Eu(III) and Tb(III) luminescent lanthanide systems derived from DTPA-bisamide and DTTA-based ligands incorporating bipyridine antenna

Four new polycarboxylate ligands H₃Lⁿ have been synthesized by the attachment of two or one 2,2′-bipyridine subunits onto a diethylenetriamine pentacarboxylic acid (DTPA-bisamide derivatives: H₃L¹, H₃L²) or a diethylenetriamine tricarboxylic acid (DTTA derivatives: H₃L³, H₃L⁴) core. The neutral Eu^III and Tb^III complexes of these chelates have been prepared and studied from their UV-vis and luminescence data. The main photophysical characteristics of these complexes, i.e. the absorption and luminescence spectra, the metal-centred lifetimes and the overall luminescence yields (Φ) were measured in buffered aqueous solutions. In addition the role played by non-radiative paths (vibrational energy transfer involving coordinated water molecules, involvement of ligand-to-metal charge-transfer excited states, or metal→ligand back-transfer) was investigated. In all complexes, we found that the bidentate bipyridine chromophore is not coordinated to the lanthanide ion, allowing one (LnL¹, LnL²) or two (LnL³, LnL⁴) water molecules to penetrate the first coordination sphere of the metal. Although the bipyridine chromophore behaves as remote (from the binding site) light-harvesting unit for the lanthanide ion in these systems, a sizeable sensitization of the Eu- and Tb-centred luminescence can be effective (LnL², LnL³, Φ=16-19% in aerated D₂O solutions). Our photophysical investigations show that overall non-radiative deactivation is not dependant of thermally activated non-radiative channels but the efficiency of the ligand→Ln intramolecular energy transfer has to be taken into account to explain the obtained results.     

Synthesis,structures and near-infrared luminescence properties of Ho and Yb coordination complexes

Four Ln³⁺ coordination complexes with the formulas [Ln(p-toluylate)₂(Ac)(H₂O)]_n (Ln=Ho 1, Yb 2) and {[Ln₂(OOCCH₂CH₂COO)₃(H₂O)₄]·6H₂O}_n (Ln=Ho 3, Yb 4) were synthesized hydrothermally. Their structures were determined by single-crystal X-ray diffraction. Complexes 1 and 2 are isomorphic and form infinite 2D network structures comprising p-toluylate and acetate (Ac^–) moieties. Complexes 3 and 4 are also isomorphic and possess infinite 2D structures in which succinate acts as bridging ligands that are connected to a 3D hydrogen bonding network by O–H…O hydrogen bonds. Solid-state IR and UV-Vis-NIR spectra, excitation and emission spectra were determined for the four complexes at room temperature. Complexes 1 and 2 exhibit characteristic NIR emission bands of Ln³⁺ ions but these are shifted and split relative to the theoretical positions. This is also evident for their UV-Vis-NIR spectra. The influence of ligands on enhancing the NIR luminescence of Ln³⁺ ions in complexes is discussed.     

Luminescence and crystal-field fitting of two optical isomeric complexes of europium

FT-IR and Raman vibrational spectra and electronic emission spectra have been recorded for enantiomers of europium complexes with DBM: dibenzoylmethanate 1,2, and TTFA: 2-thenoyltrifluoroacetonate 3,4, employing the chiral ligands L_SS(+)- and L_RR(-)-4,5-pinene bipyridine. Contrary to the previously published X-ray data, where geometrical differences were stated to occur for particular enantiomers, the vibrational (and the emission) spectra of the individual optical isomers of a complex are not distinguishable. Using excitation into the Eu³⁺⁵D₂ multiplet term, the emission intensity is weak from ⁵D₁, whereas a complex structure is observed for the ⁵D₀→⁷F_J transitions. Features in the vibronic sidebands exhibit similar derived vibrational energies to those observed in the Raman spectra. Fittings of 25 4f⁶ crystal-field energy levels of 2 and 4 have been attempted with some approximations concerning the local Eu³⁺ environments. The ⁵D₀ emission lifetimes are monoexponential and are 0.5 (1,2) and 0.9 ms (3,4) at room temperature.     

Energy, momentum, and force in classical electrodynamics: Application to negative-index media

The classical theory of electromagnetism is based on Maxwell's macroscopic equations, an energy postulate, a momentum postulate, and a generalized form of the Lorentz law of force. These seven postulates constitute the foundation of a complete and consistent theory, thus eliminating the need for physical models of polarization P and magnetization M — these being the distinguishing features of Maxwell's macroscopic equations. In the proposed formulation, P(r, t) and M(r, t) are arbitrary functions of space and time, their physical properties being embedded in the seven postulates of the theory. The postulates are self-consistent, comply with special relativity, and satisfy the laws of conservation of energy, linear momentum, and angular momentum. The Abraham momentum density p_EM(r,t) = E(r,t) × H(r,t) / c² emerges as the universal electromagnetic momentum that does not depend on whether the field is propagating or evanescent, and whether or not the host media are homogeneous, transparent, isotropic, linear, dispersive, magnetic, hysteretic, negative-index, etc. Any variation with time of the total electromagnetic momentum of a closed system results in a force exerted on the material media within the system in accordance with the generalized Lorentz law.     

Syntheses, structures and photophysical properties of heteronuclear Zn-Ln coordination complexes

Four heteronuclear Zn-Ln coordination complexes, [Nd₂Zn₂(p-toluylate)₁₀(phen)₂] (1), [Ln₂Zn₂(p-toluylate)₁₀(phen)₂]·2(HAc)_1/2 (Ln=Tb 2, Ho 3) and [PrZn₂(p-toluylate)₅(Ac)₂(phen)₂] (4) (phen=1, 10-phenanthroline), are synthesized by the hydrothermal method and their structures are measured by single-crystal X-ray diffraction. The IR and UV-vis-NIR absorption spectra and the emission spectra in the visible and near-infrared (NIR) regions of the four complexes are determined at room temperature. In the NIR region (or in the visible region), the complexes show the characteristic emission bands of Ln³⁺ ions, which may be attributed to sensitization from the ligands (the ligand directly-coordinated to Ln³⁺ ions and d-block) to Ln³⁺ ions after forming the Zn-Ln complexes. It is reported for the first time in this paper that the Zn-Pr complex 4 can exhibit the broad emission band in the NIR region. In addition, the shift, split or broadness of the ff emission bands in the NIR region of complexes 1, 3 and 4 are discussed.     

Whence the Minkowski momentum?

Electromagnetic waves carry the Abraham momentum, whose density is given by p_EM = S(r,t) / c². Here S(r,t) = E(r,t) × H(r,t) is the Poynting vector at point r in space and instant t in time, E and H are the local electromagnetic fields, and c is the speed of light in vacuum. The above statement is true irrespective of whether the waves reside in vacuum or within a ponderable medium, which medium may or may not be homogeneous, isotropic, transparent, linear, magnetic, etc. When a light pulse enters an absorbing medium, the force experienced by the medium is only partly due to the absorbed Abraham momentum. This absorbed momentum, of course, is manifested as Lorentz force (while the pulse is being extinguished within the absorber), but not all the Lorentz force experienced by the medium is attributable to the absorbed Abraham momentum. We consider an absorptive/reflective medium having the complex refractive index n₂ + iκ₂, submerged in a transparent dielectric of refractive index n₁, through which light must travel to reach the absorber/reflector. Depending on the impedance-mismatch between the two media, which mismatch is dependent on n₁, n₂, κ₂, either more or less light will be coupled into the absorber/reflector. The dependence of this impedance-mismatch on n₁ is entirely responsible for the appearance of the Minkowski momentum in certain radiation pressure experiments that involve submerged objects.     

Relative power loss of misalignment based on electro-optical printed circuit board

In this paper, the power loss values between 45° total internal reflecting waveguide mirror (TIRWM) and the polymer optical waveguide layer are obtained by vector finite element method. There are some misalignments during an actual fabrication of electro-optical printed circuit board (EOPCB). And, b, a, c correspond to the error value of alignment in the x-axis, y-axis and z-axis direction, respectively. Another, four effective refractive indices of the 45° TIRWM and polymer optical waveguide layer are calculated, separately. And, n_eff1 = 1.425211 is uniquely chosen. Next, these relative power errors Δ are calculated, when a, b, c separately change. Moreover, these error values are plotted into some curved surface figures. By these figures, it is easy to find the relationship between a, b, c and Δ. Furthermore, it is beneficial for us to avoid the region of larger power loss during an actual fabrication of EOPCB.     

TOWARDS DEEP AND SIMPLE UNDERSTANDING OF THE TRANSCENDENTAL EIGENPROBLEM OF STRUCTURAL VIBRATIONS

When using exact methods for undamped free vibration problems the generalized linear eigenvalue problem (K−ω²M) D=0 of approximate methods, e.g., finite elements, is replaced by the transcendental eigenvalue problem K (ω) D=0. Here ω is the circular frequency; D is the displacement amplitude vector; M and K are the mass and static stiffness matrices; and K (ω) is the dynamic stiffness matrix, with coefficients which include trigonometric and hyperbolic functions involving ω and mass because elements (for example, bars or beams) are analyzed exactly by solving their governing differential equations. The natural frequencies of this transcendental eigenvalue problem are generally found by the Wittrick-Williams algorithm which gives the number of natural frequencies below ω_t, a trial value of ω, as ∑J_m+s{K (ω_t)} wheres {} denotes the readily computed sign count property of K (ω) and the summation is over the clamped-clamped natural frequencies of all elements of the structure. Understanding the alternative solution forms of the transcendental eigenvalue problem is important both to accelerate convergence to natural frequencies, e.g., by plotting ∣K (ω)∣, and to improve the mode calculations, which lack the complete reliability of natural frequencies obtained by using the Wittrick-Williams algorithm. The three solution forms are: ∣K (ω)∣=0; D=0 with ∣K (ω)∣→∞; and ∣K (ω)∣≠0 with D≠0. The literature covers the first two forms thoroughly but the third form has been almost totally ignored. Therefore, it is now examined thoroughly, principally by analytical studies of simple bar structures and also by confirmatory numerical results for a rigidly jointed plane frame. Although structures are unlikely to have exactly the properties giving this form, it needs to be understood, particularly because ill-conditioning can occur for structures approximating those for which it occurs.     

Surface-modification of TiO2 with new metalloporphyrins and their photocatalytic activity in the degradation of 4-notrophenol

A new mono-functionalized porphyrin derivative, 5-mono-[4-(2-(4-hydroxy)-phenoxy)ethoxy]-10,15,20-triphenylporphyrin (3) and its Cu(II) (3a), Zn(II) (3b) and Ni(II) (3c) metalloporphyrins were synthesized and characterized by using various spectroscopic techniques. The corresponding 3a, 3b, 3c-TiO₂ photocatalysts were then prepared and characterized by means of FT-IR and diffused reflectance spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activities of 3a, 3b, 3c-TiO₂ were investigated by testing the photodegradation of 4-nitrophenol (4-NP) in aqueous solution under the halogen lamp irradiation. The results indicated that all the 3a, 3b, 3c enhanced the photocatalytic efficiency of bare TiO₂ in photodegrading the 4-NP, and 3a-TiO₂ exhibited the highest photocatalytic activity. The result is considered a combined action of potential match of 3a with TiO₂ CB and effective impregnated of 3a onto the surface of TiO₂.     

Synthesis and luminescent properties of two Schiff-base boron complexes

Schiff bases N,N′-o-phenylenebis (salicylideneimine) (H₂L¹), N,N′-p-phenylenebis (salicylideneimine) (H₂L²) and their corresponding boron complexes (BF₂)₂L¹, (BF₂)₂L² were synthesized, respectively. The two boron complexes have been characterized by ¹H NMR, mass spectrometry and elemental analysis, while the luminescent properties of them were investigated with UV-VIS spectroscopy and photoluminescence spectroscopy. Then the three-layer devices [ITO/NPB (60 nm)/(BF₂)₂L¹ (50 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (200 nm)] (device I) and [ITO/NPB (60 nm)/(BF₂)₂L² (50 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (200 nm)] (device II) were fabricated by vacuum deposition. These two devices both exhibited blue green emission at 500 nm, but showed different luminances and efficiencies.     

Synthesis, characterization and optical limiting effect of nickel complexes of multi-sulfur 1,2-dithiolene

Three nickel complexes with a new multi-sulfur 1,2-dithiolene ligand, (n-Bu₄N)[Ni(cddt)₂] 1, (Ph₄P)[Ni(cddt)₂] 2 and [Ni(cddt)₂] 3 (cddt=4a, 6, 7, 7a-5H-cyclopenta[b]-1,4-dithiin-2,3-dithiolate), have been synthesized and characterized by electrochemical measurements, IR, EPR and UV-Vis-NIR spectroscopies. The crystal structure of complex 2 is determined. Their optical nonlinearities are measured by the Z-scan technique with an 8 ns pulsed laser at 532 nm and all exhibit NLO absorptive abilities. Complexes 1 and 2 both exhibit effective self-defocusing performance (n₂=−5.81×10⁻¹⁰ esu for 1 and −4.51×10⁻¹⁰ esu for 2). The optical limiting (OL) effects were observed with nanosecond and picosecond laser pulses. The OL capability of complex 3 is superior to C₆₀ at the same experimental condition in ns measurements.     

The molecular vibration-rotation kinetic-energy operator for general internal coordinates

The molecular kinetic-energy operator for general internal coordinates is formulated in terms of simple generalisations of the matrices A, B, α, and β of Crawford. A new matrix γ of the gradients of the translational and rotational constraints facilitates the calculation of the β matrix. It is shown that the kinetic pseudo-potential U is most conveniently calculated as an atomic sum, and results are given for valence coordinates in various types of molecules.     

Three green luminescent cadmium complexes containing 8-aminoquinoline ligands: Syntheses, crystal structures, emission spectra and DFT calculations

Three complexes, Cd(8-aminoql)₂×₂ (8-aminoql=8-aminoquinoline; X⁻=ClO₄⁻, SCN⁻, 1 and 2, respectively) and Cd(8-aminoql)(N₃)₂ (3), were synthesized and structurally characterized. For each complex, the Cd²⁺ ion exhibits distorted octahedral coordination geometry. Two 8-aminoquinoline molecules and two counter-anions are coordinated to the Cd²⁺ center to form a mononuclear species with two trans-ClO₄⁻ anions for 1, while two SCN⁻ anions adopt a cis-configuration for 2. The intermolecular H-bonding interactions between the -NH₂ groups and the O atom (1) and the S atom (2) result in the formation of a 2-D layered structure. In the crystal of 3, the N₃⁻ anions bridging the neighboring Cd(8-aminoql)²⁺ units form a 1-D coordination polymer. The three complexes emit green luminescence. The emission bands possess a broad asymmetric feature, which can be assigned to L′LCT transitions based on DFT and TDDFT calculations.     

Photophysical properties of a series of high luminescent europium complexes with fluorinated ligands

A series of high luminescent europium complexes have been synthesized, such as Eu(TFNB)₃phen (1), Eu(PFNP)₃phen (2), Eu(HFNH)₃phen (3) and Eu(PFND)₃phen (4), which have β-diketone ligands containing fluorinated alkyl chains with different lengths and conjugated naphthyl groups, i.e., 4,4,4-trifluoro-1-(2-naphthyl)butane-1,3-dione (TFNB); 4,4,5,5,5-pentafluoro-1-(2-naphthyl)pentane-1,3-dione (PFNP); 4,4,5,5,6,6,6-heptafluoro-1-(2-naphthyl)hexane-1,3-dione (HFNH) and 4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-pentadecafluoro-1-(2-naphthyl)decane-1,3-dione (PFND). And 10-phenanthroline (phen) is coordinated as the neutral second ligand in 1-4. The crystal structures of 1 and 2 have been studied, which are typical and similar to that of 3. The results of TGA-DTA suggest that these Eu complexes have good thermal stabilities. By means of absorption and (time resolved) emission spectroscopy including determination of luminescence quantum yields, energy transfer dynamics and so on, the following results have been obtained: first, these Eu complexes show characteristic pure red color photoluminescence emission with high quantum efficiencies from the central Eu³⁺ ions through the excitation of the ligands; secondly, photophysical properties of 1, 2, 3 and 4, especially the lifetimes of excited states ⁵D₀ of Eu³⁺ ions and quantum efficiencies are influenced by the different lengths of fluorinated alkyl chains, though the singlets (S₁) and triplets (T₁) of the fluorinated ligands are almost the same.     

Magnetic and electronic properties of Cr- and Mn-doped SnO2: ab initio calculations

The ab initio calculations, based on the Korringa–Kohn–Rostoker (KKR) approximation method combined with the coherent potential approximation (CPA), indicated as KKR–CPA, have been used to study the stability of ferromagnetic and ferrimagnetic states, for systems that are SnO₂ doped and co-doped with two transition metals, that is, chromium and manganese. Our results indicate that the ferromagnetic state is more stable than the spin-glass state for the (Sn_1−xCr_xO₂; x = 0.07, 0.09, 0.12 and 0.15)-doped system, while the spin-glass state is more stable than the ferromagnetic state for the (Sn_1−xMn_xO₂; x = 0.02 and 0.05)-doped system. However, the ferromagnetic and/or the ferrimagnetic states are stable for the (Sn_0.98−xMn_0.02Cr_xO₂; x = 0.05, 0.09 and 0.13)-doped system depending on the Cr concentration. Moreover, we estimated the Curie temperature (T_c) for the Cr-doped tin dioxide (SnO₂), and we explained the origin of magnetic behaviour through the total density of states for different doped and co-doped SnO₂ systems.     

Nonlinear optical absorption and fluorescence of phosphine-substituted bithiophenes in the violet-blue spectral region

The nonlinear optical absorptions of two 5,5′-bis(diphenylphosphino)-2,2′-bithiophene derivatives, Ph₂(X)P(C₄H₂S)₂P(X)Ph₂ (X = O, 1; S, 2), have been investigated by direct transmission measurement with both picosecond and nanosecond laser pulses from 420 nm to 480 nm. Saturated dichloromethane solutions of 1 and 2 exhibit strong nonlinear optical absorptions in this violet-blue spectral region with that of 2 being stronger at all wavelengths. In the picosecond regime, at 420 nm, the transmittance rapidly falls to 50% when the incident fluence is 0.22 J/cm² for 1 and 0.11 J/cm² for 2. Two-photon absorption appears to be the primary mechanism for this nonlinear absorption. The two-photon absorption coefficients β for 1 (2.1 cm/GW) and 2 (4.4 cm/GM) were obtained by fitting the measurement of transmittance as the function of incident beam intensity at 420 nm. These β values are comparable with some of the best results obtained for organic materials in the green, red and infrared spectral region. Both compounds also show fluorescence with an emission peak at 390 nm for 1 and 400 nm for 2. The fluorescence of 1 is considerably stronger than is that of 2. The combination of the wide band gap and strong fluorescence emission of 1 makes it a promising candidate as a host material for blue organic light emitting diodes.     

Interaction between 1-[p-(dimethylamino) benzoyl]-4′-phenyl-semicarbazide and Cu

A new compound, 1-[p-(dimethylamino)benzoyl]-4′-phenyl-semicarbazide (1) was synthesized and showed highly selective response to Cu²⁺ over other metal ions such as Pb²⁺, Mg²⁺, Fe²⁺, Co²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Ca²⁺, Ag⁺, Na⁺, K⁺, and Li⁺. The control compound, 1-[p-(dimethylamino)benzoyl]-4-phenyl-thiosemicarbazide (2), showed different fluorescence spectral response to Cu²⁺. A 1:1 complex between Cu²⁺ and 1 was formed while 1:1 and 1:2 complexes between Cu²⁺ and 2 were formed. The binding model between the receptor (1 or 2) and Cu²⁺ was supported by IR spectra, mass spectra, and computation model. 1 possessed higher selectivity towards Cu²⁺ compared with 2 owing to the difference of complexation ability between urea and thiourea groups.     

Nature of electric and magnetic dipoles gleaned from the Poynting theorem and the Lorentz force law of classical electrodynamics

Starting with the most general form of Maxwell's macroscopic equations in which the free charge and free current densities, ρ_free and J_free, as well as the densities of polarization and magnetization, P and M, are arbitrary functions of space and time, we compare and contrast two versions of the Poynting vector, namely, S = μ_o^− 1E × B and S = E × H. Here E is the electric field, H is the magnetic field, B is the magnetic induction, and μ_o is the permeability of free space. We argue that the identification of one or the other of these Poynting vectors with the rate of flow of electromagnetic energy is intimately tied to the nature of magnetic dipoles and the way in which these dipoles exchange energy with the electromagnetic field. In addition, the manifest nature of both electric and magnetic dipoles in their interactions with the electromagnetic field has consequences for the Lorentz law of force. If the conventional identification of magnetic dipoles with Amperian current loops is extended beyond Maxwell's macroscopic equations to the domain where energy, force, torque, momentum, and angular momentum are active participants, it will be shown that “hidden energy” and “hidden momentum” become inescapable consequences of such identification with Amperian current loops. Hidden energy and hidden momentum can be avoided, however, if we adopt S = E × H as the true Poynting vector, and also accept a generalized version of the Lorentz force law. We conclude that the identification of magnetic dipoles with Amperian current loops, while certainly acceptable within the confines of Maxwell's macroscopic equations, is inadequate and leads to complications when considering energy, force, torque, momentum, and angular momentum in electromagnetic systems that involve the interaction of fields and matter.     

Sensitized luminescence of Eu and Tb macrocyclic complexes bearing benzophenone antennae

Sensitized luminescence behavior of lanthanide (Ln=Eu³⁺, Tb³⁺) macrocyclic cyclen (1,4,7,10-tetraazacyclododecane) complexes bearing one or four benzophenone (BP) moieties as antenna (LnL1 and LnL4) has been studied in water. Despite higher molar extinction coefficient of EuL4 owing to four antennae, it shows only one-thirtieth the luminescence intensity of EuL1. Energy level of triplet excited-state of BP antenna (E_T) is only a few kJ mol⁻¹ higher than that of ⁵D₂ excited-state of Eu³⁺, thus promoting a back energy transfer (BET) from ⁵D₂ of Eu³⁺ to ground-state BP antennae. On EuL4 bearing four antennae, BET occurs more rapidly than that on EuL1, thus exhibiting much weaker luminescence. For Tb complexes, the energy gap between E_T of BP antenna and ⁵D₄ excited state of Tb³⁺ is large enough (>13 kJ mol⁻¹), such that practically no BET occurs. The luminescence intensity of TbL4 is, however, lower (two-third) than that of TbL1. Time-resolved luminescence measurement reveals that hydration number of Tb³⁺ within TbL4 is twice that within TbL1. This is because the structural distortion of ligands on TbL4, caused by an intramolecular dipole-dipole interaction among the BP antennae, allows coordination of higher number of H₂O molecules to Tb³⁺, thus leading to a strong Tb luminescence quenching via O-H oscillators.     

Adsorption mechanism of physiologically active l-phenylalanine phosphonodipeptide analogues: Comparison of colloidal silver and macroscopic silver substrates

Here we present SERS spectra of several l-phenylalanine (Phe) phosphonodipeptides, i.e., l-Phe-l-Ala-PO₃H₂ (MD1), l-Phe-l-Val-PO₃H₂ (MD2), l-Phe-β-Ala-CH(OH)-PO₃H₂ (MD3), l-Phe-l-Ala-CH(OH)-PO₃H₂ (MD4), l-Ala-(3,4-dimethoxy)-l-Phe-PO₃H₂ (MD5), and l-Ala-(3,4-dimethoxy)-(des-CH₂)-l-Phe-PO₃H₂ (MD6), immobilized on electrochemically roughened silver electrodes. These spectra are analyzed by theoretical calculations using density functional theory (DFT) at the B3LYP level with 6-31++G∗∗ basis set. In addition, these spectra are compared with SERS spectra of these species adsorbed on a colloidal silver surface. We showed that on the macroscopic silver substrate, the Phe aromatic ring of MD3 and MD4 is oriented vertically, while for MD1 it almost “stands up” on this surface. In the other three cases, the Phe ring adopts a tilted orientation in regard to the substrate. We also find that the phosphonate , methyl/methane, or dimethoxy groups of MD1, MD2, MD3, MD5, and MD6 are involved in the interaction of these phosphonodipeptides with the electrochemically roughened surface. This phenomenon is clearly seen for -CH₂-/-CH₃/-OCH₃ moieties as well as for the group that adsorbs on the macroscopic silver substrates mainly via the PO fragment. We also showed that MD4 binds to the macroscopic silver substrate through the hydroxyl, amine, and phosphonate groups, while the methylene/methane moieties are remote from this surface. We found that studied phosphonodipeptides often adsorb differently on the macroscopic silver substrate and on the colloidal silver nanoparticles. For example, MD1 adopts an almost vertical orientation on the electrochemically roughened silver substrate and is tilted or close to flat on the silver nanoparticles.