Topological Design of Highly Anisotropic Aligned Hole Transporting Molecular Bottlebrushes for Solution-Processed OLEDs.

Polyvinyl polymers bearing pendant hole transport functionalities have been extensively explored for solution-processed hole transport layer (HTL) technologies, yet there are only rare examples of high anisotropic packing of the HT moieties of these polymers into substrate-parallel orientations within HTL films. For small molecules, substrate-parallel alignment of HT moieties is a well-established approach to improve overall device performance. To address the longstanding challenge of extension from vapor-deposited small molecules to solution-processable polymer systems, a fundamental chemistry tactic is reported here, involving the positioning of HT side chains within macromolecular frameworks by the construction of HT polymers having bottlebrush topologies. Applying state-of-the-art polymer synthetic techniques, various functional subunits, including triphenylamine (TPA) for hole transport and adhesion to the substrate, and perfluoro alkyl-substituted benzyloxy styrene for migration to the air interface, were organized with exquisite control over the composition and placement throughout the bottlebrush topology. Upon assembling the HT bottlebrush (HTB) polymers into monolayered HTL films on various substrates through spin-casting and thermal annealing, the backbones of HTBs were vertically aligned while the grafts with pendant TPAs were extended parallel to the substrate. The overall design realized high TPA π-stacking along the out-of-plane direction of the substrate in the HTLs, which doubled the efficiency of organic light-emitting diodes compared with linear poly(vinyl triphenylamine)s.

Nanoprojectile Secondary Ion Mass Spectrometry for Nanometrology of Nanoparticles and Their Interfaces.

Nanoscale molecular characterization plays a crucial role in enhancing our insights into fundamental and materials processes occurring at the nanoscale. However, for many traditional techniques, measurements on different ensembles are mixed and the analytical result reflects the average surface composition or arrangement. Advances in nanometrologies that allow for measurements to be differentiated based on the chemical environment examined are critical for accurate analysis. Here, we present a variant of secondary ion mass spectrometry, SIMS, termed nanoprojectile SIMS, NP-SIMS, capable of nanoscale molecular analysis. The technique examines the sample with a suite, 106-107, of individual gold nanoprojectiles (e.g., Au4004+) which stochastically probe the surface. Analysis of coemitted ions from each impact allows for the inspection of colocalized moieties within the ejected volume of a single projectile impact (10-15 nm in diameter). If some of these 106-107 measurements arise from nanodomains of similar composition, data can be grouped based on the detected secondary ions. We applied the method to examine a mixture of three different-sized nanoparticles with identical metal cores (3-5 nm in diameter), differing in the length of the attached ligand (decanetiol, tetradecanethiol, and hexadecanethiol). Using NP-SIMS, we determined the relative abundance of the three particles on the surface and isolated measurements based on the impact parameter between the impacting nanoprojectile and the surface particle, demonstrating that measurements occurring near the center of the particle can be differentiated from those at the particle-particle and particle-substrate interfaces. The results suggest that the described methodology is well-suited for molecular analysis of nanoassemblies and may be applied for tracking defects. Here we demonstrate that, using NP-SIMS, ensemble averaging can be avoided and molecular analysis can be undertaken at a scale below 5 nm, allowing for nanoscale molecular analysis of nano-objects and their interfaces.

Nanoprojectile Secondary Ion Mass Spectrometry for Analysis of Extracellular Vesicles.

We describe a technique based on secondary ion mass spectrometry with nanoprojectiles (NP-SIMS) for determining the protein content of extracellular vesicles, EVs, via tagged antibodies. The technique uses individual gold nanoprojectiles (e.g., Au4004+ and Au28008+), separated in time and space, to bombard a surface. For each projectile impact (10-20 nm in diameter), the co-emitted molecules are mass analyzed and recorded as an individual mass spectrum. Examining these individual mass spectra for co-localized species allows for nanoscale mass spectrometry to be performed. The high lateral resolution of this technique is well suited for analyzing nano-objects. SIMS is generally limited to analyzing small molecules (below ∼1500 Da); therefore, we evaluated three molecules (eosin, erythrosine, and BHHTEGST) as prospective mass spectrometry tags. We tested these on a model surface comprising a mixture of all three tags conjugated to antibodies and found that NP-SIMS could detect all three tags from a single projectile impact. Applying the method, we tagged two surface proteins common in urinary EVs, CD63 and CD81, with anti-CD63-erythrosine and anti-CD81-BHHTEGST. We found that NP-SIMS could determine the relative abundance of the two proteins and required only a few hundred or thousand EVs in the analysis region to detect the presence of the tagged antibodies.

Hypervelocity cluster ion impacts on free standing graphene: Experiment, theory, and applications.

We present results from experiments and molecular dynamics (MD) simulations obtained with C60 and Au400 impacting on free-standing graphene, graphene oxide (GO), and graphene-supported molecular layers. The experiments were run on custom-built ToF reflectron mass spectrometers with C60 and Au-LMIS sources with acceleration potentials generating 50 keV C60 2+ and 440-540 keV Au400 4+. Bombardment-detection was in the same mode as MD simulation, i.e., a sequence of individual projectile impacts with separate collection/identification of the ejecta from each impact in either the forward (transmission) or backward (reflection) direction. For C60 impacts on single layer graphene, the secondary ion (SI) yields for C2 and C4 emitted in transmission are ∼0.1 (10%). Similar yields were observed for analyte-specific ions from submonolayer deposits of phenylalanine. MD simulations show that graphene acts as a trampoline, i.e., they can be ejected without destruction. Another topic investigated dealt with the chemical composition of free-standing GO. The elemental composition was found to be approximately COH2. We have also studied the impact of Au400 clusters on graphene. Again SI yields were high (e.g., 1.25 C-/impact). 90-100 Au atoms evaporate off the exiting projectile which experiences an energy loss of ∼72 keV. The latter is a summation of energy spent on rupturing the graphene, ejecting carbon atoms and clusters and a dipole projectile/hole interaction. The charge distribution of the exiting projectiles is ∼50% neutrals and ∼25% either negatively or positively charged. We infer that free-standing graphene enables detection of attomole to zeptomole deposits of analyte via cluster-SI mass spectrometry.

"Trampoline" ejection of organic molecules from graphene and graphite via keV cluster ions impacts.

We present the data on ejection of molecules and emission of molecular ions caused by single impacts of 50 keV C602+ on a molecular layer of deuterated phenylalanine (D8Phe) deposited on free standing, 2-layer graphene. The projectile impacts on the graphene side stimulate the abundant ejection of intact molecules and the emission of molecular ions in the transmission direction. To gain insight into the mechanism of ejection, Molecular Dynamic simulations were performed. It was found that the projectile penetrates the thin layer of graphene, partially depositing the projectile's kinetic energy, and molecules are ejected from the hot area around the hole that is made by the projectile. The yield, Y, of negative ions of deprotonated phenylalanine, (D8Phe-H)-, emitted in the transmission direction is 0.1 ions per projectile impact. To characterize the ejection and ionization of molecules, we have performed the experiments on emission of (D8Phe-H)- from the surface of bulk D8Phe (Y = 0.13) and from the single molecular layer of D8Phe deposited on bulk pyrolytic graphite (Y = 0.15). We show that, despite the similar yields of molecular ions, the scenario of the energy deposition and ejection of molecules is different for the case of graphene due to the confined volume of projectile-analyte interaction. The projectile impact on the graphene-D8Phe sample stimulates the collective radial movement of analyte atoms, which compresses the D8Phe layer radially from the hole. At the same time, this compression bends and stretches the graphene membrane around the hole thus accumulating potential energy. The accumulated potential energy is transformed into the kinetic energy of correlated movement upward for membrane atoms, thus the membrane acts as a trampoline for the molecules. The ejected molecules are effectively ionized; the ionization probability is ∼30× higher compared to that obtained for the bulk D8Phe target. The proposed mechanism of ionization involves tunneling of electrons from the vibrationally excited area around the hole to the molecules. Another proposed mechanism is a direct proton transfer exchange, which is suitable for a bulk target: ions of molecular fragments (i.e., CN-) generated in the impact area interact with intact molecules from the rim of this area. There is a direct proton exchange process for the system D8Phe molecule + CN-.

The collision of a hypervelocity massive projectile with free-standing graphene: Investigation of secondary ion emission and projectile fragmentation.

We present here the study of the individual hypervelocity massive projectiles (440-540 keV, 33-36 km/s Au4004+ cluster) impact on 1-layer free-standing graphene. The secondary ions were detected and recorded separately from each individual impact in the transmission direction using a time-of-flight mass spectrometer. We observed C1-10± ions emitted from graphene, the projectiles which penetrated the graphene, and the Au1-3± fragment ions in mass spectra. During the projectile-graphene interaction, the projectile loses ∼15% of its initial kinetic energy (∼0.18 keV/atom, 72 keV/projectile). The Au projectiles are neutralized when approaching the graphene and then partially ionized again via electron tunneling from the hot rims of the holes on graphene, obtaining positive and negative charges. The projectile reaches an internal energy of ∼450-500 eV (∼4400-4900 K) after the impact and then undergoes a ∼90-100 step fragmentation with the ejection of Au1 atoms in the experimental time range of ∼0.1 µs.

Ejection-ionization of molecules from free standing graphene.

We present the first data on emission of C60- stimulated by single impacts of 50 keV C602+ on the self-assembled molecular layer of C60 deposited on free standing 2 layer graphene. The yield, Y, of C60- emitted in the transmission direction is 1.7%. To characterize the ejection and ionization of molecules, we have measured the emission of C60- from the surface of bulk C60 (Y = 3.7%) and from a single layer of C60 deposited on bulk pyrolytic graphite (Y = 3.3%). To gain insight into the mechanism(s) of ejection, molecular dynamic simulations were performed. The scenario of the energy deposition and ejection of molecules is different for the case of graphene due to the confined volume of projectile-analyte interaction. In the case of 50 keV C602+ impacts on graphene plus C60, the C atoms of the projectile collide with those of the target. The knocked-on atoms take on a part of the kinetic energy of the projectile atoms. Another part of the kinetic energy is deposited into the rim around the impact site. The ejection of molecules from the rim is a result of collective movement of the molecules and graphene membrane, where the membrane movement provides the impulse for ejection. The efficient emission of the intact molecular ions implies an effective ionization probability of intact C60. The proposed mechanism of ionization involves the tunneling of electrons from the vibrationally exited area around the hole to the ejecta.

Single impacts of keV fullerene ions on free standing graphene: Emission of ions and electrons from confined volume.

We present the first data from individual C60 impacting one to four layer graphene at 25 and 50 keV. Negative secondary ions and electrons emitted in transmission were recorded separately from each impact. The yields for C(n)(-) clusters are above 10% for n ≤ 4, they oscillate with electron affinities and decrease exponentially with n. The result can be explained with the aid of MD simulation as a post-collision process where sufficient vibrational energy is accumulated around the rim of the impact hole for sputtering of carbon clusters. The ionization probability can be estimated by comparing experimental yields of C(n)(-) with those of C(n)(0) from MD simulation, where it increases exponentially with n. The ionization probability can be approximated with ejecta from a thermally excited (3700 K) rim damped by cluster fragmentation and electron detachment. The experimental electron probability distributions are Poisson-like. On average, three electrons of thermal energies are emitted per impact. The thermal excitation model invoked for C(n)(-) emission can also explain the emission of electrons. The interaction of C60 with graphene is fundamentally different from impacts on 3D targets. A key characteristic is the high degree of ionization of the ejecta.

Nanoscopic cylindrical dual concentric and lengthwise block brush terpolymers as covalent preassembled high-resolution and high-sensitivity negative-tone photoresist materials.

We describe a high-resolution, high-sensitivity negative-tone photoresist technique that relies on bottom-up preassembly of differential polymer components within cylindrical polymer brush architectures that are designed to align vertically on a substrate and allow for top-down single-molecule line-width imaging. By applying cylindrical diblock brush terpolymers (DBTs) with a high degree of control over the synthetic chemistry, we achieved large areas of vertical alignment of the polymers within thin films without the need for supramolecular assembly processes, as required for linear block copolymer lithography. The specially designed chemical compositions and tuned concentric and lengthwise dimensions of the DBTs enabled high-sensitivity electron-beam lithography of patterns with widths of only a few DBTs (sub-30 nm line-width resolution). The high sensitivity of the brush polymer resists further facilitated the generation of latent images without postexposure baking, providing a practical approach for controlling acid reaction/diffusion processes in photolithography.

Measuring the internal energies of species emitted from hypervelocity nanoprojectile impacts on surfaces using recalibrated benzylpyridinium probe ions.

We present herein a framework for measuring the internal energy distributions of vibrationally excited molecular ions emitted from hypervelocity nanoprojectile impacts on organic surfaces. The experimental portion of this framework is based on the measurement of lifetime distributions of "thermometer" benzylpyridinium ions dissociated within a time of flight mass spectrometer. The theoretical component comprises re-evaluation of the fragmentation energetics of benzylpyridinium ions at the coupled-cluster singles and doubles with perturbative triples level. Vibrational frequencies for the ground and transition states of select molecules are reported, allowing for a full description of vibrational excitations of these molecules via Rice-Ramsperger-Kassel-Marcus unimolecular fragmentation theory. Ultimately, this approach is used to evaluate the internal energy distributions from the measured lifetime distributions. The average internal energies of benzylpyridinium ions measured from 440 keV Au400(+4) impacts are found to be relatively low (~0.24 eV/atom) when compared with keV atomic bombardment of surfaces (1-2 eV/atom).

Nanoprojectile Secondary Ion Mass Spectrometry Enables Multiplexed Analysis of Individual Hepatic Extracellular Vesicles.

Extracellular vesicles (EVs) are nanoscale lipid bilayer particles secreted by cells. EVs may carry markers of the tissue of origin and its disease state, which makes them incredibly promising for disease diagnosis and surveillance. While the armamentarium of EV analysis technologies is rapidly expanding, there remains a strong need for multiparametric analysis with single EV resolution. Nanoprojectile (NP) secondary ion mass spectrometry (NP-SIMS) relies on bombarding a substrate of interest with individual gold NPs resolved in time and space. Each projectile creates an impact crater of 10-20 nm in diameter while molecules emitted from each impact are mass analyzed and recorded as individual mass spectra. We demonstrate the utility of NP-SIMS for statistical analysis of single EVs derived from normal liver cells (hepatocytes) and liver cancer cells. EVs were captured on antibody (Ab)-functionalized gold substrate and then labeled with Abs carrying lanthanide (Ln) MS tags (Ab@Ln). These tags targeted four markers selected for identifying all EVs, and specific to hepatocytes or liver cancer. NP-SIMS was used to detect Ab@Ln-tags colocalized on the same EV and to construct scatter plots of surface marker expression for thousands of EVs with the capability of categorizing individual EVs. Additionally, NP-SIMS revealed information about the chemical nanoenvironment where targeted moieties colocalized. Our approach allowed analysis of population heterogeneity with single EV resolution and distinguishing between hepatocyte and liver cancer EVs based on surface marker expression. NP-SIMS holds considerable promise for multiplexed analysis of single EVs and may become a valuable tool for identifying and validating EV biomarkers of cancer and other diseases.

Nanoprojectile Secondary Ion Mass Spectrometry Enables Multiplexed Analysis of Individual Hepatic Extracellular Vesicles.

Extracellular vesicles (EVs) are nanoscale lipid bilayer particles secreted by cells. EVs may carry markers of the tissue of origin and its disease state which makes them incredibly promising for disease diagnosis and surveillance. While the armamentarium of EV analysis technologies is rapidly expanding, there remains a strong need for multiparametric analysis with single EV resolution. Nanoprojectile (NP) secondary ion mass spectrometry (NP-SIMS) relies on bombarding a substrate of interest with individual gold NPs resolved in time and space. Each projectile creates an impact crater of 10-20 nm in diameter while molecules emitted from each impact are mass analyzed and recorded as individual mass spectra. We demonstrate the utility of NP-SIMS for analysis of single EVs derived from normal liver cells (hepatocytes) and liver cancer cells. EVs were captured on antibody (Ab)-functionalized gold substrate then labeled with Abs carrying lanthanide (Ln) MS tags (Ab@Ln). These tags targeted four markers selected for identifying all EVs, and specific to hepatocytes or liver cancer. NP-SIMS was used to detect Ab@Ln-tags co-localized on the same EV and to construct scatter plots of surface marker expression for thousands of EVs with the capability of categorizing individual EVs. Additionally, NP-SIMS revealed information about the chemical nano-environment where targeted moieties co-localized. Our approach allowed analysis of population heterogeneity with single EV resolution and distinguishing between hepatocyte and liver cancer EVs based on surface marker expression. NP-SIMS holds considerable promise for multiplexed analysis of single EVs and may become a valuable tool for identifying and validating EV biomarkers of cancer and other diseases.

Electrochemical release of hepatocyte-on-hydrogel microstructures from ITO substrates.

This paper describes a novel platform that utilizes micropatterning and electrochemistry to release cells-on-hydrogel microstructures from conductive indium tin oxide (ITO) substrates. In this approach, UV photopolymerization was employed to micropattern heparin-based hydrogels onto glass substrates containing ITO electrodes. ITO/glass substrates were first functionalized with acrylated silane to promote attachment of hydrogel structures. The surfaces containing hydrogel micropatterns were further functionalized with poly(ethylene glycol) thiol, rendering the regions around the hydrogel structures non-fouling to proteins and cells. After incubating surfaces with collagen (I), primary rat hepatocytes were shown to selectively attach on top of the hydrogel and not on surrounding glass/ITO regions. Electrical activation of specific ITO electrodes (-1.8 V vs. Ag/AgCl reference) was then used to release cells-on-hydrogel microstructures from the substrate. Immunostaining and reverse transcription polymerase chain reaction analysis of albumin, an important indicator of hepatic function, showed that the hepatocyte-on-hydrogel microstructures released from the surface maintained their function at levels similar to hepatocytes remaining on the culture substrate. In the future, switchable conductive substrates described here may be to collect cell samples at different time points and may also be used for harvesting cell-carrying vehicles for transplantation studies.

Quantitative label-free characterization of avidin-biotin assemblies on silanized glass.

In this study, a time-of-flight secondary ion mass spectrometer TOF-SIMS, operating in the event-by-event bombardment/detection mode was used to characterize avidin-biotin assemblies on silane-modified glass substrates. SIMS was used to analyze several variants of the biointerface, including avidin physically adsorbed on a monofunctional acryl silane surface and covalently attached on monofunctional (amine terminated) and bifunctional (amine and acryl terminated) silanes. The goal of these studies was to determine density of avidin and biotin layers chemically or physically adsorbed on silanized glass substrate. An individual impact of a C(60) projectile used in this study creates a hemispherical crater (∼10 nm in diameter) and emits large numbers of secondary ions from the same nanovolume. Thus, a single impact enables one to unfold distinct secondary ions that span the thickness of the assembled film. This method was used to monitor the presence of glass, silane, and protein ions and to estimate the thickness and density of the avidin layer. In addition, we employed the double coincidence mass spectrometry approach to identify ions coemitted from a specific stratum of the biointerface. This approach was used to determine density of biotin and avidin immobilization while eliminating interferences from isobaric ions that originated from other constituents on the surface. Overall, novel TOF-SIMS quantitative approaches employed here were useful for examining complex biointerfaces and determining both lateral and in depth composition of the film.

Analysis of native biological surfaces using a 100 kV massive gold cluster source.

In the present work, the advantages of a new, 100 kV platform equipped with a massive gold cluster source for the analysis of native biological surfaces are shown. Inspection of the molecular ion emission as a function of projectile size demonstrates a secondary ion yield increase of ~100× for 520 keV Au(400)(4+) as compared to 130 keV Au(3)(1+) and 43 keV C(60). In particular, yields of tens of percent of molecular ions per projectile impact for the most abundant components can be observed with the 520 keV Au(400)(4+) probe. A comparison between 520 keV Au(400)(4+) time-of-flight-secondary ion mass spectrometry (TOF-SIMS) and matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) data showed a similar pattern and similar relative intensities of lipid components across a rat brain sagittal section. The abundant secondary ion yield of analyte-specific ions makes 520 keV Au(400)(4+) projectiles an attractive probe for submicrometer molecular mapping of native surfaces.

Characterization and Quantification of Nanoparticle-Antibody Conjugates on Cells Using C(60) ToF SIMS in the Event-By-Event Bombardment/Detection Mode.

Cluster C(60) ToF-SIMS (time-of-flight secondary ion mass spectrometry) operated in the event-by-event bombardment-detection method has been applied to: a) quantify the binding density of Au nanoparticles (AuNPs)-antiCD4 conjugates on the cell surface; b) identify the binding sites between AuNPs and antibody. Briefly, our method consists of recording the secondary ions, SIs, individually emitted from a single C(60) (1,2+) impact. From the cumulative mass spectral data we selected events where a specific SI was detected. The selected records revealed the SIs co-ejected from the nanovolume impacted by an individual C(60) with an emission area of ~ 10nm in diameter as an emission depth of 5-10 nm. The fractional coverage is obtained as the ratio of the effective number of projectile impacts on a specified sampling area (N(e)) to the total number of impacts (N(0)). In the negative ion mass spectrum, the palmitate (C(16)H(31)O(2) (-)) and oletate (C(18)H(33)O(2) (-)) fatty acid ions present signals from lipid membrane of the cells. The signals at m/z 197 (Au(-)) and 223 (AuCN(-)) originate from the AuNPs labeled antibodies (antiCD4) bound to the cell surface antigens. The characteristic amino acid ions validate the presence of antiCD4. A coincidence mass spectrum extracted with ion at m/z 223 (AuCN(-)) reveals the presence of cysteine at m/z 120, documenting the closeness of cysteine and the AuNP. Their proximity suggests that the binding site for AuNP on the antibody is the sulfur-terminal cysteine. The fractional coverage of membrane lipid was determined to be ~23% of the cell surfaces while the AuNPs was found to be ~21%. The novel method can be implemented on smaller size NPs, it should thus be applicable for studies on size dependent binding of NP-antibody conjugates.

Nanoparticle-Enabled Multiplexed Electrochemical Immunoassay for Detection of Surface Proteins on Extracellular Vesicles.

Extracellular vesicles (EVs) are lipid bilayer particles secreted from various cells. EVs carry molecular information of parent cells and hold considerable promise for early disease diagnostics. This paper describes a general strategy for multiplexed immunosensing of EV surface proteins, focusing on surface markers CD63, CD81, nephrin, and podocin to prove the concept. This sensing strategy entailed functionalizing gold nanoparticles (AuNPs) with two types of antibodies and then tagging with metal ions, either Pb2+ or Cu2+. The metal ions served as redox reporters, generating unique redox peaks at -0.23 and 0.28 V (vs Ag/AgCl) during electrochemical oxidation of Pb2+ and Cu2+, respectively. Capture of EVs on the working electrode, followed by labeling with immunoprobes and square wave voltammetry, produced redox currents proportional to concentrations of EVs and levels of expression of EV surface markers. Importantly, metal-ion tagging of immunoprobes enabled detection of two EV surface markers simultaneously from the same electrode. We demonstrated dual detection of either CD63/CD81 or podocin/nephrin surface markers from urinary EVs. The NP-enabled immunoassay had a sensitivity of 2.46 × 105 particles/mL (or 40.3 pg/mL) for CD63- and 5.80 × 105 particles/mL (or 47.7 pg/mL) for CD81-expressing EVs and a linear range of four orders of magnitude. The limit of detection for podocin and nephrin was 3.1 and 3.8 pg/mL, respectively. In the future, the capacity for multiplexing may be increased by extending the repertoire of metal ions used for redox tagging of AuNPs.

Characterization of individual ag nanoparticles and their chemical environment.

Silver nanoparticles (NPs) of approximately 5 nm diameter deposited in a single layer on glycine were examined with cluster secondary ion mass spectrometry (SIMS) in the event-by-event bombardment-detection mode. The projectiles used were Au(3)(+), C(60)(+), and Au(400)(4+) with impact energies of 34, 26, and 136 keV, respectively. The highest secondary ion yields were obtained with Au(400)(4+). The method presented can test single or multilayer organization and determine surface coverage. NPs are identified one-by-one for chemical composition. Chemical and physical information in a nonimaging mode was resolved at approximately 10 nm. Grazing vs direct impacts on NPs were identified and quantified. NP fragmentation from direct impacts with Au(400)(4+) and C(60)(+) was observed for the first time.

Molecular identification of individual nano-objects.

Secondary ion mass spectrometry (SIMS) run in the event-by-event bombardment/detection mode provides a unique ability to obtain molecular information from single nano-objects, since assays are based on secondary ion coemission from single impacts. The characterization of individual nano-objects is demonstrated with negatively charged polymer spheres that are attracted to and retained by nanoalumina whiskers. The whiskers, 2 nm in diameter and approximately 250 nm in length, are grafted to a microglass fiber with an average diameter of approximately 0.6 microm and several millimeters long. The spheres are monodisperse polystyrene nanoparticles (30 nm diameter). Massive Au projectiles, specifically 136 keV Au(400)(4+), were utilized to bombard analyte surfaces due to its high efficiency for producing multi-ion emission identified by time-of-flight mass spectrometry. Our results show that this mode of mass spectrometry can provide information on the nature, size, relative location, and abundance of nano-objects in the field of view. The key to characterizing nanodomains is to monitor the coincidental secondary ion emission from the nanovolume perturbed by single projectile impacts.