later stage of aging. Attenuated total-reflectance Fourier-transform infrared spectroscopy (FTIR-ATR) analysis showed that the relative content of carbonyl groups of NR vulcanizate with HTPB-IPDI-TPH was obviously lower than that with TPH after thermo-oxidative aging. It is suggested that ?NHCOO? groups in HTPB-IPDI-TPH enhanced the ability of trapping alkyl peroxide radicals.     

Toxic effects of copper (II) ions on bovine hemoglobin

In this paper, the toxic influence of copper ions (II) on bovine hemoglobin was investigated by the combination of ultraviolet-visible absorption, fluorescence, time-resolved fluorescence, synchronous fluorescence, and circular dichroism spectra. Driven by hydrophobic and electrostatic forces, copper ions (II) could interact with bovine hemoglobin to form bovine hemoglobin-copper ions (II) complex with one binding site. The binding constant (K) was 1.57?×?10⁴, 1.89?×?10⁴ and 2.11?×?10⁴?L/mol at 298, 304, and 310?K, respectively. The binding distance (r) was 4.24?nm. Fluorescence and time-resolved fluorescence spectra showed that bovine hemoglobin quenched by copper ions (II) was a static quenching process. Results of synchronous fluorescence spectra revealed that the microenvironment and the conformation of bovine hemoglobin were changed during the binding reaction. Data of circular dichroism spectra suggested that with the increasing concentration of copper ions (II), the secondary structure of bovine hemoglobin underwent a decrease in α-helix and alteration in backbone microenvironment. Copper ions (II) was thus evidenced to have a certain toxic effect on physical bodies.     

Studies on surface graft polymerization of acrylic acid onto PTFE film by remote argon plasma initiation

The graft polymerization of acrylic acid (AAc) was carried out onto poly(tetrafluoroethylene) (PTFE) films that had been pretreated with remote argon plasma and subsequently exposed to oxygen to create peroxides. Peroxides are known to be the species responsible for initiating the graft polymerization when PTFE reacts with AAc. We chose different parameters of remote plasma treatment to get the optimum condition for introducing maximum peroxides (2.87 × 10⁻¹¹ mol/cm²) on the surface. The influence of grafted reaction conditions on the grafting degree was investigated. The maximum grafting degree was 25.2 μg/cm². The surface microstructures and compositions of the AAc grafted PTFE film were characterized with the water contact angle meter, Fourier-transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Contact angle measurements revealed that the water contact angle decreased from 108° to 41° and the surface free energy increased from 22.1 × 10⁻⁵ to 62.1 × 10⁻⁵ N cm⁻¹ by the grafting of the AAc chains. The hydrophilicity of the PTFE film surface was greatly enhanced. The time-dependent activity of the grafted surface was better than that of the plasma treated film.     

Structure and conformation of Arg8 vasopressin modified analogs

Fourier‐transform Raman and infrared spectra were acquired for four arginine vasopressin (AVP) analogs containing L ‐diphenylalanine (Dpa): [Dpa²]AVP, [Cpa¹,Dpa²]AVP, [Dpa³]AVP, and [Cpa¹,Dpa³]AVP (where Cpa denotes 1‐mercaptocyclohexaneacetic acid). We compared and analyzed these spectra. In addition, the Raman spectra were compared to the corresponding surface‐enhanced Raman scattering spectra recorded in an aqueous silver colloidal dispersion. Silver colloidal dispersions prepared by the simple borohydride reduction of silver nitrate were used as substrates. The geometry of these molecules etched on the silver surface was deduced from the observed changes in the intensity enhancement, breadth, and shift in wavenumber of the Raman bands in the spectra of the bound versus free species. Based on the obtained data, adsorption mechanisms were proposed for each case, and the suggested adsorbate structures were compared. All the molecules were thought to adsorb onto a silver surface via a phenyl ring, free electron pairs on the sulfur atom, and CO and  CONH‐bonds. However, the orientation of these fragments on the colloidal silver surface and the strength of the interactions with this surface are different. For [Dpa³]AVP and [Cpa¹,Dpa³]AVP, a strong interaction among the—CCN‐peptide fragment and the colloidal silver surface occurs. Copyright © 2011 John Wiley & Sons, Ltd.